zotero-db/storage/R9BKD9JY/.zotero-ft-cache

S9427-AN-OMP-010/WSN-7
TECHNICAL MANUAL ORGANIZATIONAL LEVEL
RING LASER GYRO NAVIGATOR INERTIAL NAVIGATION SYSTEM, AN/WSN-7(V)1, -7(V)2, -7(V)3, PART NUMBERS CN-1695/WSN-7(V), CN-1696/WSN-7(V), and CN-1697/WSN-7(V); OPERATION AND MAINTENANCE, WITH PARTS LISTS
Northrop Grumman Corporation Sperry Marine
1070 Seminole Trail Charlottesville, VA 22901-2827
N00024-95-C-4095
N65236-02-D-3823

SUPERSEDURE NOTICE:

THIS MANUAL SUPERSEDES TMIN S9427-AN-MMO-010, REVISION 1, DATED 30 SEPTEMBER 2001, WITH CHANGE A, DATED 15 SEPTEMBER 2003 AND CHANGE B, DATED 24 MARCH 2005.

DISTRIBUTION STATEMENT C: DISTRIBUTION AUTHORIZED TO U.S. GOVERNMENT AGENCIES AND THEIR CONTRACTORS; CRITICAL TECHNOLOGY; DATED 26 MARCH 2007. OTHER REQUESTS FOR THIS DOCUMENT SHALL BE REFERRED TO NAVAL SEA SYSTEMS COMMAND (PEO IWS6LOG2)

WARNING:

THIS DOCUMENT CONTAINS TECHNICAL DATA WHOSE EXPORT IS RESTRICTED BY THE ARMS EXPORT CONTROL ACT (TITLE 22, U.S.C., SEC. 2751, ET SEQ) OR THE EXPORT ADMINISTRATION ACT OF 1979, AS AMENDED, TITLE 50, U.S.C., APP 2401 ET SEQ. VIOLATIONS OF THESE EXPORT LAWS ARE SUBJECT TO SEVERE CRIMINAL PENALTIES. DISSEMINATE IN ACCORDANCE WITH PROVISIONS OF DOD DIRECTIVE 5230.25 (D).

DESTRUCTION NOTICE:

COMPLY WITH DISTRIBUTION STATEMENT AND DESTROY BY ANY METHOD THAT WILL PREVENT DISCLOSURE OF CONTENTS OR RECONSTRUCTION OF THE DOCUMENT.

PUBLISHED BY DIRECTION OF COMMANDER NAVAL SEA SYSTEMS COMMAND

S9427-AN-OMP-010/WSN-7
TECHNICAL MANUAL ORGANIZATIONAL LEVEL
RING LASER GYRO NAVIGATOR INERTIAL NAVIGATION SYSTEM, AN/WSN-7(V)1, -7(V)2, -7(V)3, PART NUMBERS CN-1695/WSN-7(V), CN-1696/WSN-7(V), and CN-1697/WSN-7(V); OPERATION AND MAINTENANCE, WITH PARTS LISTS
Northrop Grumman Corporation Sperry Marine
1070 Seminole Trail Charlottesville, VA 22901-2827
N00024-95-C-4095
N65236-02-D-3823

SUPERSEDURE NOTICE:

THIS MANUAL SUPERSEDES TMIN S9427-AN-MMO-010, REVISION 1, DATED 30 SEPTEMBER 2001, WITH CHANGE A, DATED 15 SEPTEMBER 2003 AND CHANGE B, DATED 24 MARCH 2005.

DISTRIBUTION STATEMENT C: DISTRIBUTION AUTHORIZED TO U.S. GOVERNMENT AGENCIES AND THEIR CONTRACTORS; CRITICAL TECHNOLOGY; DATED 26 MARCH 2007. OTHER REQUESTS FOR THIS DOCUMENT SHALL BE REFERRED TO NAVAL SEA SYSTEMS COMMAND (PEO IWS6LOG2)

WARNING:

THIS DOCUMENT CONTAINS TECHNICAL DATA WHOSE EXPORT IS RESTRICTED BY THE ARMS EXPORT CONTROL ACT (TITLE 22, U.S.C., SEC. 2751, ET SEQ) OR THE EXPORT ADMINISTRATION ACT OF 1979, AS AMENDED, TITLE 50, U.S.C., APP 2401 ET SEQ. VIOLATIONS OF THESE EXPORT LAWS ARE SUBJECT TO SEVERE CRIMINAL PENALTIES. DISSEMINATE IN ACCORDANCE WITH PROVISIONS OF DOD DIRECTIVE 5230.25 (D).

DESTRUCTION NOTICE:

COMPLY WITH DISTRIBUTION STATEMENT AND DESTROY BY ANY METHOD THAT WILL PREVENT DISCLOSURE OF CONTENTS OR RECONSTRUCTION OF THE DOCUMENT.

PUBLISHED BY DIRECTION OF COMMANDER NAVAL SEA SYSTEMS COMMAND

26 MARCH 2007

S9427-AN-OMP-010/WSN-7

LIST OF EFFECTIVE PAGES

Dates of issue for original and changed pages are:

Original........0........26 MARCH 2007

Total Number of pages in this manual is 405 consisting of the following:

Page

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Change Page

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No.

No. No.

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No.

Cover . . . . . . . . . . . . . . . . . . . 0

Title . . . . . . . . . . . . . . . . . . . 0

B . . . . . . . . . . . . . . . . . . . . .0

Change Record 1/(change Record 2 Blank) . . 0

i . . . . . . . . . . . . . . . . . . . . .0

ii . . . . . . . . . . . . . . . . . . . . . 0

iii . . . . . . . . . . . . . . . . . . . . . 0

iv . . . . . . . . . . . . . . . . . . . . . 0

v . . . . . . . . . . . . . . . . . . . . .0

vi . . . . . . . . . . . . . . . . . . . . . 0

vii . . . . . . . . . . . . . . . . . . . . 0

viii (Blank) . . . . . . . . . . . . . . . . . 0

ix . . . . . . . . . . . . . . . . . . . . . 0

x (Blank) . . . . . . . . . . . . . . . . . 0

a

0

(blank/1-0) . . . . . . . . . . . . . . . . . 0

1-1 . . . . . . . . . . . . . . . . . . . . 0

1-2 . . . . . . . . . . . . . . . . . . . . 0

1-3 . . . . . . . . . . . . . . . . . . . . 0

1-4 . . . . . . . . . . . . . . . . . . . . 0

1-5 . . . . . . . . . . . . . . . . . . . . 0

1-6 . . . . . . . . . . . . . . . . . . . . 0

1-7 . . . . . . . . . . . . . . . . . . . . 0

1-8 . . . . . . . . . . . . . . . . . . . . 0

1-9 . . . . . . . . . . . . . . . . . . . . 0

1-10 . . . . . . . . . . . . . . . . . . . 0

1-11 . . . . . . . . . . . . . . . . . . . 0

1-12 . . . . . . . . . . . . . . . . . . . 0

1-13 . . . . . . . . . . . . . . . . . . . 0

1-14 . . . . . . . . . . . . . . . . . . . 0

2-1 . . . . . . . . . . . . . . . . . . . . 0

2-2 . . . . . . . . . . . . . . . . . . . . 0

2-3 . . . . . . . . . . . . . . . . . . . . 0

2-19 . . . . . . . . . . . . . . . . . . . 0 2-20 . . . . . . . . . . . . . . . . . . . 0 2-21 . . . . . . . . . . . . . . . . . . . 0 2-22 . . . . . . . . . . . . . . . . . . . 0 2-23 . . . . . . . . . . . . . . . . . . . 0 2-24 . . . . . . . . . . . . . . . . . . . 0 2-25 . . . . . . . . . . . . . . . . . . . 0 2-26 . . . . . . . . . . . . . . . . . . . 0 2-27 . . . . . . . . . . . . . . . . . . . 0 2-28 . . . . . . . . . . . . . . . . . . . 0 2-29 . . . . . . . . . . . . . . . . . . . 0 2-30 . . . . . . . . . . . . . . . . . . . 0 2-31 . . . . . . . . . . . . . . . . . . . 0 2-32 . . . . . . . . . . . . . . . . . . . 0 2-33 . . . . . . . . . . . . . . . . . . . 0 2-34 . . . . . . . . . . . . . . . . . . . 0 2-35 . . . . . . . . . . . . . . . . . . . 0 2-36 . . . . . . . . . . . . . . . . . . . 0 2-37 . . . . . . . . . . . . . . . . . . . 0 2-38 . . . . . . . . . . . . . . . . . . . 0 2-39 . . . . . . . . . . . . . . . . . . . 0 2-40 . . . . . . . . . . . . . . . . . . . 0 2-41 . . . . . . . . . . . . . . . . . . . 0 2-42 (Blank) . . . . . . . . . . . . . . . . 0 3-1 . . . . . . . . . . . . . . . . . . . . 0 3-2 . . . . . . . . . . . . . . . . . . . . 0 3-3 . . . . . . . . . . . . . . . . . . . . 0 3-4 . . . . . . . . . . . . . . . . . . . . 0 3-5 . . . . . . . . . . . . . . . . . . . . 0 3-6 . . . . . . . . . . . . . . . . . . . . 0 3-7 . . . . . . . . . . . . . . . . . . . . 0 3-8 . . . . . . . . . . . . . . . . . . . . 0 3-9 . . . . . . . . . . . . . . . . . . . . 0

2-4 . . . . . . . . . . . . . . . . . . . . 0 2-5 . . . . . . . . . . . . . . . . . . . . 0 2-6 . . . . . . . . . . . . . . . . . . . . 0 2-7 . . . . . . . . . . . . . . . . . . . . 0 2-8 . . . . . . . . . . . . . . . . . . . . 0 2-9 . . . . . . . . . . . . . . . . . . . . 0 2-10 . . . . . . . . . . . . . . . . . . . 0 2-11 . . . . . . . . . . . . . . . . . . . 0 2-12 . . . . . . . . . . . . . . . . . . . 0 2-13 . . . . . . . . . . . . . . . . . . . 0 2-14 . . . . . . . . . . . . . . . . . . . 0 2-15 . . . . . . . . . . . . . . . . . . . 0 2-16 . . . . . . . . . . . . . . . . . . . 0 2-17 . . . . . . . . . . . . . . . . . . . 0 2-18 . . . . . . . . . . . . . . . . . . . 0

3-10 3-11 3-12 3-13 3-14 3-15 3-16 3-17 3-18 3-19 3-20 3-21 3-22 3-23 3-24

. . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . . . .0

*Zero in the Change No. column indicates an original page.

3-25 . . . . . . . . . . . . . . . . . . . 0 3-26 . . . . . . . . . . . . . . . . . . . 0 3-27 . . . . . . . . . . . . . . . . . . . 0 3-28 . . . . . . . . . . . . . . . . . . . 0 3-29 . . . . . . . . . . . . . . . . . . . 0 3-30 . . . . . . . . . . . . . . . . . . . 0 3-31 . . . . . . . . . . . . . . . . . . . 0 3-32 . . . . . . . . . . . . . . . . . . . 0 3-33 . . . . . . . . . . . . . . . . . . . 0 3-34 . . . . . . . . . . . . . . . . . . . 0 3-35 . . . . . . . . . . . . . . . . . . . 0 3-36 . . . . . . . . . . . . . . . . . . . 0 3-37 . . . . . . . . . . . . . . . . . . . 0 3-38 . . . . . . . . . . . . . . . . . . . 0 3-39 . . . . . . . . . . . . . . . . . . . 0 3-40 . . . . . . . . . . . . . . . . . . . 0 3-41 . . . . . . . . . . . . . . . . . . . 0 3-42 . . . . . . . . . . . . . . . . . . . 0 3-43 . . . . . . . . . . . . . . . . . . . 0 3-44 . . . . . . . . . . . . . . . . . . . 0 3-45 . . . . . . . . . . . . . . . . . . . 0 3-46 . . . . . . . . . . . . . . . . . . . 0 4-1 . . . . . . . . . . . . . . . . . . . . 0 4-2 . . . . . . . . . . . . . . . . . . . . 0 5-1 . . . . . . . . . . . . . . . . . . . . 0 5-2 . . . . . . . . . . . . . . . . . . . . 0 5-3 . . . . . . . . . . . . . . . . . . . . 0 5-4 . . . . . . . . . . . . . . . . . . . . 0 5-5 . . . . . . . . . . . . . . . . . . . . 0 5-6 . . . . . . . . . . . . . . . . . . . . 0 5-7 . . . . . . . . . . . . . . . . . . . . 0 5-8 . . . . . . . . . . . . . . . . . . . . 0 5-9 . . . . . . . . . . . . . . . . . . . . 0 5-10 . . . . . . . . . . . . . . . . . . . 0 5-11 . . . . . . . . . . . . . . . . . . . 0 5-12 . . . . . . . . . . . . . . . . . . . 0 5-13 . . . . . . . . . . . . . . . . . . . 0 5-14 . . . . . . . . . . . . . . . . . . . 0 5-15 . . . . . . . . . . . . . . . . . . . 0 5-16 . . . . . . . . . . . . . . . . . . . 0 5-17 . . . . . . . . . . . . . . . . . . . 0 5-18 . . . . . . . . . . . . . . . . . . . 0 5-19 . . . . . . . . . . . . . . . . . . . 0 5-20 . . . . . . . . . . . . . . . . . . . 0 5-21 . . . . . . . . . . . . . . . . . . . 0 5-22 . . . . . . . . . . . . . . . . . . . 0 5-23 . . . . . . . . . . . . . . . . . . . 0 5-24 . . . . . . . . . . . . . . . . . . . 0

5-25 . . . . . . . . . . . . . . . . . . . 0 5-26 . . . . . . . . . . . . . . . . . . . 0 5-27 . . . . . . . . . . . . . . . . . . . 0 5-28 . . . . . . . . . . . . . . . . . . . 0 5-29 . . . . . . . . . . . . . . . . . . . 0 5-30 . . . . . . . . . . . . . . . . . . . 0 5-31 . . . . . . . . . . . . . . . . . . . 0 5-32 . . . . . . . . . . . . . . . . . . . 0 5-33 . . . . . . . . . . . . . . . . . . . 0 5-34 . . . . . . . . . . . . . . . . . . . 0 5-35 . . . . . . . . . . . . . . . . . . . 0 5-36 . . . . . . . . . . . . . . . . . . . 0 5-37 . . . . . . . . . . . . . . . . . . . 0 5-38 . . . . . . . . . . . . . . . . . . . 0 5-39 . . . . . . . . . . . . . . . . . . . 0 5-40 . . . . . . . . . . . . . . . . . . . 0 5-41 . . . . . . . . . . . . . . . . . . . 0 5-42 . . . . . . . . . . . . . . . . . . . 0 5-43 . . . . . . . . . . . . . . . . . . . 0 5-44 . . . . . . . . . . . . . . . . . . . 0 5-45 . . . . . . . . . . . . . . . . . . . 0 5-46 . . . . . . . . . . . . . . . . . . . 0 5-47 . . . . . . . . . . . . . . . . . . . 0 5-48 . . . . . . . . . . . . . . . . . . . 0 5-49 . . . . . . . . . . . . . . . . . . . 0 5-50 . . . . . . . . . . . . . . . . . . . 0 5-51 . . . . . . . . . . . . . . . . . . . 0 5-52 . . . . . . . . . . . . . . . . . . . 0 5-53 . . . . . . . . . . . . . . . . . . . 0 5-54 . . . . . . . . . . . . . . . . . . . 0 5-55 . . . . . . . . . . . . . . . . . . . 0 5-56 . . . . . . . . . . . . . . . . . . . 0 5-57 . . . . . . . . . . . . . . . . . . . 0 5-58 . . . . . . . . . . . . . . . . . . . 0 5-59 . . . . . . . . . . . . . . . . . . . 0 5-60 . . . . . . . . . . . . . . . . . . . 0 5-61 . . . . . . . . . . . . . . . . . . . 0 5-62 . . . . . . . . . . . . . . . . . . . 0 5-63 . . . . . . . . . . . . . . . . . . . 0 5-64 . . . . . . . . . . . . . . . . . . . 0 5-65 . . . . . . . . . . . . . . . . . . . 0 5-66 . . . . . . . . . . . . . . . . . . . 0 6-1 . . . . . . . . . . . . . . . . . . . . 0 6-2 . . . . . . . . . . . . . . . . . . . . 0 6-3 . . . . . . . . . . . . . . . . . . . . 0 6-4 . . . . . . . . . . . . . . . . . . . . 0 6-5 . . . . . . . . . . . . . . . . . . . . 0 6-6 . . . . . . . . . . . . . . . . . . . . 0

A

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S9427-AN-OMP-010/WSN-7

LIST OF EFFECTIVE PAGES - Continued

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6-7 . . . . . . . . . . . . . . . . . . . . 0 6-8 . . . . . . . . . . . . . . . . . . . . 0 6-9 . . . . . . . . . . . . . . . . . . . . 0 6-10 . . . . . . . . . . . . . . . . . . . 0 6-11 . . . . . . . . . . . . . . . . . . . 0 6-12 . . . . . . . . . . . . . . . . . . . 0 6-13 . . . . . . . . . . . . . . . . . . . 0 6-14 . . . . . . . . . . . . . . . . . . . 0 6-15 . . . . . . . . . . . . . . . . . . . 0 6-16 . . . . . . . . . . . . . . . . . . . 0 6-17 . . . . . . . . . . . . . . . . . . . 0 6-18 . . . . . . . . . . . . . . . . . . . 0 6-19 . . . . . . . . . . . . . . . . . . . 0 6-20 . . . . . . . . . . . . . . . . . . . 0 6-21 . . . . . . . . . . . . . . . . . . . 0 6-22 . . . . . . . . . . . . . . . . . . . 0 6-23 . . . . . . . . . . . . . . . . . . . 0 6-24 . . . . . . . . . . . . . . . . . . . 0 6-25 . . . . . . . . . . . . . . . . . . . 0 6-26 . . . . . . . . . . . . . . . . . . . 0 6-27 . . . . . . . . . . . . . . . . . . . 0 6-28 . . . . . . . . . . . . . . . . . . . 0 6-29 . . . . . . . . . . . . . . . . . . . 0 6-30 . . . . . . . . . . . . . . . . . . . 0 6-31 . . . . . . . . . . . . . . . . . . . 0 6-32 . . . . . . . . . . . . . . . . . . . 0 6-33 . . . . . . . . . . . . . . . . . . . 0 6-34 . . . . . . . . . . . . . . . . . . . 0 6-35 . . . . . . . . . . . . . . . . . . . 0 6-36 . . . . . . . . . . . . . . . . . . . 0 6-37 . . . . . . . . . . . . . . . . . . . 0 6-38 . . . . . . . . . . . . . . . . . . . 0 6-39 . . . . . . . . . . . . . . . . . . . 0 6-40 . . . . . . . . . . . . . . . . . . . 0 6-41 . . . . . . . . . . . . . . . . . . . 0 6-42 . . . . . . . . . . . . . . . . . . . 0 6-43 . . . . . . . . . . . . . . . . . . . 0 6-44 . . . . . . . . . . . . . . . . . . . 0 6-45 . . . . . . . . . . . . . . . . . . . 0 6-46 . . . . . . . . . . . . . . . . . . . 0 6-47 . . . . . . . . . . . . . . . . . . . 0 6-48 . . . . . . . . . . . . . . . . . . . 0 6-49 . . . . . . . . . . . . . . . . . . . 0 6-50 . . . . . . . . . . . . . . . . . . . 0 6-51 . . . . . . . . . . . . . . . . . . . 0 6-52 . . . . . . . . . . . . . . . . . . . 0 6-53 . . . . . . . . . . . . . . . . . . . 0 6-54 . . . . . . . . . . . . . . . . . . . 0 6-55 . . . . . . . . . . . . . . . . . . . 0 6-56 . . . . . . . . . . . . . . . . . . . 0

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7-1 . . . . . . . . . . . . . . . . . . . . 0 7-2 . . . . . . . . . . . . . . . . . . . . 0 7-3 . . . . . . . . . . . . . . . . . . . . 0 7-4 . . . . . . . . . . . . . . . . . . . . 0 7-5 . . . . . . . . . . . . . . . . . . . . 0 7-6 . . . . . . . . . . . . . . . . . . . . 0 7-7 . . . . . . . . . . . . . . . . . . . . 0 7-8 . . . . . . . . . . . . . . . . . . . . 0 7-9 . . . . . . . . . . . . . . . . . . . . 0 7-10 . . . . . . . . . . . . . . . . . . . 0 7-11 . . . . . . . . . . . . . . . . . . . 0 7-12 . . . . . . . . . . . . . . . . . . . 0 7-13 . . . . . . . . . . . . . . . . . . . 0 7-14 . . . . . . . . . . . . . . . . . . . 0 7-15 . . . . . . . . . . . . . . . . . . . 0 7-16 . . . . . . . . . . . . . . . . . . . 0 7-17 . . . . . . . . . . . . . . . . . . . 0 7-18 . . . . . . . . . . . . . . . . . . . 0 7-19 . . . . . . . . . . . . . . . . . . . 0 7-20 . . . . . . . . . . . . . . . . . . . 0 7-21 . . . . . . . . . . . . . . . . . . . 0 7-22 . . . . . . . . . . . . . . . . . . . 0 7-23 . . . . . . . . . . . . . . . . . . . 0 7-24 . . . . . . . . . . . . . . . . . . . 0 7-25 . . . . . . . . . . . . . . . . . . . 0 7-26 . . . . . . . . . . . . . . . . . . . 0 7-27 . . . . . . . . . . . . . . . . . . . 0 7-28 . . . . . . . . . . . . . . . . . . . 0 7-29 . . . . . . . . . . . . . . . . . . . 0 7-30 . . . . . . . . . . . . . . . . . . . 0 7-31 . . . . . . . . . . . . . . . . . . . 0 7-32 . . . . . . . . . . . . . . . . . . . 0 7-33 . . . . . . . . . . . . . . . . . . . 0 7-34 . . . . . . . . . . . . . . . . . . . 0 7-35 . . . . . . . . . . . . . . . . . . . 0 7-36 . . . . . . . . . . . . . . . . . . . 0 7-37 . . . . . . . . . . . . . . . . . . . 0 7-38 . . . . . . . . . . . . . . . . . . . 0 7-39 . . . . . . . . . . . . . . . . . . . 0 7-40 . . . . . . . . . . . . . . . . . . . 0 7-41 . . . . . . . . . . . . . . . . . . . 0 7-42 . . . . . . . . . . . . . . . . . . . 0 7-43 . . . . . . . . . . . . . . . . . . . 0 7-44 . . . . . . . . . . . . . . . . . . . 0 7-45 . . . . . . . . . . . . . . . . . . . 0 7-46 . . . . . . . . . . . . . . . . . . . 0 7-47 . . . . . . . . . . . . . . . . . . . 0 7-48 . . . . . . . . . . . . . . . . . . . 0 7-49 . . . . . . . . . . . . . . . . . . . 0 7-50 . . . . . . . . . . . . . . . . . . . 0

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7-51 . . . . . . . . . . . . . . . . . . . 0 7-52 . . . . . . . . . . . . . . . . . . . 0 7-53 . . . . . . . . . . . . . . . . . . . 0 7-54 . . . . . . . . . . . . . . . . . . . 0 7-55 . . . . . . . . . . . . . . . . . . . 0 7-56 . . . . . . . . . . . . . . . . . . . 0 7-57 . . . . . . . . . . . . . . . . . . . 0 7-58 . . . . . . . . . . . . . . . . . . . 0 7-59 . . . . . . . . . . . . . . . . . . . 0 7-60 . . . . . . . . . . . . . . . . . . . 0 7-61 . . . . . . . . . . . . . . . . . . . 0 7-62 . . . . . . . . . . . . . . . . . . . 0 7-63 . . . . . . . . . . . . . . . . . . . 0 7-64 . . . . . . . . . . . . . . . . . . . 0 7-65 . . . . . . . . . . . . . . . . . . . 0 7-66 (Blank) . . . . . . . . . . . . . . . . 0 8-1 . . . . . . . . . . . . . . . . . . . . 0 8-2 . . . . . . . . . . . . . . . . . . . . 0 8-3 . . . . . . . . . . . . . . . . . . . . 0 8-4 . . . . . . . . . . . . . . . . . . . . 0 8-5 . . . . . . . . . . . . . . . . . . . . 0 8-6 . . . . . . . . . . . . . . . . . . . . 0 8-7 . . . . . . . . . . . . . . . . . . . . 0 8-8 . . . . . . . . . . . . . . . . . . . . 0 8-9 . . . . . . . . . . . . . . . . . . . . 0 8-10 . . . . . . . . . . . . . . . . . . . 0 8-11 . . . . . . . . . . . . . . . . . . . 0 8-12 . . . . . . . . . . . . . . . . . . . 0 8-13 . . . . . . . . . . . . . . . . . . . 0 8-14 . . . . . . . . . . . . . . . . . . . 0 8-15 . . . . . . . . . . . . . . . . . . . 0 8-16 . . . . . . . . . . . . . . . . . . . 0 8-17 . . . . . . . . . . . . . . . . . . . 0 8-18 . . . . . . . . . . . . . . . . . . . 0 8-19 . . . . . . . . . . . . . . . . . . . 0 8-20 . . . . . . . . . . . . . . . . . . . 0 8-21 . . . . . . . . . . . . . . . . . . . 0 8-22 . . . . . . . . . . . . . . . . . . . 0 8-23 . . . . . . . . . . . . . . . . . . . 0 8-24 . . . . . . . . . . . . . . . . . . . 0 8-25 . . . . . . . . . . . . . . . . . . . 0 8-26 . . . . . . . . . . . . . . . . . . . 0 8-27 . . . . . . . . . . . . . . . . . . . 0 8-28 . . . . . . . . . . . . . . . . . . . 0 8-29 . . . . . . . . . . . . . . . . . . . 0 8-30 (Blank) . . . . . . . . . . . . . . . . 0 A-1 . . . . . . . . . . . . . . . . . . . . 0 A-2 . . . . . . . . . . . . . . . . . . . . 0 A-3 . . . . . . . . . . . . . . . . . . . . 0 A-4 . . . . . . . . . . . . . . . . . . . . 0

A-5 . . . . . . . . . . . . . . . . . . . . 0 A-6 . . . . . . . . . . . . . . . . . . . . 0 A-7 . . . . . . . . . . . . . . . . . . . . 0 A-8 . . . . . . . . . . . . . . . . . . . . 0 A-9 . . . . . . . . . . . . . . . . . . . . 0 A-10 . . . . . . . . . . . . . . . . . . . 0 A-11 . . . . . . . . . . . . . . . . . . . 0 A-12(Blank) . . . . . . . . . . . . . . . . 0 B-1 . . . . . . . . . . . . . . . . . . . . 0 B-2 . . . . . . . . . . . . . . . . . . . . 0 B-3 . . . . . . . . . . . . . . . . . . . . 0 B-4 . . . . . . . . . . . . . . . . . . . . 0 B-5 . . . . . . . . . . . . . . . . . . . . 0 B-6 . . . . . . . . . . . . . . . . . . . . 0 B-7 . . . . . . . . . . . . . . . . . . . . 0 B-8 . . . . . . . . . . . . . . . . . . . . 0 B-9 . . . . . . . . . . . . . . . . . . . . 0 B-10 . . . . . . . . . . . . . . . . . . . 0 B-11 . . . . . . . . . . . . . . . . . . . 0 B-12 . . . . . . . . . . . . . . . . . . . 0 B-13 . . . . . . . . . . . . . . . . . . . 0 B-14 . . . . . . . . . . . . . . . . . . . 0 B-15 . . . . . . . . . . . . . . . . . . . 0 B-16 . . . . . . . . . . . . . . . . . . . 0 B-17 . . . . . . . . . . . . . . . . . . . 0 B-18 . . . . . . . . . . . . . . . . . . . 0 B-19 . . . . . . . . . . . . . . . . . . . 0 B-20 . . . . . . . . . . . . . . . . . . . 0 B-21 . . . . . . . . . . . . . . . . . . . 0 B-22 . . . . . . . . . . . . . . . . . . . 0 B-23 . . . . . . . . . . . . . . . . . . . 0 B-24 . . . . . . . . . . . . . . . . . . . 0 B-25 . . . . . . . . . . . . . . . . . . . 0 B-26 . . . . . . . . . . . . . . . . . . . 0 B-27 . . . . . . . . . . . . . . . . . . . 0 B-28 . . . . . . . . . . . . . . . . . . . 0 B-29 . . . . . . . . . . . . . . . . . . . 0 B-30 . . . . . . . . . . . . . . . . . . . 0 B-31 . . . . . . . . . . . . . . . . . . . 0 B-32 . . . . . . . . . . . . . . . . . . . 0 B-33 . . . . . . . . . . . . . . . . . . . 0 B-34 . . . . . . . . . . . . . . . . . . . 0 B-35 . . . . . . . . . . . . . . . . . . . 0 B-36 . . . . . . . . . . . . . . . . . . . 0 B-37 . . . . . . . . . . . . . . . . . . . 0 B-38 . . . . . . . . . . . . . . . . . . . 0 B-39 . . . . . . . . . . . . . . . . . . . 0 B-40 . . . . . . . . . . . . . . . . . . . 0 B-41 . . . . . . . . . . . . . . . . . . . 0 B-42 . . . . . . . . . . . . . . . . . . . 0

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TABLE OF CONTENTS

S9427-AN-OMP-010/WSN-7

Chapter

Page

FRONT MATTER

TABLE OF CONTENTS . . . . . . . i

LIST OF ILLUSTRATIONS . . . . . . v

LIST OF TABLES . . . . . . . . . vi

FOREWORD . . . . . . . . . . vii

SAFETY SUMMARY . . . . . . . ix

1

GENERAL INFORMATION AND SAFETY

PRECAUTIONS . . . . . . . . . 1-1

1.1

SAFETY PRECAUTIONS. . . . . . 1-1

1.1.1 AN/WSN-7 General Safety Precautions. . . . . . . . . . . . 1-1

1.1.2 Dangers, Warnings, and Cautions. . 1-1

1.2

INTRODUCTION. . . . . . . . . 1-4

1.2.1 General Equipment Function. . . . 1-4

1.2.2 Normal Operation. . . . . . . . . 1-4

1.2.3 Test Features. . . . . . . . . . . 1-4

1.2.4 Power. . . . . . . . . . . . . . 1-4

1.3

AN/WSN-7(V) CONFIGURATIONS AND

INTERFACES. . . . . . . . . . . 1-4

1.3.1 Conﬁgurations. . . . . . . . . . . 1-4

1.3.2 External Data Interfaces. . . . . . 1-4

1.4

UNITS AND ASSEMBLIES. . . . . 1-5

1.4.1 DSVL Interface Modiﬁcation. . . . . 1-5

1.4.2 ATM Interface Modiﬁcation. . . . . 1-5

1.5

INS INTERFACE SYSTEMS. . . . . 1-5

1.5.1 AN/WSN-7(V) Master to AN/WSN-7(V) Slave. . . . . . . . . . . . . . 1-5

1.5.2 IP-1747/WSN Control Display Unit (CDU). . . . . . . . . . . . . . 1-5

1.6

TROUBLESHOOTING AND

MAINTENANCE CONCEPT. . . . . 1-5

1.7

LIST OF APPLICABLE DOCU-

MENTS. . . . . . . . . . . . . 1-5

1.8

EQUIPMENT AND ACCESSORIES. 1-5

2

OPERATION . . . . . . . . . . 2-1

2.1

INTRODUCTION. . . . . . . . . 2-1

2.2

CONTROLS AND INDICATORS. . . 2-1

2.2.1 Keypad Controls and Menu Display. . 2-1

2.2.2 Key Functions. . . . . . . . . . . 2-1

2.2.3 Menu Selections. . . . . . . . . . 2-1

2.3

OPERATING PROCEDURES. . . . 2-1

2.3.1 Turning on the RLGN. . . . . . . . 2-1

2.3.2 Operating Modes. . . . . . . . . 2-2

2.3.2.1 Align Mode States. . . . . . . . . 2-2

2.3.2.2 Alignment References. . . . . . . 2-2

2.3.2.3 Operating in Align Modes. . . . . . 2-2

Chapter

Page

2.3.2.4 Align Methods. . . . . . . . . . . 2-2

2.3.2.5 Selecting the Navigate Mode. . . . 2-5

2.3.2.6 Switching Between Navigate and Align Modes. . . . . . . . . . . . . . 2-6

2.3.3 Transverse Coordinates Reference and Display. . . . . . . . . . . . . . 2-7

2.3.3.1 Use of Transverse Coordinates Reference System. . . . . . . . . . . . . . 2-7

2.3.3.2 Modes for Use in Transverse Coordinates Reference System. . . . . . . . . 2-7

2.3.4 Accepting and Entering Position Fixes. . . . . . . . . . . . . . . 2-7

2.3.4.1 Applying Fix Data as a Slew. . . . . 2-7

2.3.4.2 Position Updates. . . . . . . . . . 2-8

2.3.4.3 Accepting or Rejecting Fixes. . . . 2-8

2.3.4.4 INS Processing of a Position Fix. . . 2-8

2.3.4.5 Criteria for Acceptance of a Position Fix. . . . . . . . . . . . . . . . 2-8

2.3.4.6 Enhanced Performance Position Accuracy (EP2A). . . . . . . . . . . . . . 2-8

2.3.4.7 Reset Modes and Operator Acceptance of a Position Fix. . . . . . . . . . . 2-8

2.3.4.8 Automatic Entry of a Position Fix. . . 2-9

2.3.4.9 Manual Entry of a Position Fix. . . . 2-9

2.3.4.10 Manual Fix Entry Procedure. . . . . 2-9

2.3.4.11 Manual Position Slew Procedure. . 2-10

2.3.4.12 Review Reset Data Procedure. . . 2-11

2.3.5 Selecting the Velocity Damping Mode, Source, and Filter. . . . . . . . 2-11

2.3.5.1 Selecting Damped or Undamped Operation. . . . . . . . . . . . 2-11

2.3.5.2 Selecting the Horizontal Velocity Damping Reference. . . . . . . . . . . 2-12

2.3.5.3 Selecting the Horizontal Velocity Damping Filter. . . . . . . . . . . . . . 2-12

2.3.6 Selecting Data for Display. . . . . 2-12

2.3.7 Operating Under Interfering Conditions. . . . . . . . . . . 2-12

2.3.7.1 Acknowledging and Identifying Fault Conditions. . . . . . . . . . . 2-12

2.3.7.2 Operating with System Faults. . . 2-12

2.3.7.3 Source Alternating Current (AC) Power or Synchro Reference Fault. . . . . 2-13

2.3.7.4 Indexer Faults (Code 043 or 044). 2-13

2.3.7.5 Speed Data Source Faults (Codes 036, 056, 057, 060, 061, 222, and 223). 2-13

2.3.7.6 GPS or GPS I/O Faults (Codes 368 through 383). . . . . . . . . . 2-13

Chapter

Page

2.3.7.7 Position Fix and Velocity Reference Error Faults (Codes 209, 210, 211, and 212 through 217). . . . . . . . . . 2-13

2.3.7.8 External Serial Interface or I/O Processor Faults (Codes 240 through 246, 248, 250, 251, 253 through 257, 259, 262, 264, 266, 338, 347 through 351). . . . . . 2-14

2.3.7.9 Common RAM Test Pattern Faults (Codes 019 and 252). . . . . . . . . . 2-14

2.3.7.10 Casualty Mode Faults (Codes 033, 100, 101, 102, 109, 188). . . . . . . 2-14

2.3.8 Turning off the INS. . . . . . . . 2-14

2.4

OPERATOR’S MAINTENANCE. . 2-15

2.4.1 Off-Line Test Mode. . . . . . . . 2-15

2.4.2 On-Line NTDS Interface Ports Selection and Conﬁguration. . . . . . . . 2-15

2.4.2.1 NTDS Port Conﬁguration Settings. 2-15

2.4.2.2 Super Channel Settings (Applicable to IDS 13) . . . . . . . . . . . . . . 2-15

2.4.2.3 ATM Port Conﬁguration Settings. . 2-15

2.4.3 On-Line Log Calibration. . . . . . 2-16

2.4.3.1 Changing Log Bias Calibration Tables. . . . . . . . . . . . . 2-16

2.4.4 On-Line Log Calibration (Semi-Automatic Procedure). . . . . . . . . . . 2-16

2.4.4.1 Procedure. . . . . . . . . . . 2-16

2.4.4.2 System Damping. . . . . . . . 2-16

2.4.5 On-Line Log Calibration (Automatic Procedure). . . . . . . . . . . 2-16

2.4.5.1 Monitoring and Clearing Log Bias Values. . . . . . . . . . . . . 2-17

2.4.5.2 LogCal Mode. . . . . . . . . . 2-17

2.4.5.3 Maintaining Log Bias Values. . . . 2-17

2.4.6 On-Line System Performance Monitor Function. . . . . . . . . . . . 2-17

2.4.6.1 Operation While Monitoring Performance. . . . . . . . . . 2-17

2.4.6.2 Conditions for Monitoring Performance. . . . . . . . . . . . . 2-17

2.4.7 Turning On the Performance Monitoring Function. . . . . . . . . . . . 2-17

2.4.8 Turning Off the Performance Monitoring Function. . . . . . . . . . . . 2-17

2.4.9 Performance Monitoring Fault Codes. . . . . . . . . . . . . 2-17

2.4.10 On-Line Attitude Comparison Limit and Filter Time Constant Adjustment. . 2-18

2.4.10.1 Purpose of Functions. . . . . . . 2-18

2.4.10.2 Operator Advisory Fault Codes. . 2-18

Chapter

Page

2.4.11 DR Data Output Function. . . . . 2-18

2.4.12 Viewing Memory Contents. . . . 2-18

2.4.13 On-Line Simulated Attitude, Velocity, and Position Outputs. . . . . . . . . 2-18

3

THEORY AND FUNCTIONAL

DESCRIPTION . . . . . . . . . 3-1

Section I INERTIAL THEORY . . . . . . 3-1

3.1

INTRODUCTION. . . . . . . . . 3-1

3.2

BASIC INERTIAL NAVIGATION

PRINCIPLES AND THEORY. . . . . 3-1

3.2.1 Conventional vs. Strapdown Inertial Navigation Systems. . . . . . . . 3-1

3.2.2 Inertial Navigation Systems. . . . . 3-1

3.2.2.1 Simplest (Single Axis) Inertial Navigator. . . . . . . . . . . . . 3-1

3.2.2.2 Addition of Vehicle Pitch Motion. . . 3-1

3.2.2.3 Moving Along the Meridian of a Spherical Non-Rotating Earth. . . . . . . . . 3-2

3.2.2.4 Single-Axis Schuler-Tuned Gimbaled System. . . . . . . . . . . . . . 3-2

3.2.2.5 Single-Axis Schuler-Tuned Strapdown System. . . . . . . . . . . . . . 3-2

3.2.2.6 Undamped Schuler-Tuned System Error Propagation. . . . . . . . . . . . 3-2

3.2.2.7 Effect of the Earth’s Rotation. . . . 3-2

3.2.2.8 Torquing Rates (or Coordinate Frame Rates). . . . . . . . . . . . . . 3-3

3.2.2.9 North Position Error. . . . . . . . 3-3

3.2.3 Velocity Damping of the Vertical (Schuler-Tuned) Loop. . . . . . . 3-3

3.2.3.1 Other Real World Considerations. . . 3-3

3.2.3.2 Damping the Schuler Loop. . . . . 3-3

3.2.3.3 External Velocity Damped Vertical Loop. . . . . . . . . . . . . . . 3-3

3.2.4 Strapdown Processing. . . . . . . 3-3

3.2.5 Navigation Processing. . . . . . . 3-3

3.2.5.1 Vertical Loops. . . . . . . . . . . 3-3

3.2.5.2 Earth Loop. . . . . . . . . . . . 3-4

3.2.5.3 Vertical Velocity Loop. . . . . . . . 3-4

3.2.6 Kalman Filter. . . . . . . . . . . 3-4

3.2.6.1 General. . . . . . . . . . . . . 3-4

3.2.6.2 Kalman Filter Computations. . . . . 3-4

3.2.6.3 Kalman Filter Matrix Deﬁnitions. . . 3-4

3.2.7 Position Fix and Position Slew. . . . 3-5

3.2.7.1 Fix Reset Processing by the Kalman Filter. . . . . . . . . . . . . . . 3-5

3.2.7.2 Manual Fix Entry. . . . . . . . . . 3-5

i

S9427-AN-OMP-010/WSN-7

TABLE OF CONTENTS - Continued

Chapter

Page

3.2.7.3 Fix Reset Checks. . . . . . . . . 3-5

3.2.7.4 Position Slews. . . . . . . . . . . 3-5

3.2.8 Vertical Loop Damping. . . . . . . 3-5

3.2.9 Sensor Errors and Calibration. . . . 3-6

3.2.9.1 Factory Calibration. . . . . . . . . 3-6

3.2.9.2 Operational Calibration – SelfAlign/Calibrate. . . . . . . . . . . 3-6

3.2.9.3 Self-Align/Calibrate. . . . . . . . . 3-7

3.2.9.4 Summary. . . . . . . . . . . . . 3-7

3.2.10 Kalman Filter Reinitialization. . . . . 3-7

3.2.10.1 Automatic Reinitialization of the Kalman Filter. . . . . . . . . . . . . . . 3-7

3.2.10.2 Manually Selected Reinitialization of the Kalman Filter. . . . . . . . . . . 3-7

3.2.11 Sensor Block Indexing. . . . . . . 3-7

3.2.12 Basics of Polar Navigation. . . . . 3-7

3.2.12.1 Relationships Between True and Transverse Coordinates. . . . . . 3-8

3.2.12.2 Operating in Polar Mode. . . . . . 3-8

3.2.13 Normal/Transverse Operation. . . . 3-8

3.2.13.1 Coordinate Mode Selection. . . . . 3-8

3.2.13.2 Synchro Heading Output Selection. . 3-8

3.2.14 Review of Trigonometric Functions. . 3-8

3.2.15 Inertial Navigation Vectors. . . . . . 3-8

3.2.16 Concepts of Statistical Estimation, Overview of Kalman Filter. . . . . . 3-8

3.2.16.1 Statistics and Variance. . . . . . . 3-8

3.2.16.2 Philosophy of Kalman Filter. . . . . 3-9

3.2.17 Global Positioning System (GPS) Blending . . . . . . . . . . . 3-10

3.2.17.1 Global Positioning System/Inertial Navigation System Filter. . . . . 3-10

3.2.17.2 INS Reset Smoothing. . . . . . 3-10

3.2.17.3 INS/GPS Filtering and Reset Smoothing Together. . . . . . . . . . . . 3-10

3.2.17.4 Lever Arm Corrections. . . . . . 3-10

Section II EQUIPMENT DESCRIPTION . 3-11

3.3

RLGN FUNCTIONAL DESCRIP-

TION. . . . . . . . . . . . . . 3-11

3.3.1 Basic Description of Ring Laser Gyro Operation. . . . . . . . . . . . 3-11

3.3.2 Basic RLG Design Criteria. . . . 3-11

3.3.2.1 Gas Flow. . . . . . . . . . . . 3-11

3.3.2.2 Frequency Locking. . . . . . . . 3-11

3.3.2.3 Path Length Control. . . . . . . 3-11

3.3.2.4 Random Drift Improvement. . . . 3-11

3.3.3 General Description of Functions. . 3-11

Chapter

Page

3.3.3.1 Nav Processor. . . . . . . . . . 3-12

3.3.3.2 I/O Processor. . . . . . . . . . 3-12

3.3.3.3 Support Electronics. . . . . . . 3-12

3.3.3.4 IMU. . . . . . . . . . . . . . 3-12

3.4

FUNCTIONAL DESCRIPTION OF RLGN

ASSEMBLIES. . . . . . . . . . 3-12

3.4.1 Power Distribution and Emergency Power Switching. . . . . . . . . . . . 3-12

3.4.2 Platform Indexing. . . . . . . . 3-13

3.4.2.1 Platform Indexing and Stabilization Control Circuits. . . . . . . . . . . . . 3-13

3.4.2.2 Sensor Rotation During Normal System Operation. . . . . . . . . . . . 3-13

3.4.2.3 Sensor Rotation During Off-Line Testing. . . . . . . . . . . . . 3-13

3.4.3 System Timing and Navigation Processing. . . . . . . . . . . 3-13

3.4.3.1 Nav Processor-IMU Processor Timing. . . . . . . . . . . . . 3-14

3.4.3.2 Nav Processor-IMU Processor Data Transfer. . . . . . . . . . . . 3-14

3.4.4 External Data Interfacing. . . . . 3-14

3.4.5 Internal Data Interfacing. . . . . 3-14

3.4.6 Position Sensing and Processing. . 3-14

3.4.6.1 Gyro Power and Power Control Functions. . . . . . . . . . . . 3-14

3.4.6.2 Gyro Control and Signal Processing Functions. . . . . . . . . . . . 3-15

3.4.6.3 Accelerometer Control and Signal Processing Functions. . . . . . . 3-15

3.4.7 Synchro Attitude and Velocity Data Interface. . . . . . . . . . . . 3-15

3.4.8 Hardware Monitoring and Fault/Status Output. . . . . . . . . . . . . 3-15

3.4.9 Built-In Test (BIT) and Status. . . 3-16

3.4.9.1 Off-Line Tests. . . . . . . . . . 3-16

3.4.9.2 System Conﬁdence Test. . . . . 3-16

3.4.9.3 Operator Response to Advisories and Faults. . . . . . . . . . . . . 3-16

3.4.9.4 Source AC Power or Synchro Reference Fault. . . . . . . . . . . . . . 3-16

3.4.10 NAV and I/O Processors. . . . . 3-16

3.4.11 Synchro Data Conversion and SBA Descriptions. . . . . . . . . . . 3-17

3.4.11.1 Synchro Converter CCAs (1A1A38), (1A1A39), and (1A1A40). . . . . 3-17

3.4.11.2 Synchro Buffer Ampliﬁers (SBAs) 8 VA (1A1A41) and (1A1A42). . . . . 3-17

Chapter

Page

3.4.11.3 Synchro Buffer Ampliﬁers (SBAs) 32 VA (1A1A43) and (1A1A44). . . . . 3-17

4

SCHEDULED MAINTENANCE . . . 4-1

4.1

INTRODUCTION. . . . . . . . . 4-1

4.2

BATTERY ASSEMBLY (1A1A5)

SCHEDULED MAINTENANCE. . . 4-1

4.2.1 Battery Assembly (1A1A5) Storage Procedure. . . . . . . . . . . . 4-1

4.2.2 Battery Charging. . . . . . . . . . 4-1

4.2.2.1 Internal Method for Battery Assembly (1A1A5) Charging. . . . . . . . . 4-1

4.2.2.2 Preferred External Method for Recharging Battery Assembly (1A1A5). . . . . 4-1

4.2.2.3 Alternate External Method for Recharging Battery Assembly (1A1A5). . . . . 4-1

4.2.3

Restoring Conﬁguration Data in Memory After Battery Power Has Been Interrupted. . . . . . . . . . . . 4-1

4.3

PERIODIC BATTERY ASSEMBLY

(1A1A5) OPERATIONAL CHECK. . 4-1

4.4

PERIODIC SYSTEM RECALIBRA-

TION. . . . . . . . . . . . . . . 4-2

5

TROUBLESHOOTING . . . . . . 5-1

5.1

INTRODUCTION. . . . . . . . . 5-1

5.2

FAULT ASSESSMENT. . . . . . . 5-2

5.3

TEST MODE TURN-ON. . . . . . 5-2

5.4

FAULT CODE TROUBLESHOOT-

ING. . . . . . . . . . . . . . . 5-2

5.4.1 Fault Code Identiﬁcation. . . . . . 5-2

5.4.2 On-Line Fault Code Isolation. . . . 5-2

5.4.3 Off-Line Fault Code Isolation. . . . 5-3

5.4.4 Display Shutdown Fault Codes. . . . 5-3

5.5

DISPLAY-RELATED FAULT

TROUBLESHOOTING. . . . . . . 5-3

5.5.1 Identify Display-Related Faults. . . . 5-3

5.5.2

Display Assembly (1A1A10) and Data Entry Keyboard (1A1A9) Fault Isolation. . . . . . . . . . . . . 5-3

5.5.3 Display Assembly Self-Test. . . . . 5-4

5.5.4 Display Assembly Wraparound Test. 5-4

5.6

LED AND LIGHT INDICATOR

SURVEY. . . . . . . . . . . . . 5-5

5.7

SELECTING MENUS AND OFF-LINE

TEST FUNCTIONS. . . . . . . . 5-6

5.8

SYSTEM CONFIDENCE TEST. . . 5-6

5.9

SLIP RING TROUBLESHOOTING. . 5-6

5.10 FAULT SCENARIO TROUBLESHOOTING. . . . . . . . . . . . . . . 5-7

Chapter

Page

5.10.1 Power System Fault Scenario Troubleshooting. . . . . . . . . . 5-7

5.10.2 Simulated Attitude, Velocity, and Position Outputs. . . . . . . . . . . . . 5-8

6

CORRECTIVE MAINTENANCE . . 6-1

6.1

GENERAL CORRECTIVE MAINTE-

NANCE INFORMATION. . . . . . 6-1

6.1.1 Introduction. . . . . . . . . . . . 6-1

6.1.2 Electrostatic Discharge Sensitivity. . 6-1

6.1.3 Cable Harness Lacing and Tie-Wrapping Techniques. . . . . . . . . . . . 6-1

6.1.4 Opening the Processor Cabinet for Maintenance. . . . . . . . . . . 6-1

6.1.5 Tools, Test Equipment and Support Items. . . . . . . . . . . . . . . 6-1

6.1.6 Personnel. . . . . . . . . . . . . 6-1

Section I. ADJUSTMENT AND ALIGNMENT 6-2

6.2

ESTABLISHING SYSTEM CON-

FIGURATION SETTINGS AFTER

MAINTENANCE. . . . . . . . . . 6-2

6.2.1 Restoring Installation Conﬁguration Parameters. . . . . . . . . . . . 6-2

6.2.1.1 Preliminary Information. . . . . . . 6-2

6.2.1.2 Restore RLGN Conﬁguration Parameters. . . . . . . . . . . . 6-2

6.2.2 Restore RLGN Calibration Data. . . 6-3

Section II. REMOVAL AND REPLACEMENT 6-4

6.3

CORRECTIVE MAINTENANCE (UPPER

CABINET). . . . . . . . . . . . 6-4

6.3.1 Upper Cabinet Access. . . . . . . 6-4

6.3.1.1 Maintenance Turn Off. . . . . . . 6-4

6.3.1.2 Release Upper Cabinet Door. . . . 6-4

6.3.1.3 Secure Upper Cabinet Door. . . . . 6-4

6.3.1.4 Release Cable Harness and Tie Wraps. . . . . . . . . . . . . . 6-5

6.3.1.5 Secure Cable Harness and Tie Wraps. . . . . . . . . . . . . . 6-5

6.3.2 Cable Replacement. . . . . . . . 6-5

6.3.2.1 Remove Ribbon Cable. . . . . . . 6-5

6.3.2.2 Install Ribbon Cable. . . . . . . . 6-5

6.3.2.3 Remove Serial Coaxial Cable. . . . 6-5

6.3.2.4 Install Serial Coaxial Cable. . . . . 6-5

6.3.2.5 Remove Serial Fiber Optic Cable. . . 6-5

6.3.2.6 Install Serial Fiber Optic Cable. . . . 6-5

6.3.3 CCA Replacement. . . . . . . . . 6-6

6.3.3.1 Release Wedge Locks. . . . . . . 6-6

6.3.3.2 Secure Wedge Locks. . . . . . . . 6-6

ii

S9427-AN-OMP-010/WSN-7

TABLE OF CONTENTS - Continued

Chapter

Page

6.3.3.3 Remove CCA. . . . . . . . . . . 6-6

6.3.3.4 Install CCA. . . . . . . . . . . . 6-6

6.3.3.5 Interchange CCAs to Track Fault. . . 6-7

6.3.3.6 Interchange CCAs to Return to Original Conﬁguration. . . . . . . . . . . 6-7

6.3.3.7 Replace Nav Processor CCA (1A1A13). . . . . . . . . . . . . 6-7

6.3.3.8 Field Change Nav Processor CCA (1A1A13). . . . . . . . . . . . . 6-8

6.3.3.9 Replace or Field Change I/O Processor CCA (1A1A21). . . . . . . . . . 6-8

6.3.3.10 Replace Status and Command CCA (1A1A15). . . . . . . . . . . . . 6-8

6.3.3.11 Replace IMU Processor (1A1A32) PROM. . . . . . . . . . . . . . 6-8

6.3.3.12 Transfer IMU Processor CCA (1A1A32) PROM. . . . . . . . . . . . . . 6-9

6.3.4 Backplane Replacement. . . . . . 6-9

6.3.4.1 Access Backplane. . . . . . . . . 6-9

6.3.4.2 Remove Nav Processor Backplane Assembly (1A1A11) or I/O Processor Backplane Assembly (1A1A12). . . 6-9

6.3.4.3 Install Nav Processor Backplane Assembly (1A1A11) or I/O Processor Backplane Assembly (1A1A12). . . . . . . . 6-9

6.3.4.4 Remove Support Electronics Backplane Assembly (1A1A30). . . . . . . 6-10

6.3.4.5 Install Support Electronics Backplane Assembly (1A1A30). . . . . . . 6-10

6.3.5 Power Assemblies Replacement. . 6-10

6.3.5.1 Fuse Replacement. . . . . . . . 6-10

6.3.5.2 Remove Power Line Filter (1A1A1). 6-10

6.3.5.3 Install Power Line Filter (1A1A1). . 6-11

6.3.5.4 Remove Inverter Assembly (400 Hz) (1A1A2). . . . . . . . . . . . 6-11

6.3.5.5 Install Inverter Assembly (400 Hz) (1A1A2). . . . . . . . . . . . 6-11

6.3.5.6 Remove Vital Bus CCA (1A1A3). . 6-11

6.3.5.7 Install Vital Bus CCA (1A1A3). . . 6-11

6.3.5.8 Power Supply (1A1A6) Replacement. . . . . . . . . . . . . . 6-12

6.3.5.9 Battery Charger (1A1A7) Replacement. . . . . . . . . . . . . . 6-12

6.3.5.10 Power Module (1A1A8) Replacement. . . . . . . . . . . . . . 6-12

6.3.5.11 Synchro Buffer Ampliﬁer (8 VA) (1A1A41) Replacement. . . . . . . . . . 6-13

Chapter

Page

6.3.5.12 Synchro Buffer Ampliﬁer (8 VA) (1A1A42) Replacement. . . . . . . . . . 6-13

6.3.5.13 Synchro Buffer Ampliﬁer (32 VA) (1A1A43) Replacement. . . . . . . . . . 6-13

6.3.5.14 Synchro Buffer Ampliﬁer (32 VA) (1A1A44) Replacement. . . . . . . . . . 6-14

6.3.5.15 Battery Assembly (1A1A5) Replacement. . . . . . . . . . 6-14

6.3.6 Display Assembly Replacement. . 6-15

6.3.6.1 Remove Display Assembly (1A1A10). . . . . . . . . . . . 6-15

6.3.6.2 Remove Vacuum Fluorescent Display (1A1A10A1) from Display Assembly (1A1A10). . . . . . . . . . . . 6-15

6.3.6.3 Remove Panel Interface Assembly (1A1A10A2). . . . . . . . . . 6-15

6.3.6.4 Remove Display Electromagnetic Interference Window. . . . . . . 6-15

6.3.6.5 Remove Data Entry Keyboard (1A1A9). . . . . . . . . . . . 6-16

6.3.6.6 Install Data Entry Keyboard (1A1A9). . . . . . . . . . . . 6-16

6.3.6.7 Install Display Electromagnetic Interference Window. . . . . . . 6-16

6.3.6.8 Install Panel Interface Assembly (1A1A10A2). . . . . . . . . . 6-16

6.3.6.9 Install Vacuum Fluorescent Display (1A1A10A1) to Display Assembly (1A1A10). . . . . . . . . . . . 6-17

6.3.6.10 Install Display Assembly (1A1A10). 6-17

6.4

CORRECTIVE MAINTENANCE (LOWER

CABINET). . . . . . . . . . . 6-17

6.4.1 Lower Cabinet Access. . . . . . 6-17

6.4.1.1 Remove IMU Cabinet Front Panel. 6-17

6.4.1.2 Remove Inertial Measuring Unit (1A2A1). . . . . . . . . . . . 6-18

6.4.1.3 Remove Magnetic Shield from Sensor Block Assembly. . . . . . . . . 6-18

6.4.1.4 Install Magnetic Shield on Sensor Block Assembly. . . . . . . . . . . . 6-19

6.4.1.5 Install Inertial Measuring Unit (1A2A1). . . . . . . . . . . . 6-20

6.4.1.6 Install IMU Cabinet Front Panel. . 6-20

6.4.2 Power Supply Replacement. . . . 6-21

6.4.2.1 Remove High Voltage Power Supply Assembly (1A2A1A1A4). . . . . 6-21

6.4.2.2 Installation of High Voltage Power Supply Assembly (1A2A1A1A4). . . . . 6-21

Chapter

Page

6.4.3 Gyrocompass Replacement. . . . 6-21

6.4.3.1 Gyro “A” (1A2A1A1A1) Replacement. . . . . . . . . . . . . . 6-21

6.4.3.2 Gyro “B” (1A2A1A1A2) Replacement. . . . . . . . . . . . . . 6-22

6.4.3.3 Gyro “C” (1A2A1A1A3) Replacement. . . . . . . . . . . . . . 6-23

6.4.4 Accelerometer Replacement. . . . 6-24

6.4.4.1 Remove Accelerometer. . . . . . 6-24

6.4.4.2 Install Accelerometer. . . . . . . 6-25

6.4.5 Accelerometer Stimulus Assembly Replacement. . . . . . . . . . 6-25

6.4.5.1 Remove Accelerometer Stimulus Assembly (1A2A1A1A9A1). . . . 6-25

6.4.5.2 Install Accelerometer Stimulus Assembly (1A2A1A1A9A1). . . . . . . . 6-25

6.4.6 Slip Ring Replacement. . . . . . 6-25

6.4.6.1 Slip Ring Assembly (1A2A1A1A10) Replacement. . . . . . . . . . 6-25

6.4.6.2 Slip Ring Assembly (1A2A1A1A11) Replacement. . . . . . . . . . 6-26

6.4.6.3 Slip Ring Assembly (1A2A1A1A12) Replacement. . . . . . . . . . 6-27

6.4.6.4 Slip Ring Assembly (1A2A1A1A13) Replacement. . . . . . . . . . 6-27

Section III. PRECAUTIONS FOR SHIPMENT . . . . . . . . . . . . 6-29

6.5

GENERAL PROCEDURES FOR

SHIPPING LRUs. . . . . . . . . 6-29

6.5.1 Packing and Shipment of Ring Laser Gyro Navigator. . . . . . . . . . . . 6-29

6.5.2 Packing and Shipment of Inertial Measuring Unit. . . . . . . . . 6-29

6.5.3 Packing and Shipment of Battery Assembly. . . . . . . . . . . . 6-29

6.5.4 Packing and Shipment of Ring Laser Gyro Assemblies. . . . . . . . . . . . . . . 6-29

6.5.5 Packing and Shipment of Circuit Card Assemblies. . . . . . . . . . . 6-29

6.5.6 Packing and Shipment of Chassis-Mounted Electronic Subassemblies. . . . . 6-29

7

PARTS LISTING . . . . . . . . . 7-1

7.1

INTRODUCTION. . . . . . . . . 7-1

7.2

PARTS TABLES DESCRIPTIONS. . 7-1

7.3

MANUFACTURERS. . . . . . . . 7-1

8

INSTALLATION . . . . . . . . . 8-1

8.1

INTRODUCTION. . . . . . . . . 8-1

Chapter

Page

8.2

WELDING RESTRICTIONS. . . . . 8-1

8.3

EQUIPMENT REQUIRED FOR

INSTALLATION AND OPTICAL

ALIGNMENT. . . . . . . . . . . 8-1

8.3.1 Equipment Suggested for Optical Alignment. . . . . . . . . . . . . 8-1

8.3.2 Tools, Drawings and Support Items Required for Installation. . . . . . . 8-1

8.3.3 Installation Materials Supplied with Equipment. . . . . . . . . . . . 8-2

8.4

SHIPBOARD PRE-INSTALLATION

REQUIREMENTS. . . . . . . . . 8-2

8.5

INSTALLATION OF INS ASSEM-

BLIES. . . . . . . . . . . . . . 8-2

8.5.1 Uncrating and Preparation of Equipment for Installation. . . . . . . . . . . 8-2

8.5.2 Cabinet Installation Procedure. . . . 8-2

8.5.3

Installation of Inertial Measuring Unit (1A2A1) in Measurement Cabinet Assembly. . . . . . . . . . . . . 8-3

8.5.4 Installation of Calibration PROMs Associated with the IMU. . . . . . 8-3

8.5.5 Veriﬁcation of Powered Operation. . 8-3

8.6

DETERMINING CALIBRATION AND

CONFIGURATION DATA. . . . . . 8-4

8.6.1 Optical Measurement of Cabinet Azimuth, Pitch, and Roll Alignment Correction. 8-4

8.6.2 Determining Convention for Azimuth, Pitch, and Roll Output Data. . . . . 8-5

8.6.3

Determining Lever Arms for INS Mounting Location and Position and Velocity Output Locations. . . . . . . . . . . . . 8-5

8.6.4 Determining Lever Arms for Position and Velocity Sensors. . . . . . . . . . 8-5

8.7

ENTERING INSTALLATION AND

CONFIGURATION DATA. . . . . . 8-5

8.7.1 Store Function. . . . . . . . . . . 8-5

8.7.2 Input/Output Function Selections. . . 8-5

8.7.3 Reference Devices Function Selections. . . . . . . . . . . . 8-6

8.7.4 Operator Conﬁguration Function Selections. . . . . . . . . . . . 8-6

8.7.5 Ship Conﬁguration Function Selections. . . . . . . . . . . . 8-6

8.7.6 Alignment Function Selections. . . . 8-7

8.7.7 Synchro Output Function Selections. 8-7

8.8

DETERMINING VELOCITY REFERENCE

BIAS CALIBRATION VALUES. . . . 8-7

iii

S9427-AN-OMP-010/WSN-7

TABLE OF CONTENTS - Continued

Chapter

Page

8.9

DSVL INTERFACE MODIFICATION KIT

INSTALLATION. . . . . . . . . . 8-8

8.9.1 DSVL Interface Cable Connections . 8-8

8.9.2 DSVL Installation Conﬁguration. . . 8-8

APPENDIX A BIT TEST CABLES . . . . . . A-1

A.1

INTRODUCTION. . . . . . . . . A-1

A.2

CABLE PARTS LISTING. . . . . . A-1

APPENDIX B LIST OF FAULT CODES . . . B-1

B.1

INTRODUCTION. . . . . . . . . B-1

Chapter

Page

B.2

FAULT CODES NOT RESULTING IN

FAILURES. . . . . . . . . . . . B-1

B.3

FAULT CODES FOR DEBUGGING

SOFTWARE. . . . . . . . . . . B-1

B.4

FAULT RELAYS. . . . . . . . . . B-1

B.5

ON-LINE FAULT CATEGORIES. . . B-1

B.5.1 CATEGORY 0 (Operator Advisory). . B-1

B.5.2 CATEGORIES 1 through 3 (Fault Advisory K3; System Fail K1; Malfunction K2). B-1

Chapter

Page

B.5.3 CATEGORY 4 (System Malfunction). B-1

B.5.4 CATEGORY 5 (Shutdown Status). . B-1

B.5.5 CATEGORY 6 (Reset Fault BIT). . . B-1

B.5.6 CATEGORY 7 (Delay NVRAM Update). . . . . . . . . . . . . B-1

B.5.7 CATEGORY 8 (I/O or ATM Processor Shutdown). . . . . . . . . . . . B-1

B.5.8 CATEGORY 9 (Ignore Fault). . . . . B-1

B.6

SOFTWARE ERROR WORDS. . . . B-1

Chapter

Page

GLOSSARY . . . . . . . . . . GLOSSARY-1

GLOSSARY LIST OF ACRONYMS AND ABBREVIATIONS . . GLOSSARY-1

INDEX

. . . . . . . . . . . . INDEX-1

iv

LIST OF ILLUSTRATIONS

S9427-AN-OMP-010/WSN-7

Figure

Title

Page

1-2. Typical System Conﬁguration . . . . . 1-13

2-1. Front Panel Controls and Indicators . 2-31

2-2. Keypad Controls . . . . . . . . . 2-31

2-3. Menu Status/Mode Indications . . . 2-32

2-4. Identifying Operation Menus and Data Entry . . . . . . . . . . . . . . 2-33

2-5. Dockside Align Settle States . . . . 2-35

2-6. Slave Align Settle States . . . . . 2-36

2-7. At-Sea Align Settle States . . . . . 2-37

2-8. Mode Transition Diagram . . . . . 2-38

2-9. Earth Coordinates References . . . 2-38

2-10. Position Fix, Data Entry and Review Functions . . . . . . . . . . . . 2-39

2-11. Enhanced Performance Position Accuracy (EP2A) Block Diagram . . . . . . 2-39

2-12. Position Estimate Accuracy vs. Time without Position Update . . . . . . . . . 2-40

2-13. EM Log Calibration Functions . . . 2-40

2-14. Time RMS (TRMS) Position Error Calculation Method . . . . . . . . . . . . . 2-41

3-1. Simple Strapdown System . . . . 3-19

3-2. Simple Gimbal Stabilization of the Accelerometer . . . . . . . . . . 3-19

3-3. Single-Axis Schuler-Tuned Gimbaled System . . . . . . . . . . . . . 3-20

3-4. Single-Axis Schuler-Tuned Strapdown System . . . . . . . . . . . . . 3-20

3-5. Schuler Oscillations in an Undamped Inertial Navigator . . . . . . . . . . . . 3-21

3-6. Effect of Earth’s Rotation on Local Vertical . . . . . . . . . . . . . 3-21

3-7. Earth Rate Components . . . . . 3-22

3-8. North Position Error . . . . . . . 3-22

3-9. Block Diagram of External Velocity Damped Vertical Loop . . . . . . . . . . 3-23

3-10. Strapdown Processing Block Diagram 3-24

3-11. Kalman Filter Functional Block Diagram . . . . . . . . . . . . 3-25

3-12. INS/GPS Filtering and Reset Smoothing . . . . . . . . . . . 3-25

3-13. Using Light to Measure Rotation . . 3-26

3-14. Simpliﬁed Block Diagram . . . . . 3-27

3-15. Battery Charger and Emergency Power Switching Control (Power Supply Rev A through F) . . . . . . . . . . . 3-28

3-16. Battery Charger and Emergency Power Switching Control (Power Supply Rev G) . . . . . . . . . . . . . . . 3-29

Figure

Title

Page

3-17. Power Fault Detection and Power Control Functions . . . . . . . . . . . . 3-30

3-18. Platform Indexing Control . . . . . 3-31

3-19. Platform Indexing Orientations . . . 3-32

3-20. Display and Display Interface . . . 3-33

3-21 System Timing and Navigation Processing . . . . . . . . . . . 3-34

3-22. I/O Processing and Interface . . . . 3-36

3-23. Gyro High Voltage . . . . . . . . 3-38

3-24. Ring Laser Gyros: Dither . . . . . 3-39

3-25. Ring Laser Gyros: PLC and RDI . . 3-40

3-26. Ring Laser Gyros: Accelerometers, Rotation . . . . . . . . . . . . 3-41

3-27. Synchro Data - Heading, Total Velocity . . . . . . . . . . . . . 3-42

3-28. Synchro Data - Roll/Pitch . . . . . 3-43

3-29. Synchro Data - Velocity . . . . . . 3-44

3-30. Status and Command, Functional Diagram . . . . . . . . . . . . 3-45

3-31 Performance Monitoring and Built-In Test (BIT), Functional Diagram . . . . . 3-46

5-1. Maintenance Turn-On and Test Selection Sequence . . . . . . . . . . . . 5-28

5-2. Status LEDs and EEPROM Write Enable Switch Identiﬁcation . . . . . . . 5-28

5-3. Display Test Switches, Location and Function . . . . . . . . . . . . 5-29

5-4. Display Functions, Troubleshooting Logic Diagram . . . . . . . . . . . . 5-29

5-5. Internal Cables, Distribution and Identiﬁcation Diagram . . . . . . . 5-30

5-6. Main 3-Phase AC and Non-Vital 1-Phase Synchro, Power Distribution Diagram 5-33

5-7. +25 VDC and Internally-Generated 115 VAC, 400 Hz, Power Distribution Diagram 5-34

5-8. -25 VDC and Low Voltage Power Supply A8 Output, Power Distribution Diagram . 5-36

5-9. Backplanes A11 and A12, Power Distribution Diagram . . . . . . . . . . . . 5-38

5-10. Power Fault Detection and Power Control Functions Diagram . . . . . . . . 5-41

5-11. Support Electronics Backplane (1A1A30) and IMU Cabinet (1A2), Low Voltage Power Supply . . . . . . . . . . . . . 5-42

5-12. Ring Laser Gyros, High Voltage Power Distribution and Monitoring Diagram 5-44

5-13. Roll (Outer) and Azimuth (Inner) Gimbal, Synchro and Torquer Loop Diagram 5-45

Figure

Title

Page

5-14. Ring Laser Gyros, Path Length Control and Random Drift Improvement Control Functions Diagram . . . . . . . . 5-47

5-15. Ring Laser Gyros, Dither Control Function Diagram . . . . . . . . . . . . 5-49

5-16. Ring Laser Gyros, Rotation Sensor Function Diagram . . . . . . . . . . . . 5-50

5-17. Accelerometers, Acceleration Output Function Diagram . . . . . . . . 5-51

5-18. Gyro and Accelerometer Temperature Sensing Function Diagram . . . . 5-52

5-19. Parallel Bus Data, Address and Control Functions, Distribution Diagram . . 5-53

5-20. RS-422 Serial Data Interface Functions Diagram . . . . . . . . . . . . 5-58

5-21. System Synchro Format (Heading, Roll, Pitch, and Velocity) Outputs Diagram 5-59

5-22. Synchro Format Speed (EM Log) Inputs Diagram . . . . . . . . . . . . 5-62

5-23 BIT Fault Monitoring Functions Diagram . . . . . . . . . . . . 5-63

6-1. Typical Maintenance Tools . . . . 6-48

6-2. Battery-Backed Conﬁguration Data . 6-48

6-3. Identiﬁcation of Calibration PROMs on IMU Processor CCA . . . . . . . . . 6-49

6-4. Removal of Backplane Wiring Assemblies . . . . . . . . . . . 6-50

6-5. Replacement of Battery Assembly (1A1A5) . . . . . . . . . . . . 6-50

6-6. Replacement of Display Assembly (1A1A10) . . . . . . . . . . . . 6-51

6-7. Replacement of Data Entry Keyboard (1A1A9) . . . . . . . . . . . . 6-51

6-8. Replacement of Vacuum Fluorescent Display (1A1A10A1) . . . . . . . . . . . 6-52

6-9. Inertial Measuring Unit in Measurement Cabinet Assembly . . . . . . . . 6-52

6-10. Removal of Inertial Measuring Unit from Measurement Cabinet Assembly . . 6-53

6-11. Mounting of Magnetic Shield on Sensor Block Assembly (1A2A1A1A9) . . . 6-53

6-12. Gyro and Circuit Board Mounting Locations and Orientation . . . . . . . . . 6-54

6-13. Location of Ring Laser Gyro Attachment Points . . . . . . . . . . . . . 6-54

6-14. Accelerometers Mounting Locations and Orientation . . . . . . . . . . . 6-55

6-15. Location of Slip Rings in Inertial Measuring Unit . . . . . . . . . . . . . . 6-56

Figure

Title

Page

7-1. Processor Cabinet Assembly (1A1) (Unit 1) . . . . . . . . . . . . . . . 7-54

7-2. Processor Cabinet Assembly (1A1) (Unit 1) Side Views . . . . . . . . . . . 7-55

7-3. Processor Cabinet Assembly (1A1) (Unit 1) Internal Components . . . . . . . 7-56

7-4. Processor Cabinet Assembly (1A1) (Unit 1) Topside . . . . . . . . . . . . . 7-57

7-5. Installation: Mounting Arrangement . 7-58

7-6. Front Panel: Display Assembly (1A1A10) . . . . . . . . . . . . 7-59

7-7. IMU: Measurement Cabinet Assembly (1A2) (Unit 2) . . . . . . . . . . . . . 7-60

7-8. IMU: Subassembly Identiﬁcation (1A2A1A1) . . . . . . . . . . . 7-61

7-9. IMU: Subassembly Identiﬁcation (1A2A1A1) . . . . . . . . . . . 7-62

7-10. IMU: Subassembly Identiﬁcation (1A2A1A1) . . . . . . . . . . . 7-63

7-11. IMU: Sensor Block Assembly (1A2A1A1A9) . . . . . . . . . . 7-64

7-12. High Voltage Power Supply Assembly (1A2A1A1A4) . . . . . . . . . . 7-65

8-1. Sample Installation Data Sheet (Sheet 1 of 5) . . . . . . . . . . . . . . . 8-11

8-1. Sample Installation Data Sheet (Sheet 2 of 5) . . . . . . . . . . . . . . . 8-11

8-1. Sample Installation Data Sheet (Sheet 3 of 5) . . . . . . . . . . . . . . . 8-12

8-1. Sample Installation Data Sheet (Sheet 4 of 5) . . . . . . . . . . . . . . . 8-12

8-1. Sample Installation Data Sheet (Sheet 5 of 5) . . . . . . . . . . . . . . . 8-13

8-2. Polarity Deﬁnitions for Frame Mirrors 8-13

8-3. Bias Calibration Graph Example . . 8-14

8-4. RLGN to DSVL Interface Cable Connections . . . . . . . . . . . 8-14

8-5. Mounting Base Orientation and Mounting Holes Location Diagram . . . . . . 8-15

8-6. Identifying IMU Mirrors to be used for Optical Alignment of the Cabinet . . . . . 8-16

8-7. Optical Measurement of Cabinet Mounting Misalignment . . . . . . . . . . 8-17

8-8. Determining Ship’s Azimuth, Pitch, Roll Convention . . . . . . . . . . . 8-18

8-9. Determining INS Lever Arms . . . . 8-19

8-10. Determining Position and Velocity Sensors Lever Arms . . . . . . . . . . . 8-20

8-11. Determining GPS Velocity Sensors (VGPS) Lever Arms . . . . . . . . . . . 8-21

v

S9427-AN-OMP-010/WSN-7

LIST OF ILLUSTRATIONS - Continued

Figure

Title

Page

8-12. 8-13.

Identifying Installation Conﬁguration Menus and Conﬁguration Data Entry Required . . . . . . . . . . . .
Sample Speed Bias Calibration Worksheet . . . . . . . . . . .

8-22 8-23

Figure

Title

Page

8-14. A-1. A-2.

Installation Guidance Mounting Arrangement . . . . . . . . . . 8-24
NTDS Type A Interface BIT Test Cable 1981552-1 . . . . . . . . . . . . A-4
NTDS Type D and E Interface BIT Test Cable 1981552-6 and -7 . . . . . . A-5

Figure

Title

Page

A-3. RCDU Data Interface BIT Test Cable 1981552-8 . . . . . . . . . . . . A-6
A-4. IMU Interface BIT Test Cable 1981552-10 . . . . . . . . . . . . A-7
A-5. Display Unit BIT Test Cable 1981552-11 . . . . . . . . . . . . A-8

Figure

Title

Page

A-6. INS-INS Data Interface BIT Test Cable 1981552-14 . . . . . . . . . . . . A-9
A-7. DSVL Interface BIT Test Cable 1860241 . . . . . . . . . . . . A-10
A-8. ATM Interface BIT Test Cable 1900239 . . . . . . . . . . . . A-11

LIST OF TABLES

Number

Title

Page

1-1. Design and Physical Characteristics . 1-6

1-2. Digital (RS-422A) Data Interface . . . 1-6

1-3. Analog Synchro Input/Output and Reference Characteristics . . . . . . . . . . . 1-7

1-4. Summary of AN/WSN-7(V) Units and Assemblies . . . . . . . . . . . . 1-7

1-5. AN/WSN-7(V) NTDS I/O Conﬁgurations . . . . . . . . . . . . . . . 1-9

1-6. Documents Required but Not Supplied . . . . . . . . . . . . 1-10

1-7. Documentation Supplied . . . . . 1-11

1-8. Equipment and Accessories Supplied 1-11

1-9. Equipment Required but Not Supplied 1-12

1-10. Field Changes and Factory Changes 1-12

2-1. Keypad Control Functions . . . . . 2-19

2-2. Operating Menus/Functions Description . . . . . . . . . . . . . . 2-19

2-3. Identiﬁcation of Port Type and Physical Location . . . . . . . . . . . . 2-28

2-4. Identiﬁcation of NTDS Port Interface Design Speciﬁcation . . . . . . . . . . 2-29

2-5. Simulated Outputs Description . . . 2-29

3-1. Trigonometric Functions . . . . . . 3-18

3-2. Sample Data Calculations Illustrating Concept of Variance . . . . . . . 3-18

Number

Title

Page

4-1. AN/WSN-7(V) Planned Maintenance System Requirements . . . . . . . . . . . 4-2

5-1. Test Menus/Functions Description . . 5-9

5-2. CCA LEDs and Power Indicators Illumination Survey . . . . . . . . . . . . . 5-26

5-3. Simulated Outputs Description . . . 5-27

5-4. Display Wraparound Test, Characters Display . . . . . . . . . . . . . 5-27

6-1. Summary of Corrective Maintenance Procedures . . . . . . . . . . . 6-29

6-2. Tools, Test Equipment and Support Items . . . . . . . . . . . . . . 6-30

6-3. Slip Ring Assembly Mounting Information . . . . . . . . . . . 6-32

6-4. Packaging Instructions for Ring Laser Gyro Navigator . . . . . . . . . . . . 6-33

6-5. Packaging Instructions for Inertial Measuring Unit . . . . . . . . . . . . . . 6-34

6-6. Alternate Packaging Instructions for Inertial Measuring Unit . . . . . . . . . 6-35

6-7. Packaging Instructions for Battery Assembly 1981554 . . . . . . . . . . . . 6-36

6-8. Packaging Instructions for Ring Laser Gyros 1812594-n . . . . . . . . . . . 6-37

6-9. Packaging Instructions for Nav, I/O, and ATM Processor Assemblies . . . . . . 6-38

Number

Title

Page

6-10. Packaging Instructions for Support Electronic Assemblies . . . . . . . . . . . 6-39

6-11. Packaging Instructions for Vital Bus Assembly 1978322 . . . . . . . . 6-40

6-12. Packaging Instructions for 400 Hz Inverter Assembly 1982618 . . . . . . . . 6-41

6-13. Packaging Instructions for Power Supply 1979342 . . . . . . . . . . . . 6-42

6-14. Packaging Instructions for Battery Charger 1810853 . . . . . . . . . . . . 6-43

6-15. Packaging Instructions for Power Module 1205050-3 . . . . . . . . . . . 6-44

6-16. Packaging Instructions for Display Assembly 1979344 . . . . . . . . . . . . 6-45

6-17. Packaging Instructions for Synchro Buffer Ampliﬁers 1976545 and 1976547 . . 6-46

6-18. Packaging Instructions for High Voltage Power Supply 1979045 . . . . . . 6-47

7-1. List of Major Assemblies . . . . . . 7-2

7-2. Parts List by Reference Designator Order . . . . . . . . . . . . . . . 7-4

7-3. Parts List by Diagram Location Order 7-17

7-4. Parts List by Part Number Order . . 7-35

7-5. Manufacturers List . . . . . . . . 7-53

8-1. Tools and Support Items Required for Installation . . . . . . . . . . . . 8-9

Number

Title

Page

8-2. Installation Materials and Bit Cables Kit 03956-1812650-var . . . . . . . . 8-9

8-3. Common Installation Materials Kit 03956-1812807 . . . . . . . . . . 8-9

8-4. Factory (As Shipped) NTDS Conﬁgurations . . . . . . . . . . 8-10

8-5. Identiﬁcation of NTDS Port Interface Design Speciﬁcation . . . . . . . . . . 8-10

8-6. DSVL Interface Modiﬁcation Kit Application . . . . . . . . . . . 8-10

A-1. Applicable Built-In Test Cables . . . . A-1

A-2. Built-In Test Wraparound Cables Parts List . . . . . . . . . . . . . . . A-1

B-1. Fault Code Descriptions and Fault Isolation . . . . . . . . . . . . . B-2

vi

S9427-AN-OMP-010/WSN-7

This technical manual describes the basic organization and procedures for organizational-level operation and maintenance of the CN-1695/WSN-7(V), CN-1696/WSN-7(V), and CN-1697/WSN-7(V) Inertial Navigation Systems. The purpose of this manual is for the training of and use by personnel responsible for the operation and maintenance of the AN/WSN-7(V).
This technical manual replaces TMIN S9427-ANMMO-010/WSN-7 Revision 1 with Changes A and B. This manual changes the location of inertial navigation theory to Chapter 3; incorporates detailed information on external interface devices; incorporates signiﬁcant changes to the format of Scheduled Maintenance, Troubleshooting, and Corrective Maintenance procedures; and revises and updates Chapter 7 parts list tables and associated illustrations.
The manual is a standard eight-chapter technical manual. It is printed in 11”x17” ﬂat format with no foldouts and four columns per page. Tables and illustrations are at the end of each chapter, and display shots in Chapter 2 are provided, where necessary, without ﬁgure numbers.
This is an Extensible Mark-Up Language (XML) document provided for printing in a Portable Document Format® (PDF®) ﬁle. If users are viewing the electronic version of this manual, they can navigate to a speciﬁc ﬁgure, table, or paragraph using the PDF-

FOREWORD

generated bookmarks and/or the links located within the textual content that appear highlighted in red. If users are viewing a paper copy of this manual, the links will appear as bold-face text. Additionally, bold text is used to indicate switch positions, keypad controls, screen displays, and reference designator numbers.
Ships, training activities, supply points, depots, naval shipyards, and Supervisors of Shipbuilding are requested to arrange for the maximum practical use and evaluation of NAVSEA technical manuals. All errors, omissions, discrepancies, and suggestions for improvement to NAVSEA technical manuals shall be reported as follows:
• URGENT Deﬁciencies: Report urgent deﬁciencies to Naval Systems Data Support Activity (NSDSA) by one of the following:
○ Priority naval message (Joint Message form, DD Form 173). Direct the message to Plain Language Address (PLAD): NAVSURFWARCENDIV NSDSA PORT HUENEME CA/CODE 310 TMDERS.
○ Via the NSDSA Web site at:
https://www.nsdsa2.phdnswc.navy.mil/tmder/tmder.asp
○ Via Technical Manual Deﬁciency/Evaluation Reports (TMDERs) found in the Deﬁciency Module of Technical Data Management Information System (TDMIS).

• ROUTINE Concerns: Report routine technical manual concerns by one of the following:
○ Complete paper/Web Technical Manual Deﬁciency/Evaluation Report (TMDER), NAVSEA/SPAWAR Form 4160/1 (currently Rev 7-2003). If the proper revision of this form cannot be obtained from the back of any ship or system NAVSEA/SPAWAR technical manual (including this manual), a copy must be requisitioned. Attach a copy of the technical manual title page and marked-up pages (if available) to the TMDER. Mail to:
Commander Code 310, Bldg. 1388 NAVSURFWARCENDIV NSDSA 4363 Missile Way Port Hueneme, CA 93043-4307
○ Send telefax to Defense Switching Network (DSN) 296-0726 or commercial (805) 228-0726
○ Send e-mail to: tmder@phdnswc.navy.mil.
○ Generate a TMDER from the NSDSA Web site at:
https://www.nsdsa2.phdnswc.navy.mil/tmder.asp
○ TDMIS users may submit TMDERs via the Deﬁciency Module of TDMIS. Attachments may be uploaded in TDMIS.

This technical manual is under the overall cognizance and maintenance philosophy of an In-Service Engineering Agent (ISEA) assigned to:
SPAWARSYSCEN Charleston (Attn: Code J834) Little Creek Naval Amphibious Base 2425 Stalwart Road, Bldg., 1558 Annex Norfolk, VA 23521-3325
Any questions concerning the manual’s applicability, content, distribution, or update should be directed to the assigned ISEA for resolution, by one of the following means:
• Write to the above address.
• Telephone DSN 253-7750, Ext. 228 or Commercial (757) 462-7750, Ext. 228
• Telefax (757) 462-7657
• Send e-mail to: keith.barrale@navy.mil.
PDF® is a registered trademark of Adobe Systems Incorporated in the United States and/or other countries.

vii

S9427-AN-OMP-010/WSN-7

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viii (Blank)

S9427-AN-OMP-010/WSN-7

GENERAL SAFETY INSTRUCTIONS.
This manual describes physical processes that may cause injury or death to personnel, or damage to equipment if not properly followed. This safety summary includes general safety precautions and instructions that must be understood and applied during operation and maintenance to ensure personnel safety and protection of equipment. Before performing any task, the DANGERs, WARNINGs, CAUTIONs, and NOTEs included in that task shall be reviewed and understood. These safety procedures supplement the procedures in OPNAVINST 5100.19 (Series) Navy Safety Precautions for Forces Aﬂoat.
DANGERS, WARNINGS, CAUTIONS, AND NOTES.
DANGERS, WARNINGs, and CAUTIONs are used in this manual to highlight operating or maintenance procedures, practices, conditions, or statements considered essential to protection of personnel (DANGER, WARNING) or equipment (CAUTION). Speciﬁc dangers, warnings, and cautions applying to the AN/WSN-7(V) Inertial Navigation System are summarized in Paragraph 1.1. These dangers, warnings, and cautions are repeated elsewhere in the manual following paragraph headings and immediately preceding the text to which they apply. DANGERs, WARNINGs, and CAUTIONs consist of four parts: heading (DANGER, WARNING, or CAUTION); a statement of the hazard; minimum precautions; and possible result if disregarded. NOTEs are used in this manual to highlight operating or maintenance procedures, practices, conditions, or statements that are not essential to protection of personnel or equipment. NOTEs may precede

SAFETY SUMMARY

or follow the step or procedure, depending on the information to be highlighted. The headings and their deﬁnitions are as follows:

SAFETY PRECAUTIONS.
The following safety precautions shall be observed while performing procedures in this manual:

PERSONNEL SAFETY.

Highlights an essential operating or maintenance procedure, practice, condition, or statement which, if not strictly observed, could result in immediate injury to, or death of, personnel, or threaten the primary mission of the ship.
Highlights an essential operating or maintenance procedure, practice, condition, or statement which, if not strictly adhered to, could result in injury to, or death of, personnel or long-term hazards.
Highlights an essential operating or maintenance procedure, practice, condition, or statement which, if not strictly observed, could result in damage to, or destruction of, equipment, or loss of mission effectiveness.

The Ring Laser Gyro Navigator (RLGN) in the AN/WSN-7(V) Inertial Navigation System contains voltages up to 120 VAC and 50 VDC; both voltage types are dangerous. Always observe standard safety practices and the following when working on the equipment:
• Personal Attire. Wear dry clothing. Never wear rings or other jewelry.
• Electrical Power Application. Do not work on equipment with power applied. Disconnect ship’s connectors and attach warning notices to the appropriate ship’s power circuit breaker ON switch and to the AN/WSN-7(V) RLGN.
• Electrical Power Interrupting Devices. Do not rely solely on switching devices to interrupt power, since they can be defective. When in doubt, measure the circuit with a voltmeter.
• Troubleshooting Conditions. When troubleshooting, avoid touching any surface that can conduct electricity.
• Capacitor Discharge. Discharge power circuit capacitors using an approved shorting device when working on circuits with more than 24 Volts (V).
• Warning Signs. Observe warning signs on and around the equipment being worked on and those that appear in this manual.

DO NOT REPAIR OR ADJUST ALONE.
Under no circumstances should repair or adjustment of energized equipment be attempted alone. The immediate presence of someone capable of rendering aid is required. Before making adjustments, be sure to protect against grounding. If possible, adjustments should be made with one hand, while the other hand is free and clear of equipment. Even when power has been removed from equipment circuits, dangerous potentials may still exist due to retention of charges by capacitors. Circuits must be grounded and all capacitors discharged before attempting repairs.
TEST EQUIPMENT.
Make certain test equipment is in good condition. If a test meter must be held, ground the case of the meter before starting measurement; do not touch live equipment or personnel working on live equipment while holding a test meter. Some types of measuring devices should not be grounded; these devices should not be held when taking measurements.

ix

S9427-AN-OMP-010/WSN-7

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x (Blank)

S9427-AN-OMP-010/WSN-7 THIS PAGE INTENTIONALLY BLANK

S9427-AN-OMP-010/WSN-7

(blank/1-0)

Figure 1-1. PART NUMBERS CN-1695/WSN-7(V), CN-1696/WSN-7(V), and CN-1697/WSN-7(V);

S9427-AN-OMP-010/WSN-7

CHAPTER 1 GENERAL INFORMATION AND SAFETY PRECAUTIONS

1.1 SAFETY PRECAUTIONS.
Normal precautions concerning electronic equipment should be followed for installation, operation, maintenance, and troubleshooting for the AN/WSN-7(V) Inertial Navigation System (INS). The safety summary located in the front matter of this technical manual lists general precautions applicable to this equipment.
1.1.1 AN/WSN-7 GENERAL SAFETY PRECAUTIONS. When working on the AN/WSN-7 INS, observe the following safety precautions speciﬁc to the equipment:
• Exposed Relays and Contacts. The INS contains exposed relays and contacts which can carry deadly current. Use care when working inside the Electronic Control Unit (ECU) with the system energized.
• Batteries. The INS batteries are designed to supply power to the system if ship’s power to the system is lost. To remove battery power from the system, turn off and unplug both batteries.
• Inertial Measuring Unit. The Inertial Measuring Unit (IMU) produces high voltage during normal operation. Do not perform maintenance on the IMU while it is energized.
• Heavy Components. Some components of the INS, including the batteries and IMUs, are heavy and can cause injury if they are lifted or carried improperly. Use additional personnel and/or mechanical aids to remove or install these components.
1.1.2 DANGERS, WARNINGS, AND CAUTIONS. The following DANGERs appear in the text of this manual and are repeated here for emphasis:

When troubleshooting, do not touch any live or exposed circuits inside the AN/WSN-7(V). 115 VAC and deadly current are present until power input to the RLGN is removed.
When performing corrective maintenance, ensure that all ship’s power to the AN/WSN-7(V) is turned off and tagged out in accordance with ship’s instructions.
The following WARNINGs appear in the text of this manual and are repeated here for emphasis:
The test menu prompts the operator to disconnect the cable from the jack on the Inverter Assembly and then press the ENTER key to initiate the test. 115 VAC, 400 Hz is present at this connector. Use care when disconnecting and reconnecting the cable.

When Display Assembly (1A1A10) is removed, the processor cabinet door locking arm must be removed, allowing unrestricted door movement. This could become a dangerous condition in heavy seas. When the bracket is removed, the cabinet door should be tied down to restrict movement.
The IMU weighs 162 lbs (73 kg). Two persons are required to remove the IMU from its cabinet and place it for servicing or shipment.
The Battery Assembly (1A1A5) weighs 58.2 lbs (26.4 kg). To prevent injury to personnel or damage to equipment, two persons are required to remove or install it. The handle on the front of the Battery Assembly is intended to be used only for sliding the assembly into or out of the cabinet. Do not lift or carry the assembly by this handle.

The IMU weighs 162 lbs (73 kg). Two persons are required to install this assembly in the cabinet. Be sure that the inner gimbal is rotated parallel to the outer gimbal frame to prevent the outer synchro or torquer motor from hitting the top of the cabinet during installation. Do not slide the IMU directly into the cabinet from the ﬂoor. Lift the assembly until the bottom of the mounting plate is even with the base of the cabinet and slide it into position.
The following CAUTIONs appear in the text of this manual and are repeated here for emphasis:
If PDIG is used as the sensor and degrades beyond a Figure of Merit (FM)-03, then the performance monitoring function will be disabled.
Forcing an incorrect reset will introduce a position error proportional to the reset error. This position error will propagate through the undamped Earth loop into position and attitude errors. Large position or attitude errors may cause the vertical loops to undamp and oscillate over a period of 84 minutes due to velocity errors.

The Processor Cabinet Assembly has 115 VAC power present at circuit breakers on the cabinet door and at relays mounted in the cabinet even when the SYSTEM POWER switch is turned Off.

The cables that carry ship’s AC power and synchro reference are attached directly to jacks J1 and J2 on the outside back of the AN/WSN-7(V) cabinet.

The Power Supply Assembly (1A1A6) weighs approximately 51 lbs (23 kg). To prevent injury to personnel or damage to equipment, two persons are required to remove or install it.

1-1

S9427-AN-OMP-010/WSN-7
Depending on the review mode selected, a rejected ﬁx may be entered by the operator. These functions allow the operator to force the acceptance of a good ﬁx to correct system errors. This is useful if a ﬁx is rejected as a result of errors in the system’s estimate of position. Care should be taken when manually entering or accepting a ﬁx that has been rejected. Acceptance of an unreasonable ﬁx introduces position errors and will cause calculations of position and velocity to diverge.
The RLGN will reject the manual ﬁx if the reset exceeds the error limits described in Paragraph 2.3.4.5. Care must be taken when manually accepting a ﬁx that has been rejected by the RLGN. Forcing acceptance of an unreasonable ﬁx introduces position errors and will cause the system calculations of position and velocity to diverge.
In either of these ﬁx error estimate options, the Sigma values must reﬂect the true position ﬁx accuracy. Assigning a large Sigma to an accurate ﬁx will not disturb the INS, but the reset will have only a small correction on the system. On the other hand, assigning a small Sigma to an inaccurate ﬁx will disturb the system and result in position and velocity divergence.
Forced acceptance of correct position ﬁx data over a period of time will restore the INS to full navigation data accuracy; however, forced acceptance of incorrect position ﬁx data will quickly degrade navigation performance. It may be necessary to realign the INS to restore navigation accuracy if acceptance of an invalid position ﬁx has been force-accepted.
1-2

Do not leave Battery Assembly (1A1A5) off charge for extended periods of time. If the AN/WSN-7(V) is scheduled to be turned off for more than 30 days, disconnect Battery Assembly (1A1A5) and check the open circuit voltage monthly until the AN/WSN-7(V) is placed back in operation. Recharge the battery prior to installing it back into the AN/WSN-7(V) from an auxiliary source if its open circuit voltage drops below 28.5 volts.
Fully charge the Battery Assembly (1A1A5) prior to placing it in storage to successfully hold a charge until the ﬁrst maintenance recharge.
After the Battery Assembly (1A1A5) connector is reconnected, perform Test Mode Turn-On procedure, then restore RLGN Conﬁguration Parameters.
Do not perform the Battery Assembly (1A1A5) operational check after the system has settled and is in use for navigation. This test should be scheduled to be performed at dockside and at the beginning of system operation or calibration. Excessive battery discharge during this test can result in unexpected shutdown of the system and loss of the calibration data stored in the battery-backed RAM, requiring 72 hours to achieve Navigate mode again.
Do not completely discharge Battery Assembly (1A1A5) during the periodic battery operational check. Complete battery discharge will cause the AN/WSN-7(V) to shut down, and calibration data in battery-backed RAM will be lost.

After KF Reinit has been selected, do not turn the system off until the 72-hour calibration period has completed and the system enters the NAVIGATE mode, as indicated by the word NAVIGATE in the upper left corner of the DISPLAY. If the system is turned off before the 72-hour calibration has completed, the system will restart the calibration from the beginning and will require an additional 72 hours before it will enter NAVIGATE after power is again restored.
Do not perform this test unless problems are suspected in Nav Processor CCA (1A1A13). Performing this test causes the conﬁguration parameters stored in battery-backed RAM on CCA (1A1A13) to be erased. After the test is performed, battery-backed RAM must be reloaded from EEPROM (KENV) on Status and Command CCA (1A1A15) and a 72-hour settle period is required to reestablish accuracy.
If the NTDS Type E Assembly is replaced, use care not to bend the coax cables (T968912) excessively or damage the connectors on the NTDS CCA.
If the battery cells in Battery Assembly (1A1A5) are shorted to the battery chassis, replace the Battery Assembly before replacing Battery Charger (1A1A7). Failure to do so will damage the replacement Battery Charger.
CCAs contain parts sensitive to damage by electrostatic discharge (ESD). Use ESD precautions when touching, removing, storing, or inserting any CCA.

Conﬁguration data changes are not saved in EEPROM (KENV) on Status and Command CCA (1A1A15) nor battery-backed RAM on Nav Processor CCA (1A1A13) until the Store function is complete. Conﬁguration data updates can be aborted by repeated pressing of the <CLEAR> key.
The jacks for ﬁber optic connectors are extremely fragile. Be careful not to overtighten the connector, or damage to the jack may occur.
Wedge locks provide a thermal path from the board to the heat sink. If the wedge locks are not tightened, then a loose board may rattle and may also develop hot spots that can reduce reliability.
The AN/WSN-7(V) Ring Laser Gyro Navigator (RLGN) contains Electrostatic Discharge Sensitive (ESDS) devices on various circuit cards and subassemblies. These cards and subassemblies require special care during handling and storage when they are removed from the system. As a precaution, wear a grounding strap when performing maintenance, and follow all standard practices applicable to testing, handling, and storage of ESDS devices whenever any subassembly is removed from the system.
Do not force the CCA to seat into its backplane assembly connector; forcing the CCA may bend or break the CCA’s connector pins and cause the system to fail.

Prevent damage to the PROMs during extraction and installation by using a PROM chip extractor.
Ensure switch S1 on Battery Assembly (1A1A5) is set to OFF before connecting harness connector plug P5 to jack A5J1 on Battery Assembly.
Panel Interface Assembly (1A1A10A2) contains parts sensitive to damage by electrostatic discharge (ESD). Use ESD precautions when touching, removing, storing, or inserting parts sensitive to damage by ESD.
An electromagnetic interference (EMI) shielding gasket is installed between the EMI window bezel and the outside surface of the door. Use care during removal and replacement of the bezel to prevent damage to the EMI gasket. If the gasket becomes torn, it must be replaced with a new gasket.
An EMI shielding gasket is installed between the Data Entry Keyboard and the outside surface of the door. Use care during removal and replacement of the Data Entry Keyboard to prevent damage to the EMI gasket. If the gasket becomes torn, it must be replaced with a new gasket. Be sure that gasket is positioned correctly when installing the Data Entry Keyboard. Incorrect positioning of the gasket will short the printed wiring on the CCA and cause improper operation of Keyboard functions.

The lower surface of the IMU mounting plate and the upper surface of the cabinet mounting plate contain precision-machined surfaces that are used to support and align the IMU in the cabinet. When removing and replacing the IMU in the cabinet, use care not to damage these surfaces. When the IMU is removed from the cabinet, place the IMU on a smooth, 4 ft. x 4 ft. sheet of clean plywood or two layers of heavy cardboard to prevent scratching of the mounting surfaces on the bottom side of the unit.
It is important to maintain a correct record of conﬁguration data, so the System Conﬁguration Menu can be reinitialized if stored data is lost. Immediately after installing a new IMU and associated PROMs, read the new cabinet-mounting alignment values and record them on the Installation Data Record Sheet retained with the INS. These misalignments are speciﬁc for the new IMU. Use of the previous IMU’s misalignment values will result in alignment errors being introduced into the system.
Gyros are susceptible to ESD damage if contact is made with pins of jacks A12J1, A12J2, A13J1, or A13J2. Cover these jacks with ESD-approved protective caps any time they are exposed.
Be sure that the inner gimbal is rotated parallel to the outer gimbal frame to prevent the inner synchro or torquer motor from hitting the top of the cabinet during removal. Do not slide the IMU directly out of the cabinet onto the ﬂoor. Slide the IMU out far enough for access, then lift the assembly and place it onto a clean smooth surface.

When removing, replacing, or storing the shield during maintenance, ensure that the shield components are not dented or bent. Dropping or striking a shield segment can result in degradation of the magnetic shielding characteristics of the metal. Damage to the shield could result in improper ﬁt, causing balance and acoustic noise problems, as well as degradation of the magnetic shielding properties.
During removal or replacement of the magnetic shield, use caution when rotating the Sensor Block with partially assembled segments to prevent the edge of a segment from capturing and damaging the slip ring harnesses routed inside the inner gimbal frame.
Use a standard Allen-head wrench. Use of a ball-end Allen-head wrench could cause damage to the screw.
The screws used to align the mounting plate in the cabinet base are made of nylon. These screws should be tightened just sufﬁciently to ensure ﬁrm contact between the machined alignment surfaces (5 to 7 in-lbs). Excessive tightening of these screws may cause them to break.
Use care during the removal and replacement of High Voltage Power Supply Assembly (1A2A1A1A4). Misalignment of the IMU in the isolators can occur if care is not taken. A 72-hour alignment/calibration should be performed following the removal and replacement of the High Voltage Power Supply to compensate for IMU misalignment.

S9427-AN-OMP-010/WSN-7
Ring Laser Gyros are ESDS devices. Handle in accordance with ESD procedures. Gyros are shock sensitive. Use great care when handling and storing gyros.
The surfaces on Sensor Block Assembly (1A2A1A1A9) for mounting the RLGs and accelerometers, as well as the mounting surfaces of the gyros and accelerometers, are precision-machined surfaces. Be careful not to damage these surfaces when performing repairs. Place gyros and accelerometers in a protective ESD bag and store these subassemblies in a safe place to prevent them from being damaged while they are removed from the system.
The attachment screws on each Ring Laser Gyro (RLG) should be evenly tightened to approximately the speciﬁed torque. Since the torque recommendations primarily ensure that screws are sufﬁciently tightened without being stressed or broken by over tightening, and since some mounting screws are inaccessible using some torque measuring devices, it is acceptable to tighten these screws based on the feel of effort required to tighten the screw.
Accidentally touching the bare pins of receptacle J1 on the RLG may result in the failure of its internal electronics. Therefore, after disconnecting P1 from the RLG, it is good practice to cover J1 with the electrostatic protective cover removed from the new device being installed. Reuse the same packaging materials that came with the new RLG to return the defective RLG for repair. Handle in accordance with ESD procedures.
1-3

S9427-AN-OMP-010/WSN-7
Loosen each gyro receptacle connector retaining screw alternately to prevent the screws from stripping and the connector from breaking.
To prevent the connector from breaking, do not attempt to torque the gyro receptacle connector retaining screws after they are fully seated against the gyro connector.
Tighten each gyro receptacle connectorretaining screw alternately to prevent the screws from stripping and the connector from breaking.
If more than one accelerometer is removed during maintenance and will be reinstalled, record the serial number of the accelerometer and match it with its mounting location. Be sure to replace each accelerometer in its original mounting location and orientation on Sensor Block Assembly (1A2A1A1A9) during reassembly. Accelerometer connectors are not keyed. Attach a temporary label to each accelerometer cable harness plug to identify its correct jack. Use care to connect plug on each accelerometer cable to the corresponding marked jack mounted on Sensor Block Assembly.
Use care when cutting cable ties so that wires are not damaged.
1-4

To prevent damage to the alignment surfaces on the bottom of the IMU mounting plate when the IMU is removed from the packing crate, keep the IMU mounted to the plywood shipping base prior to installation in the Measurement Cabinet Assembly.
The RLGN cabinet without the IMU installed, weighs approximately 675 lbs. (306 kg). Use proper rated hoisting equipment when installing the cabinet. To prevent damage to the surface of the mounting foundation or mounting surfaces on the bottom of the cabinet, do not attempt to slide the cabinet on the mounting foundation without lifting the cabinet. Be sure that the cabinet is positioned on the mounting foundation in correct orientation prior to removal of hoisting rig.
The lower surface of the IMU mounting plate and the upper surface of the cabinet mounting plate contain precision-machined surfaces, which are used to support and align the IMU in the cabinet. When installing the IMU in the cabinet, use care not to damage these surfaces.
Always: Review, record, and save misalignment values immediately after installing a new IMU with associated PROMs; record misalignment values to the INS Installation Data Record Sheets where the IMU is installed; use the IMU speciﬁc values recorded on the Installation Data Record Sheet to reinitialize the System Conﬁguration menu after loss of stored data.
No welding or welding cables are permitted within three feet of the IMU.

If Fault 115 is indicated, the system should not be left on for more than 30 minutes as this may result in the HVPS overheating.
1.2 INTRODUCTION.
The AN/WSN-7(V) Ring Laser Gyro Navigator (RLGN) (Figure 1-1) is part of the AN/WSN-7(V) INS. Each RLGN is a self-contained unit that employs an Inertial Measuring Unit (IMU) using three single-axis Ring Laser Gyros (RLGs) and three accelerometers as the inertial reference to determine ship’s position, velocity, heading, roll and pitch. The system continuously accepts ship’s speed information from a speed log and/or Global Positioning System (GPS), and periodically accepts ship’s position information from an external navigation reference (GPS), manually via a keypad and display on the RLGN control panels, or from the IP-1747/WSN Control Display Unit (CDU).
As shown in Figure 1-2, sheet 1 and Figure 1-2, sheet 2, each RLGN is part of a dual system that provides ship’s heading, log speed and distance, ship’s velocities, pitch, roll, attitude rates, position and time data to other ship’s systems and indicators. The AN/WSN-7(V) INS comprises two single-enclosure AN/WSN-7(V) RLGNs and a single IP-1747/WSN CDU, supported by a GPS Navigator interface and a Speed Log data interface. Only the RLGN and the power and signal interface to the RLGN are covered in this technical manual. The IP-1747/WSN is Unit 4 of the RLGN, but it has a separate technical manual. Refer to appropriate technical manuals for details on installation, operation, and maintenance of the CDU, GPS, Doppler Sonar Velocity Log (DSVL), and other support equipment. (See Table 1-6.)
1.2.1 GENERAL EQUIPMENT FUNCTION. Table 1-1 lists the major design and physical characteristics of the AN/WSN-7(V) RLGN. The RLGN requires external ship’s speed input and periodic input of position data. The RLGN uses ship’s log speed or velocities obtained from a GPS or DSVL to provide damping of vertical gyro loops. Position data from a GPS is used to calibrate gyro drifts and to provide position resets to the inertial navigation function. The inertial reference, speed, and ﬁltered position reset data are processed to generate continuous and accurate position and velocity data in addition to heading, roll, and pitch reference. The RLGN transfers data to

and from Battle Force Tactical Trainer (BFTT) equipment via the Asynchronous Transfer Mode (ATM) interface.
1.2.2 NORMAL OPERATION. The RLGN is designed to operate automatically after application of power and acceptance of the ﬁrst position reset and requires minimum operator intervention during normal operation. A 6-line, 40-character display and 28-key keypad provide display and operating controls for selection of a wide range of functions. These functions can be accessed for monitoring and modifying operating parameters, for evaluating system performance, and for selecting test and calibration modes.
1.2.3 TEST FEATURES. A Built-In Test (BIT) function incorporating both hardware and software tests continuously monitors operation and periodically performs self-tests to determine the integrity of the AN/WSN-7(V) RLGN and its inputs/outputs. Faults are automatically announced, and fault codes that indicate the type of fault detected are displayed on the local/remote control panels.
1.2.4 POWER. In the conﬁguration described in this technical manual, the RLGN requires 115 Volts, Alternating Current (VAC), 60 Hertz (Hz), 3 phase power and 115 VAC, 400 Hz, single-phase synchro reference. An internal battery and inverter provide emergency power for operation with digital output and limited synchro outputs (vital heading and synchro velocities) for approximately 30 minutes in the event of failure of the system power.
1.3 AN/WSN-7(V) CONFIGURATIONS AND INTERFACES.
1.3.1 CONFIGURATIONS. The AN/WSN-7(V) INS is available in three conﬁgurations. CN-1695/WSN7(V) is installed on selected surface combatants. CN-1696/WSN-7(V) is installed on selected cruisers and LHA-1 class ships. CN-1697/WSN-7(V) is installed on aircraft carriers and LHD-1 class ships.
1.3.2 EXTERNAL DATA INTERFACES. The basic external data interface to each RLGN consists of Naval Tactical Data System (NTDS) Standard Type A parallel slow, NTDS Standard Type D high level serial, and Type E low level serial interfaces. These interfaces are Circuit Card Assemblies (CCAs) located in the Input/Output (I/O) Card Rack Assembly. The combat systems suite or aircraft alignment aboard the ship on which the RLGN system is installed determines the speciﬁc conﬁguration of NTDS interface circuit cards.

S9427-AN-OMP-010/WSN-7

CN-1695/WSN-7(V)
NTDS Type A NTDS Type D NTDS Type E
CN-1696/WSN-7(V)
NTDS Type A NTDS Type D NTDS Type E
CN-1697/WSN-7(V)
NTDS Type A NTDS Type E

3 ea 1 ea 4 ea
5 ea 1 ea 2 ea
7 ea 1 ea

The basic external data interface also consists of a 1-pulse per second timing interface, which provides time synchronization in a dual-system conﬁguration; an RS-422 serial data interface, which exchanges position, velocity, and status information in a dual-system conﬁguration; an RS-422 interface to an external CDU; and an ATM interface to External Local Area Network (LAN). Heading, roll, pitch, north-south velocity, east-west velocity and total velocity are output as analog (synchro) data. Synchro ampliﬁers are provided for the heading, roll and pitch outputs. Table 1-2 outlines the serial interface and data message characteristics. Table 1-3 lists the synchro output characteristics and deﬁnes the synchro reference requirements.
1.4 UNITS AND ASSEMBLIES.
As shown in Figure 1-1, the RLGN Cabinet consists of an upper Cabinet Assembly and a lower Measurement Cabinet Assembly, which are separated by a heat shield. The upper cabinet houses power supplies, synchro ampliﬁers, and rack-mounted circuit cards that contain the interface, control, and data processing circuits. The lower cabinet contains the IMU components. Table 1-4 lists the units and assemblies that make up the AN/WSN-7(V) RLGN. Some assemblies contain programmed devices. Other assemblies are calibrated by installation of an associated Programmable Read-Only Memory (PROM), which contains calibration parameters that are determined at factory test and are speciﬁc to the assembly with which the PROM is supplied. These assemblies are identiﬁed with a programmed part number, which speciﬁes the hardware with the programmed conﬁguration, and with a hardware part number, which identiﬁes only the hardware without the programmed device. Normally, only the programmed part number is applicable for identifying

replaceable assemblies. The RLGN contains the following functional elements:
• IMU (1A2A1)
• IMU support electronics
• Navigation (Nav) Processor (1A1A13), I/O Processor (1A1A21), ATM Processor (1A1A4), and interface electronics
• Power Supplies (1A1A6), (1A1A8) and Battery (1A1A5) for emergency power generation
• Keypad (1A1A9) and Display Panel (1A1A10)
• IP-1747/WSN CDU
Consult the Allowance Parts List (APL) for the appropriate revision level of each assembly.
1.4.1 DSVL INTERFACE MODIFICATION. The DSVL interface (part of RLGN Field Change 1) uses I/O Channel No. 2 on Dual Panel Interface Circuit Card Assembly (CCA) (1A1A14) (previously an unused spare). This data I/O channel is wired from I/O Backplane connector J9 to an added connector 1J23 on the back of the cabinet using an added harness assembly T969380. I/O Central Processor (1A1A21) and the Navigation Central Processor (1A1A13) are replaced with a later part revision containing software support for the DSVL data interface function.
1.4.2 ATM INTERFACE MODIFICATION. (Part of RLGN Field Change 1) The ATM interface assembly consists of the ATM Processor Assembly 1A1A4A1A1 and the Peripheral Component Interface (PCI) Mezzanine 1A1A4A1A2. This data I/O channel is cabled, using ﬁber optic cable, from the front of the PCI Mezzanine to an added connector 1J22 on the back of the cabinet using harness assembly (1A1W7).
1.5 INS INTERFACE SYSTEMS.
The AN/WSN-7(V) INS interfaces with numerous ship systems using digital and analog communications.
Additional and hull-speciﬁc interface information is available in the Combat Systems Technical Operation Manual (CSTOM) and Combat Systems Operational Sequencing System (CSOSS) and in Navigation (System) Operating Procedures (NOPs) for each ship class. (See Table 1-6.)
1.5.1 AN/WSN-7(V) MASTER TO AN/WSN-7(V) SLAVE. A synchronous interface occurs between

RLGNs in an AN/WSN-7(V) navigation suite with two RLGNs. This interface exchanges position, velocity and status information between the RLGNs.
1.5.2 IP-1747/WSN CONTROL DISPLAY UNIT (CDU). The CDU is the primary man-machine interface to/from the RLGN. The CDU is part of the AN/WSN-7 INS and is identiﬁed as Unit 4 of the system. It can monitor and control the RLGNs from a separate installation location from the RLGNs. This interface sends INS Super Channel data to the CDU. Additionally, the Remote Control Display Unit (RCDU) function, which simulates the display and keypad for the RLGN, is displayed on the CDU and enables remote operation of the RLGN from the CDU. Although the CDU is part of the AN/WSN-7(V) INS, operation and maintenance instructions for the CDU are not contained in this technical manual. (See Table 1-6 for information on the CDU technical manual.)
1.6 TROUBLESHOOTING AND MAINTENANCE CONCEPT.
The AN/WSN-7(V) RLGN is designed for ease of maintenance through replacement of failed Lowest (or Line) Replaceable Units (LRUs) with replacements drawn from On-Board Repair Part (OBRP) stock. All LRUs, including power supplies and circuit boards, use plug and jack connectors for ease of replacement. The organizational level of maintenance will use the self-contained capability of system BIT and the diagnostic software program to identify faults to the LRU. RLGN alignment and conﬁguration data are stored in Non-Volatile Random Access Memory (NVRAM) and Electrically Erasable Programmable Read-Only Memory (EEPROM). Calibration information associated with the attitude and acceleration sensors is stored in PROM chips, which allow maintenance to be performed on the RLGN without the need for mechanical or electrical realignment after repairs have been performed.
1.7 LIST OF APPLICABLE DOCUMENTS.
Table 1-6 provides a list of technical manuals and speciﬁcations associated with the AN/WSN-7(V) INS, but not supplied. These documents provide operation, maintenance, and installation information; Interface Design Speciﬁcations (IDSs), which describe the various message types that can be selected for data transfer between the RLGNs and external equipment; and the NTDS digital interface speciﬁcations, which describe timing, communication protocol, and transmission characteristics of the NTDS I/Os.

Table 1-7 describes the document supplied with the equipment.
1.8 EQUIPMENT AND ACCESSORIES.
Table 1-8 provides a list of equipment and accessories supplied with the equipment. Table 1-9 provides a list of equipment required, but not supplied. Table 1-10 provides the Field and Factory Changes applicable.

1-5

S9427-AN-OMP-010/WSN-7

Table 1-1. Design and Physical Characteristics

ENVIRONMENTAL CHARACTERISTICS

Temperature

Storage:

-40° to 75° C (-40° to 167° F)

Operating:

0° to 50° C (32° to 122° F)

Extreme Operating:1 -6.7° to 65° C (20° to 149° F)

Humidity

Humidity (relative):

0 to 95%

Barometric Pressure Storage:

0.5 to 30 psi

Operating:

10 to 30 psi

Shock

Meets the requirements of MIL-STD-901D. System functions may be interrupted during application of the shock.

Vibration

Meets the requirements of MIL-STD-167-1 for Type 1.

1 The AN/WSN-7(V) RLGN is capable of withstanding environmental extremes with no interruption of system functions. The RLGN returns to operating condition at full accuracy following restoration of applicable environment and performance of a reset cycle.

Table 1-2. Digital (RS-422A) Data Interface

I/O PORT

DATA CHARACTERISTICS

RLGN to RLGN Data Rate − 38,400 bits/second Interface (J6) Transmitted Character Format:

1 start bit

8 data bits

1 stop bit

Bits total: 10

Least signiﬁcant bit is transmitted ﬁrst

Signal Polarity (Output signals are referenced to INS ground):

MARK:

RS-422 + High, RS-422 - Low

SPACE:

RS-422 + Low, RS-422 - High

Display-Control Data Rate − 9,600 bits/second

Unit Interface (J5)

Transmitted Character Format:

1 start bit

8 data bits

1 stop bit

Bits total: 10

Least signiﬁcant bit is transmitted ﬁrst

Signal Polarity (Output signals are referenced to INS ground):

MARK:

RS-422 + High, RS-422 - Low

SPACE:

RS-422 + Low, RS-422 - High

1-6

Table 1-1. Design and Physical Characteristics - Continued

ENVIRONMENTAL CHARACTERISTICS

Linear Acceleration

Operating:

Horizontal:

±0.5 g peak

Vertical:

1.0 g ±0.5 g peak

PHYSICAL/ELECTRICAL CHARACTERISTICS

Size

Height:

169.7 cm (66.8 in)

Width:

59.7 cm (23.5 in)

Depth:

73.3 cm (28.9 in)

Weight Power requirements2

381 kg (840 lbs) 105-125 VAC, 50, 60 or 400 Hz, 3-phase, 600 Volt Amps (VA) (max)

Heat dissipation

600 Watts (max)

2 The main power fault detector is conﬁgured to match input power frequency by switch S1 on Vital Bus CCA (1A1A3). The AN/WSN-7(V) is conﬁgured for 60 Hz main power input from the manufacturer.

I/O PORT
DSVL Interface (J23)

Table 1-2. Digital (RS-422A) Data Interface - Continued

DATA CHARACTERISTICS

Data Rate − 9,600 bits/second

Transmitted Character Format:

1 start bit

8 data bits

1 stop bit

Bits total: 10

Least signiﬁcant bit is transmitted ﬁrst

Signal Polarity (Output signals are referenced to INS ground):

MARK:

RS-422 + High, RS-422 - Low

SPACE:

RS-422 + Low, RS-422 - High

Table 1-3. Analog Synchro Input/Output and Reference Characteristics

SYNCHRO INPUT (SHIP’S LOG)

Reference

115 VAC, 400 Hz; 90 V L-L Synchro

Scaling1

20 - 125 Kt/Rev

Fore/Aft Gradient2

90/10 or 50/50 percent

TRANSMITTERS OUTPUT: (HEADING, ROLL, PITCH)

Type/Signal Format

Ampliﬁer: Equivalent to synchro 115 VAC 11CX4

Output Power

Heading: Total (Vital + Non-vital) = 32 VA max (400 ma/leg)

Vital = 2.5 VA max (100 ma/leg)

Roll/Pitch: 8 VA max (100 ma/leg)

Two Speed (Heading) Format

Fine 36:1 (10°/revolution)

Coarse 1:1 (360°/revolution)

1 Selectable at installation based on Speed Log output. 2 Selectable at installation.

Table 1-4. Summary of AN/WSN-7(V) Units and Assemblies

ASSEMBLY
Unit 1
(1A1) (1A1A1) (1A1A2) (1A1A3) (1A1A4) (1A1A5) (1A1A6) (1A1A7) (1A1A8) (1A1A9) (1A1A10)

NOTES

ASSEMBLY PART NO. 1981101-6

1981101-2

1981101-3

1981539-var

1, 11 11 11, 12, 13

1981532 1982618 1978322 1900040

1981554 1979342 1810853 1205050-3 1859873 1979344

NAME/FUNCTION
AN/WSN-7(V) Ring Laser Gyro Navigator (CN-1695/WSN-7) AN/WSN-7(V) Ring Laser Gyro Navigator (CN-1696/WSN-7) AN/WSN-7(V) Ring Laser Gyro Navigator (CN-1697/WSN-7) Processor Cabinet Electrical Equipment Assembly Filter, Power Line Inverter Assembly, 400 Hz Vital Bus CCA AN/WSN-7(V) ATM Processor Computer Software Conﬁguration Item (CSCI) Battery Assembly Power Supply Battery Charger Power Module Membrane Keypad Display Assembly

S9427-AN-OMP-010/WSN-7

Table 1-3. Analog Synchro Input/Output and Reference Characteristics - Continued

Two Speed (Roll and Pitch) Format

Fine 36:1 (10°/revolution) Coarse 2:1 (180°/revolution)2 or 1:1 (360°/revolution)

Synchro Velocity Output: (Vn, Ve, and Vt)

Output Power

2 VA max (20 ma/leg)

Two Speed (Vt) Format

Fine 10:1 (10 kt/revolution) Coarse 1:1 (100 kt/revolution)

Two Speed (Vn, Ve) Format

Fine 10:1 (±10 kt/revolution) Coarse 1:1 (±100 kt/revolution)

Reference Voltage (Non-Vital): Synchro reference voltage is applied to each RLGN. Reference is always derived from own ship’s 400 Hz main power. The reference voltage and the synchro signals are affected in amplitude and frequency by variations in the reference voltage.

Voltage/Frequency

115 Volts, 400 Hz

Power capacity

3 VA

Power factor

≥0.9

Grounding

Must not be grounded

Table 1-4. Summary of AN/WSN-7(V) Units and Assemblies - Continued

ASSEMBLY

NOTES

ASSEMBLY PART NO.

NAME/FUNCTION

(1A1A11)

11

1981660

Backplane Assembly, Nav Processor

(1A1A12)

1981534

I/O Processor, Backplane Assembly

(1A1A13)

2, 12, 13 1812590-XX

Nav Processor CCA (Programmed Navigation Processor)

(1A1A14)

1977455

Dual Panel Interface CCA (RLGN-to-RLGN)

(1A1A15)

1980513

Status and Command CCA

(1A1A16)

1977455

Dual Panel Interface CCA

(1A1A17)

1977538-0

IMU Interface CCA

(1A1A18)

1977569

Torquer CCA (Roll)

(1A1A19)

1977569

Torquer CCA (Azimuth)

(1A1A20)

1980488-2

Bus Interface CCA

(1A1A21)

3, 12, 13 1812591-XX

I/O Processor CCA (Programmed I/O Processor)

(1A1A23)

11

1980486-2

Dual Port Memory CCA

(1A1A30)

11

1981572

Support Electronics, Backplane

(1A1A31)

1981570

I/O Control Built-in Test Equipment (BITE) and Filter CCA

(1A1A32)

4, 11

1811791

IMU Processor CCA

1-7

S9427-AN-OMP-010/WSN-7

Table 1-4. Summary of AN/WSN-7(V) Units and Assemblies - Continued

ASSEMBLY

NOTES

ASSEMBLY PART NO.

NAME/FUNCTION

(1A1A33)

1979023

Repositioning Interface CCA

(1A1A34)

1979047

Analog-to-Digital (A/D) Multiplexer CCA

(1A1A35)

1979046

Accelerometer and Sensor Electronics Assembly

(1A1A36)

1979348

Gyro Support Electronics CCA

(1A1A37)

1979057

Support Electronics Power Supply

(1A1A38)

1979087-3

Synchro Converter CCA

(1A1A39)

1979087-3

Synchro Converter CCA

(1A1A40)

1979087-3

Synchro Converter CCA

(1A1A41)

1976545-3

Synchro Buffer Ampliﬁer (8 VA)

(1A1A42)

1976545-3

Synchro Buffer Ampliﬁer (8 VA)

(1A1A43)

1976547-4

Synchro Buffer Ampliﬁer (32 VA)

(1A1A44)

1976547-4

Synchro Buffer Ampliﬁer (32 VA)

(1A1A51) through (1A1A58)

5, 10, 11

1981087 1981561 1981559

NTDS Interface, Type A (See Table 1-5) NTDS Interface, Type D NTDS Interface, Type E

(1A1DS1),

11

(1A1DS2)

FF200CW600-28V-P Lamp or FF200-0CW-028B

(1A1MP3)

1981510

Upper Card Rack Assembly, Navigation and I/O

(1A1MP4)

1979347

Card Rack Assembly, Support Electronics

(1A1MP2)

1891448

Heat Shield Assembly

(1A1MP6)

11

11

11

1983105 4800307 1983108

Connector Plate (CN-1695/WSN-7) Connector Plate (CN-1696/WSN-7) Connector Plate (CN-1697/WSN-7)

(1A2)

1981548

Measurement Cabinet Electrical Equipment Assembly

(1A2A1)

6

1812593 or 4300859 IMU MX-11681/WSN-7 or MX-11681A/WSN-7A(V) Assembly (Matched Set, with all EPROMs)

1A1A32U13

6

1810807

IMU Assembly Calibration PROM

1A1A32U03

6

1812809

IMU Assembly Calibration PROM

(1A2A1A1)

1981549 or 4800592 IMU Assembly

(1A2A1A1A1) 7

1812594-3

RLG Assembly (Matched Set) (Gyro A)

1A1A32U15

7

1810563

RLG Calibration PROM

1-8

Table 1-4. Summary of AN/WSN-7(V) Units and Assemblies - Continued

ASSEMBLY

NOTES

ASSEMBLY PART NO.

NAME/FUNCTION

(1A2A1A1A2) 7

1812594-2

RLG Assembly (Matched Set) (Gyro B)

1A1A32U02

7

1810563

RLG Calibration PROM

(1A2A1A1A3) 7

1812594-1

RLG Assembly (Matched Set) (Gyro C)

1A1A32U04

7

1810563

RLG Calibration PROM

(1A2A1A1A4) 11

1979045

High Voltage Power Supply (HVPS)

(1A2A1A1A4A1)

1980509

HVPS “A” and “B” CCA

(1A2A1A1A5) 8

1810720

Calibrated Accelerometer (Matched Set) (Accel. A)

1A1A32U12

8

1810562

Accelerometer Calibration PROM

(1A2A1A1A6) 8

1810720

Calibrated Accelerometer (Matched Set) (Accel. C)

1A1A32U01

8

1810562

Accelerometer Calibration PROM

(1A2A1A1A7) 8

1810720

Calibrated Accelerometer (Matched Set) (Accel. B)

1A1A32U14

8

1810562

Accelerometer Calibration PROM

(1A2A1A1MP1)

1979356

Frame Assembly, Inner

(1A2A1A1MP2)

1979354

Frame Assembly, Outer

(1A2A1A1A9A1)

1980596

Accelerometer Stimulus CCA

(1A2A1A1A9W1)

T968693

Harness Assembly

(1A2A1A1A10)

1810553-1

Slip Ring Assembly (Electrical Contact Ring Capsule Assembly)

(1A2A1A1A11)

1810553-2

Slip Ring Assembly (Electrical Contact Ring Capsule Assembly)

(1A2A1A1A12)

1810553-3

Slip Ring Assembly (Electrical Contact Ring Capsule Assembly)

(1A2A1A1A13)

1810553-4

Slip Ring Assembly (Electrical Contact Ring Capsule Assembly)

(1A2A1A1B1)

1979358

Motor, Direct Current, Torquer (Outer Gimbal)

(1A2A1A1B2)

1979358

Motor, Direct Current, Torquer (Inner Gimbal)

(1A2A1A1B3)

1243107-2

Synchro Transmitter, Multispeed (Outer Gimbal)

(1A2A1A1B4)

1243107-2

Synchro Transmitter, Multispeed (Inner Gimbal)

(1A2A1A1M1)

1975362-6

Meter, Time Totalizing

Table 1-4. Summary of AN/WSN-7(V) Units and Assemblies - Continued

ASSEMBLY

NOTES

ASSEMBLY PART NO.

NAME/FUNCTION

CABLE ASSEMBLIES

1W1

T968889

Harness Assembly

1W2

T968890

Cable Assembly

1W3

T968891

Cable Assembly

1W4

T968892

Cable Assembly

(1A1W1)

9, 11

T969420

Main Cabinet Cable and Harness Assembly

(1A1W2)

T968840

Cable Assembly (Door Cable and Harness Assembly)

(1A1W3)

T967883

Ribbon Cable Assembly

1A1W4

T968841

Cable Assembly

1A1W5

T968842

Cable Assembly

1A1W6

T968894

Harness Assembly

(1A1W7)

11

1900013-1

Cable Assembly, Fiber Optic ATM/Synchronous Optical Network (SONET) Interface

1A1W10 through 5 1A1W26

(See Table 1-5)

(See Table 1-5)

P/O 1A1W1

11

T969380

Harness Assembly for DSVL

Unit 2

Same as Unit 1

Table 1-5. AN/WSN-7(V) NTDS I/O Conﬁgurations

AN/WSN-7(V)

CCA

NAME/FUNCTION

CN-1695 CN-1696 CN-1697

Locations (1A1A51) through (1A1A58) are used for NTDS Standard Interface.

(1A1A51) NTDS Interface CCA, Type

E

E

E

(1A1A52) NTDS Interface CCA, Type

E

A

A

S9427-AN-OMP-010/WSN-7

Table 1-4. Summary of AN/WSN-7(V) Units and Assemblies - Continued

ASSEMBLY

NOTES

ASSEMBLY

NAME/FUNCTION

PART NO.

NOTE

1. Inverter Assembly P/N 1982618 is manufactured with high reliability screened parts. This assembly is directly interchangeable with P/N 1980379.
2. Nav Processor CCA, 1812590-XX, is the programmed part number of unprogrammed Central Processing Unit (CPU)/Memory assembly part number 1981127. After assembly part number 1981127 is programmed with the stored program assembly, it is reidentiﬁed as part number 1812590-XX.
3. I/O Processor CCA, 1812591-XX, is the programmed part number of unprogrammed CPU/Memory assembly part number 1983195. After assembly 1983195 is programmed with the stored program assembly, it is reidentiﬁed as part number 1812591-XX.
4. IMU Processor CCA, 1811791, is the programmed part number of unprogrammed Bus Control Electronics assembly part number 1979021. After assembly 1979021 is programmed with the stored program assembly, it is reidentiﬁed as part number 1811791.
5. CCAs (1A1A51) through (1A1A58) and associated cables are selected based on the NTDS interface requirements for each installation. The assemblies and cables installed are deﬁned by the Unit 1 part number. Refer to Table 1-5 for applicability.
6. The IMU Assembly part number includes two PROMs (serialized to the IMU Assembly) programmed during factory calibration with correction parameters which are used by the system to compensate for mechanical offsets in the IMU normal and inverted positions.
7. Each RLG Assembly part number includes a PROM (serialized to the RLG) programmed during factory calibration with correction parameters which are used by the system to compensate for mechanical offsets in the RLG.
8. Each Accelerometer Matched Set part number includes a PROM (serialized to the accelerometer) programmed during factory calibration with correction parameters which are used by the system to compensate for mechanical offsets in the Accelerometer.
9. If the RLGN has Field Change 1 (DSVL Interface), then the Harness Assembly (1A1W1) part number is T969420.
10. Part Number 1981087 (Rev A) is unacceptable if Programmable Array Logic (PAL) chip U11 part number is 1812652 (Rev A). Acceptable PAL U11 part number is 1812652 (Rev B).
11. Part of Field Change 1.
12. Part of Field Change 2 or 3.
13. Part of Field Change 4.

CCA (1A1A53) (1A1A54) (1A1A55)

Table 1-5. AN/WSN-7(V) NTDS I/O Conﬁgurations - Continued

AN/WSN-7(V)

NAME/FUNCTION

CN-1695 CN-1696 CN-1697

NTDS Interface CCA, Type

E

E

A

NTDS Interface CCA, Type

E

D

A

NTDS Interface CCA, Type

D

A

A

1-9

S9427-AN-OMP-010/WSN-7

Table 1-5. AN/WSN-7(V) NTDS I/O Conﬁgurations - Continued

AN/WSN-7(V)

CCA

NAME/FUNCTION

CN-1695 CN-1696 CN-1697

(1A1A56) NTDS Interface CCA, Type

A

A

A

(1A1A57) NTDS Interface CCA, Type

A

A

A

(1A1A58) NTDS Interface CCA, Type

A

A

A

Cables used with the NTDS interface are determined by the part number of the system.

1A1W10

Coaxial Cable Assembly T968912

*

*

*

1A1W11

Coaxial Cable Assembly T968912

*

*

*

1A1W12

Coaxial Cable Assembly T968912

*

*

*

1A1W13

Coaxial Cable Assembly T968912

*

*

*

1A1W14

Coaxial Cable Assembly T968912

*

*

1A1W15

Coaxial Cable Assembly T968912

*

*

1 Part of Field Change 1.

Table 1-6. Documents Required but Not Supplied

DOCUMENT NO. NAVSEA Dwg. No. 7100680 NAVSEA Dwg. No. 7100681 NAVSEA Dwg. No. 7100682
NAVSEA Dwg. No. 7100683
NAVSEA Dwg. No. 7100684
NAVSEA Dwg. No. 7100685
MIL-STD-1397B(NAVY)
NAVSEA S9427-AN-IDS-010/WSN-7
NAVSEA SE174-AB-IDS-010/GPS
NAVSEA T9427-AB-IDS-050/WSN-7
EE17A-AA-OMI-010 (Windows software version) with Change A

DESCRIPTION
Inertial Navigation System AN/WSN-7(V) Drawing List
Inertial Navigation System AN/WSN-7(V) Block Diagram
Inertial Navigation System AN/WSN-7(V) Summary List of Installation Materials
Inertial Navigation System AN/WSN-7(V) Input/Output Sheets
Inertial Navigation System AN/WSN-7(V) Cable Running Sheets
AN/WSN-7(V) Ring Laser Gyro Navigator Outline and Installation Drawing
Military Standard Input/Output Interfaces, Standard Digital Data, Navy Systems
Interface Design Speciﬁcation, Super Channel to User for the AN/WSN-7(V) Ring Laser Gyro Navigator (RLGN)
Interface Design Speciﬁcation for Shipboard External Computer and Navigation Satellite Timing and Ranging (NAVSTAR) Global Positioning System
Interface Design Speciﬁcation, Aircraft Carrier Navigation System (CVNS) to External Computer
Operator and Maintenance Manual, Organizational Level for Control Display Unit, IP-1747/WSN-7 and Secondary Control Display Unit, IP-1746/WSN-7A

1-10

CCA 1A1W16 1A1W17 1A1W30 1A1W10 1A1W20
1A1W21 1A1W22 1A1W23 1A1W24 1A1W25 1A1W26

Table 1-5. AN/WSN-7(V) NTDS I/O Conﬁgurations - Continued

AN/WSN-7(V)

NAME/FUNCTION

CN-1695 CN-1696 CN-1697

Coaxial Cable Assembly T968912

*

*

Coaxial Cable Assembly T968912

*

*

Coaxial Cable Assembly T968914

*

*

Coaxial Cable Assembly T968914

*

*

Cable and Harness Assembly T9689131

*

*

*

Cable and Harness Assembly T9689131

*

*

*

Cable and Harness Assembly T9689131

*

*

*

Cable and Harness Assembly T9689131

*

*

*

Cable and Harness Assembly T9689131

*

Cable and Harness Assembly T9689131

*

Cable and Harness Assembly T9689131

*

Table 1-6. Documents Required but Not Supplied - Continued

DOCUMENT NO.

DESCRIPTION

EE17A-AA-OMI-A10 (Linux software version)

Operator and Maintenance Manual, Organizational Level for Control Display Unit, IP-1747/WSN-7 and Secondary Control Display Unit, IP-1746/WSN-7A

EE17A-AC-IEM-010/ EE17A-AD-IEM-010

IP-1747/WSN Control Display Unit and IP-1746/WSN-7A Secondary Control Display Unit Interactive Electronic Technical Manual and Interactive Courseware

NAVSEA S9427-AN-IDS-010/WSN-7 Interface Design Speciﬁcation, Superchannel to User for the AN/WSN-7 Ring Laser Gyro Navigator (RLGN) System

NAVSEA S9427-AN-IDS-020/WSN-7 Interface Design Speciﬁcation, Inertial Navigation System AN/WSN-7(V) to External Computer - for Low Level Serial (MIL-STD-1397B Type E) Digital Communication

NAVSEA S9427-AN-IDS-030/WSN-7 Interface Design Speciﬁcation, Inertial Navigation System AN/WSN-7(V) to Users - for MIL-STD-1397 Type D Serial Channels No. 1 and No. 2

NAVSEA S9427-AN-IDS-040/WSN-7 Interface Design Speciﬁcation, Inertial Navigation System AN/WSN-7(V) to External Computer in an Output Only Conﬁguration - for Parallel Channels

NAVSEA S9427-AN-IDS-050/WSN-7 Interface Design Speciﬁcation, Ring Laser Gyro Navigator (RLGN) System to External Computer

NAVSEA S9427-AN-IDS-070/WSN-7 Inertial Navigation System AN/WSN-7 External Computer for Parallel (MIL-STD-1397B Type A) Input/Output Digital Communication, Interface Design Speciﬁcation

NAVSEA S9427-AP-IDS-010/RLGN

Navigation Operational Program Interface Design Speciﬁcation for Use with the Ring Laser Gyro Navigator (RLGN)

Table 1-6. Documents Required but Not Supplied - Continued

DOCUMENT NO.

DESCRIPTION

NAVSEA S9427-AP-IDS-020/RLGN

Navigation Operational Program Interface Design Speciﬁcation for Use with the Ring Laser Gyro Navigator (RLGN)

NAVSEA S9427-AP-IDS-030/RLGN

Navigation Operational Program Interface Design Speciﬁcation for Use with the Ring Laser Gyro Navigator (RLGN)

NAVSEA S9427-AP-IDS-040/RLGN

Navigation Operational Program Interface Design Speciﬁcation for Use with the Ring Laser Gyro Navigator (RLGN)

NAVSEA S9427-AN-IDS-080/WSN-7 Interface Design Speciﬁcation for the AN/WSN-7(V) Ring Laser Gyro Navigator (RLGN) to user via ATM Local Area Network (LAN)

03956 SCM-25417

Interface Design Speciﬁcation for the AN/WQN-2 Doppler Sonar Velocity Log (DSVL) to AN/WSN-7(V) Ring Laser Gyro Navigator (RLGN) Interface

Table 1-7. Documentation Supplied

TMIN/VID NO./ IDENTIFICATION NO.

NSN

TITLE/DESCRIPTION

S9427-AN-OMP-010/WSN-7, Rev 1

Technical Manuals

0910-LP-102-7705

Technical Manual, Organizational Level, Ring Laser Gyro Navigator Inertial Navigation System, AN/WSN-7(V)1, -7(V)2, -7(V)3, Part Numbers CN-1695/WSN-7(V), CN-1696/WSN-7(V), and CN-1697/WSN-7(V); Operation and Maintenance with Parts Lists

QTY. 1 ea

QTY 1
1 1

Table 1-8. Equipment and Accessories Supplied

ITEM NAME OR NOMENCLATURE

UNIT NUMBER OVERALL DIMENSIONS WEIGHT

HEIGHT WIDTH DEPTH

AND VOL-

UME

Ring Laser Gyro Navigator (RLGN) CN-1695/WSN-7(V), CN-1696/WSN-7(V), CN-1697/WSN-7(V)

1, 2

66.8 in. 23.5 in. 28.9 in. 840 lb.

Processor Cabinet Electrical Equipment Assembly

(1A1)

Inertial Measurement Cabinet Assembly

(1A2)

S9427-AN-OMP-010/WSN-7

Table 1-6. Documents Required but Not Supplied - Continued

DOCUMENT NO.

DESCRIPTION

Part Number 03956-JA17-6608

DSVL Data Interface Supplement for CN-1695(V)/WSN7(V) Ring Laser Gyro Navigator (RLGN)

03956-PL1813788-Var

DSVL Interface Field Change Kit Parts List

NAVSEA SE178-A2-MMM-010

Doppler Sonar Velocity Log (DSVL), AN/WQN-2(V)2 through 2(V)7, Electronic Equipment, Operation and Maintenance Instructions

03956-4300201-1

ATM Interface Field Change Kit

S9427-AN-FCB-001/WSN-7

AN/WSN-7/7A(V) Field Change Bulletin 1

S9427-AN-FCB-002/WSN-7

AN/WSN-7/7A(V) Field Change Bulletin 2

S9427-AN-FCB-003/WSN-7

AN/WSN-7/7A(V) Field Change Bulletin 3

S9427-AN-FCB-004/WSN-7

AN/WSN-7/7A(V) Field Change Bulletin 4

S9427-AN-FCB-006/WSN-7

AN/WSN-7/7A(V) Field Change Bulletin 6

S9427-AN-FCB-009/WSN-7

AN/WSN-7/7A(V) Field Change Bulletin 9

Table 1-7.
TMIN/VID NO./ IDENTIFICATION NO.

Documentation Supplied - Continued

NSN

TITLE/DESCRIPTION

S9427-AN-IEM-010/REV1

CD-ROMs

0913-LP-101-6143

Interactive Electronic Technical Manual and Interactive Courseware for Navigation Unit, Ring Laser Gyro Navigator, AN/WSN-7(V)1, (V)2, (V)3 Inertial Navigation System

QTY.

1-11

S9427-AN-OMP-010/WSN-7

Table 1-9. Equipment Required but Not Supplied

SUBCATEGORY (SCAT)
CODE

TEST EQUIPMENT CATEGORY

–

Digital Multimeter

TEST EQUIPMENT
MODEL NUMBER
89536-77/AN

–

Wild T2

––

Theodolite(2

each)

EQUIPMENT TEST
PARAMETERS

APPLICATION

––

Continuity testing and

analog signal and

voltage checks

±0.5 arc seconds Equipment Installation

Table 1-10. Field Changes and Factory Changes

CHANGE NUMBER Field Change 1 (ECP N84-1) (ECOs 525, 526, 531, 539, 541, 546, 547, 548, 563, 577, 583, 588, 698, 702, 736, 802)
Field Change 2 (ECP N84-2) (ECOs N84-814, -815, -816) Field Change 3 (ECP N84-2) (ECOs N84-814, -815, -816)

PURPOSE

DESCRIPTION

1. Adds a new ﬁber-optic I/O interface [ATM/Network Time Protocol (NTP)].
2. Adds BFTT interface.

1. Upgrades the revision level of the Nav Processor and I/O Processor CCAs.
2. Modiﬁes the IMU High Voltage Power Supply.

3. Adds AN/WQN-2 DSVL interface.
4. Revises the AN/WSN-7(V)2 I/O conﬁguration.
5. Adds a feature for improving the RLGN position accuracy during periods of valid GPS data.
6. Adds support for the NTDS Type A I/O Interface.
7. Improves selected LRUs due to parts obsolescence or improvement of reliability.
8. Makes improvements to Navigation and I/O Operational programs.

3. Modiﬁes the IP-1747/WSN CDU.
4. Modiﬁes the NTDS Type A interface CCA.
5. Modiﬁes the Navigation rack and Support Electronics backplane assemblies.
6. Changes the part number for two indicator lamps to improve reliability.
7. Adds the DSVL interface.
8. Alters the NTDS I/O conﬁguration of the CN-1696/WSN-7 by removing one NTDS Type E interface and replacing it with an NTDS Type A interface.
9. Adds ATM hardware.
10. Updates the revision levels of the IMU, Vital Bus, 400 Hz Inverter Assembly, and Dual Port Memory CCAs.

Upgrades ﬁrmware to enable

Upgrades the revision level of the ATM,

AN/WSN-7(V) to interface with Nav Processor, and I/O Processor CCAs.

BFTT equipment, without the

need for the external ATM switch.

Upgrades ﬁrmware to enable AN/WSN-7(V) to interface with BFTT equipment, without the need for the external ATM switch if Field Change 2 has not been installed.

Upgrades the revision level of the ATM, Nav Processor, and I/O Processor CCAs if Field Change 2 has not been installed.

Table 1-10. Field Changes and Factory Changes - Continued

Field Change 4
(ECOs N84-869, -870, -871)

1. Installs Nav Processor CCA P/N 1812590Rev-AB.
2. Installs I/O Processor CCA P/N 1812591Rev-W.
3. Installs ATM Processor CCA P/N 1900040Rev-C.

Upgrades the revision level of the ATM, Nav Processor, and I/O Processor CCAs.

Field Change 6

Installs MX-11681A/WSN-7 Inertial Measuring Unit

Sound isolates the Inertial Measuring Units to lessen structure-borne noise from the equipment to the ship’s hull.

Field Change 9

1. Replaces NTDS Type D and Converts AN/WSN-7(V)2 to NTDS Type E CCAs with NTDS AN/WSN-7(V)3 Type A CCAs, P/N 1981087

2. Installs Connector Plate P/N 1983108

1-12

S9427-AN-OMP-010/WSN-7

Figure 1-2. Typical System Conﬁguration (Sheet 1 of 2)

1-13

S9427-AN-OMP-010/WSN-7

1-14

Figure 1-2. Typical System Conﬁguration (Sheet 2 of 2)

S9427-AN-OMP-010/WSN-7

CHAPTER 2 OPERATION

2.1 INTRODUCTION.
This chapter identiﬁes all Ring Laser Gyro Navigator (RLGN) operator’s control functions available through the Front Panel, describes their use, provides instructions for turning on and operating the RLGN, and presents information for identifying fault conditions. The Front Panel controls and indicators are shown in Figure 2-1.
When following operating procedures, note that the text appearing in bold between <> symbols refers to labeled keys on the keypad. For example, <DISPLAY>. Items in bold refer to text that appears in the display. For example: NAV-C.
Unnumbered images are provided in some of the procedures in this chapter to show how the display should look upon completion of the step preceding it.
NOTE
Either RLGN can be selected for operation from the IP-1747/WSN Control Display Unit (CDU).
Operator’s procedures associated with testing, troubleshooting, optical alignment, and installation conﬁguration of the AN/WSN-7(V) RLGN are included in the appropriate chapters later in this technical manual.
After power is turned on, the operation sequence and control for start-up self-test, reference alignment, and automatic input of position ﬁx data is controlled by an internal microprocessor. Parameters set during installation identify sensor inputs and the installed conﬁguration of the Inertial Navigation System (INS).
2.2 CONTROLS AND INDICATORS.
2.2.1 KEYPAD CONTROLS AND MENU DISPLAY. All operations, including mode control, sensor selection, data entry, and parameter display, as well as initiation of calibration, self-test, and installation setup, are performed using displayed menus and the keypad on the front of the RLGN.
2.2.2 KEY FUNCTIONS. The keypad, shown in Figure 2-2, is used in conjunction with the displayed menus to perform all control and data entry functions.

The keys are divided into four categories: Menu Selection, Data Entry, Display Control, and Alarm Acknowledge. Some keys perform dual functions. The operation of these keys is automatically determined by the selected menu, mode, or operation being performed. The function of each key is listed in Table 2-1.
2.2.3 MENU SELECTIONS. Table 2-2 lists the functions included in the four menus associated with operation and presents a brief description of the control and data functions associated with each. Figure 2-3 identiﬁes the general menu layout and data presentation for the operations-related menus and provides a listing of all mode and status indications that may be displayed on the top line of the Menu Display Panel. The top line indicates the system operating state, selected navigation aid, selected velocity reference, selected damping mode, selected coordinates (normal or transverse), and code for any detected fault. The next two lines display position, velocity, heading, day, and time. The last three lines present variable information and control functions, as determined by the selected menu and page. Figure 2-4 presents the full menu tree listing all functions available for display during normal operation.
2.3 OPERATING PROCEDURES.
NOTE
The following procedure assumes that the INS has been previously set up, all sensor inputs are conﬁgured, the sensors are turned on, and INS calibration has previously been performed.
The following sections outline the procedure for turning on and operating the RLGN in a normal situation.
2.3.1 TURNING ON THE RLGN. To turn on power and enter the STANDBY mode:
a. Clear any existing tags from 115 Volts, Alternating Current (VAC), 60 Hertz (Hz) and/or 115 VAC, 400 Hz power panels supplying the RLGN using standard safety tag-out procedures.
b. Set the switches at 115 VAC, 60 Hz or 115 VAC, 400 Hz power panels supplying the RLGN to ON.

c. On the RLGN, set the POWER, SYNCHRO REF, and VITAL REF circuit breakers to ON.
d. Set POWER switch to ON. Observe that POWER indicator lights.
e. Observe that display indicates STANDBY in the upper-left corner and no fault codes are displayed.
The unit will remain in STANDBY until the ﬁrst valid position ﬁx is accepted (either manually entered or from an external position reference source). f. Press the <DISPLAY> key to select the Display menu.
g. Press the <NEXT PAGE> key until 4 of 4 appears in the lower right corner of the display.

h. Select Day/Time by pressing the <1> key. The Julian date will read 001, and the Greenwich Mean Time (GMT) will display the time elapsed since the RLGN was turned on.
i. Press the <CLEAR> key to reject the current day and time. The display will show the Julian day and prompt you to accept or reject the information.
j. Press the <CLEAR> key to reject the Julian day entry and enter the correct Julian day. Press the <ENTER> key to accept the entry. The display will show the GMT and prompt you to accept or reject the information.
k. Press the <CLEAR> key to reject the GMT entry and enter the correct time. Press the <ENTER> key to accept the entry. The display will show the Julian day and GMT.

2-1

S9427-AN-OMP-010/WSN-7

l. Press the <SENSOR> key to select the Sensor menu.
m. Select DOCK ON, PDIG ON, or SLAVE ON and press the <ENTER> key to select Align mode.
Manually enter position (if DOCK ON selected) or select other position and velocity reference(s) as appropriate for the start-up environment. Refer to Paragraphs 2.3.2.2 and 2.3.2.4. 2.3.2 OPERATING MODES. Three Operating Modes are associated with start-up, settling, and normal on-line operation. These are: STANDBY, ALIGN, and NAVIGATE. 2.3.2.1 Align Mode States. The Align mode has four possible states. The indication for each of these states is: • ALIGN – Coarse Align currently being performed. • ALIGN-C – Coarse Align complete, Fine Align currently being performed. • ALIGN-F – Fine Align complete, ready to enter Navigate mode.

• NAV-C – Coarse Align complete, Fine Align currently being performed with system in Navigate mode supplying reduced accuracy position and velocity data.
The actual time required for the system to settle to within speciﬁcation accuracy is determined by several factors. These include: geographic position, heading and speed of the ship, time of entry and accuracy of ﬁrst position reset, the alignment method selected, and whether or not the navigation system has been previously calibrated. Regardless of the align method selected, a previously calibrated system requires between 16 and 20 hours to reach speciﬁed full navigational accuracy. A system that has not previously completed calibration requires between 68 and 72 hours to reach speciﬁed full navigational accuracy. The sequence of alignment and settling states, and the minimum and maximum time required to complete each state and settle to speciﬁed accuracy are indicated in Figures 2-5 through 2-7.
2.3.2.2 Alignment References. The RLGN requires velocity and position data to be provided while it is in the Align mode. The data may come from external sources, such as speed and position sensors installed on the ship, or from manual or automatic entries. The available data sources, or alignment references, vary depending on the ship’s RLGN conﬁguration. The alignment reference sources on page 1 of the Sensor menu determine the alignment references that are used. There are three reference sources used to align the system: DOCKside, PDIG, and SLAVE. To select a reference source, perform the appropriate procedure described in Paragraph 2.3.2.4.
DOCKside – The system sets the horizontal velocity to zero and requires manual entry of a position ﬁx. The position data is used as the reference while the ship remains stationary at dockside. When the ship is stationary, Dockside Align is the preferred and most accurate method of alignment, as it uses a ﬁxed position and a velocity of zero.
PDIG – This system uses a digital position source such as Global Positioning System (GPS) to provide the position reference. Velocity data comes from an installed velocity reference source or from manual entry. At-Sea Align using GPS resets is the second most accurate method of alignment, but is the preferred method if the ship is moving.
SLAVE – The other RLGN provides both position and velocity reference data during alignment. For SLAVE to be selected, the other RLGN must ﬁrst be turned on and settled. Slave Align is the least ac-

curate method of alignment as it will never be more accurate than the master system that is the source of position and velocity. The resulting alignment will not be as accurate as a Dockside or At-Sea (using GPS resets) alignment.
2.3.2.3 Operating in Align Modes. Once a reference source has been selected, the RLGN changes from STANDBY mode to ALIGN mode. In the ﬁrst few minutes of this period, it determines roll and pitch attitude and displays the mode word “ALIGN.” During ALIGN, the INS aligns heading by aligning the inertial platform with respect to the earth’s rotation. Once the heading is coarse aligned, the mode word changes from “ALIGN” to “ALIGN-C.” At ALIGN-C, the RLGN attitude outputs are of gyrocompass quality and can be used for stabilization or steering purposes. The RLGN continues to align to the accuracy required for an inertial navigator (Fine Align). When heading is ﬁne aligned, the mode word transitions from "ALIGN-C" to "ALIGN-F." During a DOCKSIDE align, once ALIGN-F has been reached, the RLGN can be put into NAVIGATE mode by deselecting DOCKSIDE as a reference. If DOCKSIDE is deselected while coarse aligned (ALIGN-C is displayed), the RLGN will continue to align with available position and velocity data. While underway (At-Sea Align) and with a PDIG reference such as GPS selected, the RLGN will automatically transition into NAVIGATE mode once ALIGN-F has been reached. If the RLGN is operating from calibration values stored in battery-backed Random Access Memory (RAM), ALIGN-F should be reached in 20 hours or less. If the calibration values stored in battery-backed RAM have been lost due to maintenance on the RLGN, or if the Kalman ﬁlter has been reinitialized in order to perform a new dockside calibration, then ALIGN-F should be reached in 72 hours or less. Analog synchro attitude outputs are continuously provided from the RLGN during align. For example, the heading synchro output will slew as the RLGN slews its calculated heading during ALIGN. By the time ALIGN-C has been reached, the heading synchro output will represent ship’s heading. The Not Ready (Fail) relay indicates that the RLGN is not ready in the deenergized state (so that the RLGN is Not Ready if power is turned off). On power-up, the processor initializes the Status and Command Assembly to keep the relay in the deenergized state. When ALIGN-C has been reached, the relay is energized, indicating that the RLGN is ready to deliver attitude data. If the on-line Built-In Test (BIT) detects a critical failure, as detailed in Fault Code Table B-1, the relay will be deenergized.

2.3.2.4 Align Methods. The align methods determine the alignment references that the RLGN will use. Three align methods are available for selection by the operator: Dockside, At-Sea, and Slave.
2.3.2.4.1 Dockside Align. Dockside Align is preferred if the ship will remain stationary for at least four hours after the system is turned on and Slave Align cannot be performed because the other navigator is not currently settled in the Navigate mode. Dockside Align is the most accurate as it uses a ﬁxed position source and a velocity of zero. The 72-hour calibration should be performed in Dockside to get the best calibration and the best navigation performance. The 20-hour align is also better if performed in Dockside. If the ship must be moved during a Dockside Align, change to At-Sea or Slave, as available, to complete the entire 72-hour calibration. The ﬁrst 24 hours of a 72-hour calibration are the most critical part of the calibration and should always be performed in Dockside, then the RLGN can be taken out of Dockside to another align mode. Always come out of Dockside before the ship is moved, or the alignment will be corrupted. Refer to Figure 2-5 when performing Dockside Align, and proceed as follows:
a. Press the <SENSOR> key, and then press the <1> key to select DOCK ON and enter Dockside Align. Observe that the display shows the GMT and prompts the operator to accept or reject the time shown.
b. Press the <ENTER> key to accept the time or the <CLEAR> key to reject and reset the time. The display will show the “Vertical Deﬂection North” with a value of 00.0 arc sec and prompt the operator to accept or reject it.

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c. Press the <ENTER> key to accept the Vertical Deﬂection North Value. The display will show the “Vertical Deﬂection East” with a value of 00.0 arc sec and prompt the operator to accept or reject it.
d. Press the <ENTER> key to accept the Vertical Deﬂection East value. The display will show the latitude and prompt the operator to accept or reject the latitude value.
e. Accept or reject the latitude value. If the displayed value is incorrect, enter the ship’s latitude within 0.01 Nautical Mile (nm) accuracy. The display will show the longitude and prompt the operator to accept or reject the longitude value.

g. If the information is correct, press the <ENTER> key. The RLGN checks the values for reasonableness and then enters the Dockside Align mode. ALIGN is displayed in the mode ﬁeld (upper left) and DOCK is the displayed Navigation Aid (NAVAID).
2.3.2.4.2 Slave Align. Slave Align is used only if the ship is at sea and an At-Sea Align using GPS resets cannot be performed. Slave Align requires the other RLGN to be in the Navigate mode and available to provide a velocity and position source. A Slave Align will never be more accurate than the master system that is the source of position and velocity, so the resulting alignment will not be as good as an At-Sea Align using GPS resets. Although Slave Align can be used at dockside, the preferred method is Dockside Alignment. (Refer to Paragraphs 2.3.2.4.1 and 2.3.2.4.4.) Refer to Figure 2-6 when performing Slave Align and proceed as follows:
a. Press the <SENSOR> key, and then select SLAVE ON to enter Slave Align.

NOTE When Slave Align is selected, velocity and position resets and velocity damping reference input is provided by the other navigator. b. During Coarse Align, verify that ALIGN and SLAVE appear in the upper-left ﬁelds of the display.
c. Upon completion of Coarse Align, verify ALIGN-C appears in the upper-left ﬁeld of the display, indicating performance of Fine Align.
d. Upon completion of Fine Align, verify ALIGN-F appears in the upper-left ﬁeld of the display, indicating completion of Fine Align.

f. Verify that NAVIGATE appears in the upper-left ﬁeld of the display, indicating entry into the Navigate mode.
2.3.2.4.3 At-Sea Align. At-Sea Align is the preferred method if the ship is moving or will be leaving dockside within four hours of RLGN initial start up. When in At-Sea Align using GPS position resets, the resulting alignment will only be as good as the GPS position. GPS positions are normally very accurate and consistent, so the At-Sea alignment will be quite good, though, it will not be as good as a Dockside Align. At-Sea Align should be used to complete an alignment if the ship must be moved after starting the RLGN in Dockside Align. Refer to Figures 2-6 and 2-7 when performing At-Sea Align, and proceed as follows:
a. Press the <SENSOR> key. If DOCK ON has been previously selected, select DOCK OFF.

f. Accept or reject the longitude value. If the displayed value is incorrect, enter the ship’s longitude within 0.01 nm accuracy. The display shows the ship’s ﬁx and prompts the operator to accept or reject the information.

e. Press the <SENSOR> key to access the Sensor menu. Manually select the Navigate mode by selecting SLAVE OFF and then selecting a valid velocity-damping source.

b. Press the <SENSOR> key and select PDIG ON.

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c. Press the <ENTER> key. The display will change to show digital position reference options.
d. Press the <1> key to select GPS as the digital position reference.
e. Press the <ENTER> key. The display will change to show that the GPS has been accepted as a position reference.
NOTE Automatic acceptance or operator review of position ﬁx data prior to acceptance of position ﬁxes by the RLGN is selectively controlled by setting the Reset function on the Mode menu. Selection of the Reset function is a matter of operation preference. A suggested method is to set the Reset function to Review and manually review the ﬁrst ﬁx from the navigation aid. Then set the Reset function to Auto to allow all subsequent ﬁxes to be automatically accepted/rejected without operator intervention. Operator advisory faults will alert the operator of bad ﬁx data.

f. To select a RESET mode, press the <MODE> key to select the Mode menu.
g. Press the <5> key to select RESET mode.
h. Press the <NE+> key or the <SW−> key to select REVIEW or AUTO mode.
i. Press the <ENTER> key. j. Select the velocity reference by pressing the
<SENSOR> key and selecting Page 2 of the Sensor Menu.
k. To select the GPS as the velocity reference, press the <3> key.

l. Press the <ENTER> key. The display will change to show digital velocity reference options.
m. If VGPS is not displayed, press the <1> key to toggle the options until VGPS is displayed as the Digital Source and press the <ENTER> key. The display will show the current GPS North, East, and Vertical velocities.
n. Press the <ENTER> key again to accept the GPS as the Digital Velocity source. The system will display notiﬁcation that it has accepted the velocity reference.
o. The system will automatically sequence to the Navigate mode upon completion of ALIGN-F.
2.3.2.4.4 Preferred Align Method. Dockside Align provides the most accurate method of alignment and is the preferred alignment method if the ship is not moving and will not move for at least four hours. If the ship is moving or will move after four hours in Dockside Align, the preferred method is At-Sea Align using GPS resets. Slave Align is the least accurate and should only be used when Dockside or At-Sea and GPS is unavailable.

2.3.2.4.5 Coarse vs. Fine Align. In all align methods, the settling sequence consists of a Coarse Align state, followed by a Fine Align state. During settling, the system continually examines system variances. When the examined values settle to within speciﬁed levels, the alignment state is automatically changed and all outputs that have become valid (within speciﬁed limits) become available for reference purposes. Upon completion of Coarse Align, heading, roll, and pitch references are valid. Upon completion of the Fine Align state, position and velocity data are valid. Each of these states must be achieved before the system will enter the Navigate mode.
Upon completion of Dockside Fine Align, the system must be manually selected to enter Navigate mode by selection of a velocity damping reference source. Upon completion of At-Sea Coarse Align, at four hours, the system automatically switches to the NAV-C mode and continues to use the currently selected velocity damping and position references. The system continues to settle in the NAV-C mode for an additional 16 hours while supplying position and velocity data at less than full-speciﬁcation accuracy during a portion of that time interval. During the NAV-C mode of operation, Navigation Digital Data will be available to some users. Because the Navigation Bit is not set, some user systems that require full accuracy will not receive Navigation Data until full Navigate mode is entered.
a. Align Method Steps. The align method is chosen based on ship’s operating schedule and available position and velocity data references. The basic operating sequence is as follows:
NOTE
The ﬁrst mode is entered when the POWER Switch is turned on. While Standby mode is active, the word STANDBY appears in the upper-left area of the display.
(1) STANDBY mode - Turn Power switch ON and note the word STANDBY on the display. Standby mode is exited by pressing the <SENSOR> key and then selecting an Align mode on Page 1 of the Sensor Menu and entering a valid position ﬁx. The Standby mode is active for a minimum of 20 seconds and remains active until an Align mode is selected.

2-4

(2) Coarse ALIGN (Dockside) - To select Dockside Alignment, select DOCK ON on Page 1 of the Sensor menu, then enter a time and position ﬁx within 0.01 nm accuracy. While Coarse Align in Dockside is being performed, the words ALIGN and DOCK appear in the upper-left ﬁelds of the display.
The time that Coarse Align mode is active depends on whether or not the system has been previously calibrated, and on latitude. When Coarse Align has been completed, the word ALIGN changes to ALIGN-C, indicating that the system has completed Coarse Align and has entered Fine Align.
(3) Coarse ALIGN (Slave) - To select Slave Alignment, select SLAVE ON on Page 2 of the Sensor menu. To select Slave Align, the other navigation system must be settled in Navigate mode and the Ship’s Inertial Navigation System (SINS)-SINS data interface must be conﬁgured and selected ON. While Coarse Align in Dockside is being performed, the words ALIGN and

SLAVE appear in the upper-left ﬁelds of the display.
The time that Coarse Align mode is active depends on whether or not the system has been previously calibrated, and on latitude. When Coarse Align has been completed, the word ALIGN changes to ALIGN-C indicating that the system has completed Coarse Align and has entered Fine Align.
(4) Fine ALIGN (Dockside or Slave) - Upon completion of Coarse Align, Fine Align is automatically entered. While Fine Align is being performed, ALIGN-C appears in the upper-left ﬁeld of the display. When Fine Align is entered, the heading, roll, and pitch references are valid.
Minimum settle time in Fine Align before the Navigate mode can be entered is either 20 hours or 72 hours, depending on whether or not the system has been previously calibrated. After the Fine Align sequence is completed in either Dockside or Slave, the word ALIGN-C changes to ALIGN-F, indicating that the system has completed Fine Align and is ready for the operator to manually select conditions to enter the Navigate mode.
(5) NAVIGATE (Selected from Dockside or Slave) - If the system has been selected to align at Dockside or Slave, the Fine Align (ALIGN-F) mode remains active until the Navigate mode is manually selected by the operator.
To change the system to NAVIGATE from Dockside or Slave, remove Dockside or Slave Align reference (select DOCK OFF or SLAVE OFF), and then select a valid velocity damping reference. When the Navigate mode is entered, the word ALIGN-F changes to NAVIGATE.

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A velocity reference must be selected at this time to provide velocity damping. A position reference may be selected to continue operation with position resets. If no valid position reference is selected, the system will continue to operate in NAVIGATE, using the last valid position reset.
(6) Coarse ALIGN (At-Sea) - To select Align At-Sea, select PDIG ON on Page 1 of the Sensor menu. Valid ship’s speed and position reference input must be available and selected. While Coarse Align At-Sea is being performed, the words ALIGN and PDIG (or other selected position reference) appear in the upper-left ﬁelds of the display.
NOTE
Regardless of the Reset mode selected, all ﬁxes will be automatically accepted by the system during the ﬁrst 128 minutes when the system is being aligned at sea.
As with Dockside Align, settle time in Coarse Align depends on whether or not the system has been previously calibrated, and on ship’s latitude, heading, and speed. When Coarse Align has been completed, the word ALIGN changes to ALIGN-C, indicating that the system has completed Coarse Align and has entered Fine Align.
(7) Fine ALIGN (At-Sea) - Upon completion of Coarse Align, Fine Align is automatically entered. While Fine Align is being performed, ALIGN-C appears in the upper-left ﬁeld of the display. When Fine Align is entered, the heading, roll, and pitch references are valid.
Minimum settle time in Fine Align before the Navigate mode can be entered is either 4 hours or 72 hours, depending on whether or not the system has been previously calibrated. After the Fine Align sequence is completed, the system automatically switches through the ALIGN-F state to either the transitional NAV-C settle state

or directly to the full accuracy NAVIGATE mode.
(8) NAV-C/NAVIGATE (At-Sea) - When a previously calibrated navigation system has been selected to align At-Sea, the transition from Fine Align mode to NAV-C mode is automatic. This reduced accuracy Navigation mode is implemented after four hours, when speciﬁed minimum accuracy requirements are met.
When the system enters NAV-C, the navigation processing function sets internal status indications. The I/O processing function translates these indications from data output messages that inform users that the reduced-accuracy NAV-C mode is currently active. This function allows external equipment to use navigation data before the speciﬁed full accuracy NAVIGATE mode is entered at the end of the 20-hour period.
At the end of the 20-hour period, a previously calibrated system automatically exits NAV-C and enters NAVIGATE mode, and the status indications in the data output messages are set to inform users that full accuracy navigation data is currently available.
If the navigation system has not previously completed a 72-hour calibration, the system remains in the Fine Align mode until the 72-hour calibration has been completed and then switches directly from Fine Align (ALIGN-C indication) to NAVIGATE mode. No valid position or velocity data is provided as an output until the system enters NAVIGATE mode. Other than selecting mode transitions as shown in Figure 2-8, the operator has no control over selection of the NAV-C and NAVIGATE states.
2.3.2.5 Selecting the Navigate Mode. (Refer to Figure 2-8). Once the RLGN has settled to Fine Align state in the At-Sea Align mode, the RLGN switches automatically from Fine Align to the Navigate mode when error estimate criteria are met. If the RLGN has settled to Fine Align state (ALIGN-F indication) using the Dockside reference (DOCK ON), the operator must remove the selected reference (DOCK OFF) and select a velocity reference. The RLGN will then switch from Fine Align to the Navigate mode. The RLGN will determine position by dead reckoning until a position reference source is selected. In the same manner, when SLAVE is se-

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lected as the reference, SLAVE must be deselected to enter the Navigate mode. To enable the transition from Dockside or SLAVE Fine Align to Navigate mode, proceed as follows: a. Observe that display indication has changed
from ALIGN-C to ALIGN-F.
b. Check that velocity and position reference sources are operating.
c. Press the <SENSOR> key on the keypad.
d. Press the <1> key to select DOCK OFF.
e. Press the <ENTER> key and observe the Horizontal Reference menu.

f. Press the <1> key to select VMAN ON.
g. Press the <ENTER> key and observe Manual Velocity Entry.
h. Verify that 000.00 knots is displayed. If not, press the <CLEAR> key and enter 000.00.
i. Press the <ENTER> key. Verify that Navigation Aid is accepted.
j. Verify that the system has entered Navigate mode by observing NAVIGATE in the top left of the display.

gate mode, the RLGN can be switched to an alignment mode without having to recycle power. This capability is useful when the ship returns to dockside and the INS will be left operating. If the ship is to remain docked for more than 20 hours, use the following procedure to select Align at dockside (DOCK ON) and enter the ship’s position on each RLGN. The RLGN will exit the Navigate mode and return to the Align mode. Maintaining INS operation in Align at dockside eliminates any parameter drift if the navigation aid (GPS) and/or velocity reference is turned off. Twenty hours is required to realign the INS to full accuracy. IMPORTANT - If the ship will remain at dockside for less than 20 hours, continue operation in the Navigate mode. Continue accepting position ﬁxes from selected position sensor, or periodically enter position ﬁxes manually if the position sensor is not operational.
NOTE Selecting ALIGN while at dockside (DOCK ON) will down mode the RLGN. Navigation data will not be available to various digital users, for example, user systems that require full NAVIGATE mode for operation. Verify with all users of digital navigation data prior to selecting DOCK ON. To switch from Navigate mode to Align at dockside mode:
a. Press the <SENSOR> key. Observe that Position Reference menu is displayed.
b. Press the <1> key to select DOCK as the navigation aid, and observe that DOCK ON is displayed.

c. Press the <ENTER> key and observe that the correct GMT is being updated.
d. Press <ENTER> key. Observe that VERTICAL DEFLECTION NORTH is displayed.
e. If Vertical Deﬂection North displays 00.0 arc seconds, press the <ENTER> key. If it does not, press the <CLEAR> key. Enter +00.0.
f. Press the <ENTER> key. Observe that VERTICAL DEFLECTION EAST is displayed.

2.3.2.6 Switching Between Navigate and Align Modes. Once the RLGN is operating in the Navi-
2-6

g. If Vertical Deﬂection East displays 00.0 arc seconds, press the <ENTER> key. If it does not, press the <CLEAR> key. Enter +00.0.

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h. Press the <ENTER> key. Observe that the LATITUDE is displayed.
i. Press the <CLEAR> key and enter the Dockside Latitude.
j. Press the <ENTER> key. Observe that the LONGITUDE is displayed.
k. Press the <CLEAR> key and enter the Dockside Longitude.
l. Press the <ENTER> key and verify that the displayed position is correct.
m. If the displayed position is correct, press the <ENTER> key again. The RLGN checks the entry for reasonableness and accepts it.

Within a few minutes, ALIGN is displayed in the upper left-hand ﬁeld and DOCK is the displayed NAVAID.
n. The RLGN will automatically sequence through the align modes. Upon completion of Coarse Align, ALIGN-C will be displayed in the upper left-hand ﬁeld. Approximately 20 hours after align is initiated, the display will transition from ALIGN-C to ALIGN-F, indicating that Fine Align is complete.
To switch from Align mode back to Navigate mode, proceed as follows:
a. Check that the position sensor and velocity reference sources are operating.
b. Press the <SENSOR> key, select DOCK OFF, and select position sensor (PDIG ON).
c. Press the <SENSOR> key, select Page 2 of Sensor Menu, and select applicable horizontal velocity damping source ON. NOTE If in ALIGN-F, the RLGN will automatically enter Navigate mode, and the display will change to indicate NAVIGATE.
2.3.3 TRANSVERSE COORDINATES REFERENCE AND DISPLAY.

NOTE
If the INS operates near a geographic pole for an extended period of time, the internal estimate of heading error will increase in accordance with expected Root Mean Square (RMS) heading error. If the internal estimate of heading error exceeds a limit after the system has achieved NAVIGATE mode, and current latitude is less than 84 degrees, then operator advisory Fault Code 49 will be announced. To realign heading and reduce the 24-hour heading oscillation and subsequent navigation errors, the operator should enter position ﬁx data as available. A sequence of at least three position ﬁxes is required with an approximate three- to eight-hour interval between ﬁxes. Additional position ﬁxes (10-12) will provide improved realignment. GPS position ﬁxes are generally the most accurate position source for realignment. This realignment method will have minimal impact on system availability.
2.3.3.1 Use of Transverse Coordinates Reference System. In a gyro-stabilized platform, torque values based on the tangent (tan) and secant (sec) of latitude are used in system control loops. While the INS is a strapdown system based on ring lasers, calculations involving these functions are also used. As the INS approaches 90 degrees latitude, these values become indeterminate (approach inﬁnity) and are no longer valid for calculations. In addition, at high latitudes, the magnitude of east/west vectors has less validity. For this reason, an alternate (Transverse) Earth coordinates reference system is used when the INS is operating at latitudes greater than approximately 85 degrees. The Transverse north pole is located at the intersection of the geographic 180-degree meridian and the equator. The geographic 90-degree and 270-degree meridians become the Transverse equator, and the geographic equator becomes the Transverse 90-degree and 270-degree meridians. (Refer to Figure 2-9.)
2.3.3.2 Modes for Use in Transverse Coordinates Reference System. Three modes are available for selecting operation using Transverse coordinates reference. These modes – AUTO, MNORM, and MTXVS – are selected from Page 1 of the Mode menu. Select AUTO under normal conditions. When AUTO is selected, the INS automatically switches from normal to Transverse coordinates reference when the INS crosses 86 degrees north/south latitude. The INS switches

back to normal coordinates when the INS crosses back through 84 degrees. Select MNORM to force the INS to continue using the normal (geographic) reference regardless of operating latitude. Select MTXVS to force the INS to use Transverse coordinates reference regardless of operating latitude and longitude. The selected mode and the operating mode presently being used by the INS is displayed in the COORDinates ﬁeld of the display (see Figure 2-3). Displayed indications are as follows:
• ANORM - AUTO selected, normal coordinates being used
• ATXVS - AUTO selected, Transverse coordinates being used
• MNORM - Normal coordinates manually selected
• MTXVS - Transverse coordinates manually selected
In addition to the operating mode, the position and heading can be displayed in either normal or transverse coordinates regardless of the selected INS operation reference. Select the position display from the AUX FUNC menu, Page 2, Normal/Transverse function. This function is a toggle selection. When Transverse position and heading are being displayed, the Latitude (LAT), Longitude (LON), and Heading (HDG) indications are replaced by Transverse Latitude (TLT), Transverse Longitude (TLN), and Transverse Heading (THD), respectively.
2.3.4 ACCEPTING AND ENTERING POSITION FIXES. INS position resets are based on inertial position, an uncertainty area (system accuracy) deﬁned by INS sigma latitude (SN), sigma longitude (SE), and position ﬁx data. The estimated values of SN and SE increase with time but are decreased by the application of a position ﬁx. Entry of valid ﬁx data with suitable ﬁx variances should always improve system accuracy.
Forcing an incorrect reset will introduce a position error proportional to the reset error. This position error will propagate through the undamped Earth loop into position and attitude errors. Large position or attitude errors may cause the vertical loops to undamp and oscillate over a period of 84 minutes due to velocity errors.
2.3.4.1 Applying Fix Data as a Slew. For conditions where the system has operated for an extended

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term without a position update, the system sigma latitude and longitude values will have increased. Application of a single accurate ﬁx will produce a position reset that is approximately equal to the ﬁx error and will correct drift parameters. A single ﬁx may not update the position completely. If application of successive ﬁxes and gradual convergence of the Kalman ﬁlter to the correct position over time are not acceptable for tactical reasons, then the ﬁx data should be applied again as a slew.
2.3.4.2 Position Updates. Position updates are handled by the Kalman ﬁlter and can be applied as either position ﬁx resets or position slews, and are described as follows:
a. Position Fix. A position ﬁx will reset both position and drift coefﬁcients; however, the amount of position movement will depend on the weighting given to the ﬁx. This calculation is based on the system’s internal estimate of position and the ﬁx data. The effect of the ﬁx is calculated by the Kalman ﬁlter and can be displayed for review before acceptance. Fixes can be received via the data interfaces from an external source, such as GPS, or can be entered manually by the operator. Whether accepted automatically or entered manually, once the ﬁx reset is applied, its effects cannot be undone.
b. Position Slew. A position slew allows the operator to enter position data to update system position without causing a reset using the Mode menu, Slew function. This process resets the navigator’s position only to the entered ﬁx position but does not change Kalman ﬁlter parameters or underlying system drifts. Position slews can only be entered manually by the operator.
2.3.4.3 Accepting or Rejecting Fixes. The reset mode allows the operator to select how automatic ﬁxes are accepted or rejected, enables review of last accepted ﬁx data, and enables review and manual acceptance of pending ﬁxes that the system has rejected as unreasonable. The Fix Review mode can be selected from the Mode menu, Reset Mode function. The mode selected on this menu determines how the system involves the operator in the review and acceptance of ﬁxes from external position sensors. Manual ﬁxes can be entered into the system at any time using the Mode menu, Fix function. When ﬁxes are entered manually, the system checks the ﬁx data for reasonableness in the same manner as for ﬁxes received from external position sensors. If the manually entered ﬁx data is determined to be invalid, an appropriate fault code and a Reset Data menu are

displayed. This menu allows the operator to review the entered ﬁx data and either force acceptance or discard the data. At any time, the operator can review the data for the last position ﬁx accepted by the system. This function is selected from the Display menu, Page 3, Reset Data function. Figure 2-10 presents an outline of the various states associated with the position ﬁx functions.
2.3.4.4 INS Processing of a Position Fix. When a ﬁx is entered, either manually or automatically from a navigation aid such as GPS, the Kalman ﬁlter compares the inertially derived position with the available position reference (ﬁx) data. It operates on these measurements to generate corrections to the modeled system states. The process attributes navigational errors to sensor or system drifts, and then modiﬁes the Kalman parameters to neutralize the error pattern. Corrections are made to latitude, longitude, velocities, tilts, heading, gyro biases, non-reversing rotation rate biases, scale factors, misalignments, and horizontal accelerometer biases. The Kalman ﬁlter operates on the ﬁx as entered. Fix processing within the Kalman ﬁlter calculates the latitude and longitude resets using the difference between system position and ﬁx position. The Kalman ﬁlter calculates a weighting based on the estimate of system accuracy (SN and SE) as compared to the ﬁx accuracy, deﬁned by Fix Sigma North (FSN) and Fix Sigma East (FSE). This weighting is used to determine the proportion of the difference in position to be applied as the position reset. If a ﬁx is entered with a small sigma value (high accuracy), then a large percentage of the difference in position will be applied as a reset.
The difference between the INS (system) position and the ﬁx position does not determine the weighting. The weighting is determined by the estimated system accuracy and ﬁx accuracy. The estimated value of system error increases with time, but is decreased by the application of ﬁx data as a reset. This method results in a higher weighting being given to ﬁx data following a long navigate period, as compared to ﬁx data entered at relatively short intervals. The latitude and longitude weighting or gain (K) is calculated using the system sigma values at the time of ﬁx and the ﬁx sigma values [or the sigma values calculated from Radial Position Error (RPE) data], which are used as entered:
• K = (system sigma)2/[(system sigma)2 + (ﬁx sigma)2]
• FSN and FSE = 0.40854 x RPE

The north and east distances that the reset will move the INS position (DN and DE) are given by:
• Reset = K x (ﬁx position - system position)
2.3.4.5 Criteria for Acceptance of a Position Fix. When a position ﬁx is entered, the Kalman ﬁlter checks the ﬁx using the following limits:
(Position error)2 = (system lat - ﬁx lat)2 + [(system lonﬁx lon) x cos(ﬁx lat)]2
Error limit = 9 x (SN2 + FSN2 + SE2 + FSE2) + K (offset)
If (Position Error)2 is greater than the error limit, then an operator advisory (Fault Code 209) is announced, and the ﬁx is rejected and may be held for review. The INS resets for latitude, longitude, velocity, and various system feedback parameters are also checked using appropriate limits similar to the above limit on ﬁx position error. If a reset exceeds an error limit, then an operator advisory (Fault Codes 212 through 217) will be declared. The operator is alerted (using Fault Codes 218 through 222) to ﬁx data or a reset outside acceptable bounds. If the ﬁx data is unreasonable or if a reset exceeds a speciﬁed limit, the operator should then review the reset DN and DE (the north and east distances the reset will move the system solution) and either correct the ﬁx data or, if the ﬁx data is known to be accurate, accept it and force the reset.
2.3.4.6 Enhanced Performance Position Accuracy (EP2A). (Refer to Figure 2-11) The EP2A feature of the INS addresses the residual errors that remain in the INS position solution. The INS errors are characteristically slowly varying; e.g., the 84.4-minute Schuler period and the 24-hour earth loop. In contrast, the errors in the GPS aiding source are short period, typically on the order of seconds to minutes, and are more random in nature; e.g., ionospheric and multipath errors. The INS uses EP2A to estimate the current value of the slowly varying INS error and to “average out” the short-period GPS errors to provide a Real-time estimate of the correction to the Kalman-derived INS position:
EP2A is automatically applied to the INS position solution whenever the following conditions are satisﬁed:
• GPS is the selected position reference source.
• The GPS position is lever-arm corrected to the aiding INS.
• The INS operating mode is NAV or NAV-C.
• INS latitude is less than 89°.

• The INS reset mode is AUTO or AUTO/REVIEW.
• The INS is receiving continual GPS updates.
In the absence of GPS ﬁxes, or if the GPS position diverges from the INS position estimate by more than 200 meters, the EP2A ﬁlter is allowed to decay back to the Kalman ﬁlter position estimate. After a period of approximately 12½ minutes without GPS ﬁxes, the EP2A correction decays to zero, giving an INS estimated position that is equal to the Kalman ﬁlter estimate.
The Kalman ﬁlter solution is independent of, and unaffected by, the EP2A algorithm. The EP2A estimate is applied to the INS estimated position after the Kalman ﬁlter. The Kalman ﬁlter itself and other parameters estimated by the Kalman ﬁlter, such as velocity and attitude, are not affected by EP2A.
2.3.4.7 Reset Modes and Operator Acceptance of a Position Fix. The Reset mode (MODE Menu, Reset Mode function) deﬁnes the conditions for ﬁx entry and is set by the operator. The effect of the ﬁx is calculated and can be displayed for review before acceptance; but once the reset is applied, its effects cannot be undone. The operator may select from the following reset modes:
NOTE
Regardless of the Reset mode selected, all ﬁxes will be automatically accepted by the system during the ﬁrst 128 minutes when the system is being aligned At-Sea.
a. REVIEW Reset mode. An operator’s acceptance/rejection is required after review of the reset data. When a position ﬁx is received, the RLGN will prompt the operator by announcing a fault and by displaying Fault Code 221. To review and either accept or reject the ﬁx data, select DISPLAY menu, Page 3, Reset Data function.
NOTE
The ﬁx must be either accepted or rejected or the RLGN will not process new ﬁx data for 10 minutes.
b. AUTO REVIEW Reset mode. Position ﬁxes or resets that meet the error limit criteria are applied without operator review. Position ﬁxes or resets that do not meet the error limit criteria are held for operator review. When a position ﬁx or reset is rejected, the RLGN will prompt the operator by announcing a fault and by displaying a

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fault code. To review the out of limit ﬁx data, select DISPLAY menu, Page 3, Reset Data function. If the ﬁx is not reviewed within 10 minutes, the ﬁx data is discarded. Additional ﬁxes received during this time are not processed and may be overwritten by later ﬁxes.
c. AUTO Reset mode. Position ﬁxes or resets that do not meet the error limit criteria are not applied. Position ﬁxes that do meet the error limit criteria are applied to the INS without operator review.
Depending on the review mode selected, a rejected ﬁx may be entered by the operator. These functions allow the operator to force the acceptance of a good ﬁx to correct system errors. This is useful if a ﬁx is rejected as a result of errors in the system’s estimate of position. Care should be taken when manually entering or accepting a ﬁx that has been rejected. Acceptance of an unreasonable ﬁx introduces position errors and will cause calculations of position and velocity to diverge.
NOTE
Any position ﬁx for which the resulting radial position reset exceeds 5 NM should be reviewed closely before acceptance. Any ﬁx that exceeds the range of the latitude and longitude reset (DN and DE) display (± 100 NM) is immediately suspect.
2.3.4.8 Automatic Entry of a Position Fix. Fixes may be entered automatically via the Naval Tactical Data System (NTDS) data interface from a navigation aid such as the GPS. Using SENSOR menu, Page 1, toggle PDIG to ON. Depending on the Reset mode selected at the MODE menu, Reset mode function, these ﬁxes will be automatically accepted or rejected by the INS, or the operator will be prompted to review the ﬁx data and manually accept or reject the ﬁx (see above).
NOTE
Automatic position or speed inputs are not allowed when the INS is operating in Dockside mode.

2.3.4.9 Manual Entry of a Position Fix.
The RLGN will reject the manual ﬁx if the reset exceeds the error limits described in Paragraph 2.3.4.5. Care must be taken when manually accepting a ﬁx that has been rejected by the RLGN. Forcing acceptance of an unreasonable ﬁx introduces position errors and will cause the system calculations of position and velocity to diverge. A manual position ﬁx may be entered at any time when the RLGN is in the Navigate mode, even when navigation aids are selected for automatic entry of position ﬁxes. To perform a manual position reset (i.e., to enter a ﬁx), the operator must enter ﬁx time, latitude, longitude, and estimate of ﬁx accuracy (Sigma value of the ﬁx) in nautical miles. After the ﬁx data is entered through the display, the RLGN will not immediately use the data for reset, but will ﬁrst calculate the system parameters based on the ﬁx data. The operator must review the calculated effect of accepting the ﬁx by examining the delta (DN and DE) and sigma (FSN and FSE) latitude and longitude values. The operator then accepts or rejects the ﬁx data using the procedure described in Paragraph 2.3.4.10. If the operator does not accept or reject the ﬁx data, the RLGN will retain only the last accepted ﬁx. 2.3.4.10 Manual Fix Entry Procedure.
a. Press the <MODE> key and select Fix.
b. Current time is displayed and may be accepted by pressing the <ENTER> key

c. To enter any other time (up to a maximum of one hour in the past) press the <CLEAR> key and enter the ﬁx time in HH:MM:SS format.
d. Use the <BACK SPACE> key to eliminate keypunch errors.
e. Press the <ENTER> key to accept the entry. f. The display will now prompt for entry of ﬁx lati-
tude. Current system latitude is displayed, and may be accepted by pressing the <ENTER> key.
g. To enter a different value, press the <CLEAR> key and enter ﬁx latitude in DD°MM.mm′ format. Press the <NE+> key to enter the North Hemisphere, or the <SW−> key to enter the South Hemisphere.

h. Press the <ENTER> key to accept the entry. i. The display will now prompt for entry of ﬁx lon-
gitude. Current system longitude is displayed, and may be accepted by pressing the <ENTER> key.
j. To enter a different value, press the <CLEAR> key and enter ﬁx longitude in DD°MM.mm′ format. Press the <NE+> key to enter the East Hemisphere, or the <SW−> key to enter the West Hemisphere.
k. Press the <ENTER> key to accept the entry. l. The display will now present two options for en-
try of ﬁx error estimate, 1/North and East Error or 2/Radial Position Error.
Select one of the following options:

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In either of these ﬁx error estimate options, the Sigma values must reﬂect the true position ﬁx accuracy. Assigning a large Sigma to an accurate ﬁx will not disturb the INS, but the reset will have only a small correction on the system. On the other hand, assigning a small Sigma to an inaccurate ﬁx will disturb the system and result in position and velocity divergence. (1) North and East Error:
(a) Press the <1> key to select North and East Error format. The display will now prompt for entry of ﬁx Sigma North. Current Sigma North (SN) is displayed and may be accepted by pressing the <ENTER> key.
(b) To enter a different value, press the <CLEAR> key and enter ﬁx Sigma North (SN) in xx.x NM format.

(2) Radial Position Error:
(a) Press the <2> key to select Radial Position Error (RPE) format. RPE is equal to 95% Circular Error Probable (CEP). The CEP deﬁnes that circular area within which the actual ship’s position exists with a certain deﬁned probability. The RPE deﬁnes that probability as 95% (i.e., the size of the CEP is deﬁned by RPE such that there is a 95% probability that the ship’s position exists within the CEP). The display will now prompt for entry of RPE.
Current INS RPE is displayed and may be accepted by pressing the <ENTER> key.
(b) To enter a different value, press the <CLEAR> key and enter ﬁx RPE in xx.x NM format. Press the <ENTER> key to accept the entry. The INS now uses the RPE to calculate FSN and FSE.

o. If the ﬁx parameters are within the error limits, the RLGN will prompt the user with "REASONABLE."
If outside the error limits, the RLGN will prompt the user with "UNREASONABLE." In either case, choose one of the following options:
(1) Accept the ﬁx by pressing the <ENTER> key.
(2) Reject the ﬁx by pressing the <CLEAR> key.
(3) Do nothing and allow the ﬁx to be overwritten by the next incoming ﬁx. NOTE
The RLGN maintains a history of position data to allow ﬁx computations using the data obtained up to 60 minutes prior to the current time. Fault Code 218 will be declared if the ﬁx data is more than 60 minutes old. 2.3.4.11 Manual Position Slew Procedure.
a. Press the <MODE> key and press the <5> key to select RESET MODE.

c. Take a position ﬁx using the best available reference, usually a GPS ﬁx. Take a mark of position and note the exact GMT of the mark. NOTE Perform the following steps as soon as possible following the ﬁx taken in Step c. Accuracy of the slew will be degraded by time and ship’s maneuvering.
d. At the AN/WSN-7(V) keypad, press the <MODE> key.
e. Press the <3> key to select SLEW. Observe that GMT is displayed.

Press the <ENTER> key to accept the

entry. The display will now prompt for m. The display will now show the complete ﬁx

f. Press the <CLEAR> key. Enter GMT from Step

entry of ﬁx Sigma East (SE). Current

data, and prompt the operator to enter the ﬁx

c.

Sigma East (SE) is displayed and may be accepted by pressing the <ENTER> key.

by pressing the <ENTER> key or reject by

pressing the <CLEAR> key.

b. Use the <NE+> key or <SW−> key to toggle the

reset mode to REVIEW.

n. When the ﬁx data is correct, press the <EN-

(c) To enter a different value, press the <CLEAR> key and enter ﬁx Sigma

TER> key and the RLGN will calculate and display the reset parameters.

East (SE) in xx.x NM format. Press

the <ENTER> key to accept the entry.

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g. Press the <ENTER> key. Observe that LATITUDE is displayed.
h. Press the <CLEAR> key. Enter Latitude from Step c.
i. Press the <ENTER> key. Observe that LONGITUDE is displayed.
j. Press the <CLEAR> key. Enter Longitude from Step c.

k. Press the <ENTER> key. Observe that the new position as entered is displayed.
l. To reject the new position, press the <CLEAR> key. To accept the new position, press the <ENTER> key. Observe that Position is accepted.
2.3.4.12 Review Reset Data Procedure. You can review reset data for the most recent ﬁx, including ﬁx data, type of ﬁx (manual or GPS), and date and time of ﬁx. a. Press the <DISPLAY> key and press the
<NEXT PAGE> key until 3 of 5 appears in the lower right corner of the display.

b. Press the <5> key and select RESET DATA. The ﬁx latitude and longitude will be displayed, along with the ﬁx accuracy (FSN and FSE), and the type of ﬁx taken.
c. Press the <NEXT PAGE> key. The ﬁx day and time will be displayed.
d. Press the <NEXT PAGE> key again to display the system accuracy (SN and SE) and the difference in position (DN or DE).
e. Press the <NEXT PAGE> key again to display the time since the last reset.

2.3.5 SELECTING THE VELOCITY DAMPING MODE, SOURCE, AND FILTER. Velocity reference data is used by the Kalman ﬁlter to provide damping for the vertical (Schuler-tuned) loops. The velocity reference to be used by the system is selected by the operator and is available from external sources (speed logs or GPS receivers) via the data interfaces, or it can be entered manually. The selected velocity reference provides the Kalman ﬁlter with water speed or ground speed reference data in the ship’s coordinates (fore/aft and port/starboard) or geographic coordinates (north and east). If the port/starboard water speed is not available (as in the case of a single-axis speed log), an estimate of the port/starboard water speed is calculated using the inertial fore/aft velocity, heading rate, and side-slip coefﬁcient. If the Dockside mode is selected, the fore/aft and port/starboard ground speed used by the Kalman ﬁlter is set to 0.0 knots. The selected velocity reference (after log bias, lever arm, and side-slip corrections are applied) is resolved into appropriate components and compared with the inertial-derived velocities. The differences are multiplied by optimal gains in the Kalman ﬁlter and corrections are fed back into the vertical loops to achieve optimally damped loops. The Kalman ﬁlter controls the automatic selection of damping or undamping during turns or backing, or when there is a signiﬁcant discrepancy between log and inertial solutions. Automatic undamping and redamping are accomplished by applying accept/reject criteria to the ﬁltered inertial reference velocity differences.
2.3.5.1 Selecting Damped or Undamped Operation. Based on the selection of the damping mode (MODE menu, Damping function), damping of the horizontal velocity loops will either be automatically selected based on the ﬁltered velocity or will be manually selected to fully damped or fully undamped operation.
a. When Auto damping is selected, the system automatically selects damped (AUTOD displayed) or undamped (AUTOU displayed) mode based on comparison of the reference velocity with the system’s inertial velocity. As long as this corrected difference does not exceed the inertial limit, the system uses reference velocity to damp inertial velocities. If the corrected difference between the reference velocity and inertial velocity exceeds an internal limit, the system will automatically switch to undamped mode. Automatic damping (Auto selected) is the preferred mode since it provides velocity damping and minimizes the effects of ship’s speed reference errors due to ship maneuvers or other sources.

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b. When Man Damp is selected, the system is forced into the damped mode (MAND displayed) regardless of the reference comparison. The operator can use this function to force the system to accept data from the velocity source and keep the system damped. Selection of Man Damp can be used as an operator-selected reset if advisory Fault Code 223 is displayed, indicating that the system has remained undamped for an excessive period of time with Auto damping selected. Man Damp can also be used as an operator-selected reset when ship’s speed is being manually entered. Refer to Paragraph 2.3.7.5.
c. In addition, selection of Man Damp may be necessary whenever the ship is operating in an area of large gravity anomalies. Selecting Man Damp will prevent the system from going into undamped operation, induced by gravity changes in the system’s inertial velocity estimate.
d. When Man Undamp is selected, the system is forced into the undamped mode (MANU displayed) and velocity damping is inhibited regardless of the reference comparison. This function is useful if the system is in NAVIGATE mode and damping velocity is incorrect or not available from the selected device. An example of this condition would be the case where an Electromagnetic (EM) Log with a retractable sword is the selected damping source, but it cannot be used until operating depth permits. Another example of when Man Undamp is used is during ship high speed maneuvers.
2.3.5.2 Selecting the Horizontal Velocity Damping Reference. When automatic damping is selected, damping and undamping of the velocity loop is determined by the ﬁltered velocity differences. The system periodically tests the criteria for determining the damping mode, and it switches from damped to undamped operation whenever the ﬁltered velocity difference exceeds the set criteria.
The transition from undamped operation to damped operation will occur whenever the ﬁltered velocities’ differences have settled to within the set criteria. The available speed reference for velocity damping is determined by the system conﬁguration. The speed reference is selected on SENSOR Menu, Page 2. When multiple speed references are available, the selection for best operation is the following (in order):
1. Two- or three-axis GPS (best source)
2. Two- or three-axis Speed Log (water speed)
3. Single-axis Speed Log (water speed)

4. Manual speed (entered in the event of loss of all valid speed references)
2.3.5.3 Selecting the Horizontal Velocity Damping Filter. This function, selected from AUX FUNC menu Page 1, Sys Conﬁg, allows the operator to choose either Kalman or Third Order as the horizontal velocity ﬁlter. The default ﬁlter type is selected as an off-line conﬁguration. If Third Order is conﬁgured, Kalman can be selected on-line, or vice versa. The ﬁlter type selected on-line will remain selected only as long as the system is turned on. If the system is turned off, the conﬁgured default ﬁlter type will be automatically selected for use when the system is turned on again. Both the Kalman ﬁlter and the Third Order ﬁlter compare the difference between the inertial and reference velocity and generate a feedback, which is used to damp horizontal velocity errors at Schuler-tuned frequencies.
Each ﬁlter type provides essentially the same function when operating in Navigate mode, with the exception that Kalman provides light damping of Earth loop errors. Since Kalman provides the feedback for system align and calibration, regardless of the conﬁguration, Kalman is automatically selected at start-up and remains active until the system enters the Navigate mode. If Third Order is conﬁgured as the default ﬁlter or is selected by the operator using this function, the system will switch to Third Order only when it has settled and enters the Navigate mode. If the system exits Navigate mode while Third Order is selected, the Kalman ﬁlter will automatically be selected during the time that the Align mode is active. When the system returns to Navigate mode, Third Order will then be automatically reselected.
2.3.6 SELECTING DATA FOR DISPLAY.
NOTE
Data on the DISPLAY menu, Page 3, is associated with the position ﬁxes. This data is useful for reviewing parameters prior to selecting the Reset Data function to accept or reject ﬁx data when Review or Auto Review is selected for the Reset mode.
The operator can select any display of parameters and data in addition to the normal position, heading, velocity, day and time display. Display of additional parameters is not necessary for normal operation; however, selection of these display functions is useful for manually verifying data transmitted to external systems. Data is selected for display by pressing the <DISPLAY> key and selecting the PAGE with the parameters to be displayed. (See Table 2-2.)

2.3.7 OPERATING UNDER INTERFERING CONDITIONS. During on-line operation of the RLGN, interfering conditions such as fault conditions associated with hardware and software functions, I/O bus data input checks, I/O bus wrap-around testing, and Inertial Measuring Unit (IMU) functions may occur that require certain actions to be performed.
2.3.7.1 Acknowledging and Identifying Fault Conditions. At start-up and during operation, the RLGN BIT function continually monitors hardware and software functions and checks calculation results for reasonableness. In addition, the RLGN checks data input on the I/O bus and performs wrap-around testing of I/O outputs. Any fault condition detected by BIT is announced by a visual alarm. Each detected condition results in the generation of a fault code, which is stored in battery-backed RAM if the fault is still active when acknowledged for display and review. Based on the type of fault code displayed, the operator may acknowledge the fault by pressing the <ALARM ACK> key and choosing to continue system operation, or he may take the RLGN out of service for navigation. Certain faults automatically shut down the RLGN and cannot be overridden by the operator. The following list outlines the major fault classiﬁcations of interest to the operator:
1. Operator advisory fault codes inform the operator that manual intervention is required to review data or to select functions related to system operation. An example of an operator advisory is Fault Code 221 (Position Fix Waiting for Review).
2. Non-critical fault codes indicate that a fault condition exists that may be bypassed by changing operation modes or selecting other sensors, or by manual entry of data. Non-critical codes generally result from conditions which allow continued operation at reduced capability or at degraded performance levels. Non-critical faults may also result from a fault condition in the I/O, data messages, or in equipment external to the INS. An example of a non-critical code is Fault Code 45 (Loss of Vital Heading Synchro Reference).
3. Critical fault codes indicate that a fault condition exists that makes the INS unusable as a reference source. Critical faults may or may not result in automatic shutdown of the RLGN.
Appendix B provides a table listing all of the possible BIT fault codes and associated fault/status relay settings. Table B-1 indicates the source of the fault and the fault classiﬁcations. The table also provides di-

agnostic information and references off-line BIT to be performed to verify and troubleshoot the fault condition. In addition to the valid fault codes, several spare code numbers are listed. Spare codes are reserved for future expansion and will not be announced for fault conditions.
Fault and status indicators may also be installed external to the system. These can be controlled by fault and status relays (K1, K2, K3, and K7) to either illuminate or extinguish upon detection of the fault or status condition. (Refer to Figure 5-5, sheet 1.) Relay K1 functions as both a status and a fault relay. This relay initially remains reset when the system is in STANDBY to provide an external indication that the system is not ready, and then sets when the system enters the Align mode. The relay remains set unless a fault condition occurs.
2.3.7.2 Operating with System Faults. If a fault is detected during operation, the visual alarm is activated, and the fault code generated by the BIT function is displayed in the upper-right corner of the display. Before acknowledging each fault, ﬁrst record the displayed fault code number. For each fault condition, determine the fault type and proceed as follows:
NOTE
The fault codes are to be recorded in the event that the fault is intermittent. Only faults that are active at the time of acknowledgment are stored in battery-backed RAM; as such, they are available for review at another time.
Operator Advisory. Acknowledge advisory and perform required action.
Non-critical fault.
a. Acknowledge the fault by pressing the <ALARM ACK> key, and observe navigation system operation to determine if the fault is cleared or if the fault condition is again announced.
b. If the fault condition is repeated, acknowledge the fault and determine operating status or alternate mode for continued operation.
c. Record the fault code(s) displayed for future troubleshooting reference.
Casualty fault.

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NOTE
Faults in this category are associated with Inertial Measuring Unit functions. If a casualty fault is announced, the system will continue to operate using Dead Reckoning but will have degraded accuracy and functionality.
a. Acknowledge the fault by pressing the <ALARM ACK> key and observe RLGN operation to determine if the fault is cleared or if the fault condition is again announced.
b. If the fault condition is repeated, the system can continue operating for limited use.
c. Acknowledge the fault and determine operating status or alternate mode for continued operation.
d. Record the fault code(s) displayed for future troubleshooting reference.
e. Shut down the system and perform fault testing as soon as situation status allows.
Critical fault.
NOTE
Faults in this category indicate that further operation of the system is not advised.
a. Record all fault code(s) displayed for future troubleshooting reference. Turn off System Power switch and tag the RLGN OUT OF OPERATION.
b. Perform fault testing. (Refer to Chapter 5.)
RLGN automatic shutdown.
NOTE
Faults in this category automatically cause system power to be turned off.
a. Turn off System Power Switch and main Power Circuit Breaker and tag the RLGN OUT OF OPERATION.
b. Perform fault testing. (Refer to Chapter 5.)
The following paragraphs outline the recommended operator’s action with selected non-critical and casualty faults.
2.3.7.3 Source Alternating Current (AC) Power or Synchro Reference Fault. The RLGN contains an internal Power Supply (1A1A6), which provides

an output of +25 Volts, Direct Current (VDC) power during normal operation from the ship’s AC power source. The +25 VDC is distributed via the Terminal Junction System (TJS) to all end users. The Battery Charger (1A1A7) produces -25 VDC power using the +25 VDC as its input power under all conditions. The -25 VDC is also distributed via the TJS to all users on the bus. The Battery Charger also maintains the charge on the Battery Assembly (1A1A5) using the +25 VDC output from the Power Supply. The Inverter Assembly (1A1A2), which operates from the +25 VDC bus, generates 115 VAC, 400 Hz for the components on the vital synchro reference circuit as long as the RLGN is energized. In the event that the ship’s main power bus is interrupted or out of tolerance, the Battery Assembly, working through the Battery Charger, provides emergency ±25 VDC power for continuous operation. BIT functions on the Vital Bus Circuit Card Assembly (CCA) (1A1A3) monitor main AC power and non-vital reference supplied to the RLGN, and provide control that automatically turns off all non-vital synchro outputs in the event that a source power or non-vital synchro reference fault is detected. When the external power is reestablished within the correct limits, the RLGN automatically switches back to AC operation and restores non-vital synchro outputs.
2.3.7.3.1 Fault Code 034. In the event of loss of main 3-phase AC power, the RLGN can operate from its internal battery for approximately 30 minutes. To conserve battery power, the RLGN will discontinue output of synchro roll, pitch, and non-vital heading, but will continue to supply synchro Vital Heading and synchro Velocity (Vt, Vn and Ve) data and reference to the vital repeater(s) and velocity users.
2.3.7.3.2 Fault Code 037. Fault Code 037 indicates that the internal battery voltage is low. If the RLGN has been turned off for an extended period of time, allow it to operate for at least two hours to recharge the battery. If Fault Code 037 is detected during normal operation, or if the battery fails to charge to its normal level, the battery may require replacement. The RLGN will operate properly with this fault; however, it may not continue to operate in the event of a fault in the 3-phase AC power source.
2.3.7.3.3 Fault Code 045. A fault in the internally generated vital synchro reference Inverter Assembly (1A1A2) will result in loss of heading output to the synchro Vital Heading repeaters. Non-vital synchro heading, roll, and pitch output will continue to be valid; however, external systems that use synchro heading data from the vital reference will be affected.
2.3.7.3.4 Fault Code 046. In the event of loss of the non-vital synchro reference input, the RLGN will continue to operate normally from 3-phase AC

power. The RLGN will discontinue output of synchro roll, pitch, and non-vital heading, but will continue to supply synchro Vital Heading and synchro Velocity (Vt, Vn and Ve) data and reference to the vital repeater(s) and velocity users.
2.3.7.4 Indexer Faults (Code 043 or 044). An internal circuit fault, which results in loss of correct control of either the inner (azimuth) or outer (roll) indexer, causes the affected control loop to shut down. Since indexer rotation is provided primarily for alignment and mechanical canceling of drift offsets, the RLGN will continue to operate in a strapdown mode. In the event that Fault Code 043 or 044 is displayed, select the AUX FUNC Menu, Indexers function and reselect indexer operation. If the fault is repeated, Fault Codes 043 and 044 can be ignored until the RLGN can be turned off for repair conveniently. The RLGN will operate with a degradation of system performance.
NOTE
Attitude Comparison Limit Faults (Codes 384 through 386) may be announced if one RLGN in a dual system is operating with an indexer fault. Refer to Paragraph 2.4.10.
2.3.7.5 Speed Data Source Faults (Codes 036, 056, 057, 060, 061, 222, and 223). Loss of speed data or unreasonable speed input will cause the system to switch to undamped operation. Loss of log data can result from the selected velocity reference or speed sensor equipment being turned off or switched to a Test mode at the source. In installations where more than one synchro speed reference can be externally selected to provide the synchro speed input to the INS (such as synchro input from Rod 1 and Rod 2), loss of log may result from changing the external selection without the current externally selected source being selected at the INS.
If any of the indicated fault codes is displayed, it may be necessary to select a different velocity reference source or select manual entry of ship’s speed. If the system is operating with Auto damping selected, and if the computation of percent time undamped during the current 128-minute period exceeds 75% undamped, an operator advisory (Fault Code 223) will be displayed. This code alerts the operator to take corrective action. If the operator does not change the damping selection, the system will automatically go into the forced damped mode (AUTOD displayed) for the next 128 minutes using the currently selected speed data source as the velocity reference.

If Code 223 is displayed, the operator should review the status of the selected velocity reference source. If the selected velocity reference is found to be accurate, then the operator may elect to manually select forced damping of the system (select Man Damp) for approximately two hours and then return to Auto damping. If the operator ﬁnds that the selected velocity reference is not sufﬁciently accurate to provide velocity damping, then the operator should select SENSOR Menu, Page 2, and select a different source as the velocity reference. The operator should then select Man Damp for approximately two hours, or force undamping of the system (select Man Undamp). Undamp should be selected when velocity reference is not valid. Selecting either Man Damp or Man Undamp will reset the 128-minute comparison timer. If a correct data input source cannot be reestablished, select manual damping of the system (select Man Damp), select SENSOR Menu, Page 2, VMAN ON and manually input ship’s forward water speed from the keypad. Ship’s speed should be monitored by the operator, and the manually entered value should then be changed whenever the ship’s speed changes by more than ±10 percent from the set value or whenever manually entered speed is selected as the velocity reference source.
2.3.7.6 GPS or GPS I/O Faults (Codes 368 through 383). Failure of the GPS position sensor input to the INS will result in slow degradation in the accuracy of the estimate of position. Position performance degrades approximately as a function of the square root of time as shown in Figure 2-12. INS performance can be maintained by selecting a different position sensor (if conﬁgured for additional position sensor) or by periodically entering a position ﬁx manually. To manually enter position ﬁx data, select MODE menu, Fix function (refer to Figure 2-4). The chart in Figure 2-12 is shown for illustration of proportion only; no units are implied.
2.3.7.7 Position Fix and Velocity Reference Error Faults (Codes 209, 210, 211, and 212 through 217).
2.3.7.7.1 Fault Code 209. Fault Code 209 indicates that the position ﬁx data does not agree with the RLGN-calculated position within the system reasonableness bounds.

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Forced acceptance of correct position ﬁx data over a period of time will restore the INS to full navigation data accuracy; however, forced acceptance of incorrect position ﬁx data will quickly degrade navigation performance. It may be necessary to realign the INS to restore navigation accuracy if acceptance of an invalid position ﬁx has been force-accepted.
2.3.7.7.2 Fault Codes 210 and 211. These fault codes indicate that the reference velocity data does not agree with the RLGN-calculated velocity within the system reasonableness bounds.
2.3.7.7.3 Fault Codes 212 through 217. These fault codes indicate that a potential reset resulting from either position or reference velocity data is outside the system reasonableness bounds. If position data is outside the system reasonableness bounds and the position ﬁx was processed in a Review or Auto/Review mode, then the operator should review the data for correct latitude, longitude, ﬁx time, and ﬁx variance. If the data is found to be incorrect, then the operator can reject the ﬁx. If the data is found to be correct, then the operator can force acceptance of the ﬁx. The error codes will occur again on a forced acceptance of the position ﬁx. If reference velocity data is outside the system reasonableness bounds, the operator should review the provided velocity data during the time when faults are being reported (only multiple fault occurrences will degrade navigation performance). The RLGN may undamp if Auto damping is selected (refer to Paragraph 2.3.5.1). If reference velocity data is found to be invalid or noisy, then another velocity reference should be selected (refer to Paragraph 2.3.5.2). If reference velocity is found to be continuously valid, then the INS should be manually damped for approximately two hours, then returned to Auto damping. If the faults recur, the INS may need realignment using Dockside Align mode to restore full navigation accuracy.
2.3.7.8 External Serial Interface or I/O Processor Faults (Codes 240 through 246, 248, 250, 251, 253 through 257, 259, 262, 264, 266, 338, 347 through 351). Detection of a fault that results in any of the listed fault codes will cause the I/O Processor to shut down. While the RLGN may continue to operate normally and provide local display of data outputs of synchro format data, communications between the two RLGNs, input of GPS data, and all other input and output NTDS data messages will be halted. To restart the I/O Processor, proceed as follows:

NOTE
If the I/O Processor restart is successful, the "Enabled" message will change from ﬂashing to non-ﬂashing. If the restart is not successful, the "Enabled" message will continue ﬂashing.
a. Clear the fault code(s).
b. Press the <AUX FUNC> key and select I/O Restart.
c. Set the I/O Processor to Enabled.
d. If the fault condition is cleared by restarting the I/O Processor, normal operation can be resumed. If the fault condition recurs, press the <AUX FUNC> key and select I/O Conﬁg (refer to Paragraph 2.4.2), disable all interface ports, and then select the I/O Restart function to enable the I/O Processor.
e. If the fault condition is cleared, enable each interface port (one at a time), and check operation to determine if the fault is in the I/O communications interface port or in an external device.
f. If the condition cannot be corrected by use of the above procedures, shut down the RLGN (refer to Paragraph 2.3.8) and restart in the off-line Test mode so that troubleshooting can be performed to isolate and correct the fault condition. (Refer to Chapter 5.)
2.3.7.9 Common RAM Test Pattern Faults (Codes 019 and 252). Communication between the Navigation Processor and the I/O Processor functions are periodically checked by the exchange of a test pattern through the common RAM on Dual Port Memory CCA (1A1A23). The test patterns are alternately written into the common memory by the I/O Processor and read by the Navigation Processor, or written by the Navigation Processor and read by the I/O Processor. If the Navigation Processor detects a pattern error, Fault Code 019 is announced. If the I/O Processor detects a pattern error, and I/O data transfer capability permits, Fault Code 252 is announced. A repeated occurrence of either of these fault codes may indicate a bit fault in the common RAM or intermittent cable problems. I/O communication problems may exist which will be conﬁrmed by the occurrence of other I/O message-related fault codes.
2.3.7.10 Casualty Mode Faults (Codes 033, 100, 101, 102, 109, 188). The Casualty mode is deﬁned as the occurrence of a fault that would normally

cause system shutdown, but is not due to any processor error or condition that could prevent processor execution. If a fault occurs that sets the casualty mode bit, the Navigation Processor will continue to execute selected tasks to perform the Dead Reckoning function. Dead Reckoning computation is done using the operator-selected speed reference and the best available attitude data, which is RLGN attitude data when valid, or any gyrocompass data otherwise. Position data is not valid during Align/Calibrate or during operation in the Casualty mode. Output of attitude, velocity, and position will be provided from the Dead Reckoning function using input from external gyro heading and attitude reference and ship’s speed references.
When RLGN position data is valid (RLGN operating in Navigation mode), the RLGN position is used to update the Dead Reckoning position as a slew every 1.024 minutes and manual position data or data from a selected position reference is not used to correct the Dead Reckoning position. When the RLGN position data is not valid (RLGN operating in Align/Calibrate or Casualty mode), manually entered position data and position data from a selected position reference will be used to correct the Dead Reckoning position with manual position data having priority.
2.3.7.10.1 Faults Causing Casualty Mode Detection. If a casualty fault condition is detected at system power-up, the system will start up in the Casualty mode. Detection of any of the following faults will result in automatic selection of Casualty mode operation:
1. Fault Code 033. Loss of lower unit (IMU) synchro reference; (115 VAC, 400 Hz from Inverter Assembly 1A1A2).
2. Fault Code 100. IMU Calibration Programmable Read-Only Memory (PROM) Checksum error at system start-up 1A1A32U13.
3. Fault Code 101. Navigation Processor has detected two consecutive input errors in data from IMU Processor [I/O Control (BITE) and Filter CCA (1A1A31)].
4. Fault Code 102. Gyro dither frequency error (any gyro).
5. Fault Code 109. IMU synchro (1X and 36X inner gimbal or 1X and 36X outer gimbal) angles disagree by more than 5 degrees.
6. Fault Code 188. Failure of IMU Processor to re-enter background processing [Assembly (1A1A31)].

2.3.8 TURNING OFF THE INS. To de-energize the AN/WSN-7(V), proceed as follows:
NOTE
System serial numbers are read from calibration [Electrically Erasable Programmable Read-Only Memory (EEPROM)] each time the system is turned on and are compared with previously stored values. If numbers are different [indicating that service has been performed that changed one of the calibrated Lowest Replaceable Units (LRUs)], the system automatically reverts to uncalibrated status and performs a 72-hour self-calibration. Refer to Figures 2-5 through 2-7. Default settings for operation are determined by selections set on the Operator Conﬁguration menu in the Installation Conﬁguration; refer to Figure 8-12. The system reverts to Kalman as the default for velocity damping during alignment.
a. Note any fault codes indicated on the Display.
b. On the RLGN, set the SYSTEM POWER switch to OFF. Observe that the POWER indicator extinguishes.
When the SYSTEM POWER switch is set to Off, the RLGN saves all valid data and menu settings in battery-backed RAM to be used when it is again turned on. These include:
Last position (latitude/longitude and Transverse latitude/longitude)
System self-calibration (72-hour calibration) values
Log Calibration Table values
Kalman ﬁlter calibration data
Installation conﬁguration data
System serial numbers
c. On the RLGN, set the POWER, SYNCHRO REF, and VITAL REF circuit breakers to OFF.
d. If signiﬁcant maintenance is to be performed on the RLGN and personal safety is a factor, secure 115 VAC 60 Hz and 115 VAC 400 Hz power to the RLGN at the ship’s power panels, and tag out these breakers following standard tag-out procedures.

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2.4 OPERATOR’S MAINTENANCE.
2.4.1 OFF-LINE TEST MODE. This mode is selected by turning off the RLGN and then setting the SYSTEM POWER switch to ON while the <TEST> key is held depressed. When Test mode is selected, the RLGN cannot be used for navigation. Selection of the Test mode, available menus and associated built-in test functions is covered in Chapter 5. Installation Menus selected via this mode are described in Chapter 8.
2.4.2 ON-LINE NTDS INTERFACE PORTS SELECTION AND CONFIGURATION. This function, selected from AUX FUNC menu, I/O Conﬁg, is similar to the off-line I/O Bus Conﬁguration (refer to Chapter 8). Available menus allow the active status and operation parameters of the individual NTDS and Asynchronous Transfer Mode (ATM) input and output ports to be reconﬁgured during on-line operation. For an NTDS or ATM port to be reconﬁgured, the port must have been previously selected, as ﬁtted in the off-line conﬁguration. Changes to port conﬁgurations selected in the on-line I/O Conﬁg function are maintained in battery-backed memory when the system is turned off. The selected conﬁguration settings are used when the system is again turned on.
2.4.2.1 NTDS Port Conﬁguration Settings. The following listing outlines the selection and modiﬁcation of each NTDS port conﬁguration setting:
NOTE
The letter preﬁx on each port designation identiﬁes the physical location of the NTDS I/O board that contains the port set. Refer to Table 2-3.
"_1" ports are NTDS Type D or Type E serial input or Type A or Type B parallel I/O or ATM I/O port.
"_2" ports are NTDS Type D or Type E serial output ports.
a. NTDS Port = (port designation). Step function selects port to be enabled/ disabled or reconﬁgured (up to 16 maximum available).
b. Page 1:
(1) Port nn = ENBL/DSBL. Enables or disables selected port. The options listed on Pages 1, 2, and 3 of the menu function allow speciﬁc message protocol and data ﬁelds to be selected or enabled for each ﬁtted port, even if the port is selected as disabled.

(2) IDS = 00 through 31. The number displayed in this ﬁeld is a code that indicates the NTDS Interface Design Speciﬁcation (IDS) assigned to the port during system installation conﬁguration. Data in this ﬁeld cannot be changed from this on-line I/O Conﬁguration mode. The number 00 in this ﬁeld indicates that the selected port is not ﬁtted. Refer to Table 2-4 for the Port Speciﬁcation and Type indicated by each IDS number. Refer to Chapter 8 for the number listing of factory-conﬁgured I/O ports and settings.
(3) Retries = ENBL/DSBL. (Applicable to IDS 08, 09, and 10) If ENBL is selected, the I/O processor will repeat the output message one time if acknowledge is not received. If DSBL is selected, output message is transmitted only once.
(4) Secondary = ENBL/DSBL. (Applicable to IDS 14 and 15) For redundant I/O interface function, ENBL selected sets a message bit that identiﬁes status of the selected port (and data) to the receiving equipment as secondary.
c. Page 2:
(1) Day = ENBL/DSBL. (Applicable to IDS 11) If ENBL is selected, allows the RLGN to transmit Julian Day data to the OU-174/WSN-5 Data Converter Group. If DSBL is selected, the RLGN will not transmit Julian Day data over this connection.
(2) P Sen Fmt = AR57A/AS130. (Applicable to IDS 11) This setting determines the format (AR57A or AS130) for transmitting position change senescence data to the OU-174/WSN-5 Data Converter Group.
(3) Forced External Function (EF) = ENBL/DSBL. (Applicable to IDS 04, 08 and 11) If receiving equipment does not implement an EIE line to indicate that it is ready to receive data, selecting ENBL causes the parallel output data message to be transmitted regardless of EIE status.
(4) Parity = ENBL/DSBL. (Applicable to IDS 07, 09, and 10) Enables or disables message parity bit checking protocol for serial output.
d. Page 3:
(1) Nav Msg = ENBL/DSBL. (Applicable to IDS 04, 08, 09, and 10) Enables or dis-

ables the Navigation Data Periodic message transmitted at 1 Hz in the output data.
(2) Precision = HIGH (NORM). (Applicable to IDS 04, 07, 08, 09, and 10) Sets position data in the Navigation Data Periodic message precision to high or normal precision.
(3) Attd Msg = ENBL/DSBL. (Applicable to IDS 04, 08, 09, and 10) Enables or disables the Attitude Data Periodic message output data.
(4) Msg Rate = 8 Hz (16 Hz). (Applicable to IDS 04, 08, 09, and 10) Changes transmit rate for Attitude Data message.
2.4.2.2 Super Channel Settings (Applicable to IDS 13)
a. Page 1:
(1) Port nn = ENBL/DSBL. Enables or disables selected port. The options listed on Pages 1, 2, and 3 of the menu function allow speciﬁc message protocol and data ﬁelds to be selected or enabled for each ﬁtted port, even if the port is selected as disabled.
(2) IDS = 13. The number displayed in this ﬁeld is a code that indicates the Super Channel IDS assigned to the port during system installation conﬁguration. Data in this ﬁeld cannot be changed from this on-line I/O Conﬁguration mode. Refer to Table 2-4 for the Port Speciﬁcation and Type indicated by each IDS number. Refer to Chapter 8 for the listing of factory-conﬁgured I/O ports and settings.
(3) Ext Fix = ENBL/DSBL. If ENBL is selected, allows RLGN to accept a ﬁx from an external computer, other than GPS, over the Super Channel interface. If DSBL is selected, no external computer ﬁxes will be accepted.
(4) GPS Fix = ENBL/DSBL. If ENBL is selected, allows RLGN to accept GPS ﬁxes over the Super Channel interface. If DSBL is selected, no GPS ﬁxes will be accepted.
b. Page 2:
(1) Rmt Cntrl = ENBL/DSBL. If ENBL is selected, allows the RLGN to accept Remote Control input over the Super Channel interface. If DSBL is selected, no Remote Control input will be accepted.

(2) Vref Input = ENBL/DSBL. If ENBL is selected, allows RLGN to accept reference velocities over the Super Channel interface. If DSBL is selected, velocity references will not be accepted over the Super Channel interface.
(3) Attd Data = ENBL/DSBL. If ENBL is selected, allows the RLGN to accept backup attitude data over the Super Channel interface. If DSBL is selected, no backup attitude data will be accepted over the Super Channel interface.
(4) Waypoint = ENBL/DSBL. This setting is currently not in use. Should be set to DSBL.
c. Page 3:
(1) Depth = ENBL/DSBL. This setting is not used on surface vessels. Should be set to DSBL.
(2) Fcn 8 = ENBL/DSBL. Reserved. Should be set to DSBL.
(3) Fcn 9 = ENBL/DSBL. Reserved. Should be set to DSBL.
(4) Fcn 10 = ENBL/DSBL. Reserved. Should be set to DSBL.
2.4.2.3 ATM Port Conﬁguration Settings.
a. ATM Port = I. Step function selects port to be enabled/disabled or reconﬁgured.
b. Page 1:
(1) Port I = ENBL/DSBL. Enables or disables selected port. The options listed on Pages 1, 2, and 3 of the menu function allow speciﬁc message protocol and data ﬁelds to be selected or enabled for each ﬁtted port, even if the port is selected as disabled.
(2) IDS = 16. Number displayed in this ﬁeld is a code that indicates the ATM IDS assigned to the port during system installation conﬁguration. Data in this ﬁeld cannot be changed from this on-line I/O Conﬁguration mode. The number 00 in this ﬁeld indicates that the selected port is not ﬁtted. Refer to Table 2-4 for the Port Speciﬁcation and Type indicated by each IDS number. Refer to Chapter 8 for the listing of factory-conﬁgured I/O ports and settings.

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(3) Ext Fix = ENBL/DSBL. If ENBL is selected, allows RLGN to accept a ﬁx from an external computer, other than GPS, over the ATM interface. If DSBL is selected, no external computer ﬁxes will be accepted.
(4) GPS Fix = ENBL/DSBL. If ENBL is selected, allows RLGN to accept GPS ﬁxes over the ATM interface. If DSBL is selected, no GPS ﬁxes will be accepted.
c. Page 2 :
(1) Fcn 3 = ENBL/DSBL. Reserved. Should be set to DSBL.
(2) Vref Input = ENBL/DSBL. If ENBL is selected, allows RLGN to accept reference velocities over the ATM interface. If DSBL is selected, velocity references will not be accepted over the ATM interfaces.
(3) Attd Data = ENBL/DSBL. If ENBL is selected, allows the RLGN to accept backup attitude data over the ATM interface. If DSBL is selected, no backup attitude data will be accepted over the ATM interface.
(4) Fcn 6 = ENBL/DSBL. Reserved. Should be set to DSBL.
d. Page 3:
(1) Depth = ENBL/DSBL. If ENBL is selected, allows RLGN to accept depth inputs via the ATM interface. If DSBL is selected, depth will not be accepted over the ATM interface.
(2) Battle Force Tactical Training (BFTT) Input = ENBL/DSBL. If ENBL is selected, RLGN will accept BFTT data over the ATM interface and will distribute simulated data to NTDS I/O as instructed by BFTT port selection. If DSBL is selected, RLGN will not accept BFTT simulated data. Users will only receive real data.
(3) Grav Grad = ENBL/DSBL. If ENBL is selected, RLGN will accept Gravity Gradient data for vertical deﬂection compensation over the ATM interface. If DSBL is selected, gravity gradient data will not be accepted over the ATM interface.
(4) Sea/Submarine Launched Cruise Missile (SLCM) Input = ENBL/DSBL. If ENBL is selected, RLGN will accept the SLCM enable/disable message over the ATM inter-

face. SLCM enable/disable is applicable to submarine systems only.
2.4.3 ON-LINE LOG CALIBRATION. (Refer to Figure 2-4.) Like other conﬁguration and calibration data, log bias data entered using the off-line functions associated with calibration of the Electromagnetic (EM) Log(s) is initially stored and maintained in EEPROM (KENV) on Status and Command CCA (1A1A15). Unless changed, the values (stored in two log bias calibration tables) are maintained as the backup values for initializing the system. Copies of this data are also stored in two log bias calibration tables, which are maintained in battery-backed RAM on Nav Processor CCA (1A1A13). The data maintained in the battery-backed RAM is used by the Navigation Processor to correct speed data received from the selected EM Log during operation. On-line functions allow the values stored in batterybacked RAM to be examined, cleared, or selectively changed using on-line log calibration functions.
2.4.3.1 Changing Log Bias Calibration Tables. Currently, two functions are available for changing the log bias calibration tables. These are a semi-automatic procedure and a fully automatic procedure.
2.4.3.1.1 Semi-Automatic Procedure. The semi-automatic Log Calibration procedure requires at-sea calibration runs, which prompt changes to ship’s heading and speed. Correctly followed, this procedure generates log bias calibration values at four-knot increments for the selected EM Log. After being accepted, these values remain ﬁxed and are used for calibrating input speed during all subsequent operation.
2.4.3.1.2 Fully Automatic Procedure. The fully automatic Log Calibration mode can be selected to continuously generate bias calibration values for the selected EM Log. This mode continuously changes the values stored in battery-backed RAM based on speed and heading data processed by the Kalman ﬁlter. Bias data is updated automatically and current data is used for calibrating input speed at any given time. Once a manual calibration has been accomplished as in Paragraph 2.4.3.1.1, then this is the preferred mode (refer to Paragraph 2.4.5.2).
2.4.3.1.3 Battery-Backed RAM. Whether the semi-automatic or the automatic Log Calibration procedure is used, if the system is turned off, values stored in battery-backed RAM are used when the system is again turned on. To ensure against loss of the bias values if the battery is removed (loss of 6 VDC to the battery-backed memory), the contents of the log bias calibration tables in battery-backed RAM can be transferred to the non-volatile EEPROM (KENV) (refer to Paragraph 6.2).

2.4.4 ON-LINE LOG CALIBRATION (SEMI-AUTOMATIC PROCEDURE). (Refer to Figure 2-13.)
NOTE
When performing this procedure, the system must be settled and damped with the EM Log to be calibrated selected as velocity input. During each calibration run, the ship must maintain a steady course at the calibration speed for at least four minutes; it must then perform a heading change between 80 and 280 degrees; and it must then maintain the new course at the calibration speed for at least four additional minutes. Up to 10 speed calibration bias values may be determined and stored by repeating this procedure.
This function, selected from AUX FUNC menu Page 2, Log Cal, is similar to the bias calibration selected from the off-line Velocity Reference Devices conﬁguration (refer to Chapter 8). The difference is that menus are provided that prompt the sequence for entry of run speeds, time, and heading changes during the bias calibration procedure, and the system calculates the bias value for correcting the input data for each selected speed. This function operates independently of the Velocity Bias Calibration, which is used in the off-line System Conﬁguration to manually enter calibration bias values for the EM Log(s). When Log Cal is selected and performed on-line, the on-line copy of the calibration bias tables for the selected EM Log (Rod 1 or Rod 2) velocity references can be changed.
2.4.4.1 Procedure. To perform the on-line Log Calibration, proceed as follows:
a. With either Rod 1 or Rod 2 selected as the Velocity Reference Device, press the <AUX FUNC> key.
b. Press the <NEXT PAGE> key until Page 2 is displayed.
c. Press the <5> key to select the Log Cal function.
d. When the ship has reached the ﬁrst calibration run speed, manually enter the ship’s current speed for the calibration run.
e. Maintain steady course at the selected speed, and press the <ENTER> key to start the measurement for the ﬁrst phase of the calibration run.
f. After four minutes, the menu will prompt a heading change. Turn to a new heading at least 80

degrees (but less than 280 degrees) from the current heading.
g. When the ship is settled on the new heading, press the <ENTER> key to start the measurement for the second phase of the calibration run.
h. After four minutes, the menu will display the Log Bias for the calibration speed. At this point the bias value can either be accepted by pressing the <ENTER> key, or rejected by pressing the <CLEAR> key.
i. Repeat the calibration for up to 10 different speeds that incrementally cover the operating speed range of the ship.
NOTE
In the event that a calibration is performed on the EM Log, and the Bias potentiometers are adjusted, the AN/WSN-7(V) LogCal Biases need to be zeroed, or a new on-line EM Log calibration must be performed to maintain system performance.
2.4.4.2 System Damping. The system must be damped while the Log Calibration is collecting data. If the system is undamped upon entry, an alarm will be generated and the calibration will be aborted. If the system becomes undamped before phase two is started, an alarm will be generated and the calibrate function will wait until the system becomes damped before permitting phase two to be started. The system may go undamped before phase two begins due to the required maneuver. During on-line Log Calibration, an alarm will be generated and the calibration will be aborted if the operating parameters are outside certain limits. Conditions that will cause an alarm and abort the calibration could be any of the following:
1. Actual speed differs by more than two knots on the two legs.
2. Heading change not within the range of >80 and <280 degrees.
3. Heading change greater than 5 degrees during 4-minute period while calibration data is being taken.
4. More than 15 minutes elapsed between end of ﬁrst measurement period and start of second measurement period.
2.4.5 ON-LINE LOG CALIBRATION (AUTOMATIC PROCEDURE). (Refer to Figure 2-13) This function,

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selected from MODE menu, LogCal Mode, generates EM Log bias calibration values by using the Kalman ﬁlter to process data from the selected speed sensor (Rod 1 or Rod 2). Calibration bias values generated by the online LogCal mode modify the speed calibration bias tables in battery-backed RAM. These values overwrite any values previously stored in the log bias calibration tables, including those generated using the semi-automatic LogCal function described in Paragraphs 2.4.4, 2.4.4.1, and 2.4.4.2.
2.4.5.1 Monitoring and Clearing Log Bias Values. (Refer to Figure 2-13) The log bias values for Rod 1 and Rod 2 currently stored in battery-backed RAM can be examined at any time by selecting Show Biases ROD1(2) functions on the DISPLAY, page 2, Log Biases menu. If it is determined that existing stored log bias values are grossly in error, all values in the log bias calibration tables can be independently cleared of all bias data by selecting the Clear Biases ROD1(2) functions.
2.4.5.2 LogCal Mode. Unlike the bias values that have been determined and entered in the calibration bias tables as a result of running planned maneuvering and speed calibration runs, the automatic LogCal mode continuously monitors ship’s speed and heading. Using ﬁltered values, the mode continuously updates the bias values for those speeds at which valid data samples are available. This log calibration mode provides the advantage that when the LogCal mode is selected, the bias calibration is optimized for the speeds at which the vessel most normally operates. The drawback is that log bias calibration values are not generated for speed ranges at which the vessel has not been operated during the time when the LogCal mode is selected. For this reason, it may be advisable to initially correct the log bias calibration values as near as practical for the full range of ship’s speeds using off-line function for manual data entry or to perform the on-line semi-automatic procedure. The ship can then be successfully operated in the LogCal mode.
2.4.5.3 Maintaining Log Bias Values. The last stored log bias values generated by this mode are maintained in battery-backed RAM when the system is turned off or when the LogCal mode is selected Off. These values are used when the system is again turned on.
2.4.6 ON-LINE SYSTEM PERFORMANCE MONITOR FUNCTION. This function, selected from AUX FUNC menu Page 3, Performance Monitor, allows navigation performance to be monitored periodically

while the system is operating on-line in a dynamic environment. The function provides menus for setting the length of time that the monitoring function is enabled, and for presenting calculated system performance parameters as a percentage of the speciﬁed performance.
2.4.6.1 Operation While Monitoring Performance. Running the Performance Monitor function does not affect the navigational performance of the system during the monitoring period; however, the ﬁrst position ﬁx after the Performance Monitor function is activated is applied as a position slew to update the system’s position to the reference position. Additional position ﬁx data received by the system during the time that the Performance Monitor function is active is only used for comparison with system-determined position and is not applied as a position ﬁx update.
2.4.6.2 Conditions for Monitoring Performance. The Performance Monitor function is normally selected with the ship at dockside (DOCK ON) and the dockside position data is used as the performance comparison reference during the monitoring time. The Performance Monitoring function can also be selected while the ship is operating at sea, provided that the operating environment permits accurate position data to be received at least once every 10 minutes during the time that the Performance Monitor function is to be active. If position data is not received by the system within the time limit, the Performance Monitor function will automatically terminate and advisory Fault Code 399 will be displayed.
2.4.7 TURNING ON THE PERFORMANCE MONITORING FUNCTION. Proceed as follows:
NOTE
Ensure that all external position sensors on Page 1 of the SENSOR menu are selected to OFF prior to turning on the performance monitoring function.
a. Press the <AUX FUNC> key.
b. Press the <NEXT PAGE> key until Page 3 is displayed.
c. Press the <2> key to select Mon Perform.
d. Press the <2> key to select Monitor Data.
e. When the Performance Monitor function is selected, make the following menu selections to start the monitoring mode:

(1) Select AUX FUNC menu Page 3, Performance Monitor. The display will change to Performance Monitor menu.
(2) Press the <1> key to select MONITOR = ON. The function will toggle ON only when the system is fully calibrated, aligned, and in damped Navigate mode, with a valid velocity reference selected. When the monitor function is turned on, a menu will be displayed which allows the operator to enter the length of time that the monitor function will run.
(3) Length of Time to Monitor: (1-336) HRS - Press the <CLEAR> key to clear time and then enter new value in the speciﬁed range.
f. After Length of Time has been entered, select SENSOR menu Page 1 and select the position reference sensor. DOCK ON, PDIG, and SLAVE are the only choices indicated when the Position Monitor function is turned on. DOCK ON should be selected only when navigating at dockside.
If PDIG is used as the sensor and degrades beyond a Figure of Merit (FM)-03, then the performance monitoring function will be disabled.
g. To monitor system performance data, again select AUX FUNC menu Page 3, Performance Monitor. Then select 2 Monitor Data. While the Performance Monitoring function is active, three pages of performance data with the following information are provided:
Page 1:
Monitor Start Time
Monitor Elapsed Time – Total time that Performance Monitor function has been running.
Page 2:
POS SOURCE – Indicates Position Source selected on SENSOR menu when the Performance Monitor function was initiated.
TRMS position error – Indicates the Time Root Mean Square (RMS) value of the position error,

as calculated from the start time of the Performance Monitor function, as a percentage of a normalized system speciﬁcation value. For an explanation of TRMS calculation method, refer to Figure 2-14.
Page 3:
RMS Velocity North – Indicates RMS value of the north/south velocity for the elapsed monitor period as a percentage of a normalized system speciﬁcation value.
RMS Velocity East – Indicates RMS value of the east/west velocity for the elapsed monitor period as a percentage of a normalized system speciﬁcation value.
NOTE
RMS Velocity will only be calculated for DOCK reference.
2.4.8 TURNING OFF THE PERFORMANCE MONITORING FUNCTION. The Performance Monitor function will end automatically when the selected elapsed time has been completed. To turn off the Performance Monitor function at any time, select AUX FUNC menu, Page 3, Performance Monitor, and set MONITOR = OFF. When the Performance Monitor function is terminated, the MODE function Reset mode selection defaults to AUTO/REVIEW (AUTO accept of reasonable position ﬁxes and operator REVIEW of unreasonable position ﬁxes) and the selected position reference remains valid. All further valid position ﬁx data are applied to the system as position ﬁxes.
2.4.9 PERFORMANCE MONITORING FAULT CODES. If the position reference becomes invalid or is not selected when the Performance Monitor function is selected, or if system performance is determined to be out of speciﬁcation during running of the function, fault codes will be announced. These codes are Operator Advisory and do affect system operation. Possible fault codes are as follows:
• Fault Code 395. Position variance greater than normalized speciﬁcation value.
• Fault Code 396. RMS East-West Velocity greater than normalized speciﬁcation value.
• Fault Code 397. RMS North-South Velocity greater than normalized speciﬁcation value.
• Fault Code 398. TRMS Position greater than normalized speciﬁcation value.

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S9427-AN-OMP-010/WSN-7

• Fault Code 399. No Position Reference available.
2.4.10 ON-LINE ATTITUDE COMPARISON LIMIT AND FILTER TIME CONSTANT ADJUSTMENT. These functions, selected from AUX FUNC menu, Page 1, Key 2 and menu, Page 3, Key 1, allow the operator to change the threshold and ﬁlter settings used for determining the difference allowed in attitude output between the two inertial navigators in a dual installation. These functions override the default settings selected at installation through the Operator Conﬁguration Function Selections (refer to Paragraph 8.7.4). Values set on-line by the operator remain in effect only until the system is turned off. Whenever the system is turned off and is then restarted, the installation-selected values are restored as the default settings.
2.4.10.1 Purpose of Functions. These functions are provided so that the threshold can be changed to prevent false alarms from being announced as a result of the installation values being set at too tight a tolerance for current ship dynamics, such as during heavy weather conditions.
2.4.10.2 Operator Advisory Fault Codes. Due to ﬂexing of the ship and different local dynamics resulting from mounting position with respect to the ship’s heading, roll, and pitch axis, if the Attitude Comparison Threshold is set too low or if the Filter Time Constant is too short, attitude difference fault codes may be announced even though both inertial navigators are operating independently within speciﬁcation. These codes are Operator Advisory and do not affect system operation. Possible fault codes are as follows:
• Fault Code 384: Heading; RLGN No. 1 and No. 2 disagree by greater than Attitude Comparison Threshold.
• Fault Code 385: Roll; RLGN No. 1 and No. 2 disagree by greater than Attitude Comparison Threshold.
• Fault Code 386: Pitch; RLGN No. 1 and No. 2 disagree by greater than Attitude Comparison Threshold.
2.4.11 DR DATA OUTPUT FUNCTION. The Dead Reckoning (DR) data output function is selected from AUX FUNC menu, Page 3. This function allows the operator to select either navigation system inertial data (NAV) (normal operation), or DR data as the output to data users. The inertial navigator defaults to NAV inertial data output whenever the system is turned on. This is the data output that normally remains selected.

Three menu control/display functions are provided. These functions allow the operator to:
1. View the current DR data and review its validity (Display menu, Page 4, DR Data).
2. Select output of either NAV inertial data from the selected navigation system, or, select DR data output to users (AUX FUNC menu, Page 3, NAV/DR Out).
3. Reset the DR position either to the navigation system position, or, to manually enter a DR position reset (AUX FUNC menu, Page 3, DR Position Reset).
Depending on the system conﬁguration, an external heading reference is input to the inertial navigator either directly as synchro heading from a gyrocompass, or, as digital (IDS 020) data from the Ship’s Control System (SCS) via a NTDS Type B interface. When available, the external heading reference source is used to resolve the selected velocity for DR data calculation. Regardless of whether DR data is currently selected for output, the navigation system continually calculates DR data from the selected velocity resolved about the heading. If GPS is selected as the velocity reference (surface operation) then the DR is driven from the GPS Vn and Ve velocity.
When DR data is selected for output, heading, roll, and pitch outputs are passed through the navigation system from the external gyro source. If an external heading source is not available, the navigation system calculates DR data from the selected velocity resolved about its own inertial generated heading. Heading, roll, and pitch outputs will also be the inertial quantities. Since inertial attitude is not valid until the navigation system reaches ALIGN-C, DR data cannot be calculated under this condition until ALIGN-C is reached.
The ﬁrst time that DR data is selected for output, an asterisk will be displayed on the DR Data function. This indicates that the DR position has not been initialized. If an asterisk is displayed at any time when DR Data output is selected, the operator must select the DR Position Reset function and initialize the DR position data. Once initialized, the DR data will remain valid until there is no valid heading reference (or loss of GPS input if GPS is the selected velocity reference). If DR data becomes invalid, an asterisk will again be displayed.

NOTE
During SLAVE align, the source of Vref from the system being slave aligned will always be Vn and Ve from the other system and not from EM Log resolved about heading.
2.4.12 VIEWING MEMORY CONTENTS. The contents of each memory location in the Navigation Processor can be inspected while the system is operating on-line. This function, selected from AUX FUNC menu Page 2, is incorporated into the operating program primarily to assist software development and has no operation or maintenance signiﬁcance for the level of information addressed by this technical manual. To inspect Navigation Processor memory, proceed as follows:
NOTE
The contents of memory locations cannot be changed using this function.
a. Press the <AUX FUNC> key.
b. Press the <NEXT PAGE> key until Page 2 is displayed.
c. Press the <6> key to select Mem Inspect.
d. Follow menu prompts to select the memory type (16- or 32-bit).
e. Enter the address (in hexadecimal) of the ﬁrst memory location to be inspected.
f. To step up or down sequentially through the memory address, press the <NE+> key or <SW−> key.
g. To change to a new starting address, press the <CLEAR> key, select the change address function, and enter a new starting address.
2.4.13 ON-LINE SIMULATED ATTITUDE, VELOCITY, AND POSITION OUTPUTS. The on-line Simulated Outputs function is similar to the off-line Simulated Outputs function described in Chapter 5. This function provides a means of generating static output data values from the RLGN while the unit is operating in a normal mode. This function is available for checking the operation of external systems that receive data from the RLGN. The simulated values are applied on all applicable conﬁgured synchro and digital I/O functions. When the Simulated Outputs function is selected, a status bit is set in all output NTDS

messages and simulate relay 1K6 is set (energized) to indicate to the receiver that the data is simulated. To select and enable the simulated outputs functions, proceed as follows:
a. Press the <AUX FUNC> key.
b. Press the <NEXT PAGE> key until Page 3 is displayed.
c. Press the <1> key to select Simulated Outputs.
d. Observe that the Simulated Outputs Menu is displayed.
NOTE
This menu provides an enable/disable toggle function for the simulated outputs and provides three categories of menus which may be selected for setting the output data values. Displayed functions are:
• Enable Simulated Outputs = ON (or OFF)
• Modify Attitude Output
• Modify Velocity Output
• Modify Position Output
e. At the Simulated Outputs Menu, if Enable Simulated Outputs is set to OFF, press the <1> key to toggle the selection to ON.
f. Select the applicable category of operation functions the <2> key, <3> key, or <4> key.
g. When any category of operation functions is selected, a list of associated parameters will be displayed. To change the value of any parameter, press the number key corresponding to the number of the parameter. (The display will indicate the currently set data value for the parameter and the bottom line will display "ENTER to accept, CLEAR to reject.") To change the data, press the <CLEAR> key. (The data value will change to a data entry ﬁeld to allow entry of a new value and the operator entry will be echoed directly into the ﬁeld). After the new value has been entered, press the <ENTER> key.
Table 2-5 provides a brief outline of the simulated output settings associated with each of these functions.

2-18

Table 2-1. Keypad Control Functions

KEY

FUNCTION

Menu Selection keys consist of:

MODE

Selects Page 1 of Mode Menu.

AUX FUNC

Selects Page 1 of Auxiliary Functions Menu.

SENSOR

Selects Page 1 of Sensor Menu.

DISPLAY

Selects Page 1 of Display Menu.

TEST

Selects Page 1 of Self-Test Functions Menu. (Functions only during power-up)

NEXT PAGE

Sequentially selects display of additional menu pages for each function.

Data Entry keys consist of:

0 through 9

Selects numbered function on displayed menu and used to enter numeric data.

A through F

Alternate function reserved for entry of hexadecimal values. (Hexadecimal entry is not active in normal operating modes.)

CLEAR

Clears displayed or manually entered data without entering the value.

ENTER

Accepts displayed or manually entered data for entry into selected function.

BACK SPACE

Erases last entered numeric character for re-entry.

N/E+

Enter North (N) or East (E) for position or positive (+) for numeric values requiring sign.

Table 2-2. Operating Menus/Functions Description

PAGE FUNCTION

BRIEF DESCRIPTION

NOTE

In the following table, functions indicated with an asterisk (*) are displayed on the menu when Field Change 3 has been accomplished, but are not available for use until Field Change 4 has been accomplished.

Items with a double asterisk (**) are displayed on the menu only if installation conﬁguration settings indicate that the function is installed and is available for use. Refer to Chapter 8 for installation conﬁguration setup.

Items with a triple asterisk (***) are displayed on the menu only if Field Change 4 has been accomplished.

SENSOR Functions

SENSOR control functions are associated with selecting the alignment reference source upon startup, selecting and/or manually entering the position reference, and selecting and/or entering the speed and depth references. SENSOR control functions are presented and accessed via three display menu pages.

Page 1 of the SENSOR menu provides control functions associated with selecting the RLGN alignment source.

1 1. DOCK

OFF: Disables Dockside data as the position.

S9427-AN-OMP-010/WSN-7

Table 2-1. Keypad Control Functions - Continued

KEY

FUNCTION

S/W–

Enter South (S) or West (W) for position or minus (-) for numeric values requiring sign.

Display Control keys consist of:

TRACK/HOLD

Toggle on/off function used to freeze display of any continuously changing data which is selected for viewing.

BRIGHT

Increases display illumination.

DIM

Decreases display illumination.

ALARM ACK

Removes the fault code from the display and clears the Advisory Relay and the Malfunction Relay when a fault condition is detected.

The general procedure for key/menu operation is:

1. Press a Menu Selection key (MODE, AUX FUNC, SENSOR or DISPLAY) to select the menu with desired function.

2. If selected menu has more than one page, press the <NEXT PAGE> key to step through pages (page display sequence cycles back to Page 1 after last page is displayed).

3. When function is located, press the Number key corresponding to number beside function to select the function.

4. If data entry is required, either press the <ENTER> key to accept displayed value or press the <CLEAR> key to clear displayed value for entry of new value.

5. Enter value using Data Entry keys and press the <ENTER> key to accept value. Correct error during data entry using the <CLEAR> key or the <BACK SPACE> key.

PAGE

Table 2-2. FUNCTION

2. PDIG

3. SLAVE

4. BFTT OFF/ON*

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
ON: Enables Dockside data as the position and inputs zero velocity reference.
OFF: Disables GPS input (PDIG) (via dedicated NTDS interface), and allows data from an External Computer (selected NTDS interface data from port other than GPS interface) as the digital position sensor source.
ON: Enables GPS input (PDIG) (via dedicated NTDS interface) as the digital position sensor source.
OFF: Disables the second RLGN as the position reference for the ﬁrst RLGN.
ON: (after alignment of second RLGN): Enables the second RLGN as the position reference for the ﬁrst RLGN.
ON: (prior to alignment of second RLGN): Initiates at-sea alignment within the second RLGN.
OFF: Disables operator command to “quickly abort” transmission of BFTT Simulated data.
ON: Enables operator command to “quickly abort” transmission of BFTT Simulated data.

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S9427-AN-OMP-010/WSN-7

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

Page 2 of the SENSOR menu provides control functions associated with selecting the RLGN’s velocity reference used to damp the velocity loop.

2 1. VMAN

Displays current value set for manually entered ship’s speed.

OFF: Disables manual speed input to the navigation processor.

ON: Enables manual entry or change of fore or aft speed value.

2. VSYN

OFF: Disables a conﬁgured synchro velocity input to be selected as the speed data source.

ON: Enables a conﬁgured synchro velocity input to be selected as the speed data source.
NOTE

If more than one synchro velocity source is available (e.g., Rod1 and Rod2 EM Log), it may be necessary to switch external equipment to provide the correct data to the RLGN synchro velocity input.

3. VDIG **

OFF: Disables a conﬁgured, digital velocity input as the speed data source.

ON: (INS conﬁgured for digital speed input via NTDS or ATM interface): Enables a conﬁgured, digital velocity input as the speed data source.

Page 3 of the SENSOR menu (normally conﬁgured only for submarine installations) provides control functions associated with selecting the depth sensor source and vertical velocity reference to be used.

3 1. DMAN **

Displays current value set for manually entered ship’s keel depth below the surface.

MAN OFF: Disables the manual depth input to the navigation processor.

MAN ON: Enables manual depth data input and change to the navigation processor.

2. DDIG **

OFF: Disables depth data input from digital depth sensor for RLGNs conﬁgured to accept digital depth input.

ON: Enables depth, data input from digital, depth sensor for RLGNs conﬁgured to accept digital depth input.

3. Vertical Velocity OFF: Disables vertical velocity input on RLGNs conﬁgured for a three-axis, digital speed and depth input. Enables or disables the vertical velocity input.

ON: Enables vertical velocity input on RLGNs conﬁgured for a three-axis, digital speed and depth input. Enables or disables the vertical velocity input. Horizontal velocity inputs are not affected.

Functions on Page 4 of the SENSOR menu are used for selecting a heading source and entering heading data during High Latitude ALIGN.

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

4 1. HMAN

Operator may manually specify a normal or transverse coordinate

OFF/NORM/TXVS heading. Used if no other heading source is available. Manual input

***

of heading may be necessary during High Latitude ALIGN, if the

backup compass is providing attitude data via synchro interface

(no digital source of heading available) and the other RLGN is

inoperative. Manual heading will be taken as a single heading

measurement at the time of operator pressing ENTER key.

2. SINS2 OFF/ON Turn on if secondary RLGN is operative during High Latitude ALIGN.

***

Status word in RLGN/RLGN interface indicates valid/invalid and

normal/transverse.

3. HDIG OFF/ON ***

Turn on during High Latitude ALIGN if external digital heading source is available. Status word in Super Channel interface indicates valid/invalid.

MODE Functions

MODE control functions are associated with the position ﬁlter and navigation calculation modes.

MODE control functions are presented and accessed via one display menu page.

The MODE menu provides control functions associated with the position ﬁlter and navigation calculation modes.

1 1. Damping

Auto: INS is automatically switched between damped and undamped operation depending upon reference velocity data validity and ship’s dynamics, such as turn rate.

Man Damp: When selected, system is forced to remain damped, regardless of velocity input or ship dynamics. Change to Man Undamp for undamped operation can only occur when manually selected.

Man Undamp: When selected, system is forced to remain undamped. Change to Man Damp for manually damped operation can only occur when manually selected.

2. Fix

Displays present Fix Entry and GMT.

ENTER: Accepts present Fix values.

CLEAR: Enables manual position ﬁx data entry via the keypad. Position data is used to correct the INS estimate of position and to update the Kalman ﬁlter. Other Kalman ﬁlter parameters are not reset when ﬁx is entered via this function.

3. Slew

Displays present slew Position Reference and GMT.

ENTER: Accepts Position Reference values.

CLEAR: Enables manual position slew to be entered via the keypad. Position data is used to reset INS estimate of position only.

4. Norm/Txvs

1. System normal/transverse mode: Provides three control function options for selecting Earth coordinates reference used to calculate position and heading.

2-20

PAGE

Table 2-2. FUNCTION

5. Reset Mode 6. LogCal Mode

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
AUTO: When selected, INS automatically switches between normal and transverse coordinates reference when normal coordinates latitude is approximately +85°. (Transverse mode should be used above 85°.)
MNORM: When selected, INS remains in normal coordinates mode regardless of latitude.
MTXVS: When selected, INS remains in transverse coordinates mode regardless of latitude.
2. Synchro heading: Provides three control function options for synchro heading output formats, which may be selected independently from System normal/transverse mode.
Follow system mode: When selected, synchro heading output automatically provides transverse heading when the system is operating in transverse coordinates reference, and provides normal heading when the system is operating in normal reference mode.
Normal coordinates: When selected, the synchro heading output is always displayed in normal coordinates regardless of whether the system is operating in transverse or in normal reference mode.
Txvs coordinates: When selected, the synchro heading output is always displayed in transverse coordinates regardless of whether the system is operating in transverse or in normal reference mode.
Provides three control function options for accepting navigation aid position ﬁxes.
Review: Requires that the operator review ﬁx data and either accept or reject each position ﬁx. With this mode selected, when a position ﬁx is received from the navigation aid, the operator is prompted by display of Code 221. The operator must then select the Reset Data function (DISPLAY, Page 3, Reset Data) to review the ﬁx values.
Auto Review: Similar to Review mode except that the INS automatically accepts valid ﬁxes and allows the operator to review ﬁxes that do not meet valid criteria. If the operator does not accept or reject the ﬁx within 10 minutes, the ﬁx data is discarded and the ﬁx is rejected by the INS.
Auto: INS automatically accepts or rejects each position ﬁx from the navigation aid without prompting the operator to review the ﬁx. Display of accepted, last rejected, or pending ﬁx is available in the Reset data display.
Provides two control function options for disabling and enabling Electromagnetic Logs (EM Logs).
Not Selected: Disables automatic EM Log (Rod 1 or Rod 2) calibration during normal vessel operation.
Selected: Enables automatic EM Log (Rod 1 or Rod 2) calibration during normal vessel operation. Also, the selected EM Log’s calibration tables are automatically updated with Kalman ﬁlter bias calibration values.

S9427-AN-OMP-010/WSN-7

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

AUXiliary FUNCtions

AUXiliary FUNCtions control functions are associated with changing conﬁguration settings, displaying stored fault codes, performing display self-test, setting display update rate, selecting output of simulated position, heading, and velocity, calibrating the speed log data, monitoring system performance, and transferring waypoints. Changes to settings made using the AUX FUNC menus override defaults set by Installation Conﬁguration as long as the AN/WSN-7(V) remains turned on. Except for changes made to speed log calibration tables, all selections return to installation defaults upon completion of the Normal Shutdown procedure. AUX FUNC control functions are presented and accessed via three display menu pages.

Page 1 of the AUX FUNC menu provides control functions associated with the Remote Control Display Unit (RCDU), System Conﬁguration, Faults, Indexers, I/O Conﬁguration, and I/O Restart.

1 1. RCDU Lockout The RCDU Lockout control function is associated with controlling AN/WSN-7(V) operation from a separate control unit.

RCDU Locked =

Yes: Locks out interface port to CD-125/WSN-7 RCDU or IP-1747/WSN CDU so that the AN/WSN-7(V) can be controlled solely from its control/display. The CDU still works to collect data across the Super Channel.

No: Enables interface port to CD-125/WSN-7 RCDU or IP-1747/WSN CDU so that the AN/WSN-7(V) can be controlled from the RCDU or CDU.

2. System Conﬁguration

System Conﬁguration control functions are associated with velocity damping ﬁlters, mode functions menu conﬁguration, attitude comparison, faults, Indexers, I/O conﬁguration. These System Conﬁguration control functions are presented and accessed via six display menu pages.

(Page 1 of 6)

Sys Conﬁg (Page 1) is associated with setting system “Master” status and velocity damping ﬁlter control functions. Velocity damping ﬁlters are explained in Paragraph 2.3.5.3.

1. This RLGN Master =

No: Disables the AN/WSN-7(V) as the Master system.

Yes: Enables the AN/WSN-7(V) as the Master system and affects only a status word output in the NTDS interface messages. Does not affect system master/slave timing protocol as it relates to clock and position reset functions.

2. Velocity damping =

KALMAN: Enables Kalman ﬁlter velocity damping.

THIRD ORDER: Enables Third Order velocity damping. System must be in Navigate mode for Third Order to be selected.

(Page 2 of 6)

Sys Conﬁg (Page 2) is associated with setting the control function options that the operator will be able to review and select via the Mode function menu’s Norm/Txvs control function.

1. Normal/Transverse =

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S9427-AN-OMP-010/WSN-7

PAGE

Table 2-2. FUNCTION

(Page 3 of 6)
(Page 4 of 6) (Page 5 of 6) (Page 6 of 6) 3. Faults 4. Indexers

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
AUTO/MANUAL: Enables and presents to the operator both the AUTO and the MANUAL control function options.
MANUAL ONLY: Disables and replaces AUTO/MANUAL, and enables and presents the MANUAL ONLY control function option.
2. Reset Mode =
AUTO, AUTO/REVIEW, REVIEW: Enables and presents to the operator all three Reset Mode control function options.
AUTO/REVIEW, REVIEW: Enables and presents to the operator the AUTO/REVIEW and the REVIEW control function options only.
REVIEW: Enables and presents to the operator the REVIEW control function option only.
Sys Conﬁg (Page 3) is associated with setting attitude comparison control function options.
1. Att Comp Threshold: On dual system installations, allows the alarm threshold setting for difference in attitude (heading, roll, and pitch) output to be set from the on-line menu to temporarily override the default value set at installation.
2. Att Comp Filter Constant: On dual system installations, allows the time constant setting, used by the system for determining the difference in attitude, to be set from the on-line menu to temporarily override the default value set at installation.
Sys Conﬁg (Page 4) is associated with setting the system Subnet Mask and Internet Protocol (IP) addresses.
1. Subnet Mask = xxx.xxx.xxx.xxx
2. IP Address = xxx.xxx.xxx.xxx
Sys Conﬁg (Page 5) is associated with setting the system ARP address.
1. ARP Address = xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Sys Conﬁg (Page 6) is associated with setting the system NTP address.
1. NTP Address = xxx.xxx.xxx.xxx
The Faults control function menu displays a list of active faults, which persist after pressing the <ALARM ACK> key to acknowledge the fault. The Faults control function is presented and accessed via one display menu page.
The Indexers control function menu is associated with inner and outer gimbal torquer settings. The Indexers control function is presented and accessed via one display menu page. Torquers are normally enabled and this function is not used during normal operation. Torquers can be enabled without removing system power in the event that they are automatically disabled as a result of detection of a fault in the torquer loop.
1. Inner indexer:

2-22

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

On: Enables the inner (azimuth) torquer (1A2A1A1B2).

OFF: Disables the inner (azimuth) torquer (1A2A1A1B2).

2. Outer indexer:

On: Enables the outer (roll) torquer (1A2A1A1B1).

OFF: Disables the outer (roll) torquer (1A2A1A1B1).

5. I/O Conﬁguration The I/O Conﬁg control function menu is associated with NTDS/ATM, INS and DSVL digital I/O settings. These I/O Conﬁg control functions are presented and accessed via three display menu pages.

(Page 1 of 3)

I/O Conﬁg Page 1, I/O Port, is associated with system, NTDS, digital I/O settings. NTDS ON/OFF – Allows the operator to select each NTDS, Super Channel, or ATM port, turn the port on or off, and selectively activate or deactivate message data ﬁelds. From I/O Conﬁg page 1, choose NTDS Super Channel, or ATM to edit I/O conﬁguration settings.
NOTE

IDS conﬁguration may be changed in Off-Line Test mode only.

The NTDS Conﬁguration Settings control function menu lists control function options on three display menu pages, which allow speciﬁc message protocol and data ﬁelds to be selected or enabled for each ﬁtted port, even if the port is selected as disabled.
NOTE

The letter preﬁx on each port designation identiﬁes the physical location of the NTDS I/O board that contains the port set. Refer to Table 2-3.

a. NTDS Port = (port designation). Step function selects port to be enabled/disabled or reconﬁgured (up to 16 maximum available).

b. NTDS Port Conﬁguration Settings, Page 1:

(1) Port nn =

DSBL: Disables the selected NTDS port.

ENBL: Enables the selected NTDS port.

(2) IDS = Applicable to IDS 00 through 31.

(3) Retries = Applicable to IDS 08, 09, and 10.

DSBL: Disables I/O processor output message retries. Message is transmitted only once, even when acknowledgement is not received.

ENBL: Enables the I/O processor output message to repeat once, if acknowledgement is not received.

(4) Secondary = Applicable to IDS 14 and 15.

DSBL: Disables a message bit setting that identiﬁes the selected port’s status and data to the receiving equipment as secondary when redundant I/O interface functionality is implemented.

PAGE

Table 2-2. FUNCTION

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
ENBL: Enables a message bit setting that identiﬁes the selected port’s status and data to the receiving equipment as secondary when redundant I/O interface functionality is implemented.
c. NTDS Port Conﬁguration Settings, Page 2:
(1) Day = ENBL/DSBL. (Applicable to IDS 11) If ENBL is selected, allows the RLGN to transmit Julian Day data to the OU-174/WSN-5 Data Converter Group. If DSBL is selected, the RLGN will not transmit Julian Day data over this connection.
(2) P Sen Fmt = AR57A/AS130. (Applicable to IDS 11) This setting determines the format (AR57A or AS130) for transmitting position senescence data to the OU-174/WSN-5 Data Converter Group.
(3) Forced EF = ENBL/DSBL. (Applicable to IDS 04, 08 and 11). If receiving equipment does not implement an EIE line to indicate that it is ready to receive data, selecting ENBL causes the parallel output data message to be transmitted regardless of EIE status.
(4) Parity = ENBL/DSBL. (Applicable to IDS 07, 09 and 10). Enables or disables message parity bit checking protocol for serial output.
d. NTDS Port Conﬁguration Settings, Page 3:
(1) Nav Msg = ENBL/DSBL. (Applicable to IDS 04, 08, 09, and 10). Enables or disables the Navigation Data Periodic message transmitted at 1 Hz in the output data.
(2) Precision = HIGH (NORM). (Applicable to IDS 04, 07, 08, 09, 10). Sets position data in the Navigation Data Periodic message precision to high or normal precision.
(3) Attd Msg = ENBL/DSBL. (Applicable to IDS 04, 08, 09, and 10). Enables or disables the Attitude Data Periodic message output data.
(4) Msg Rate = 8 Hz (16 Hz). (Applicable to IDS 04, 08, 09, and 10). Changes transmit rate for Attitude Data message.
The Super Channel conﬁguration settings control function menu lists control function options on three display menu pages, which allow speciﬁc message protocol and data ﬁelds to be selected or enabled for each ﬁtted port, even if the port is selected as disabled.
a. Super Channel Port Conﬁguration Settings, Page 1:
(1) Port nn = ENBL/DSBL. Enables or disables selected port. The options listed on Pages 1, 2, and 3 of the menu function allow speciﬁc message protocol and data ﬁelds to be selected for each ﬁtted port, even if the port is selected as disabled.
(2) IDS = 13. The number displayed in this ﬁeld is a code that indicates the Super Channel IDS assigned to the port during system installation conﬁguration. Data in this ﬁeld cannot be changed from this on-line I/O Conﬁguration mode. Refer to Table 2-4 for the Port Speciﬁcation and Type indicated by each IDS number. Refer to Chapter 8 for the listing of factory-conﬁgured I/O ports and settings.

S9427-AN-OMP-010/WSN-7

PAGE

Table 2-2. FUNCTION

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
(3) Ext Fix = ENBL/DSBL. If ENBL is selected, allows RLGN to accept a ﬁx from an external computer, other than GPS, over the Super Channel interface. If DSBL is selected, no external computer ﬁxes will be accepted.
(4) GPS Fix = ENBL/DSBL. If ENBL is selected, allows RLGN to accept GPS ﬁxes over the Super Channel interface. If DSBL is selected, no GPS ﬁxes will be accepted.
b. Super Channel Port Conﬁguration Settings, Page 2:
(1) Rmt Cntrl = ENBL/DSBL. If ENBL is selected, allows the RLGN to accept Remote Control input over the Super Channel interface. If DSBL is selected, no Remote Control input will be accepted.
(2) Vref Input = ENBL/DSBL. If ENBL is selected, allows RLGN to accept reference velocities over the Super Channel interface. If DSBL is selected, velocity references will not be accepted over the Super Channel interface.
(3) Attd Data = ENBL/DSBL. If ENBL is selected, allows the RLGN to accept backup attitude data over the Super Channel interface. If DSBL is selected, no backup attitude data will be accepted over the Super Channel interface.
(4) Waypoint = ENBL/DSBL. This setting is currently not in use. Should be set to DSBL.
c. Super Channel Port Conﬁguration Settings, Page 3:
(1) Depth = ENBL/DSBL. This setting is not used on surface vessels. Should be set to DSBL.
(2) Fcn 8 = ENBL/DSBL. Reserved. Should be set to DSBL.
(3) Fcn 9 = ENBL/DSBL. Reserved. Should be set to DSBL.
(4) Fcn 10 = ENBL/DSBL. Reserved. Should be set to DSBL.
The ATM Port, conﬁguration settings, control function menu lists control function options on three display menu pages, which allow speciﬁc message protocol and data ﬁelds to be selected or enabled for each ﬁtted port, even if the port is selected as disabled.
a. ATM Port = I. Step function selects port to be enabled/disabled or reconﬁgured.
b. ATM Port Conﬁguration Settings, Page 1:
(1) Port I = ENBL/DSBL. Enables or disables selected port. The options listed on Pages 1, 2, and 3 of the menu function allow speciﬁc message protocol and data ﬁelds to be selected or enabled for each ﬁtted port, even if the port is selected as disabled.
(2) IDS = 16. Number displayed in this ﬁeld is a code which indicates the ATM Interface Design Speciﬁcation (IDS) assigned to the port during system installation conﬁguration. Data in this ﬁeld cannot be changed from this on-line I/O Conﬁguration mode. The number 00 in this ﬁeld indicates that the selected port is not ﬁtted. Refer to Table 2-3 and Table 2-4.

2-23

S9427-AN-OMP-010/WSN-7

PAGE

Table 2-2. FUNCTION

(Page 2 of 3) (Page 3 of 3)

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
(3) Ext Fix = ENBL/DSBL. If ENBL is selected, the RLGN will accept a ﬁx from an external computer, other than GPS, over the ATM interface. If DSBL is selected, no external computer ﬁxes will be accepted.
(4) GPS Fix = ENBL/DSBL. If ENBL is selected, the RLGN will accept GPS ﬁxes over the ATM interface. If DSBL is selected, no GPS ﬁxes will be accepted.
c. ATM Port Conﬁguration Settings, Page 2:
(1) Fcn 3 = ENBL/DSBL. Reserved. Should be set to DSBL.
(2) Vref Input = ENBL/DSBL. If ENBL is selected, the RLGN will accept reference velocities over the ATM interface. If DSBL is selected, velocity references will not be accepted over the ATM interfaces.
(3) Attd Data = ENBL/DSBL. If ENBL is selected, the RLGN will accept backup attitude data over the ATM interface. If DSBL is selected, no backup attitude data will be accepted over the ATM interface.
(4) Fen 6 = ENBL/DSBL. Reserved. Should be set to DSBL.
d. ATM Port Conﬁguration Settings, Page 3:
(1) Depth = ENBL/DSBL. If ENBL is selected, the RLGN will accept depth inputs via the ATM interface. If DSBL is selected, depth will not be accepted over the ATM interface.
(2) BFTT Input = ENBL/DSBL. If ENBL is selected, the RLGN will accept BFTT data over the ATM interface and will distribute simulated data to NTDS I/O, as instructed by BFTT port selection. If DSBL is selected, RLGN will not accept BFTT simulated data. Users will only receive real data.
(3) Grav Grad = ENBL/DSBL. If ENBL is selected, the RLGN will accept Gravity Gradient data for vertical deﬂection compensation over the ATM interface. If DSBL is selected, gravity gradient data will not be accepted over the ATM interface.
(4) SLCM Input = ENBL/DSBL. If ENBL is selected, the RLGN will accept the SLCM enable/disable message over the ATM interface. SLCM enable/disable is applicable to submarine systems only.
I/O Conﬁg Page 2, INS = ON/OFF, is associated with INS to INS interfacing in dual AN/WSN-7(V) installations.
On: Enables INS-INS interfacing.
Off: Disables INS-INS interfacing.
I/O Conﬁg Page 3, DSVL = ON/OFF, is associated with navigation systems that interface with a DSVL.
On: Enables the data port for DSVL interfacing.
Off: Disables the data port for DSVL interfacing.

2-24

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

6. I/O Restart

The I/O Restart control function menu is associated with I/O and ATM processor settings. I/O Restart is used to enable an I/O or ATM Processor disabled by BITE when a fault condition is detected. This control function does not require INS power to be cycled for the processor to be enabled. This control function is enabled by default when the INS is turned on.

Enable: Restarts (enables) I/O or ATM Processor operation without recycling power.

Page 2 of the AUXILIARY FUNC menu provides control functions associated with the Display Test, Display Rate, Display Normal/Txvs, KF Reinitialize, Log Calibration, and Memory Inspection.

2 1. Display Test

The Display Test control function initiates a dynamic self-test of the display. Test continues until one of the display menu keys is pressed.

2. Display Rate

The Display Rate control function selects display update rate.

1 Hz: Updates display data once every second.

2 Hz: Is the default rate, and updates display data once every two seconds.

3. Normal/Txvs

The Display Normal/Txvs control function selects coordinates format for position and heading display. This function affects display format only and does not affect calculation mode.

Normal: Renders coordinate format as LAT XXX.XX N and LON XXX.XX W.

Txvs: Renders coordinate format as TLT XXX.XX S and TLN XXX.XX W.

4. KF Reinitialize

The KF Reinitialize control function is not used for normal INS operation. This control function should be used ONLY when INS performance is veriﬁed as outside of speciﬁcation and when it is certain that Kalman Filter reinitialization will realign and restore INS attitude and position accuracy.

5. Log Calibration

The Log Calibration control function presents an operator interface that enables data entry during a controlled calibration run. Refer to Paragraphs 2.4.3, 2.4.4, and 2.4.5.

6. Mem Inspt

The Memory Inspection (Mem Inspt) control function enables the operator to observe the data values currently stored in memory. This function allows each memory address location to be selected and to be sequentially stepped up or down. This function is intended primarily as a software development tool.

Page 3 of the AUXILIARY FUNC menu provides control functions associated with Simulated Output, Monitor Performance, Auxiliary Panel, NAV/DR Out, Digital-to-Synchro (D/S) Test, and DR Reset.

Table 2-2. PAGE FUNCTION
3 1. Simulated Output
2. Monitor Performance (Page 1 of 2)

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
The Simulated Output control function is associated with producing and transmitting simulated values. This menu lists control function options on four display menu pages, which allows the operator to select a simulation mode for system data output and to enter simulated values for heading, roll, pitch, position, and velocity on all outputs. Selection of this function and output of simulated values does not affect system operation. Digital data messages contain status bits which are set to indicate that output data is simulated. Relay K6 is set to provide indication that analog outputs are simulated when this mode is active. When this mode is exited, the system remains in the Simulate mode for a short period of time while system output parameters are being slewed back to correct values. When all values are reset, the system reverts automatically to normal output.
a. Enable On/Off
On: Enables simulated system data output, and enables the Modify Attitude, Modify Velocity, and Modify Position control functions to be selected and edited.
OFF: Disables simulated system data output, and disables the Modify Attitude, Modify Velocity, and Modify Position control functions.
b. Modify Attitude – Enable On/Off control function must be set to On to select and edit.
(1) Roll: Displays and enables editing of current Roll data via the display keypad.
(2) Pitch: Displays and enables editing of current Pitch data via the display keypad.
c. Modify Velocity – Enable On/Off control function must be set to On to select and edit.
(1) VN: Displays and enables editing of current Velocity North (VN) data via the display keypad.
(2) VE: Displays and enables editing of current Velocity East (VE) data via the display keypad.
d. Modify Position – Enable On/Off control function must be set to On to select and edit.
(1) Lat: Displays and enables editing of current latitude (Lat) data via the display keypad.
(2) Lon: Displays and enables editing of current longitude (Lon) data via the display keypad.
The Monitor Performance control function is associated with dynamic system performance testing while the system is operating in the Navigate mode. This menu lists control function options on two display menu pages.
1. Monitor On/Off: Presents the option to control the monitoring of the dynamic system performance test.
On: Enables monitoring of dynamic system performance test.

S9427-AN-OMP-010/WSN-7

PAGE

Table 2-2. FUNCTION

(Page 2 of 2)

3. Auxiliary Panel 4. NAV/DR Out

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
Off: Disables monitoring of dynamic system performance test.
2. Monitor data: Presents data monitoring options on three menu pages.
Page 1 – Monitor Start Time: Displays dynamic system performance test start time and enables start time editing.
Page 1 – Monitor Elapsed Time: Displays elapsed time since the dynamic system performance test’s start time.
Page 2 – Position Sensor: Displays position sensor source.
Page 2 – TRMS Position Error: Displays TRMS position error data as a percentage of system performance speciﬁcation.
Page 3 – RMS Vel North: Displays Velocity North data as a percentage of system performance speciﬁcation.
Page 3 – RMS Vel East: Displays Velocity East data as a percentage of system performance speciﬁcation.
The Auxiliary Panel control function is associated with indicating when an IP-1747/WSN Control Display Unit (CDU) or Factory Interface Monitor (FIM) is installed and interfacing with the INS.
Monitor: Indicates an IP-1747/WSN CDU is installed and is interfacing via the system’s I/O interface port.
FIM: Indicates an FIM is installed and is interfacing with the INS. This value may be toggled to Monitor, thereby forcing the system’s I/O interface open and enabling CDU operation without requiring the INS power to be cycled.
The NAV/DR Output control function is associated with INS NAV and DR data output to users.
NAV: (Default) Enables NAV inertial data to be output from the INS to users.
DR: Disables NAV inertial data output, and enables DR data output from the INS to users.

2-25

S9427-AN-OMP-010/WSN-7

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

5. D/S Test

The D/S Test control function is associated with a short loop, on-line wraparound test of the digital synchro converters.

a. Periodic:

On: Enables the automatic testing of the D/S converters at periodic intervals.

Off: Disables the automatic testing of the D/S converters at periodic intervals, and sets the test to be performed ONLY when the INS is started.

b. On Demand Test:

On: Enables manual testing of the D/S converters at any time.

Off: Disables manual testing of the D/S converters.

6. DR Reset

The DR Reset control function is associated with determining the validity of, and resetting, DR position values. If the DR data menu shows asterisks, the DR solution is invalid and the operator should enter this menu and reset the DR position.

Reset DR to Inertial: Resets DR data to inertial position values.

Reset DR to Manual: Enables DR latitude and longitude values to be manually entered.

DISPLAY Functions

The Display Functions control functions are associated with INS parameters and output data, and their presentation for review. Output data available for review includes position, velocity, heading, and day/time information. Display control functions are presented and reviewed via ﬁve display menu pages. Select Display Functions by pressing the <DISPLAY> key. Select the menu page by pressing the <NEXT PAGE> key. Select the parameter to be displayed by pressing the number key corresponding to the number of the parameter.

Page 1 of the DISPLAY functions menu provides control functions associated with velocity, roll, pitch, heading and depth.

1 1. Vn/Ve 2. Vfa/Vps

Vn: Displays the ship’s North/South inertial velocity in Knots (KTS). Ve: Displays the ship’s East/West inertial velocity in Knots (KTS). Vfa: Displays the ship’s fore/aft inertial velocity in Knots (KTS).

Vps: Displays the ship’s port/starboard (stbd) inertial velocity in Knots (KTS).

3. Roll/Rate

Roll: Displays the ship’s roll angle.

Rate: Displays the ship’s roll rate in Degrees per Second (°/SEC).

4. Pitch/Rate

Pitch: Displays the ship’s pitch angle.

Rate: Displays the ship’s pitch rate in Degrees per Second (°/SEC).

5. Hdg/Rate

Hdg: Displays the ship’s heading.

Rate: Displays the ship’s turn rate in Degrees per Second (°/SEC).

6. Depth *

On INS conﬁgured with a selected depth input source, displays depth in Feet (FT).

2-26

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

Page 2 of the DISPLAY functions menu provides control functions associated with reference velocities, divergence values in heading, roll, and pitch, ship course, and log biases.

2 1. Ref Vn/Ve

Ref Vn: Displays the ship’s North/South components of the selected reference velocity in Knots (KTS).

Ref Ve: Displays the ship’s East/West components of the selected reference velocity in Knots (KTS).

2. Ref Vfa/Vps

Ref Vfa: Displays the ship’s fore/aft components of the selected reference velocity in Knots (KTS).

Ref Vps: Displays the ship’s port/starboard (stbd) components of the selected reference velocity in Knots (KTS).

3. Vk/Ref Vk

Vk: Displays the vertical component of ship’s velocity (Vk) in Knots (KTS).

Ref Vk: Displays the selected reference velocity (Ref Vk) in Knots (KTS).

4. Divergence (Page 1 of 2)

With dual INS installations, displays the difference between the heading, roll, and pitch values as determined by each navigation system.

Hdg: Displays heading (Hdg) for each INS in minutes.

Roll: Displays roll for each INS in minutes.

Pitch: Displays pitch for each INS in minutes.

(Page 2 of 2)

With dual INS installations, displays the difference between the position values as determined by each navigation system.

Lat: Displays latitude (Lat) for each INS in minutes.

Lon: Displays longitude (Lon) for each INS in minutes.

5. Course

Displays ship’s present direction of motion without regard to ship’s heading. Display range 0.00° to 359.99°.

6. Log Biases

Displays up to ten log biases at speed values for Rod 1 and Rod 2 speed sources.

Clear Biases Rod 1: Enables the operator to erase Rod 1’s bias values as stored in memory.

Show Biases Rod 1: Enables the operator to review Rod 1’s bias values as stored in memory.

Clear Biases Rod 2: Enables the operator to erase Rod 2’s bias values as stored in memory.

Show Biases Rod 2: Enables the operator to review Rod 2’s bias values as stored in memory.

Page 3 of the DISPLAY functions menu provides control functions associated with position and velocity variance and divergence, ocean current velocities, reset data and RLGN designation.

Table 2-2. PAGE FUNCTION
3 1. Sigma N/E
2. Sigma Vn/e 3. DVn/DVe 4. OCn/OCe 5. Reset Data
6. RLGN Designation

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
Displays position variance estimates.
Sigma N: Displays 1-sigma estimate for North (N) velocity in Nautical Miles (NM).
Sigma E: Displays 1-sigma estimate for East (E) velocity in Nautical Miles (NM).
RPE: Displays 1-sigma estimate for Radial Position errors (RPE) in Nautical Miles (NM).
Displays velocity variance estimates.
Sigma Vn: Displays 1-sigma estimate for North (N) velocity in Knots (KTS).
Sigma Ve: Displays 1-sigma estimate for East (E) velocity in Knots (KTS).
Displays the difference between INS inertial velocity and selected reference velocity.
DVn: Displays the difference between North (n) INS inertial velocity and selected reference velocity in Knots (KTS).
DVe: Displays the difference between East (e) INS inertial velocity and selected reference velocity in Knots (KTS).
Displays the estimated ocean currents velocities. Displayed values are only true if a water speed velocity reference is selected.
OCn: Displays the estimated North (n) ocean currents velocities in Knots (KTS).
OCe: Displays the estimated East (e) ocean currents velocities in Knots (KTS).
Displays the last received ﬁx values to allow the operator to review the ﬁx data. This menu should be selected by the operator to review the ﬁx data to be within acceptable limits prior to accepting or rejecting the ﬁx, when either Review or Auto/Review is selected for entry of ﬁx reset data.
FixLAT: Displays the last received Latitude (LAT) ﬁx value to allow the operator to review, and accept or reject the ﬁx data.
FixLON: Displays the last received Longitude (LON) ﬁx value to allow the operator to review, and accept or reject the ﬁx data.
FSN: Displays the last received FSN ﬁx value to allow the operator to review, and accept or reject the ﬁx data.
FSE: Displays the last received FSE ﬁx value to allow the operator to review, and accept or reject the ﬁx data.
GPS: Displays the last received Global Positioning System (GPS) ﬁx value to allow the operator to review, and accept or reject the ﬁx data.
Displays the RLGN’s designation when part of a dual RLGN INS without requiring the RLGN to be shut down and restarted in Test mode. The RLGN designation is used by some IDS users.

S9427-AN-OMP-010/WSN-7

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

This RLGN 1: Identiﬁes the RLGN as number 1 in a dual RLGN INS.

This RLGN 2: Identiﬁes the RLGN as number 2 in a dual RLGN INS.

Page 4 of the DISPLAY functions menu provides control functions associated with date/time settings, system part identiﬁcation numbers, accelerometer and gyro bias data, DR data, and BFTT data.

4 l. Day/Time

Displays and allows the date and time to be edited.

Day: Displays the Julian day and time and allows values to be changed.

Time: Displays the time in military 24-hour format.

2. Part No.

This control function displays six menu pages containing: serial numbers and information for the RLGN and its sensor block components and assemblies; part numbers and revision numbers for RLGN programs; vendor ID numbers; and network information.

(Page 1 of 6)

Presents Accelerometer identiﬁcation information.

A Accel SN: Displays the A Accelerometer’s serial number.

B Accel SN: Displays the B Accelerometer’s serial number.

C Accel SN: Displays the C Accelerometer’s serial number.

(Page 2 of 6)

Presents Gyro identiﬁcation information.

A Gyro SN: Displays the A Gyro’s serial number.

B Gyro SN: Displays the B Gyro’s serial number.

C Gyro SN: Displays the C Gyro’s serial number.

(Page 3 of 6)

Presents INS identiﬁcation information.

Platform SN: Displays the RLGN’s platform serial number.

Sensor Block SN: Displays the RLGN’s IMU sensor block serial number.

Serial Number AN/WSN-7(V): Displays the RLGN’s serial number.

(Page 4 of 6)

Presents processor and IMU program identiﬁcation information.

Nav Prog PN: Displays the Nav Processor’s program part number.

IMU Prog PN: Displays the IMU program part number.

IO Program PN: Displays the IO Processor’s program part number.

(Page 5 of 6)

Presents ATM program and Peripheral Component Interface (PCI) identiﬁcation information.

ATM Prog PN

PCI Vendor ID

PCI Device ID

PCI Class Code

2-27

S9427-AN-OMP-010/WSN-7

Table 2-2. PAGE FUNCTION
(Page 6 of 6)
3. Accelerometer Bias
4. Gyro Bias
5. DR Data

Operating Menus/Functions Description - Continued
BRIEF DESCRIPTION
Presents PCI subsystem and Media Access Control (MAC) address identiﬁcation information.
PCI Subsystem Vendor
PCI Subsystem ID
MAC Address
Displays accelerometer bias estimates.
A Accel °/Hr: Displays A accelerometer (Accel) bias estimates in micro gravities within a range of plus or minus (±) 9999 micro-g.
B Accel °/Hr: Displays B accelerometer (Accel) bias estimates in micro gravities within a range of plus or minus (±) 9999 micro-g.
C Accel °/Hr: Displays C accelerometer (Accel) bias estimates in micro gravities within a range of plus or minus (±) 9999 micro-g.
Displays gyro bias estimates:
A Gyro °/Hr: Displays A Gyro bias estimates in degrees within a range of plus or minus (±) 2.1333°/hour.
B Gyro °/Hr: Displays B Gyro bias estimates in degrees within a range of plus or minus (±) 2.1333°/hour.
C Gyro °/Hr: Displays C Gyro bias estimates in micro gravities within a range of plus or minus (±) 2.1333°/hour.
This on-line menu displays the DR data as calculated by the RLGN. This data includes latitude, longitude, total velocity and heading. The selection of output data (inertial or DR) has no effect on this display. If the DR data display shows asterisks, it indicates that the DR solution is invalid. The DR solution can become invalid, for example, if the DR position hasn’t been initialized or heading reference is temporarily lost. A DR position reset is required. Once a DR reset is commanded, the DR data values will no longer be asterisks (assuming heading reference is not lost). (See AUXiliary FUNctions, Page 3, DR Reset.)

PORT SET
A1/A2 B1/B2 C1/C2 D1/D2

Table 2-3. Identiﬁcation of Port Type and Physical Location

CCA LOCATION

RECORD BOARD TYPES AND IDS CODES

INSTALLED (IN THIS SYSTEM)

NTDS I/O BOARD TYPE

IDS CODE

Part Number 1981101-6 AN/WSN-7(V)1

(1A1A51)

Type E (Serial)

(1A1A52)

Type E (Serial)

(1A1A53)

Type E (Serial)

(1A1A54)

Type E (Serial)

2-28

Table 2-2. Operating Menus/Functions Description - Continued

PAGE FUNCTION

BRIEF DESCRIPTION

LAT: Displays the DR latitude (LAT) calculated by the RLGN.

LON: Displays the DR longitude (LON) calculated by the RLGN.

Vt: Displays the DR total velocity (VT) calculated by the RLGN. HDG°: Displays the DR heading (HDG) calculated by the RLGN.

6. BFTT Data*

When the RLGN is in BFTT mode, displays the BFTT Simulated data being transmitted.

Page 5 of the DISPLAY functions menu provides control functions associated with Grid coordinates and Laser Intensity Monitor (LIM) Voltage.

5 1. Grid N/E***

Grid = °/S

Grid = °/W

2. LIM Volts***

The LIM volts control function menu displays the LIM voltage for the A, B, and C gyro in an RLGN.

A = Displays the LIM value for A gyro in volts (V). A LIM value greater than +1.1 volts indicate that the A gyro is within acceptable operating speciﬁcation.

B = Displays the LIM value for the B gyro in volts (V). A LIM value greater than +1.1 volts indicate that the B gyro is within acceptable operating speciﬁcation.

C = Displays the LIM value for the C gyro in volts (V). A LIM value greater than +1.1 volts indicate that the C gyro is within acceptable operating speciﬁcation.

Table 2-3. Identiﬁcation of Port Type and Physical Location - Continued

PORT SET

CCA LOCATION

RECORD BOARD TYPES AND IDS CODES

INSTALLED (IN THIS SYSTEM)

NTDS I/O BOARD TYPE

IDS CODE

E1/E2

(1A1A55)

Type D (Serial)

F1/F2

(1A1A56)

Type A (Parallel)

G1/G2

(1A1A57)

Type A (Parallel)

H1/H2

(1A1A58)

Type A (Parallel)

I1/I2

(1A1A4)

ATM

16

Table 2-3. Identiﬁcation of Port Type and Physical Location - Continued

PORT SET

CCA LOCATION

RECORD BOARD TYPES AND IDS CODES INSTALLED (IN THIS SYSTEM)

NTDS I/O BOARD TYPE

IDS CODE

Part Number 1981101-2 AN/WSN-7(V)2

A1/A2

(1A1A51)

Type E (Serial)

B1/B2

(1A1A52)

Type A (Parallel)

C1/C2

(1A1A53)

Type E (Serial)

D1/D2

(1A1A54)

Type D (Serial)

E1/E2

(1A1A55)

Type A (Parallel)

F1/F2

(1A1A56)

Type A (Parallel)

G1/G2

(1A1A57)

Type A (Parallel)

H1/H2

(1A1A58)

Type A (Parallel)

I1/I2

(1A1A4)

ATM

16

Table 2-4. Identiﬁcation of NTDS Port Interface Design Speciﬁcation

IDS CODE
00 01 021 03 04 051 061 07

NTDS TYPE
-
A B A A B B D

DIRECTION
Input/Output Input/Output Input/Output Input/Output Input/Output
Output Input/Output

SPECIFICATION
Not ﬁtted NAVSEA SE174-AB-IDS-010/GPS NAVSEA SE174-AB-IDS-010/GPS T9427-AN-IDS-050/WSN-7 S9427-AN-IDS-070/WSN-7 S9427-AP-IDS-010/RLGN S9427-AP-IDS-020/RLGN S9427-AN-IDS-030/WSN-7

1 IDS Code applies only to submarine installations.

Table 2-5. Simulated Outputs Description

SIMULATED FUNCTION

DESCRIPTION

ENTRY RANGE

2 Modify Attitude Output Functions (Select by pressing the <2> key)

1 Roll

Sets a positive or negative roll angle, which is output -45 to +44.99 degrees from Synchro Buffer Ampliﬁer 8 VA (1A1A41).

S9427-AN-OMP-010/WSN-7

Table 2-3. Identiﬁcation of Port Type and Physical Location - Continued

PORT SET

CCA LOCATION

RECORD BOARD TYPES AND IDS CODES INSTALLED (IN THIS SYSTEM)

NTDS I/O BOARD TYPE

IDS CODE

Part Number 1981101-3 AN/WSN-7(V)3

A1/A2

(1A1A51)

Type E (Serial)

B1/B2

(1A1A52)

Type A (Parallel)

C1/C2

(1A1A53)

Type A (Parallel)

D1/D2

(1A1A54)

Type A (Parallel)

E1/E2

(1A1A55)

Type A (Parallel)

F1/F2

(1A1A56)

Type A (Parallel)

G1/G2

(1A1A57)

Type A (Parallel)

H1/H2

(1A1A58)

Type A (Parallel)

I1/I2

(1A1A4)

ATM

16

Table 2-4. Identiﬁcation of NTDS Port Interface Design Speciﬁcation - Continued

IDS CODE

NTDS TYPE

DIRECTION

SPECIFICATION

08

A

Output

S9427-AN-IDS-040/WSN-7

09

E

Output

S9427-AN-IDS-020/WSN-7

10

E

Input/Output

S9427-AN-IDS-020/WSN-7

11

A

12

-

Output -

T9427-AN-IDS-060/WSN-7 (Reserved)

13

E

Input/Output

S9427-AN-IDS-010/WSN-7 (Super Channel)

141

B

Input/Output

S9427-AP-IDS-030/RLGN

151

B

Input/Output

S9427-AP-IDS-040/RLGN

16 17-31

ATM -

Input/Output -

S9427-AN-IDS-080/WSN-7 (Reserved)

SIMULATED FUNCTION 2 Pitch
3 Heading

Table 2-5. Simulated Outputs Description - Continued

DESCRIPTION

ENTRY RANGE

Sets a positive or negative pitch angle, which is output from Synchro Buffer Ampliﬁer 8 VA (1A1A42).
Sets a heading angle, which is output from Synchro Buffer Ampliﬁers 32 VA (1A1A43) and 32 VA (1A1A44).

-45 to +44.99 degrees 0 to 359.99 degrees

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S9427-AN-OMP-010/WSN-7

Table 2-5. Simulated Outputs Description - Continued

SIMULATED FUNCTION

DESCRIPTION

ENTRY RANGE

3 Modify Velocity Output Functions (Select by pressing the <3> key)

1 Vel N (North Velocity)

Sets a north/south velocity value, which is output -128 to +127.99 knots from Synchro Converter CCA (1A1A38) (in synchro data format) and in all applicable NTDS output data messages.

2 Vel E (East Velocity)

Sets an east/west velocity value, which is output -128 to +127.99 knots from Synchro Converter CCA (1A1A38) (in synchro data format) and in all applicable NTDS output data messages.

4 Modify Position Output Functions (Select by pressing the <4> key)When entering latitude and longitude, the N/S ﬁeld is set with the <NE+> key or <SW−> key.

1 Latitude

Sets a latitude value, which is output in all applicable 0 to 90 degrees

NTDS output data messages.

0 to 59.99 minutes

2 Longitude

Sets a longitude value, which is output in all applicable NTDS output data messages.

0 to 180 degrees 0 to 59.99 minutes

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S9427-AN-OMP-010/WSN-7

Figure 2-1. Front Panel Controls and Indicators

Figure 2-2. Keypad Controls

2-31

S9427-AN-OMP-010/WSN-7

2-32

Figure 2-3. Menu Status/Mode Indications

S9427-AN-OMP-010/WSN-7

Figure 2-4. Identifying Operation Menus and Data Entry (Sheet 1 of 2)

2-33

S9427-AN-OMP-010/WSN-7

2-34

Figure 2-4. Identifying Operation Menus and Data Entry (Sheet 2 of 2)

S9427-AN-OMP-010/WSN-7

Figure 2-5. Dockside Align Settle States

2-35

S9427-AN-OMP-010/WSN-7

2-36

Figure 2-6. Slave Align Settle States

S9427-AN-OMP-010/WSN-7

Figure 2-7. At-Sea Align Settle States

2-37

S9427-AN-OMP-010/WSN-7

2-38

Figure 2-8. Mode Transition Diagram

Figure 2-9. Earth Coordinates References

S9427-AN-OMP-010/WSN-7

Figure 2-10. Position Fix, Data Entry and Review Functions

Figure 2-11. Enhanced Performance Position Accuracy (EP2A) Block Diagram

2-39

S9427-AN-OMP-010/WSN-7

2-40

Figure 2-12. Position Estimate Accuracy vs. Time without Position Update

Figure 2-13. EM Log Calibration Functions

S9427-AN-OMP-010/WSN-7

Figure 2-14. Time RMS (TRMS) Position Error Calculation Method

2-41

S9427-AN-OMP-010/WSN-7 THIS PAGE INTENTIONALLY BLANK
2-42 (Blank)

S9427-AN-OMP-010/WSN-7

CHAPTER 3 THEORY AND FUNCTIONAL DESCRIPTION

SECTION I INERTIAL THEORY

3.1 INTRODUCTION.
This chapter provides basic inertial navigation theory and system operational theory.
It describes the ways in which AN/WSN-7(V) functions support ship navigation and outlines the physically independent assemblies that work together to provide or support an AN/WSN-7(V), navigation-essential function.
Understanding AN/WSN-7(V) operational theory is essential to using the AN/WSN-7(V) following the procedures in later chapters.
This chapter is divided into two sections. Section I describes the theory used in inertial navigation systems. Section II describes the components and systems used in the AN/WSN-7(V) Ring Laser Gyro Navigator.
A detailed description of the physics, calculations, and compensation methods involved in the inertial navigation process requires extensive mathematical analysis, which is beyond the scope of this discussion.
3.2 BASIC INERTIAL NAVIGATION PRINCIPLES AND THEORY.
3.2.1 CONVENTIONAL VS. STRAPDOWN INERTIAL NAVIGATION SYSTEMS. There are two fundamental differences between the AN/WSN-7(V) and conventional inertial systems: strapdown and indexing.
In a conventional inertial system, the accelerometers are mounted on an inner stable platform which is held level by the gyroscopes inside three or four gimbals. This Base Motion Isolation (BMI) means that the accelerometers work in true level (Earth plane) and see only ship’s positional movement, without any components caused by pitch and roll motion. The accelerometer readings are double integrated to give changes in latitude and longitude.

In a strapdown system, the gyros and accelerometers are hard-mounted and sense ship’s motion, seeing pitch and roll components and their rates, as well as geographic movement. The composite rotation and acceleration measurements are fed into the system computer, which contains strapdown software. The strapdown software in the computer maintains a computer model true level from the gyro inputs, and uses a true Direction Cosine Matrix (DCM) to convert the accelerometer readings from deck plane to true.
Integration of the accelerometer readings after subtraction of Coriolis and gravity terms gives north (Vn), east (Ve) and vertical (Vk) velocities. Division of the Vn and Ve components by Earth’s radius and integrating produces changes in system latitude and longitude.
The AN/WSN-7(V) Inertial Navigation System (INS) is a strapdown system based on the principle of using the standing waves generated in a closed path laser beam to detect angular rotation of an inertial reference platform. Three Ring Laser Gyros (RLGs or gyros) are mounted perpendicular to each other to detect rotation of an inertial platform about the X, Y, and Z axes. Three accelerometers, one mounted parallel to each axis of rotation, detect motion of the inertial platform in each axis. The rotation and acceleration motions are processed by an internal computer, which determines the orientation and velocity vector of the inertial platform.
The AN/WSN-7(V)’s three RLGs and three accelerometers are mounted on a sensor block. The sensor block is mounted in azimuth (inner) and roll (outer) gimbals which are controlled by direct drive torquer motors and slab synchros to provide sensor block stabilization and two-axis indexing. The sensor block is stabilized against ship motions in roll and pitch by outputs from the strapdown process. Indexing involves periodically rotating the sensor block cluster of gyros and accelerometers through ±90° or ±180° in roll or azimuth, in a speciﬁc sequence. The indexing cycle is designed to average out, or

commutate, drifts in all directions. The ±90° shift in azimuth interchanges the A and B gyro orientation to enable an optimum averaging of gyro drifts and misalignments.
3.2.2 INERTIAL NAVIGATION SYSTEMS. An inertial navigator is any self-contained system that answers the basic questions:
• Where am I?
• Where am I going?
Depending on the conﬁguration, the following questions can also be answered:
• How fast am I going?
• What is my attitude?
• What is my acceleration?
• What are my attitude rates?
3.2.2.1 Simplest (Single Axis) Inertial Navigator. The basic model (Refer to Figure 3-1) assumes a ﬂat non-rotating Earth, constant normal g, and constrained path.
The inertial navigator extrapolates current position and velocity starting with a known position and velocity. An inertial navigator does not yield absolute position, just a change in position from some starting point. The initial conditions (Xo, Vo, θ0 in simplest example) must be provided by external means or some combination of external systems and self-alignment.
All inertial system errors build up with time. For this simple example, accelerometer bias error AB yields: δx = ∫t0t [∫t0 dt] dt = ½ABt2 Error source categories in this simple system would include:
1. Instrumentation errors, including accelerometer (bias, scale factor, quantization, and environmental effects).
2. Accelerometer mounting misalignments.

3. Initial condition (position and heading) errors: (σXo, σVo, σθ0).
4. Computing errors in the integrations.
3.2.2.2 Addition of Vehicle Pitch Motion. The accelerometer measures speciﬁc force = acceleration (a) - gravity (g). If pitched upward, obtain ax cos u + g sin u. For small u, obtain an acceleration error of g u, leading to a horizontal distance error = 1/2gut2. Two basic approaches are used to correct for the effect of earth’s gravity; these are:
1. Stabilized (Gimbaled) Platform.
2. Strapdown Conversion.
3.2.2.2.1 Gimbaled Stabilization. Assuming that the objective is to determine horizontal velocity and position, the accelerometer input axis can be maintained horizontal at all times, in spite of the vehicle pitch motions. This is accomplished by the addition of a gyroscope and a platform servo system.
The gyro Spin Reference Axis (SRA) wants to remain ﬁxed in inertial space. If there were no gimbal friction, the platform would remain horizontal (in the non-rotating earth model). Because of friction, the platform will move off the horizontal. The gyro senses this motion about its input axis and yields a pickoff signal about its output axis. This signal drives the platform back to the horizontal via a fast reaction servo ampliﬁer and gimbal torque motor. This is known as a local level orientation system.
Each additional element in the system introduces new instrumentation error sources. For example, a gyro bias drift produces a gyro pick-off output when there is no actual input motion. This propagates as shown in Figure 3-2, for this open-loop simple navigator. The gimbal servo also does not do a perfect job of nulling the effects of vehicle dynamics. In marine inertial navigators, gyroscopic drift error is much more critical for precision navigation than the accelerometer errors.
Considerations of the gimbaled system include:
Advantages:

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S9427-AN-OMP-010/WSN-7

1. High accuracy (North and East accelerometers do not see a component of gravity).
2. Self-alignment by gyrocompassing.
3. Sensor calibration by platform rotations.
4. Gimbal angle readout generally used to supply roll, pitch, and azimuth data.
Disadvantages:
1. Complexity and cost.
2. Reliability (bearings, slip rings, spinning mass gyroscopes, and torque motors).
3. Adds gyroscope and gimbal servo follow-up errors.
4. Gyro drift WD creates platform tilt WDt, leading to acceleration error, or tilt-induced velocity, approximately equal to gWDt and position error:
δ 1/6gWDt3
3.2.2.2.2 Strapdown Stabilization. In a pure strapdown system, the inertial sensors are strapped down to the vehicle without any gimbal isolation. The gyroscopes measure the vehicle rates (with respect to inertial space), which are integrated into the vehicle attitude (initial attitude must be predetermined). This is also the attitude of the accelerometers. The accelerometer measurements are transformed about the attitude (or Direction Cosine) matrix into the desired horizontal and vertical axis. Refer to Figure 3-1.
The advantages of the pure strapdown system are the reduced complexity and improved reliability of not having gimbals and gimbal servos. The disadvantages all stem from the loss of the isolation from vehicle motions that the gimbals and gimbal servos provide.
The strapdown gyros must measure very high rates (tens of degrees/second) compared to earth-rate levels (tens of degrees/hour) in gimbaled systems, while still contributing the same drift levels. The computer must be very high speed to integrate these vehicle rates accurately. In addition, the accelerometers must measure large components of gravity, instead of being continually horizontal, making scale-factor and misalignment errors more critical.
The Direction Cosine attitude matrix of the strapdown system can be looked at as a stabilized platform model. Attitude errors are analogous to the tilts of the stabilized platform model.
Considerations of the strapdown system include:
Advantages:
1. Simple structure; i.e., no gimbals, no gimbal servos.

2. Reliability.
3. Stabilized platform model is maintained in Direct Current (DC) matrix.
4. Pitch angle can be obtained from software.
Disadvantages:
1. Inertial components are not isolated from software.
2. More difﬁcult to align.
3. More difﬁcult to calibrate.
4. Computing rates for strapdown conversion must be very high; however, modern computer technology makes strapdown systems practical.
While the basic errors in a strapdown system propagate into navigational accuracy in the same manner as in a gimbaled system, the nature of the error sources and how they originate can be quite different.
Strapdown Error Propagation:
Gyro drift WD integrates into computed pitch error δP = WDt
• PC = PT + δP
Attitude matrix is tilted off of true horizontal
• cos PC cosPT - δPsinPT sin PC sinPT + δPcosPT
Substitution in matrix transformation yields:
• aHC = aH + (g • δP) δa = gδ P = gWDt
• δPOSITION = 1/6 gWDt3 (same as for gimbaled system)
3.2.2.3 Moving Along the Meridian of a Spherical Non-Rotating Earth. As illustrated in Figure 3-6, if we extend the simple navigator closer to the real world by moving North along the meridian of a spherical non-rotating earth with radius R, the following three conditions apply:
1. A gimbaled system gyroscope whose Spin Reference Axis (SRA) was pointed along the intial veritical in inertial space would remain pointed in that direction.
2. The platform of the accelerometer would not remain horizontal. To maintain the platform horizontal with respect to the earth’s surface, the gyroscope must be torqued at a transport rate (V/R).
3. The integration of the North pointing acceleration yields North velocity (Vn and the integra-

tion of Vn/R (after insertion of the initial latitude) yields the latitude position of the vehicle.
In a strapdown system, the gyro, which measures all rates with respect to inertial space, will measure this transport rate (V/R). An integration of this rate would indicate that the vehicle has a pitch angle when there is none. The V/R must be subtracted from the gyromeasured inertial rate to obtain the desired body rate with respect to the horizontal earth rate. This is analogous to torquing.
Since V in a pure inertial system is obtained from the integral of the accelerometer measurement, there is a V/R feedback loop created. This feedback loop is known as the Schuler-tuned loop.
3.2.2.4 Single-Axis Schuler-Tuned Gimbaled System. The Schuler-tuned loop yields the same equations of motion as that of an undamped pendulum having a length equal to that of the earth’s radius (approximately an 84-minute period of oscillation). This is also referred to as a vertical earth loop.
3.2.2.5 Single-Axis Schuler-Tuned Strapdown System. As illustrated in the following ﬁgures: Figure 3-3 and Figure 3-4, a strapdown system yields the same Schuler-tuned loop as that of a gimbaled system. The Direction Cosine attitude matrix is analogous to a stabilized platform model.
For small vertical error gsinθy gθy; and the characteristic differential equation is that of an undamped pendulum having a length = R:

d2θy +
dt2

g θy = 0
R

The characteristic Schuler period is:

T = 2π √

R

= 84 minutes

g

The chart shown in Figure 3-5 represents data taken on a purely undamped inertial navigator. The 84-minute Schuler oscillations are clearly evident.
3.2.2.6 Undamped Schuler-Tuned System Error Propagation. An error analysis of the Schuler-tuned system for gyro bias drift and accelerometer bias error yields the propagation relationships shown below:
It is evident that the gyro bias drift causes a North distance error that builds up linearly with time, with a Schuler oscillation around the build-up. For times which are very short compared to the 84-minute

Schuler period, the propagation relationship is the same as that previously given for the simple open-loop system.
The accelerometer bias errors yield a north distance error that is bounded in time with a Schuler oscillation. For times that are very short compared to the Schuler period, the propagation relationship is the same as that previously given for a simple open-loop system.
From the relationships of the time terms, it can be seen that the gyro precision is much more critical than that of the accelerometer.
3.2.2.7 Effect of the Earth’s Rotation. If the analogy is extended further toward the real world by going to a rotating earth, it can be seen from the following two ﬁgures: Figure 3-6 and Figure 3-7, that Earth rate is another rate with respect to inertial space that tends to move a gyro-stabilized platform off of the local level. An additional Earth rate torquing term is required to maintain a local level platform.
In a strapdown system, appropriate Earth rate terms must be subtracted from the gyro-measured rate with respect to inertial space to yield body rate with respect to an Earth horizontal frame.
As shown in Figure 3-7, the Earth rate along a polar axis can be broken down into a North component (ΩecosL) and a vertical-down component (-ΩesinL). The required torquing terms are thus functions of latitude. Since latitude is a double integration of acceleration, additional feedback loops are created when the Earth rate terms are applied. The resultant feedback loop is called the Earth loop.

North distance error δDN due to gyro bias drift:

For small t

R

g

DN = Rwd [ t – √ g sin (√ R t) ] ⇒ 1/6 gwDt

North distance error δDN due to accelerometer bias:

For small t

R δDN = g AB [ 1 – cos (√

g t ) ] ⇒ ½ ABt2
R

An additional Earth rate torquing term is required to maintain a local level platform. In strapdown systems, Earth rate must be subtracted from gyro inertial rate to yield body rate with respect to an Earth horizontal frame. These Earth rate terms are functions of latitude:

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S9427-AN-OMP-010/WSN-7

• (ΩEN = ΩEcosL; (ΩEV = - ΩEsinL)
These feedbacks create an undamped Earth loop.
3.2.2.8 Torquing Rates (or Coordinate Frame Rates). An extension to three axes is made to indicate the combined transport rates (vehicle moving over the earth) and Earth rates (earth moving with respect to inertial space) torquing terms required around each gyro axis to maintain a local level, North-slaved platform. This platform is physical in a gimbaled system and a stabilized model in a Direction Cosine Matrix of a strapdown system.
These rate terms can be derived by applying a righthand rule to each rate. Thus, a positive North velocity of the vehicle yields a rate (WE) of VN/R in the negative East direction. A positive East velocity at latitude L yields a rate (WP) of Ve/R cosL along a polar direction. This polar axis rate can be broken down into a North component (Ve/R cosL) x cosL = Ve/R and a vertical (WK) azimuth (k axis) component -(Ve/R cosL) x sinL = -Ve/R x tanL.
To maintain a local level, North-slaved platform (or a phantom DC matrix relative to N, E, D) (three-axis system):

WN = ΩE cos L +

VE R

= ( ΩE + λ’) cos L

WE = –

VN R

= – L’

WK = – ΩE sin L –

VE R

tan L = – (ΩE + λ’ ) sin L

Where: L = Latitude, λ = Longitude,

L’ = Latitude Rate, λ’ = Longitude Rate

The transport rates can be expressed in terms of latitude rate and longitude rate in place of the Vn/R and Ve/RcosL.
Earth loop period:

TE =

√ (ΩE +

2π

VE

)2

R cos L

For marine case at normal latitudes this can be simpliﬁed to:
TE2π/ΩE = 24 hours

3.2.2.9 North Position Error. Figure 3-8 represents data from an AN/WSN-7(V). The 24-hour period Earth loop oscillation is evident.
3.2.2.9.1 Another Effect of Earth’s Rotation and Transport Rates. Additional kinematic acceleration terms:
1. Accelerometers measure A-G, where A is kinematic acceleration with respect to inertial space.
2. Terms are a function of accelerometer axes orientation.
3. For north and east horizontal accelerometers, with no vertical velocity:

AN =

dVN dt

+ 2VE Ω E sin L +

V

2 e

R

tan L

AE =

dVE dt

– 2VN Ω E sin L –

Vn R

VE tan L

4. The Coriolis acceleration terms (2V ΩE sin L) and centrifugal type acceleration terms should be subtracted from the accelerometer data to yield:
dVN/dt and dVE/dt
Note that these terms are functions of velocity and latitude, creating additional feedback loops.
3.2.3 VELOCITY DAMPING OF THE VERTICAL (SCHULER-TUNED) LOOP.
3.2.3.1 Other Real World Considerations. The real world is in the shape of a spherical ellipsoid, not a sphere. This ﬂattening at the poles yields differences in earth radii and gravity as functions of latitude. The real world does not have an equal distribution of mass. This yields variations in the amplitude (gravity anomaly) and direction (verﬁcal deﬂection) of gravity. If not compensated for, the vertical deﬂections (which act like gravity tilts) will create disturbances and errors in every inertial navigator. In a similar manner, large differences in local mass, such as underwater mountains or the edge of deep trenches, can cause local gravity anomalies.
3.2.3.2 Damping the Schuler Loop. In pure undamped inertial systems, certain errors; e.g., vertical tilt, will continuously oscillate at Schuler periods (84 minutes). Random noise sources lead to vertical errors, which build up with √t. These oscillations can be

damped out. An undamped Schuler loop is dynamically exact; there are no errors caused by vehicle dynamics on a constant gravity earth (assuming no sensor errors).
1. Use of internal loop damping will sacriﬁce dynamics exactness.
2. Use of an external reference (external velocity reference) for damping preserves dynamic exactness; however, the external reference introduces errors due to inaccuracies in the velocity values obtained from the external reference.
3.2.3.3 External Velocity Damped Vertical Loop. The ship’s Electromagnetic (EM) Log, or Doppler Sonar Velocity Log (DSVL) if so equipped, is typically used to provide reference velocity for the inertial navigation system damping. Damping parameters must be selected such that they balance log errors (e.g., ocean current variations) against inertial errors (e.g., vertical deﬂections) and achieve a good damped response. Figure 3-9 illustrates an External Velocity Damped Vertical Loop.
3.2.4 STRAPDOWN PROCESSING. The AN/WSN-7(V) uses DCM transformations in its strapdown algorithms to convert between the reference frames in use. The AN/WSN-7(V) uses three basic coordinate frames:
1. Sensor block frame (b); a, b, c (RLG axes)
2. Earth reference frame (n); n, e, k (north, east, down)
3. Dock coordinate frame (l); x, y, z (forward, athwartships, down)
The gyro and accelerometer data is sampled by the Navigation (Nav) Processor at 50 Hz. This is the basic update rate for the strapdown process. A block diagram of the strapdown process is given in Figure 3-10.
The raw gyro data is compensated and corrected for various bias, scale-factor, linearity, and misalignment errors, including temperature effects and coning corrections. The corrected gyro rates represent all body motions with respect to inertial space. Earth rates and vehicle transport rates (due to the vessel’s movement across the Earth surface) are subtracted from the gyro rates to yield body rates with respect to an Earth-ﬁxed reference frame. These latter rates are then appropriately integrated to provide a Euler parameter and direction cosine representation of sensor block attitude relative to an Earth (n, e, and k) reference frame.

The raw accelerometer readings are similarly corrected, and the acceleration vector then transformed from the sensor block frame (b) into the Earth frame (n). After velocities and movements are computed, these are also used to update the Earth and transport rates, providing the coordinate frame rate feedback to the next iteration of the DCM inner element (BA) used to process RLG information.
Angular information is then converted back to the deck frame (l) in an outer DCM element (BD), which is driven by the sensor block angles for azimuth (Ga) and roll (Gr). The Euler angles (ship heading, roll, and pitch) are then extracted, and their rates derived and extrapolated. The smoothing and extrapolation algorithms operate at 800 Hz and provide ﬁltered attitude rates that represent actual ship motion with negligible dynamic error, while attenuating spurious higher frequencies. The smoothing of extrapolated attitude data ensures that there are no step changes of output angle.
3.2.5 NAVIGATION PROCESSING. The navigation software includes various lever arm corrections (to give velocities and position at desired locations), and a sideslip coefﬁcient correction for lateral velocity.
The north, east, and vertical acceleration increments (An, Ae, and Av) from the strapdown function (refer to Figure 3-10) are corrected for gravity and Earth Coriolis, and integrated to yield inertial north (Vn) and east (Ve), and vertical velocities (Vk). Vn and Ve are divided by appropriate Earth radii to produce latitude and longitude vehicle rates, which are integrated to give the change in system latitude and longitude. The Earth rates (derived from latitude) and vehicle rates are fed back to the strapdown function where they are appropriately subtracted from gyro-measured rates used to modify sensor block attitude.
3.2.5.1 Vertical Loops. The vertical loops are deﬁned as the control channels keeping the strapdown stabilized platform model DCM level, and in the local vertical.
The stabilized platform model carries out the same job as the stable table/base motion isolation in a conventional inertial system. Its “level” (and hence the system vertical) is established during gyrocompassing (coarse align) and then maintained by adjusting the angles contained in the DCM to offset any movement (rotational change), as measured by the individual gyros.
This “stabilized platform model” level can oscillate with the same 84-minute and 24-hour periods as a

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S9427-AN-OMP-010/WSN-7

conventional inertial system. Its stability is a function of log damping and the accuracy of navigational ﬁxes used for resets/updates. Log damping is incorporated to damp out oscillations about the vertical. Data from a ship’s log is used to provide an independent source of velocity information. Automatic damping/undamping is controlled by the Kalman Filter (KF).
3.2.5.2 Earth Loop. The gyros measure all sensor block rotation rates with respect to inertial space, whether due to the earth, the ship, or the two-axis indexing. The Earth loop is a discrete feedback loop that corrects the gyro rates for the effects of Earth rotation basis. The Earth rates are derived from system latitude and are fed back and subtracted from the gyro rates prior to integration of the gyro rates to maintain the “stabilized platform model” (DCM).
Any latitude error (due to an accumulation of navigation errors, a ﬁx error, or uncompensated system drift rates) causes incorrect computing of Earth rates. These incorrect Earth rates, which are fed back and subtracted from the gyro rates prior to attitude integrations, lead to an improper DCM, which yields improper heading and tilts. The DCM errors cause an improper transformation of accelerations, yielding errors in north and east velocities, which in turn produce errors in latitude and longitude. For marine velocities, if undamped, Earth loop error propagation involves 24-hour periodic oscillation terms. The Earth loop in the AN/WSN-7(V) is slightly damped by action of the Kalman ﬁlter corrections based on reference velocity measurements, depending on the error models employed for the log reference relative to the error models employed for the inertial sensors.
3.2.5.3 Vertical Velocity Loop. The vertical velocity loop is separate from the strapdown and Kalman operations, and handles the vertical acceleration (mostly from the C accelerometer), which is integrated once to give vertical velocity and then again to give depth change.
Accurate vertical velocity is obtained by operating on the inertial vertical velocity in a damped third-order loop conﬁguration, using a depth reference (depth reference set = 0.0 for surface ships) or a reference vertical velocity. The integral of vertical velocity is matched against depth (or zero mean sea level for surface ships) to yield certain vertical axis bias and scale-factor calibrations.
3.2.6 KALMAN FILTER.
3.2.6.1 General. A Kalman Filter (KF) is a digital ﬁlter able to track the mean signal within noisy

data. The AN/WSN-7(V) uses a 26-state KF with the Kalman parameters (K1 – K26) forming the inputs or corrections to many of the Nav Processor software processes. The KF has three main functions:
1. To monitor system parameters (especially gyro/accelerometer bias, scale factor, and misalignment) measured during alignment.
2. To process position updates.
3. To control log damping.
The KF also computes estimates of ocean current velocities and speed log biases. Corrections are made to the various error states in the system (velocity errors, accelerometer errors, tilt-states, and gyro bias drifts). Estimates are also made of ocean currents and Log bias. A block diagram of the Kalman Filter operations is shown in Figure 3-11, and the equations used are listed in Paragraph 3.2.6.2.. 3.2.6.2 Kalman Filter Computations. Time Extrapolation:
• XN+1 = PHI *XN • PN+1 = PHI * PN * PHIT + QP
Measurement Update:
• XN+1 = XN- + KN * (Z − H * XN-)
• PN+ = PN- - KN * H * PN-
where:
• X = State Error Vector
• P = State Covariance Matrix
• PHI = State Transition Matrix from time TN to TN+1
• Q = System Noise Matrix
• QP = Integral of Q * dt from TN to TN+1
• dt = Kalman Filter Time Step = TN+1 - TN
• Z = Measurement Vector
• H = Measurement Matrix • K = Kalman Gains = (PN- * HT) * (H * PN- * HT + R)-1
• R = Measurement Noise Matrix
Subscripts N’ N+1 refer to values at time TN and TN+1. Subscript N+ refers to the values after a measurement update cycle. Subscript N- refers to the values before a measurement update cycle. 3.2.6.3 Kalman Filter Matrix Deﬁnitions. The various matrices employed in the Kalman Filter are deﬁned as follows:

• The X Matrix is a listing of the state variables being involved in the KF.
• The K Matrix is the set of optimal gains used to multiply the measurement differences to generate the feedback corrections.
• The H Matrix is the set of measurement factors that relate the difference measurements (Z) being made to the error states (Z = HX).
• The P Matrix is the state-covariance matrix. This matrix represents the expected statistical errors of the state variables. The diagonal elements are the variances associated with each state and the off-diagonal elements are the covariances, which relate the expected values of the errors in one state to those in some other state.
• The Po Matrix is the initial set of variances associated with each state variable.
• The Φ Matrix is the state-transition matrix, which relates the current values of the state variables to the value at a future time. Φ is given by Φ = I + A∆ t, where I is the identity matrix (all diagonal terms equal 1) and the A matrix relates the derivatives of the state-variables to the state-variables (X=AX+N) (where N is the matrix of white-noise errors).
• The R Matrix is the diagonal matrix of the expected Reference White-Noise Errors. These would include expected Log Errors.
• The Q Matrix is the diagonal matrix of expected System White-Noise Errors. These would include expected gyro white-noise drifts.
The Kalman Filter process continually generates the best estimate (minimum variances) of the system state matrix X(t). To differentiate between the actual values of the system state variables and the KF estimates of these variables, the KF estimates are called X’(t). Since X’(t) represents the best estimate of what the system error states are at the time t, then – X’(t) would be a matrix of the corrections to be applied if the reset were to be made at that time. If a particular error state correction is applied, then the X’(t) is set to zero following the correction for those states. If the reset is held off or is never corrected (may not be feasible), the KF provides for the minimum variance propagation of X’(t).
The AN/WSN-7(V) employs the KF for optimal position ﬁx reset as well as for optimal damping. Whenever an external position reference [e.g., Global Positioning System (GPS)] ﬁx is acquired, the Kalman Filter:

1. Measures the difference between System Latitude and Reference Latitude, and between System Longitude and Reference Longitude.
2. Multiplies the difference by optimal gains.
3. Feeds corrections back to various system error states.
These operations follow the same general relationships described for optimal damping. The AN/WSN-7(V) also employs the Kalman Filter during special 72-hour alignment/calibration periods to calibrate gyro bias drifts, A and B gyro scale factors, gyro misalignments, and A and B axis accelerometer biases. These state variables are made observable by indexing motions of the two-axis indexer. Advantage is made of the knowledge that average reference velocity is zero during a Dockside Align/Calibrate, or that accurate GPS ﬁxes are occurring frequently during At-Sea Align/Calibrate. The resultant overall AN/WSN-7(V) Kalman Filter contains 26 error states as delineated below. Several of these state variables are frozen after the align/calibrate process has completed. Kalman Filter Error States:
• Velocity North
• Velocity East
• Tilt North
• Tilt East
• Heading
• Latitude
• Longitude X cos Lat
• A Gyro Bias Drift*
• B Gyro Bias Drift*
• C Gyro Bias Drift*
• North Bias Drift
• Azimuth Bias Drift
• A Accelerometer Bias
• B Accelerometer Bias
• A Gyro Scale Factor*
• AB Gyro Misalign*
• AC Gyro Misalign*
• B Gyro Scale Factor*
• BA Gyro Misalign*
• BC Gyro Misalign*

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• CA Gyro Misalign*
• CB Gyro Misalign*
• North Ocean Current
• East Ocean Current
• Log Bias Fore/Aft
• Log Bias Port/Stbd
Gyro Bias Drifts, Misalignments, and Scale Factors will be unchanged when in Navigate.
3.2.7 POSITION FIX AND POSITION SLEW. Position updates are handled by the Kalman Filter and can be applied in two ways: either as position ﬁx resets or as position slews.
1. Position Fix - A position ﬁx will reset both position and drift coefﬁcients; however, the amount of position movement will depend on the weighting given to the ﬁx. This calculation is based on the system’s internal estimate of position and the ﬁx data. The effect of the ﬁx is calculated by the KF and can be displayed for review before acceptance, but once the ﬁx reset is applied, its effects cannot be undone. Fixes can be entered manually by the operator, or can be received via the data interfaces from an external source such as GPS.
2. Position Slew – A position slew allows the operator to enter position data to update system position without causing a reset. This process does not change KF parameters or underlying system drifts.
3.2.7.1 Fix Reset Processing by the Kalman Filter. System position is based on inertial calculations and an uncertainty area (system accuracy) deﬁned by system sigma latitude [sigma north (SN)] and sigma longitude [sigma east (SE)]. The estimated values of SN and SE increase with time, but are decreased by the application of a ﬁx.
When a ﬁx is entered, either manually or received via the data interface, the Kalman Filter compares the inertially-derived position with the available position reference (ﬁx) data and operates on these measurements to generate corrections to the modeled system states. The process attributes navigational errors to sensor or system drifts, and then modiﬁes the Kalman parameters to neutralize the error pattern. Corrections are made to latitude, longitude, velocities, tilts, heading, gyro biases, non-reversing rotation rate biases, scale factors, and misalignments and horizontal accelerometer biases.

The Kalman Filter is very closely coupled to the Inertial Measuring Unit (IMU), and there is no easy distinction between raw and ﬁltered positions. Earlier navigation systems stored several ﬁxes and/or allowed data to be modiﬁed before the new ﬁlter was implemented. With the AN/WSN-7(V) this is not possible because the Kalman Filter operates on one ﬁx, as entered. The effect of the ﬁx is calculated and can be displayed for review before acceptance, but once the ﬁx reset is applied, its effects cannot be undone.
When a ﬁx is entered, the Kalman Filter checks that the ﬁx data and resulting resets are within acceptable limits. The operator is alerted to ﬁx data or a reset outside acceptable bounds by fault codes.
Fix processing within the Kalman Filter calculates the latitude and longitude resets using the difference between system position and ﬁx position. The KF calculates weighting based on the estimate of system accuracy (SN and SE) as compared to the ﬁx accuracy [ﬁx sigma latitude (FSN) and longitude (FSE)]. This weighting is used to determine the proportion of the difference in position [reset north distance (DN) and reset east distance (DE)] to be applied as the position reset.
If a ﬁx is entered with a small sigma value (high accuracy), then a large percentage of the ﬁx error will be applied as a reset. The relative difference between the system position and the ﬁx position does not determine the weighting; the weighting is determined only by the estimated system accuracy and ﬁx accuracy. The estimated value of system accuracy increases with time, but is decreased by the application of ﬁx data as a reset. This results in a higher weighting being given to ﬁx data following a long navigate period as compared to ﬁx data entered closely spaced in time.
Entry of valid ﬁx data with suitable ﬁx variances should always improve system accuracy, but forcing an incorrect reset will introduce a position error proportional to the reset error. This position error will propagate through the undamped Earth loop into position and attitude errors. Large position or attitude errors may cause the vertical loops to undamp (period 84 minutes) due to velocity errors.
For submarine applications where extended dive operations without an update have occurred, the system sigma latitude and longitude values will have increased. Application of a single accurate ﬁx will produce a position reset that is approximately equal to

the ﬁx error and will correct drift parameters. A single ﬁx may not update the position completely, but if this is necessary for tactical picture reasons, and if application of successive ﬁxes and gradual convergence of the Kalman to the correct position over time are not acceptable, then the ﬁx should be applied again as a slew.
3.2.7.2 Manual Fix Entry. When a ﬁx is entered manually, the data entered includes time of ﬁx, ﬁx latitude and longitude, and ﬁx accuracy. Fix accuracy is expressed either as separate sigma latitude (FSN) and sigma longitude (FSE) to one sigma conﬁdence level (68% expected error limits), or as Radial Position Error (RPE) to 95% Circular Error Probability (CEP), with equal latitude and longitude error sizes, both to 0.1 NM.
When using RPE ﬁx entry, the system calculates equivalent FSN and FSE values as follows:
FSN and FSE = 0.40854 x RPE
The latitude and longitude weighting or gain (K) is calculated using the system sigma values at the time of the calculations, and the ﬁx sigma values (or the sigma values calculated from RPE data) which are used as entered:
K = (system sigma)2 / (system sigma)2 + (ﬁx sigma)2
E.g., for a system sigma of 0.45 NM and:
1. A ﬁx sigma of 0.1 NM, then K = 0.9529
2. A ﬁx RPE of 0.1 NM (ﬁx sigma = 0.40854 x 0.1 NM), then K = 0.99992
3. A ﬁx sigma of 0.0 NM, the default of 0.0005 NM gives K = 0.999998
The north and east distances the reset will move the system position (DN and DE) are given by:
Reset = K x (ﬁx - system)
Manual entry of GPS data with a true CEP of 0.01 NM, using ﬁx sigma of 0.0 NM will result in a system gain (and resulting reset) larger than justiﬁed. If the ﬁx sigma value cannot be entered exactly, it should be rounded up. The difference in gain is small for a single ﬁx, and application of multiple ﬁxes will converge the system to the ﬁx position even with reduced gains. This problem does not exist with ﬁxes entered via the data interface because the GPS message format allows greater precision of ﬁx variance.
3.2.7.3 Fix Reset Checks. When a ﬁx is entered, the data is checked to be within the following limits:
1. (Position error)2=(system Lat − ﬁx Lat)2 + ((system Lon − ﬁx Lon) x cos(ﬁx Lat))2

2. Error limit = 9 x (SN2 + FSN2 + SE2 + FSE2)
If the position error squared is greater than the error limit, then Fault Code 209 will be declared. Additionally, the system resets for latitude, longitude, velocity, and various system feedback parameters are checked using appropriate limits similar to the above limit on position error. If a reset exceeds a speciﬁed limit, then fault codes in the range 212 to 217 will be declared.
If the ﬁx data is unreasonable, or a reset exceeds a speciﬁed limit, the operator should then review the ﬁx DN and DE (the North and East distances the reset will move the system solution), and either correct the ﬁx data or, if the ﬁx data is known to be accurate, accept it and force the reset.
NOTE
Any position ﬁx for which the resulting radial position reset exceeds 5NM should be reviewed closely before accepting the data for application. Any ﬁx that exceeds the range of the latitude and longitude reset (DN and DE) display (±100 NM) is immediately suspect.
The AN/WSN-7(V) maintains a history of position data to allow ﬁx computations using data obtained up to 60 minutes prior to the current time. Fault Code 218 will be declared if the ﬁx data is more than one hour old.
3.2.7.4 Position Slews. The AN/WSN-7(V) provides a facility that enables the operator to slew (update) the system position without causing a system reset. This process does not change KF parameters or underlying system drifts.
When the slew entry facility is selected, the operator is prompted to enter the time of slew and the latitude and longitude to which the system position is to be slewed. When the slew data is entered and accepted, the system checks that the data is reasonable. If the data is reasonable, the system position is updated.
3.2.8 VERTICAL LOOP DAMPING. In the AN/WSN-7(V), reference velocity data is employed primarily to provide damping to the Schuler loops. Damping to the Schuler loop involves:
1. Measuring the difference between system velocity and reference velocity.
2. Multiplying this difference by appropriate gains and ﬁltering operators.

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3. Feeding back the multiplied differences as corrections to various system error states.
Examples of possible error states are accelerometer errors, vertical tilts, velocity errors, and gyro drifts.
The damping operation can be “a group of parameters” where the feedback gains are generally constant or Kalman Filter optimal damping can be employed.
If the difference velocity is fed back as a correction to the accelerometer output through an appropriate constant gain and high-pass ﬁlter, a third-order damped Schuler loop is obtained. This yields a good damped response and a zero steady-state system error in response to a constant bias error in the Log reference. The AN/WSN-7(V) employs third-order damping as an operator-selected optional mode.
The preferred damping mode in the AN/WSN-7(V) is Kalman Filter optimal damping. Kalman Filter Schuler loop damping is analogous to the previously described grouped parameter damping loop. The feedback gains are time-varying instead of constant. Depending on the expected errors of the inertial sensors and the reference velocity sensors, the feedback gains are optimally determined.
The velocity reference to be used by the system is selected by the operator. It is available from external sources (speed logs or GPS receivers) via the data interfaces or can be entered manually. The selected velocity reference provides the Kalman Filter with water speed or ground speed reference data in the ship water coordinates (fore/aft and port/starboard) or geographic coordinates (north and east). If the port/starboard water speed is not available (as in the case of a single-axis speed log), an estimate of the port/starboard water speed is calculated using the inertial fore/aft velocity, heading rate, and side-slip coefﬁcient. If the Dockside mode is selected, the fore/aft and port/starboard ground speed used by the Kalman Filter is set to 0.0 knots.
The selected velocity reference (after log bias, leverarm and side-slip corrections are applied) is resolved into appropriate components and compared with the inertial-derived velocities. The differences are multipled by optimal gains in the KF and corrections are fed back into the vertical loops to achieve optimally damped loops.
The KF controls the automatic selection of damping or undamping during turns, or when there is a signiﬁcant discrepancy between log and inertial solutions. Automatic undamping and redamping are accomplished by applying accept/reject criteria to the ﬁltered inertial reference velocity differences.

The KF damping control can be overriden by operator selection. The operator can force the system to operate continuously in ether an undamped or damped Schuler loop conﬁguration. The damping modes that can be selected by the operator are:
1. Auto – The KF determines the damping status. Damping is automatically removed when the selected velocity reference accurace degrades as a result of maneuvers or signal loss. Damping is automatically reimposed when the velocity reference stabilizes or returns. Fault Code 222 will be declared if the selected reference velocity is not available, and Fault Code 223 will be declared if the system has been undamped for 84 minutes or longer.
2. Manual Damped – Velocity damping is applied continuously regardless of the quality of the selected velocity reference.
3. Manual Undamped – Velocity damping is inhibited.
3.2.9 SENSOR ERRORS AND CALIBRATION. Each individual RLG and accelerometer has a range of instrument errors. The principal errors are:
1. Scale factor (SF). The ratio of change in output to change in input.
2. Bias error. A steady output seen when no input is present.
3. Alignment error. The actual (measuring) axis of the instrument is displaced from the design-input axis deﬁned by its mountings. The result is that the instrument is sensitive in other directions, and the actual output may include pick-up or cross coupling from other inputs.
Many of these errors are temperature-sensitive and are measured by the manufacturer during ﬁnal production test of the particular sensor. The AN/WSN-7(V) uses a total of seven separate plug-in Programmable Read-Only Memory (PROM)s to hold the manufacturer’s calibration coefﬁcients for each accelerometer and RLG and the IMU Assembly. The calibration PROMs are installed in the IMU Processor board during installation.
3.2.9.1 Factory Calibration. The factory calibration:
1. Normalizes every IMU such that ﬁeld replacement, without any additional special calibration, is possible.
2. Normalizes the Sensor Block Assembly (SBA) and sensor mounting surfaces (gyro and accelerometer). This is critical to maintain atti-

tude and velocity accuracy during indexing and ship’s motion.
3. Requires the use of special test equipment that may only be available at the manufacturer’s facilities.
4. Stores results on the IMU calibration PROM that is installed on the IMU Processor CCA.
3.2.9.2 Operational Calibration – Self-Align/Calibrate.
3.2.9.2.1 General. The system mathematically aligns inertial sensors with respect to gravity and earth’s rotation (gyrocompassing). The Kalman Filter estimates residual (the portion not already compensated for in either sensor PROM or IMU PROM) sensor biases, scale factors, and misalignments. The Self-Align calibration is key to achieving long-term navigation performance. The Kalman Filter estimates of residual errors make ﬁeld replacement of sensors and the entire IMU possible.
3.2.9.2.2 Calibration Terms and Deﬁnitions. dTHB0 (Gyro A Bias), dTHB1 (Gyro B Bias) and dTHB2 (Gyro C Bias):
Axes 0 and 1 are nominally horizontal, and 2 is nominally vertical. These values, as displayed in Factory Interface Monitor (FIM), the Control Display Unit (CDU) (IP-1747) or PAGE 4 item 4 of the operation menu, are total values. This means they are initialized at the values of gyro PROMs and residual amounts are added or subtracted. These values are updated only during a 72-hour calibration; they are not affected during a 20-hour align or in navigate mode. To monitor the gyros, record the gyro bias values displayed on Page 4, item 4 of the operation menu at the beginning of a 72-hour calibration. The values will be stable at 24 hours into the calibration. Record the gyro bias values after 24 hours; a change from the PROM value of greater than 0.020°/hour is suspicious. This could indicate the gyro PROMs are in the wrong position, or the IMU was swapped without changing the PROMs. The estimation process for the C gyro bias is not as repeatable at the A and B gyro bias values. Nonetheless, for a given IMU, gyro biases should repeat to within 0.010°. The exact value of the bias is not very important to an indexed system, but the values may be used as a conﬁdence check of the align/calibrate process.
dTHBN (residual IMU north bias) and dTHBK (residual IMU vertical bias):
These residual drifts in the geographic frame should be less than 0.004°/hour in magnitude, and should repeat to within 0.001°/hour. These values are adjusted during navigate after a ﬁx. During align/calibrate, errors in reference latitude on the order of 0.005° or vertical deﬂections on the order of 20 arc

seconds will cause signiﬁcant shifts in the N and K estimates. These N and K shifts will balance a reference latitude or vertical deﬂection error and will not seriously affect navigation performance until a large change in latitude has been made. Variations toward the end of the estimation period are typically less than 0.0001°/hour.
KdVB0 (A accelerometer bias) and KdVB1 (B accelerometer bias):
At the beginning of a 72-hour calibration, these values start at the PROM value just like the gyro biases. The Kalman Filter will begin estimating the horizontal accelerometer bias values about 20 minutes into the 72-hour calibration. Typically, these values settle to within 100-micro-gs of the PROM value. A difference in excess of 200 micro-gs is suspicious. Variation near the end of the calibration period is typically less than 5 micro-gs. Again, recording these values before and after a calibration is a good conﬁdence check of the calibration process. These values are adjusted during a 20-hour align and with very low gain during navigate. Accelerometer biases can be seen at the display menu PAGE 4 item 3.
DVb3 (C accelerometer bias) and DAM33 (C accelerometer scale factor):
These are calculated by the vertical velocity loop, not the Kalman Filter. The C axis values are only calculated in the dockside mode. Since there is no pitch gimbal, during navigate, the C accelerometer will not necessarily maintain a nominal vertical orientation. The C accelerometer bias should be within 200 micro-gs of the PROM value, and scale factor should stay within ±500 ppm. These quantities are estimated as soon as the system is put into the dockside mode. When the system is taken out of the dockside mode, any vertical velocity error remaining is put into a K bias (dVVBK). The C accelerometer bias value is not important to navigation performance, but will affect attitude and velocity noise with roll indexing.
DGM11 (A gyro scale factor), DGM22 (B gyro scale factor) and DGM33 (C gyro scale factor):
DGM11 and DGM22 are estimated by the Kalman Filter starting about an hour into the Align/Calibrate and are frozen after 24 hours. These values are not adjusted during a 20-hour align or in navigate. DMG33 is currently not used by the system. RLG scale factor is extremely stable; variations greater than ±10 ppm would be unusual. The Kalman Filter estimates the difference values between the factory PROM established values. The values should be less than 50 ppm in magnitude and are typically less than 10 ppm.
DGM12 (gyro A misalignment into B), DGM13 (gyro A misalignment into C), DGM21 (gyro B misalignment into A), DGM23 (gyro B misalignment into C), DGM31 (gyro C misalignment into A) and DGM32 (gyro C misalignment into B):

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These are the remaining deltas after factory calibration has corrected for sensor block mounting surfaces and gyro input axis corrections. These values are typically less than 100 micro radians and repeat within 20 micro radians. If a gyro is remounted, the value may change by more than 20 micro radians, but will tend to stay below 100 micro radians; this is also true if a gyro is replaced. These values are estimated beginning 1 hour after calibration begins and will be frozen after 24 hours. These values are not adjusted during a 20-hour align or in navigate.
3.2.9.3 Self-Align/Calibrate. When the system is started up, the contents of each calibration PROM are copied to the Nav Processor working area [Random Access Memory (RAM)].
The two-axis indexing pattern used in the AN/WSN-7(V) makes speciﬁc inertial sensor biases, misalignments and scale-factor errors observable against dockside and at-sea reference velocity and position data. To achieve this self-calibration capability, the following states are incorporated in the Kalman Filter:
• A Gyro bias
• A Gyro scale-factor
• A-to-B Gyro misalignment
• A-to-C Gyro misalignment
• B Gyro bias
• B Gyro scale-factor
• B-to-A Gyro misalignment
• B-to-C Gyro misalignment
• C Gyro bias
• C-to-B Gyro misalignment
• C-to-A Gyro misalignment
• A Accelerometer bias
• B Accelerometer bias
The Kalman Filter estimates and self-calibrates all the above states as their effects in response to indexing motions are observed. The C accelerometer bias and scale factor are monitored by the vertical velocity loop. The initial 72-hour dockside calibration align period after system installation is sufﬁcient to self-calibrate all of these parameters to acceptable levels. A 20-hour align uses previously calculated values and does not modify those values, except the accelerometer bias values.
During Dockside Align, the system uses the roll and azimuth indexing motions to separately put the A, B,

and C sensors into test positions. The Kalman Filter and vertical velocity loop can then measure the actual instrument bias, scale factor, and misalignment errors against known Earth rates and local gravity (by measurement in the vertical, then inversion and remeasurement), and develop additional reﬁnements to the calibration coefﬁcients provided by the sensor PROMs. The ﬁnal calibrated values are stored in battery-backed RAM on the Nav Processor board and are applied thereafter to correct the (raw) sensor readings back to absolute (true) values on which navigational calculations can be based. Subsequent align periods can then be reduced to 20 hours. If an inertial component is replaced, or the battery-backed RAM data is lost or invalid, then another 72-hour calibration align period is required.
3.2.9.4 Summary.
The 72-hour calibration:
1. Is a true calibration mode.
2. Calculates and applies all bias values and scale factor corrections.
3. Is entered whenever no valid calibration data exists, after Kalman reinitialization, after IMU or sensor replacement, or after loss of memory (battery disconnected or Navigation Processor Memory CCA replaced). Calibration data may be retrieved from the other system if the INS-INS link is active, bypassing the need for a 72-hour calibration.
4. Should be initiated (time permitting) whenever operator believes previous calibration data may be corrupted.
The 20-hour align:
1. Is only an alignment mode, and uses previous calibration data.
2. Only adjusts the accelerometer bias values.
3.2.10 KALMAN FILTER REINITIALIZATION. Reinitialization of the Kalman Filter resets all sensor calibrations to their stored PROM values. A 72-hour calibration period is required following a KF reinitialization before the system is available for precision navigation. KF reinitialization can be automatic or can be manually selected by the operator.
3.2.10.1 Automatic Reinitialization of the Kalman Filter. The Kalman parameters from the last Dockside Align are held in battery-backed RAM on the Nav Processor board. If the Nav Processor board has been replaced, or if the system fails its battery-backed RAM checksum test during

the initialization sequence, the stored sensor calibration parameters are not usable, and the system will automatically cause a KF reinitialization to occur.
If an inertial sensor has been replaced, various calibration parameters need to be redetermined. When the system is started up, the software compares the serial numbers of the calibration PROMs with the values stored in the battery-backed RAM. If any differences are detected, the system assumes that an RLG or accelerometer (or the complete IMU Assembly) has been replaced and automatically causes a KF reinitialization to occur.
If a 72-hour calibration has not been completed, optimum calibration of all parameters has not occurred. The system automatically causes a KF reinitialization to occur when the system is turned on or when Dockside Align mode is next selected.
3.2.10.2 Manually Selected Reinitialization of the Kalman Filter. The operator can manually select a KF reinitialization by following the appropriate menu procedures.
If an align process is not successful (as indicated after one hour in align by velocity differences greater than 0.05 knots in Dockside Align mode or KF faults), system recalibration should be carried out using an appropriate align mode and KF reinitialization. Full calibration will be restored by Dockside, Slave, or At-Sea Align 72-hour align.
If navigation performance shows abnormal errors (excessively large position errors or KF faults), recalibration should be carried out using an appropriate align mode and KF reinitialization. Full calibration will be restored by Dockside, Slave, or At-Sea Align 72-hour align.
3.2.11 SENSOR BLOCK INDEXING. The sensor block is periodically rotated within the Indexer Assembly in a speciﬁc sequence designed to enhance system performance by averaging out, or commutating gyro/accelerometer biases on all three axes and averaging out many other error sources. Reorientating the sensor block allows the software to correct for long-term errors and allows mechanical biases to be averaged out.
Roll and azimuth indexing is achieved by two servocontrolled loops. Overall control of the indexing sequence is carried out in the Nav Processor software, and this includes both the desired angle (the indexing sequence plan) and the comparator (feedback) function of generating servo drive signals during the movement phase.

For the ﬁrst 80 seconds of operation following startup and initialization, the sensor block is positioned by being driven in roll and azimuth to null the synchro outputs before the indexing sequence is started.
There are 64 distinct indexing cycles (phases) to the indexing sequence. During the later stages of align and during Navigation, every 5.0 minutes the sensor block is moved through ±90° or ±180° in roll or azimuth. The sensor block passes through all 64 phases in 320 minutes and the sequence is then repeated. If the next phase in the proﬁle speciﬁes that a failed axis is to be slewed, the indexing is advanced again until a non-failed axis is slewed.
During indexing, the software checks for excessive azimuth and roll rates. If an excessive rate is identiﬁed, a fault is declared and the appropriate torquer is disabled. The software also checks for non-follow-up of torque commands. If non-follow-up is detected, a fault is declared and the appropriate torquer is disabled.
The periods between the indexing motions are referred to as the dwell periods. During dwell periods, the sensor block is maintained at the attitude speciﬁed by the indexing proﬁle for a predetermined time before being indexed to a new orientation.
Roll motions are stabilized against ship motions by outputs from the strapdown process. This apparent coarse BMI is not vital to attitude or short-term navigation, but ensures ship motions do not negate an indexing move and unbalance the overall cycle, to the detriment of long-term performance.
If the indexer motions become faulty, each indexer can be disabled by the operator via the front panel. Loss of one (or both) indexer motions will not immediately affect navigational performance, because the gyros and accelerometers continue to monitor any changes in sensor block orientation; however, it would degrade long-term accuracy because some errors and drifts are no longer physically averaged out.
3.2.12 BASICS OF POLAR NAVIGATION. Use of the normal (true) coordinate system is impractical for navigation at the Earth’s poles because:
1. True longitude and true heading are indeterminate
2. True longitude rate and true heading rate become inﬁnite
3. True heading accuracy deteriorates (varies as sec L)

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One solution is the use of a transverse coordinate system for polar region operation.
3.2.12.1 Relationships Between True and Transverse Coordinates. The following relationships between true and transverse coordinates are obtained by spherical trigonometry:
• cos LatT sin LonT = cos Lat sin Lon
• sin β cos Lat = sin LonT
• sin β cos LatT = sin Lon
• sin Lat = cos LatT cos LonT
• sin LatT = -cos Lat cos Lon
• cos Lat cos β = -cos Lon T sin LatT
• cos Lon sin Lat = cos LatT cos β
Where β is the angle between true north and transverse north from the current position.
Using the above relationships, one can obtain true latitude and longitude in terms of Transverse Latitude and Transverse Longitude and vice versa.
For example, the coordinates of SPAWARSYSCEN in Norfolk, Virginia, are:
Lat = 36° 55.14 NLatT = -11° 00.32 S
Lon = -76° 11.13 WLonT = -052° 16.21 W
Transverse Coordinate Frame Rates to Maintain Transverse North-Oriented, Local Level Platform
WNT = -WE cos IT sin LT + IT cos LT (1)
WET = -WE sin IT − LT (2)
WKT = -WE cos IT cos LT − IT sin LT (3)
3.2.12.2 Operating in Polar Mode. At high latitudes the AN/WSN-7(V) operates using a transverse coordinate system (Polar mode). The Polar mode can be selected to activate automatically when true latitude is greater than 86°, and to deactivate when latitude is less than 84°. The polar mode can also be manually selected.
In the vicinity of true pole, polar heading is decoupled from both transverse latitude and transverse longitude. A position ﬁx will not correct polar heading and polar heading error builds up as integral of z-axis gyro drift. Because of two-axis indexing, which averages out z-axis bias drift, polar heading accuracy is inherently better in AN/WSN-7(V) than in other navigators. Polar heading error in AN/WSN-7(V) builds up as At, due to white noise random drift (which is not averaged out). In most other systems, polar heading error builds up as t or t2.
Polar Mode Algorithms include the following operations:

1. Strapdown computations maintain attitude direction cosine matrix relative to a transverse frame.
2. Euler angle extraction of this matrix yields roll, pitch, and polar heading.
3. Accelerometer outputs are transformed by the transverse DC matrix, yielding transverse coordinate accelerations.
4. Transverse accelerations are integrated to yield transverse velocities.
5. Transverse velocities are integrated to yield transverse latitude and transverse longitude.
6. Earth rates and transport rates are obtained as functions of transverse parameters.
7. Kalman Filter operates in transverse coordinates with transverse position ﬁx resets.
8. True coordinates are derived for display purposes.
The indexing sequence ensures that the sensor block (and C gyro/accelerometer) is either upright or inverted, and this is used to self-calibrate the C accelerometer bias and scale factor corrections. Indexing involves rotating the sensor block through eight possible orientations relative to vehicle frame.
3.2.13 NORMAL/TRANSVERSE OPERATION. The AN/WSN-7(V) can be operated either using the normal (true) coordinates of conventional latitude and longitude, or in transverse (polar) coordinate mode. The transverse mode is designed for use in polar regions with the transverse pole (imaginary pole) located on the equator at 180° E/W.
3.2.13.1 Coordinate Mode Selection. Selection of the required coordinate mode is made by the operator. Possible selections for the coordinate mode are:
1. AUTO − The system automatically changes mode based on geographic coordinates. This is the usual operating setting. The change from normal to transverse (polar) takes place at 86° going north, but reverts back to normal mode at 84° going south. This 2° hysteresis avoids excessive mode changes for vessels operating near the changeover latitude.
2. MNORM − The system is forced to operate in the normal mode. A fault is declared if the system latitude >86°.
3. MTXVS − The system is forced to operate in the transverse (polar) mode. A fault is declared if the system transverse latitude >86°.

The operator can elect to have position and heading information displayed in either normal or transverse (polar) coordinates regardless of the current coordinate mode without changing the system coordinate mode.
3.2.13.2 Synchro Heading Output Selection. AN/WSN-7(V) systems that are conﬁgured with synchro data output provide a facility which allows the operator to select a different reference coordinate frame for the synchro output of heading from that selected for digital heading output. The coordinate mode for synchro heading output can be set to follow the system coordinate mode, or can be set to normal or transverse independent of the system coordinate mode.
Navigate or At-Sea align: Only adjusts the accelerometer bias and residual north and vertical bias, with lower gain. Residual north and vertical bias are only adjusted with a ﬁx.
3.2.14 REVIEW OF TRIGONOMETRIC FUNCTIONS. From Table 3-1 it can be seen that:
1. The value of functions that are affected is directly proportional as the Sin of latitude is minimum at the equator and will increase as latitude increases.
2. The value of functions that are affected is directly proportional as the Cos of latitude is maximum at the equator and will decrease as latitude increases.
3. The value of functions that are affected is directly proportional as the Tan of latitude is minimum at the equator, will increase as latitude increases, and become indeterminate at the north (or south) pole. This condition requires the use of a special navigation reference mode when operating at high latitudes.
3.2.15 INERTIAL NAVIGATION VECTORS. Vectors are parameters that have both magnitude and direction.
The vectors of importance to inertial navigation will be dealing with linear acceleration and angular rotation rate. Each of these vectors can be measured in practice by instruments that have their input axes directly along the axes of the coordinate frame in which the vector components are to be evaluated.
In the case of the angular rate vector, gyroscopes are used to measure each angular rate component. If the gyros utilized are single-axis sensing instruments, three gyros will be needed to measure each of the three X, Y, Z angular rate components along the axes of the selected coordinate frame.

In the case of the linear acceleration vector, accelerometers are utilized to measure the acceleration components. Typically, three accelerometers are utilized to measure each of the three X, Y, and Z components of the acceleration vector along the selected coordinate frame axes.
3.2.16 CONCEPTS OF STATISTICAL ESTIMATION, OVERVIEW OF KALMAN FILTER. Inertial navigators develop errors as a function of operating time. Errors result from initial misalignments or from physical (gyro) imperfections, which cause drift rates that can change with time. These output errors characteristically propagate in predictable patterns. To ensure that the output remains within accuracy requirements, it is necessary to periodically correct these outputs. This process of computing and applying the correction is called resetting.
The basic method developed and still in use for some inertial navigators is the three-ﬁx reset technique. This method requires three ﬁxes within a 24-hour period to compute the necessary corrections and makes the following assumptions: (1) the ﬁxes are error free, and (2) the apparent drift rates of the gyros are essentially constant.
As the accuracy of inertial navigators increased, different reset techniques were developed. All of these were basically a reﬁnement of the three-ﬁx reset technique until 1960 when Doctor R. E. Kalman introduced his concept of optimum estimation. His approach has proven to be particularly well-suited for optimizing the performance of modern inertial navigation systems.
By adopting the Kalman Filter, measurement errors (errors in the ﬁx) and system noise (random changes in the apparent gyro drift rates) can be compensated for when calculating reset computations. The purpose of this section is to discuss the basic concepts of the Kalman statistical estimation process.
3.2.16.1 Statistics and Variance. The averaging of quantities in an effort to obtain the true value and to reduce the effect of random error is the simplest form of statistical estimation. The following example of the use of averaging will illustrate some of the fundamental concepts of statistical estimation:
It is desired to use a tachometer to measure the rpm of a precision constant-speed electric motor, nominally rated at 100 rpm ±1 rpm. It is also known that the tachometer used has an error nominally in the range of ±3 rpm. As a result, a series of ﬁve rpm measurements might yield the following values:
(1) 103.0 rpm

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(2) 101.2 rpm
(3) 98.0 rpm
(4) 96.0 rpm
(5) 101.0 rpm
All the measurements seem to be reasonable in view of the = 3.0 rpm error of the tachometer and the = 1.0 rpm uncertainty in the value of the motor speed. The average of the ﬁve tachometer measurements (99.84 rpm) would be considered the best estimate of the actual motor speed. If the true motor speed was exactly 100 rpm (constant for all ﬁve measurements), then the error in the estimate would be -0.16 rpm - a considerable improvement over the nominal tachometer error -3.0 rpm.
The averaged tachometer measurement of 99.84 rpm is considered the best estimate because it is implicitly assumed that (1) the tachometer errors are random in nature and that they tend to cancel each other if averaged, and (2) the motor speed is constant. This demonstrates an important principle: the use of any statistical estimation technique (of which averaging is one example) requires that something be known (or assumed) about (1) the statistics of the measurement errors (in the preceding example, the average value of the tachometer errors tends to become more accurate (and decrease) as the number of averaged measurements increases), and (2) the statistics of the variations in the value of the quantity being measured (in the preceding example, motor speed) is assumed constant.
The conﬁdence that one has in the average value of a set of measurements depends upon the amount that the individual measurements differ relative to the average. The larger the differences, the greater the chance that the error in the average will be large. The sample variance is a measure of the range of variation of the measurements. The larger the sample variance, the more likely that the measured average value differs from the true value by a given amount.
The sample variance for the given set of motor speed measurements listed in column 1 of Table 3-2, is determined as follows
1. The average value of the set of measurement Xi is computed by summing the entries and dividing by the number of entries as in column 1. (The result is called the sample average as distinguished from the true average that one would obtain from an extremely large set of measurements made with many tachometers.)

2. The variation of each measurement ∆σ from the previously computed sample average is obtained next. It is given in column 2. (The average of the variations ∆σavg cannot be used to measure the range of the variation because it is generally near zero due to ± sign changes.)

3. The square of the variation is given in column 3. The average value of the square of the variation is known as the sample variance.

4. Because the square of the variation is always

positive and because it is mathematically rela-

tively easy to use, it is the conventional mea-

sure of the statistical variability of a single mea-

surement. In the example given in Table 3-2,

the sample symbol σ2

variance (∆σ)2avg is 5.636 rpm. is used to designate variance

The σ2 =

(∆σ)2.

The square root of the variance, σ is called the standard deviation. For the example, the sample standard deviation is 2.374, and, to a ﬁrst approximation, 68 percent of all measurements of motor speed will be in the range 99.3 ±2.374 rpm.
NOTE

In the same way that the sample average is an approximation to the true average, the sample variance is an approximation to the true variance - that is, the average square deviation that one would obtain from an extremely large set of measurements taken with many instruments. Techniques are available to determine the number of measurements required to yield a computed variance which is within any desired accuracy of the true variance. In INS applications, past INS performance and careful experimentation are used to compute the variances of performance parameters.

The sample standard deviation can also be used to estimate the error in the measured average motor speed. The true motor speed can be expected, with about 95% conﬁdence, to be within the range,

2( ∆σ ) 2 avg

[

]½

n –1

where n is the number of measurements in the set used to determine X and ( ∆σ) 2 avg.

where n is the number of measurements in the set used to determine X and (∆σ)2avg.
For the example given in Table 3-2, the true motor speed lies in the range 99.3 ±1.119 rpm.

In the preceding example of the measurement of motor speed, however, not all of the information was used in the averaging method to arrive at its best estimate of motor speed. The information not used was (1) the nominal error (that is, the expected error) in any individual tachometer measurement was ±3.0 rpm, and (2) the nominal error of uncertainty (the expected error) in the motor-speed rating was ±1.0 rpm. In the Kalman Filter technique, this extra information is used to develop more valid estimates than would be possible by ordinary arithmetic averaging. Before describing the Kalman Filter technique (in terms of the preceding example of the measurement of motor speed), however, it is necessary to examine the nature of the expected errors as follows:
The values of the expected errors in the tachometer measurements and in the motor-speed rating are derived from a statistical analysis of tachometer errors and motor-speed variations, respectively. Reduced to its essentials, statistical analysis can be described as the tabulation (or plotting) of the relative frequencies - that is, the probabilities of the occurrence of events. To say that a particular event has a 25% probability indicates that, over a long enough period of time, the event will occur 25% of the time. In the case of the tachometer measurements, this would be the plotting of the relative frequencies of occurrence of values of tachometer errors.
3.2.16.2 Philosophy of Kalman Filter. The concept of the Kalman Filter can be explained by analogy to the simpler process of averaging. The Kalman ﬁlter will be shown to reduce to a form of averaging. Given the nominal rating of the motor speed (100.0 rpm) and the (ﬁrst) tachometer reading of 103.0 rpm, an estimate of the actual value of the motor speed can be obtained by averaging the nominal rating and the tachometer reading of the motor speed. (Making an estimate in this way by averaging is reasonable because the expected error in the nominal rating is equal to, or smaller than, the nominal error in the tachometer measurements.) Thus,
(1)

rpm2 =

100.0 rpm + 103.0 rpm
2

= 101.5 rpm

Estimate rpm2 is subscripted 2 because it is the second estimate of true value. The nominal rating is the ﬁrst estimate of the value.
Equation (1) can be rearranged in the following manner to yield the same results.

(2)
rpm2 = rpm1 + ½ [(rpm meas)1 – rpm1] = 101.5 rpm = 100.0 rpm + ½ [103.0 rpm – 100.0 rpm] = 101.5 rpm
The averaging factor is 1/(n+1). It can be shown that if the expected errors in tachometer readings and in nominal rating are the same, the Kalman weighting factor can be reduced to the form of the averaging factor.
In general, the estimates produced by averaging a series of quantities can be calculated by using a recursive (iterative) relationship. For the motor speed problem, this relationship is given as follows:
(3)
rpmn+1 = rpmn + 1/(n + 1) [(rpm meas)n – rpmn]
From the preceding discussion, it is apparent that the Kalman Filter technique is a recursive form of averaging, using a different weight factor. The Kalman weighting factor takes into account the facts known about the particular error statistics involved. (Conversely, the averaging factor can be said to be a Kalman weighting factor which assumes equal errors in measurement and nominal rating.) Note that the Kalman weighting factor used in the motor-speed example takes into account the relative inaccuracy of the tachometer because it gives weighting of 0.1 instead of 1/2 (that is 0.5). (The choice of 0.5 would imply that tachometer error and motor-speed variation have the same variance.)
These estimates are generated by a prediction process and then updated (correctly) by a measurement process. Based on either prior operating experience and/or engineering analysis, a prediction can be made of the nominal system values existing at a particular time. Thereafter, in the absence of information provided by external measurements, knowledge of the dynamics of the system is used to form a math model of the system. The math model is used to extrapolate the predictions - i.e., predict new values. The accuracy of these predictions (estimates) can be improved by use of external measurements. That is, if some or all of the system values at a particular time can be measured, the measurement can be compared with the prediction (estimate) of the system values for that time. The difference (called the measured error) between the measured and predicted values is a measure of the error in the predictions.
The application of the Kalman Filter enters at this point. Since both the prediction and the measurement process may be subject to error, neither the predicted nor the measured values may be the best

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estimate of the true values. The weighted average is the best estimate of the true value.
3.2.17 GLOBAL POSITIONING SYSTEM (GPS) BLENDING
3.2.17.1 Global Positioning System/Inertial Navigation System Filter. Inertial navigators exhibit position errors on the order of hours and days due to Schuler oscillations and the 24-hour Earth oscillation. In the short term, however, inertial navigators are quite stable. In contrast, the GPS provides excellent long-term stability, but a signiﬁcant amount of short-term variation. Combining INS and GPS position information can yield an estimated position that is stable and accurate in all time scales.
The INS output position is revised by applying a correction based on the difference between INS estimated position and a GPS ﬁx. Whenever the AN/WSN-7(V) ﬁx mode is AUTO or AUTO/REVIEW and regular, frequent GPS ﬁxes are available, the software continuously updates an estimate of the north and east INS/GPS position differences. By applying these differences to the INS positions after the ﬁnal stage of the Kalman ﬁlter, the AN/WSN-7(V) is able to provide reliable Estimated Position (EP) that are within a few meters of GPS.
3.2.17.2 INS Reset Smoothing. Application of a GPS reset can result in a change of several tens of meters in the Kalman ﬁlter estimated INS position. This abrupt displacement can have a detrimental effect on systems which rely on receiving continuous, accurate, and smooth estimated positions. To mitigate these effects, application of the reset is applied gradually during the minute immediately following the Kalman update.
3.2.17.3 INS/GPS Filtering and Reset Smoothing Together. To illustrate the combined effects applying the INS/GPS ﬁlter and reset smoothing, refer to Figure 3-12. In Figure 3-12, view a, we see the behavior of a typical INS that is experiencing, for the purposes of illustration, an exaggerated Vn (north velocity) error. In Figure 3-12, view b, a reset has been applied which brought the INS EP nearly back to the GPS ﬁx position. However, the continued Vn error causes the INS EP to walk back away from the ship’s track. If this is continued, as in Figure 3-12, view c, a sawtooth effect is seen, where successive GPS ﬁxes correct the INS EP, only to have the estimated position continue to diverge from the track.
In Figure 3-12, view d, we see the effects of reset smoothing. The dashed line is a representation of where the INS estimated position would have been if no reset had been applied; the Vn error would cause

the EP to continue to diverge from the nominal track. With reset smoothing in effect, the magnitude and direction of the Kalman reset are calculated as in a typical INS. However, rather than immediately applying the complete reset, successively larger proportions of the reset are applied over the interval between ﬁxes. As can be seen in Figure 3-12, view e, this has the effect of eliminating the sawtooth track of the EP.
Note, however, that velocity errors can result in an INS estimated position that differs from GPS. Nearly all of the remaining difference between the INS EP and GPS can be eliminated by measuring the residual INS/GPS north (and east) offset and then combining successive measurements into an estimate of the offset at the time of a new GPS ﬁx. By incorporating a low-pass ﬁlter into the model of the estimator, both residual INS offset and high frequency (short time period) GPS position variations can be nearly eliminated, as illustrated by Figure 3-12, view g.
In Figure 3-12, view h, the Geographic Plot illustrates the ship’s track, GPS ﬁx position, and Smoothed INS/GPS track. For this example, the ship is on an approximate northerly course, turns clockwise, and steadies on an approximate southerly course. GPS ﬁx data has variations throughout the example shown. By utilizing the smoothed reset data, the INS track closely approximates the true track of the ship, without the short-term variations of GPS. This provides gradual correction to the INS rather than stepped changes.
3.2.17.4 Lever Arm Corrections. In most surface AN/WSN-7(V) installations, one NTDS output channel of the ship’s GPS receiver is routed to one of the two RLGN systems, typically the AFT RLGN. The second system receives GPS ﬁx information by way of the RS-422 RLGN-RLGN data link. The GPS receiver is presented with lever arm distances and INS attitude information that allow it to correct its output position to the IMU of the controlling RLGN. That system then applies the necessary lever arm corrections for the other RLGN before placing the ﬁx information onto the RLGN-RLGN link. As a result, each RLGN receives periodic position updates that are correct for, or referenced to, each IMU.
In the submarine AN/WSN-7A(V) conﬁguration, the NTDS outputs from both GPS channels are routed to system 1 and system 2 independently. Lever arm corrections for unit 1 and unit 2 are applied by each of the system’s processors for periodic position updates that are correct for, or referenced to, IMU 1 and IMU 2, respectively.

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SECTION II EQUIPMENT DESCRIPTION

3.3 RLGN FUNCTIONAL DESCRIPTION.
The AN/WSN-7(V) INS is based on the principle of using the standing waves generated in a closed path laser beam to detect angular rotation of an inertial reference platform. Three RLGs (or gyros) are mounted perpendicular to each other to detect rotation of an inertial platform about the X, Y, and Z axes. Three accelerometers, one mounted parallel to each axis of rotation, detect motion of the inertial platform in each axis. The rotation and acceleration motions are processed by an internal computer, which determines the orientation and velocity vector of the inertial platform.
Updated by receiving periodic position ﬁxes from a navigation reference such as a GPS receiver, and ship’s speed information, the RLGN provides continuous high accuracy geographic position, platform attitude, acceleration, and velocity data for use by other equipment which require these data as inputs.
3.3.1 BASIC DESCRIPTION OF RING LASER GYRO OPERATION. The following discussion is intended to provide a basic knowledge of the manner in which an optical device can be utilized to provide an inertial reference and to outline the design criteria which must be met to implement this function.
Using light to measure rotation is based on the principle that since the speed of light is constant, the time required for a light beam to traverse a given distance is independent of motion of the medium in which the light is traveling. For this reason, if the light beam were to travel around a circular pathway, the time required to complete one revolution (360 angular degrees) would be independent of whether the pathway were stationary or rotating.
As an analogy for using this effect to measure rotation, suppose that an observer on the pathway emits two beams of light in opposite directions and then measures the time required for each beam to complete one revolution and return to the observer’s position. If the pathway is stationary, both beams would be received back at the observer’s position at the same time. This condition is shown in Figure 3-13, A. If the pathway is rotating, however, the observer moves toward one beam and moves away from the

other beam while the beams are traversing the pathway. If the pathway is rotating in the same direction as the light beam, the path length back to the observer is effectively lengthened. Conversely, if the pathway is rotating in the direction opposite to the light beam, the path length back to the observer is effectively shortened. The time difference between reception of the two beams would be a measure of the rate at which the path is rotating, and the sequence in which the beams are received would indicate the direction of rotation. This condition is shown in Figure 3-13, B. The rotation-induced difference in path length is referred to as the Sagnac effect.
In actual practice in an RLG, the circular path is replaced with a polygon path (triangular in the case of the INS) which is constructed using mirrors at each corner of the polygon. The pathway consists of a sealed channel, which is ﬁlled with a mixture of gasses that emit light when ionized. High voltage applied to electrodes in the channel ionizes the gas and causes lasing action. When the ring is stationary, lasing in the ring generates a standing light wave, which is analogous to two counter-propagated light beams. The interference between the beams generates a series of nodes (stationary points or points of minimum intensity) and antinodes (points of maximum oscillation) as shown in the left view in Figure 3-13, C. Because the frequency of the laser is very high, more than a million nodes and antinodes are generated in a path less than one-half meter in circumference.
When the frame to which the laser path is attached rotates, the standing wave in the path remains ﬁxed in an inertial (non-rotating) frame of reference. In the analogy, an observer rotating with the ring would pass the nodes and antinodes of the standing wave as the path rotated. By counting the number of nodes passed (and by knowing the time and distance between nodes), the observer could accurately determine the rate and angle of rotation (right view in Figure 3-13, C).
3.3.2 BASIC RLG DESIGN CRITERIA. While the principles behind the RLG are rather simple, several problems must be addressed before these principles can be implemented in an actual rotation sensor. These problems and their solutions are outlined

in the following paragraphs to provide a background for understanding the function and operation of circuits which are described later in this chapter.
3.3.2.1 Gas Flow. In an idealized gyro, the standing wave generated in the light beam would remain stationary when the path was not rotating. In actual practice, ﬂow of the ionized gas inside the ring produces a bias effect which causes the standing wave to rotate even when the ring is stationary. The gas ﬂow is a result of the high voltage between the cathode and anode used to ionize the gas. Electrons in the gas drift toward the positive anode and positive ions drift toward the negative cathode. This action induces net ﬂow in the neutral atoms in the gas around the ring. To compensate for this effect, a balanced ionization circuit is used which consists of one cathode and two evenly spaced anodes placed on opposite sides of the ring. By measuring the current in each ionization path and controlling the ionization voltages, counter-rotating motions of the electrons and ions can be established which cancel the induced ﬂow of gas in the ring.
3.3.2.2 Frequency Locking. Another problem is frequency locking of the standing wave. At low rotation rates, the standing wave tends to lock to the ring and move with the ring as the ring rotates. This effect is analogous to friction in a mechanical gyro. Frequency locking is caused by the backscatter of photons at the mirrors. If the mirrors were perfect reﬂectors, the laser beam would propagate around the path without any photons being reﬂected back along the incident path. In practice, a small percentage of the incident light wave is backscattered from the mirror surface and is 180 degrees out of phase with the incident wave. This phase shift causes the beam to "want" to reﬂect at a node on the mirror surface. At low rotation rates, the node generated at the mirror surface tends to move with the mirror, causing the standing wave to move with it. The effects of frequency locking are eliminated by mechanically rotating (dithering) the optical path back and forth at a high rate. This action maintains a high rate of motion in the gyro even when the platform is rotating at a very low rate. Since no net rotation is introduced by the dithering action, the effect of dithering is canceled in the processed signal.

3.3.2.3 Path Length Control. The intensity of a laser beam is dependent on the spacing of the reﬂective surfaces as a multiple of the wave length of the light. Ideally, if the positions of all mirror surfaces in a laser could be ﬁxed so that the length of the lasing path was held constant at exactly some multiple of the wave length of the light, the laser would operate at maximum efﬁciency and intensity. Stability of the laser path length is maintained primarily by using a material for the laser which has a very low coefﬁcient of expansion. In addition, the RLGs in the RLGN utilize dynamic mirror positioning known as Path Length Control (PLC) to adjust the path length. In this design, two of the mirrors are mounted on piezoelectric transducers which allow them to be moved inward or outward to adjust the path length. Circuits in the system constantly monitor laser intensity and apply bias voltages to the piezoelectric transducers which position the mirrors to maintain maximum intensity of the beam.
3.3.2.4 Random Drift Improvement. Mirror quality also affects operation of the gyro. In addition to using the most advanced techniques available to ensure high mirror quality, the RLGs used in the RLGN employ the dynamic positioning capability of the gyro mirrors to dynamically reposition the laser beam on the mirror surfaces. This is done by differential positioning of the two adjustable mirrors such that the laser ring is shifted in position across the mirror’s surface without changing the total path length. This function, known as Random Drift Improvement (RDI) ﬁnds the best surface on the mirrors and reduces mirror degradation resulting from positioning of the beam at a static point on the mirror’s surface.
3.3.3 GENERAL DESCRIPTION OF FUNCTIONS. (Refer to Figure 3-14.) The RLGN consists of a Display and Keypad Assembly, power switching and conditioning circuits, alarm relay circuits, electronic circuits associated with control data processing and Input/Output (I/O) functions, electronic circuits associated with position sensing functions, and the electronic circuits and subassemblies contained in the IMU. The RLGN can be controlled at either the Display and Keypad Assembly on the RLGN cabinet, or from the IP-1747/WSN CDU, which is remotely located from the RLGN cabinet. The Display and

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Keypad Assembly, the subassemblies associated with power switching and DC power supply, the SBAs, and the fault relays are mounted directly to the RLGN cabinet. All other electronic subassemblies are mounted in three printed circuit card racks and are interconnected by backplane wiring boards. Each rack contains Circuit Card Assemblies (CCAs), which are grouped by the overall operating function performed by the collective circuits; these are:
1. Nav Processor
2. I/O Processor
3. IMU Support Electronics
All three card (CCA) racks are mounted on the inside of the Processor Cabinet Assembly door.
3.3.3.1 Nav Processor. The Nav Processor rack contains the RLGN central processor with control program memory and control program. All data is transferred between the central processor and functions contained on other CCAs in the Nav Processor via an address and data bus on the backplane. Data transfer and control functions performed by other circuits in the Nav Processor consist of: serial (RS422A) interface to the local and remote Display and Keypad functions, dual port memory interface to the I/O Processor, and serial (RS-422A) data interface to the Support Electronics function.
In addition to the system control and navigation processing functions, circuits in the Nav Processor also perform the following:
• Monitor power and system fault status
• Control setting of status and alarm relays
• Provide synchro-to-digital conversion for synchro speed input
• Provide digital-to-synchro conversion of heading, roll, and pitch attitude data output to the SBAs
• Provide digital-to-synchro conversion for output of velocities
• Control the gimbal torquer motors to rotate the Sensor Block in the IMU
The Nav Processor rack consists of Wirewrap Backplane Assembly (1A1A11) and the following CCAs:
1. Nav/Central Processor CCA (1A1A13)
2. Status and Command CCA (1A1A15)
3. Dual Panel Interface CCA (1A1A16)
4. IMU Interface CCA (1A1A17)

5. Torquer CCA (1A1A18) (roll)
6. Torquer CCA (1A1A19) (azimuth)
7. Bus Interface CCA (1A1A20)
8. Asynchronous Transfer Mode (ATM) CCA (1A1A4)
RLGNs with synchro attitude (heading, roll, pitch) output, synchro velocity output, and synchro speed input also contain the following CCAs in the Nav Processor card rack:
1. Synchro Converter CCA (1A1A38) (1X/36X heading output, 1X/10X total velocity output, and synchro speed input)
2. Synchro Converter CCA (1A1A39) (2X/36X roll and 2X/36X pitch output)
3. Synchro Converter CCA (1A1A40) (1X/10X Vn and 1X/10X Ve velocity output)
3.3.3.2 I/O Processor. The I/O Processor rack contains a central processor with program memory and I/O control program. All data is transferred between the processor and functions contained on other CCAs in the I/O Processor via an address and data bus on the backplane. Data transfer and control functions performed by other circuits in the I/O consist of an RS-422A serial interface to communicate between two navigation systems and the dual port memory, which provides the data interface to the Nav Processor.
The basic I/O Processor rack with the digital (RS422A) data interface consists of I/O Processor Backplane Assembly (1A1A12) and the following CCAs:
1. I/O Processor CCA (1A1A21)
2. Dual Panel Interface CCA (1A1A14)
3. Dual Port Memory CCA (1A1A23)
Depending on the system I/O requirements, up to eight Naval Tactical Data System (NTDS) standard interface assemblies can be installed in the I/O Processor card rack. The backplane is conﬁgured such that any type NTDS card can be installed in any NTDS location in the rack. Interface cards that provide parallel data (Type A) interconnect to a connector plate on the cabinet via corresponding jacks on the I/O Processor Backplane Assembly. Interface cards that provide serial data (Type E or Type D) interconnect to the connector plate directly via coaxial cables and edge connectors on the circuit cards.
3.3.3.3 Support Electronics. The Support Electronics rack consists of circuits associated with the following:

• Control of the sensor functions, processing, and conversion of data from the RLGs and accelerometers
• Detecting the rotational position of the Sensor Block Assembly from the gimbal synchros
• Detecting faults in the Support Electronics circuits
• Sensor functions and data communication with the Nav Processor
The Support Electronics rack contains a local DC power supply, which operates from 28 Volts, Direct Current (VDC) and supplies power to all other circuits and subassemblies in the Support Electronics rack and the IMU.
The Support Electronics consists of Support Electronics Backplane Wiring Assembly (1A1A30) and the following CCAs:
1. Support Electronics Power Supply (1A1A37)
2. IMU Processor CCA (1A1A32)
3. I/O Control (BITE) and Filter CCA (1A1A31)
4. Repositioning Interface CCA (1A1A33)
5. A/D Multiplexer CCA (1A1A34)
6. Accelerometer and Sensor Electronics Assembly (1A1A35)
7. Gyro Support Electronics CCA (1A1A36)
3.3.3.4 IMU. The lower Measurement Equipment Electrical Cabinet Assembly (1A2) contains the position sensing subassembly, which is called the IMU. This integrated assembly (1A2A1A1) consists of a base plate on which an outer support frame is mounted using a shock isolating structure. The outer frame supports a gimbal frame, which in turn supports the Sensor Block Assembly (1A2A1A1A9). The sensor elements (RLGs and accelerometers) are mounted on the Sensor Block Assembly, which by virtue of its mounting arrangement can rotate freely both in azimuth and in the roll axis of the cabinet.
The mechanical subassemblies that make up the IMU consist of:
1. Mounting and alignment base plate
2. Six shock isolation mounting struts
3. An outer shock-isolated frame, which supports an inner gimbaled frame
4. A Sensor Block Assembly

The inner gimbal frame is mounted to and supported in the outer frame by a torquer motor subassembly and a dual resolution synchro subassembly. The Sensor Block Assembly is mounted to and supported in the inner gimbal frame in a similar manner. Electrical connections and signals to the inner synchro, torquer motor, and subassemblies mounted on the Sensor Block Assembly are passed through the outer frame and gimbal frame using wiring harnesses, which are part of slip ring subassemblies. These subassemblies are mounted concentric to the rotation axis of each synchro and torquer motor.
The Sensor Block Assembly contains the RLGs and accelerometers, and a High Voltage Power Supply. Precision-machined mounting surfaces on the Sensor Block Assembly allow the RLGs and accelerometers to be removed and replaced during maintenance without the requirement for mechanical alignment.
The following subassemblies are mounted on the Sensor Block Assembly (1A2A1A1A9):
1. Ring Laser Gyro A (X axis) (1A2A1A1A1)
2. Ring Laser Gyro B (Y axis) (1A2A1A1A2)
3. Ring Laser Gyro C (Z axis) (1A2A1A1A3)
4. High Voltage Power Supply (1A2A1A1A4)
5. Accelerometer A (X axis) (1A2A1A1A5)
6. Accelerometer C (Y axis) (1A2A1A1A6)
7. Accelerometer B (Z axis) (1A2A1A1A7)
8. Accelerometer Stimulus (1A2A1A1A9A1)
3.4 FUNCTIONAL DESCRIPTION OF RLGN ASSEMBLIES.
3.4.1 POWER DISTRIBUTION AND EMERGENCY POWER SWITCHING. (Refer to Figure 3-15, Figure 3-16, Figure 3-17, Figure 5-6, Figure 5-7, Figure 5-8, and Figure 5-9.) The AN/WSN-7(V) uses 115 Volts, Alternating Current (VAC), 50/60 Hz, 3-phase ship’s power as its supply source during normal operation. Each phase of the main Alternating Current (AC) power is applied to the Power Supply (1A1A6) and Vital Bus CCA (1A1A3) through a POWER circuit breaker (1A1CB1) and a SYSTEM POWER toggle switch (1A1S1) located on the front panel of the AN/WSN-7(V). As shown in Figure 3-15, the Power Supply contains a delta/wye transformer and a full-wave rectiﬁer circuit, which converts the 115 VAC, 3-phase main power to produce an unregulated +25 VDC source power. The +25 VDC is distributed as the primary power source

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S9427-AN-OMP-010/WSN-7

for generating all other power (other than non-vital synchro reference) used by the AN/WSN-7(V), and is applied to a DC inverter circuit in the Battery Charger (1A1A7) to maintain the charge on the internal 28-volt Battery (1A1A5).
The charging circuit on the Battery Charger (1A1A7) consists of an inverter drive oscillator circuit on subassembly 1A1A7A1, which controls application of the +25 VDC to the primary of transformer 1A1A7L6 through switching transistor 1A1A7Q4. The transformer output is rectiﬁed by diode 1A1A7CR3 and applied as the charging current to the battery. A Silicon Controlled Rectiﬁer (SCR) 1A1A7Q3 in parallel with the charge current path prevents the battery voltage from being applied to the +25 VDC power circuit during normal operation. A separate transformer winding and rectiﬁer circuit in the Power Supply produces a second +25 VDC power output (25 V Sense), which is used in the Battery Charger (1A1A7) to sense the presence of main AC power to the Power Supply.
In the event of an interruption of the main ship’s power source, loss of the power fault detection signal (25 V Sense) from the Power Supply and the Battery Enable signal (Batten) from the Vital Bus Assembly causes circuits in the Battery Charger to generate a switching enable level on the gate of SCR 1A1A7Q3 in the Battery Charger. When 1A1A7Q3 is switched on, a circuit is completed that bypasses 1A1A7CR1 and applies the +28 VDC output power from the battery onto the +25 VDC circuit. System operation is then maintained without interruption. Loss of the 25 V Sense input indicates that either the main ship’s AC power has failed, or that the AN/WSN-7(V) is turned off at either the POWER circuit breaker or at the SYSTEM POWER toggle switch (1A1S1).
To prevent the Battery Charger from switching to battery power when the system is manually turned off, the Battery Enable signal from the Vital Bus Assembly is present only when the SYSTEM POWER toggle switch (1A1S1) is set ON and a 5 VDC return is applied through the switch contacts (/PWR ON) to the Battery Enable logic on the CCA. The 5 VDC return is also applied through a set of contacts on the SYSTEM POWER toggle switch (1A1S1) when the switch is set OFF. This status level (/System Off) is applied to the circuits in the display and to circuits on CCAs in the Nav Processor card rack. Pull-up resistors in the circuits on the CCAs initiate various reset functions when this circuit is opened at system power-on. While operation of the power conversion circuits is independent of the frequency of the input power, frequency conﬁguration switch 1A1A3S1 on

Vital Bus CCA (1A1A3) must be set to correspond to the input power frequency. This switch selects the timing clock rate applied to the power fault detector circuits on the CCA. Incorrect setting of the switch will result in false detection of a power fault (Fault Code 34 will be displayed); however, the AN/WSN-7(V) will continue to operate.
In addition to the charging control and battery switching control functions, the Battery Charger contains a DC inverter circuit 1A1A7Q5, 1A1A7Q6, 1A1A7L7, 1A1A7L8 and associated diodes), which generates 25 VDC power used by other circuits in the AN/WSN7(V). The Battery Charger will continuously produce -25 VDC via an internal inverter circuit in all power mode conditions. The -25 VDC is distributed to all -25 VDC users via the terminal junction system wiring bus.
3.4.2 PLATFORM INDEXING. (Refer to Figure 3-18.) The Sensor Block Assembly is mounted in a gimbal ring in such a manner that the Sensor Block is free to rotate without limits in azimuth. The gimbal ring is, in turn, mounted in the IMU frame such that the ring (and Sensor Block Assembly) can also rotate without limits in the pitch axis of the mounting reference. This design permits the orientation of the sensor axis for each gyro and accelerometer to be periodically reversed during operation. Periodic reversal of each sensor axis cancels the cumulative effects of small bias in the output signals.
3.4.2.1 Platform Indexing and Stabilization Control Circuits. The platform indexing function is implemented in each axis by a multispeed (1X and 36X) synchro capsule and a DC torquer motor, which are mounted concentrically with the gimbal axis. The gimbal’s position data from the synchros is converted to digital data by synchro-to-digital (S/D) converter circuits and applied to the data bus through a digital data multiplexer on Repositioning Interface CCA (1A1A33), as shown in Figure 3-18. The synchro data is used by the Nav Processor to measure the offset of the gimbals from the synchro reference zero position. The Nav Processor uses this information to calculate the torque value and direction required to rotate the gimbal(s), or to maintain the gimbal(s) at the desired angle. A digital torque control data word is periodically transmitted from the Nav Processor CCA to the associated Torquer CCA (1A1A18) or (1A1A19). This data is latched and is processed by a digital-to-analog converter and ampliﬁer on the Torquer Assembly to generate an analog signal, which is used to control the amplitude and direction of the current applied by the driver circuit. Differences in gain requirements of the roll

(1A1A18) and azimuth (1A1A19) torquer circuits are compensated by jumper paths on Nav Processor Wirewrap Backplane Assembly (1A1A11). The analog signal is applied directly to the ampliﬁer in CCA location (1A1A18) via jumper path between CCA pins C33 and C35. For CCA location (1A1A19), the analog signal is applied through a dropping resistor on the CCA via jumper path between pins C33 and C34.
The driver consists of a balanced circuit, which applies power from either the +25 VDC or -25 VDC source to one (power) input of the torquer motor. The other input (return) to the torquer motor is returned to 25 VDC ground on the Torquer Assembly. A voltage divider in the return path on the CCA samples the torquer motor current for feedback to the drive circuit. A monitoring circuit measures the average drive signal amplitude applied to the output stage. This circuitry takes the absolute value of the drive signal, applies a long time constant ﬁlter, compares this signal to a trip threshold (10 VDC), and latches the output stage off (disables the torquer) when the threshold has been exceeded.
The hardware torquer disabled status may be read by the processor via the torquer disabled status signal from the Torquer Assembly to the Status and Command Assembly. If the torquer is to be re-enabled under software control, the processor must ﬁrst reset and then set the torquer enable command signal going from the Status and Command Assembly to the Torquer Assembly. An excessive drive signal causing a hardware disable will occur in the event of either an output short circuit or open circuit (i.e., any condition that prevents the current control loop on the Torquer Assembly from functioning normally). The effect of a high drive signal level on the monitoring circuit is cumulative. High drive signal levels coming too close together or for too long will trip the monitor circuit, but will not trip the monitor circuit if short enough and far enough apart.
3.4.2.2 Sensor Rotation During Normal System Operation. At power turn-on, the Sensor Coordinate Frame is initially set as shown in Figure 3-19. After the system enters the Align mode, the outer and inner gimbals are indexed (rotated) in a sequence of 64 rotations, which reposition the coordinate frame. The sequence of rotation of the coordinate frame allows the IMU Processor Memory Assembly to determine and compensate for errors associated with the system’s gyro bias drifts and accelerometer bias errors, and also to determine and correct for errors introduced by offset of mechanical components within the system.

Since the gimbals are periodically rotated through a series of orientations, instantaneous heading, pitch, and roll orientation of the ship is determined by the Nav Processor and is not directly related to the actual orientation of the platform. The strapdown algorithm run by the Nav Processor maintains the mathematical description of the orientation of the sensor block with respect to a local level/north-oriented reference frame. The gimbal angles read by the inner and outer axis synchros allow the Nav Processor to sense where the base of the IMU is with respect to the Sensor Block. This allows the system to mathematically determine the ship’s heading, roll and pitch. In the event of a failure of the platform indexing function, the platform torquers are turned off and the rotation sequence is halted. The system will continue to provide position and velocity output at an accuracy that will degrade over time. Unless there is a gimbal synchro failure, system roll and pitch output will also continue to be valid.
3.4.2.3 Sensor Rotation During Off-Line Testing. In the off-line Test mode, the capability to rotate the Sensor Coordinate Frame is used to dynamically test the accelerometers and RLGs. Accelerometer Test 329 sequentially changes the orientation of the accelerometers and checks the acceleration values introduced by the earth’s gravity. RLG Tests 330 and 331 sequentially rotate the inner and outer gimbals at a ﬁxed rate and check the RLG’s count outputs. The orientation sequence for Accelerometer Test 329 is shown in Figure 3-19.
3.4.3 SYSTEM TIMING AND NAVIGATION PROCESSING. (Refer to Figure 3-21). Processing of the attitude and sensors data in the IMU Electronics is performed at a 50 Hz rate with updated data being available for transmission to the Nav Processor function at the end of every 20-millisecond period. Routines performed in the Nav Processor are primarily scheduled at an 800 Hz rate (1.25-millisecond periods), with different subroutines being performed during each 1.25-millisecond period under direction of the executive function of the Nav Processor control software. Input and processing of IMU data is interrupt-synchronized to occur every 20 milliseconds during a speciﬁc 1.25-millisecond period. In a similar manner, output of attitude data is interrupt-synchronized to the timing and transfer of data from the IMU Processor to the Nav Processor. Communication between the Nav Processor and the IMU Processor is accomplished through two-way serial data messages, which are synchronized to the completion of the signal/data processing that takes place in the IMU Electronics.

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S9427-AN-OMP-010/WSN-7

3.4.3.1 Nav Processor-IMU Processor Timing. Since system attitude data supplied by the IMU Electronics to the Nav Processor is time critical, input and processing of platform orientation and sensor data from the IMU Electronics is synchronized to the IMU data processing cycle. Synchronization of the Nav Processor to the IMU Processor is accomplished by an 800 Hz (1.25 millisecond) timing clock, which is generated from the 3.84 MHz signal (DF CLK) derived from the 7.68 MHz master clock on Accelerometer and Sensor Electronics Assembly (1A1A35). The 800 Hz clock is applied as an interrupt (IRQ5) to Nav Processor CCA (1A1A13) and to I/O Processor CCA (1A1A21).
In addition to the 800 Hz interrupt clock, a timing synchronization pulse (STROBE) is generated at a 50 Hz rate synchronous with every sixteenth 800 Hz clock pulse. The STROBE is gated by the SAMPLE output from the Accelerometer and Sensor Electronics Assembly (1A1A35). SAMPLE is set high when the gyro and accelerometer data sample is ready for output.
Synchronization of the Nav Processor to the IMU timing is performed through reading of a status bit set in memory on Dual Port Memory CCA (1A1A23). The 50 Hz strobe [Buffered Lower Unit Strobe (BLUS)] is applied via the IMU Processor Memory Assembly to set a strobe status bit in memory on the Dual Port Memory Assembly. The status bit follows the level of the STROBE signal. Each processor reads the strobe status every 1.25 milliseconds when the 800 Hz interrupt (IRQ5) is detected. Detection of the strobe status causes the processors to reset an internal software counter, which is then incremented every 1.25 milliseconds to synchronize the processing activities. This action allows the processors to anticipate the occurrence of the next strobe (and data sample) for synchronization of data transfer from the IMU with the Nav Processor operations. Calculation and output of system attitude data is also time critical. This data is calculated by the Nav Processor and is biased to compensate for processing and transmission delays.
To synchronize attitude data transmitted via the serial data output to the actual ship’s dynamics, the serial data interface function is also synchronized to the 800 Hz clock and 50 Hz strobe from the IMU Electronics. In addition to being applied to the Nav Processor, the 800 Hz clock signal is routed through Bus Interface CCA (1A1A20) and Dual Port Memory CCA (1A1A23), and is applied as an interrupt (IRQ1) to the I/O Processor causing the I/O Processor to check the

strobe status in the same manner as the Nav Processor.
3.4.3.2 Nav Processor-IMU Processor Data Transfer. Transmission of data from the IMU to the Nav Processor is initiated by a command word generated by the Nav Processor. In the correct 1.25-millisecond time period (synchronous to and immediately following the beginning of the 50 Hz strobe from the IMU), the Nav Processor transmits a command word (data request message) to the IMU Processor. The Nav Processor may request any one of up to 32 different possible messages (modes) via this command word. The mode selected by the Nav Processor determines the type of data to be transmitted back to the Nav Processor by the IMU Processor. The 50 Hz strobe is also applied as an interrupt (IRQ0) to the IMU Processor to initiate the data read and format operation.
Upon receipt of the command word, the IMU Processor (1A1A32) immediately reads the necessary accelerometer and gyro data from the Accelerometer and Sensor Electronics Assembly (1A1A35), calculates and formats the requested data for each of the 32 words of the data message, and then transmits the complete message to the Nav Processor.
Because reception of the request message, reading and formatting of IMU data, transmission of the data to the Nav Processor, and processing of the data by the Nav Processor is performed in a single 1.25-millisecond period, data is transmitted between the processors at a 1 MHz bit rate. The command word and each word of the 32-word data message consists of 16-bits, which are Manchester encoded. The most signiﬁcant bit of each word is transmitted ﬁrst. The ﬁrst word of the data message is a return copy of the command word received from the Nav Processor. The following 30 words contain IMU-related data, PROM data, and status and fault words. The last word in each data message is a checksum of the preceding 31 words.
3.4.4 EXTERNAL DATA INTERFACING. (Refer to Figure 3-22.) All system data interface takes place through the I/O Processor function. This function consists of Dual Port Memory CCA (1A1A23), I/O Processor CCA (1A1A21), Dual Panel Interface CCA (1A1A14), and the suite of NTDS Interface CCAs (1A1A51 through 1A1A58). The interface for input and output of digital data from the Nav Processor is controlled through I/O Processor CCA (1A1A21). All data transfer between the Nav Processor and the I/O processor takes place via the parallel data buses on

the associated backplane assemblies, which communicate via a common access memory register located on Dual Port Memory CCA (1A1A23). Data for output from the AN/WSN-7(V) is transferred from the Nav Processor via Dual Port Memory to the I/O Processor where it is reformatted and is then output to the selected I/O assemblies. Timing for output of system data is synchronized by interrupts generated from the 800 Hz clock and STROBE signals generated in the IMU Electronics function. The I/O Central Processor provides the data output message formatting, input data message decoding, I/O Bit processing, and control for the I/O boards independent of the Nav Processor function. I/O functions performed by the I/O Processor are outlined in the following sections.
3.4.5 INTERNAL DATA INTERFACING. Nav Processor to Support Electronics Processor - The parallel bus data interface with the Nav Processor consists of local address decoding logic, 16-bit parallel data buffers, and ﬂip-ﬂop latching circuits that hold each output data word being transmitted, or that accumulate each input data word being received via a single-channel RS-422A serial data I/O interface port. The serial data interface to the Support Electronics consists of input and output shift registers and an RS-422A serial data interface circuit. Serial data is transferred asynchronously between the Nav Processor and Support Electronics functions. Timing information critical to processing the data from the Support Electronics and synchronizing external data I/O to the AN/WSN-7(V) is provided by an 800 Hz clock signal and a timing strobe that originate from the sensor sampling and synchronization logic on the I/O Control Assembly in the Support Electronics. These signals are passed directly through buffers on the IMU Interface Assembly to the Navigation Central Processor and to Bus Interface CCA (1A1A20).
3.4.6 POSITION SENSING AND PROCESSING. (Refer to Figure 3-23, Figure 3-24, Figure 3-25, and Figure 3-26.) The Position Sensing functions generate and process the inertial orientation and acceleration reference signals, which are processed by the Nav Processor. Functions include the following:
• Generation of angular rate and acceleration outputs from the RLGs and Accelerometers located on the IMU Sensor Block
• Conversion of the analog rate and acceleration signals to digital format
• Generation of the high voltage power for the RLGs

• Dynamic control associated with the RLGs
• Generation of the primary system timing reference
Except for high voltage power generation and control functions provided by the High Voltage Power Supply Assembly (1A2A1A1A4), all functions related to Position Sensing are located on circuit boards in the IMU Support Electronics card rack.
3.4.6.1 Gyro Power and Power Control Functions. Functions associated with high voltage power for the RLGs consist of high voltage power generation, laser current sensing, high voltage power switching, and current control. Circuits that perform these functions are located on the High Voltage Power Supply Assembly (1A2A1A1A4), which is located on the Sensor Block Assembly. Source power for the High Voltage Power Supply Assembly is supplied by +28 VDC from Support Electronics Power Supply CCA (1A1A37). The +28 VDC power is used for generation of the -930 VDC and +3500 VDC power (used for ionizing the laser gas in the gyros), and +280 VDC (used to supply the circuits that drive the piezoelectric transducers for the PLC and RDI functions).
High voltage DC generation functions consist of two separate power supply circuits. Transformer 1A2A1A1A4T1 and associated rectiﬁer circuits generate 3500 VDC power, and transformer 1A2A1A1A4T2 and associated rectiﬁer circuits generate both the -930 VDC and +280 VDC power. The +28 VDC input is regulated and applied to the input winding of each supply transformer. Each leg of the transformer’s input winding is alternately switched by a common driver circuit to allow conduction through the transformer.
The 3500 VDC supply output is applied directly to the anode of each RLG. The -930 VDC supply output is applied to the cathode of each RLG through a transistor in a current control circuit. When the system is initially turned on, both 3500 VDC and -930 VDC power are applied to each gyro. As soon as lasing action in the RLGs causes current in the high voltage path of all three RLGs to increase to a predetermined level, a switching circuit removes the drive signal from the input winding of transformer 1A2A1A1A4T1, causing the 3500 VDC output to turn off. Completion of the circuit from -930 VDC through the RLGs back to ground via a diode in the 3500 VDC supply rectiﬁer circuit maintains power necessary for continued laser action.

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S9427-AN-OMP-010/WSN-7

A direct feedback circuit from each gyro

[1A2A1A1A4VR5,

1A2A1A1A4Q7

and

1A2A1A1A4Q8 for gyro (1A2A1A1A1)] moni-

tors current in the laser cavity and maintains

constant current by controlling the gain of the

transistor [1A2A1A1A4Q9 for gyro (1A2A1A1A1)] in

the -930 VDC supply path to the associated gyro. A

comparator circuit in the current feedback circuit for

each gyro detects excessively high or low current.

3.4.6.2 Gyro Control and Signal Processing Functions. Functions associated with control of the RLGs consist of gyro dither control, dynamic control of laser mirrors position, and detection and processing of rotation signals. Circuits for controlling and driving the gyro dither function are located on Gyro Support Electronics CCA (1A1A36) and Repositioning Interface CCA (1A1A33). These circuits are primarily free-running, positive-feedback loops that apply power to piezoelectric transducers located in the suspension-mounting axis of the associated RLG. One transducer (dither pickoff) supplies a signal to a driver circuit, which drives another set of transducers that rotate the gyro assembly. The three driver circuits are identical. Oscillation rate of each gyro is determined by the pickoff transducer.

Circuits associated with the laser PLC and RDI functions are located on Gyro Support Electronics CCA (1A1A36) and High Voltage Power Supply Assembly (1A2A1A1A4). Three identical circuits generate modulation signals, which are applied to the drive signals that drive the piezoelectric transducers. The transducers position the mirrors in the associated RLG. A current feedback (PWR DET) sample from the gyro is applied to a demodulator circuit, and the amplitude of the modulation signal is detected to determine the direction of mirror position, which produces an increase in laser current. This demodulated feedback is then used to control the level of the drive signal for the mirrors.

One modulator/demodulator function controls the position of both mirrors to increase or decrease the laser path length. The other modulator/demodulator function controls the position of both mirrors differentially so that the laser path is shifted without changing the total path length. Circuits associated with processing of the analog (count) rotation sensing signals from the RLGs are located on I/O Control (BITE) and Filter CCA (1A1A31) and Accelerometer and Sensor Electronics Assembly (1A1A35).

The circuits on (1A1A31) consist of a state logic decoder, which generates a pulse output for each transition of the up and down rotation signals. Depending on the phase relation of the up and down signal

(direction of gyro rotation), the generated pulses are output on either the clockwise or counterclockwise pulse output. The sensor electronics on Accelerometer and Sensor Electronics Assembly (1A1A35) accumulates the clockwise and counterclockwise gyro rotation signals from the I/O Control and Filter Assembly in up/down counter functions at a 50 Hz sample rate to determine the rotation angle of each gyro during the sample period.
3.4.6.3 Accelerometer Control and Signal Processing Functions. The accelerometer signal processing circuits are contained on Accelerometer and Sensor Electronics Assembly (1A1A35). These circuits consist of three identical balanced bridge circuits, which operate from a precision voltage reference source on the CCA. The accelerometer signals are applied to these circuits, which sample the accelerometer current and convert the analog signal to a digital up or down count. The frequency of the count is directly proportional to the acceleration (accelerometer current), and the output (up count or down count) is determined by the direction of the measured acceleration (negative or positive current ﬂow). The signal input from each accelerometer is also applied through an operational ampliﬁer to the analog-to-digital (A/D) Multiplexer Assembly for accelerometer performance testing by the built-in test (BIT) function. The sensor electronics on Accelerometer and Sensor Electronics Assembly (1A1A35) accumulates the clockwise and counterclockwise gyro rotation signals from the Gyro Support Electronics CCA (1A1A36) in up/down counter functions at a 50 Hz sample rate to determine the rotation angle of each gyro during the sample period. In the same manner, the sensor electronics accumulate up and down counts from the accelerometer processing circuits on the CCA to determine acceleration. Upon completion of the data sample accumulation period, the processing logic 1A1A35U39 sets the SAMPLE output high. This action gates the STROBE output and the buffered 50 Hz (B 50HZ H) output from I/O Control (BITE) and Filter CCA (1A1A31) high, initiating the processing cycle for reading of the data by the IMU Processor. The resultant data is transferred as parallel digital words, which are transferred synchronously on the input data bus to the IMU Processor on IMU Processor CCA (1A1A32). The rotation rates are processed to develop the PLC Reset Disable (PLC RST DSBL) signal, which is applied to the PLC logic on Gyro Support Electronics CCA (1A1A36). This signal inhibits reset of the PLC control function while high rates are being detected. Self-testing of the CCA functions is controlled by the processor

in IMU Processor CCA (1A1A32) through the sensor electronics function. The CPU on IMU Processor CCA (1A1A32) initiates a self-test at power-up, which checks operation of the CCA electronics. During self-test, the normal inputs from the gyros and accelerometers are replaced by inputs from the self-test circuits on the Accelerometer and Sensor Electronics Assembly.
3.4.7 SYNCHRO ATTITUDE AND VELOCITY DATA INTERFACE. (Refer to Figure 3-27, Figure 3-28, Figure 3-29, and Figure 5-21.) The AN/WSN-7(V) has capability for input of synchro format speed and depth data, and for output of synchro format heading, roll, pitch, and velocity data. All S/D conversion for input of synchro format speed and synchro format depth data, and all digital-to-synchro (D/S) data conversion for output of heading, roll, pitch, and velocity take place on identical Synchro Converter CCAs (1A1A38), (1A1A39), and (1A1A40). These CCAs operate in conjunction with four SBAs, which provide load drive capability and switching for output of vital and non-vital heading, and non-vital roll and pitch data. A relay multiplex network on each Synchro Converter Assembly allows alternate internal signal paths to be chosen to select the input to the S/D converter (U3) on each CCA. During normal operation, all relays in the multiplex network are deenergized and the synchro speed (or depth) input channel is switched to the S/D converter. During off-line self-test, the relays can be addressed (selected by a data word from the Nav Processor) to sequentially route each S/D converter output back into the D/S converter for comparison of the digital data values transmitted from the Nav Processor, with the values generated by the D/S converters. This action is performed in the synchro short loop wraparound tests 533, 535, 537, 539, 541, 543, 546, 547, 548, 549, 591, and 592. Alternately, the relays can select the synchro output from each SBA for conversion by the S/D converter for comparison of the digital data values transmitted from the Nav Processor, with the values output from the system on each synchro output channel. This action is performed in synchro wraparound tests 534, 536, 538, 540, 542, and 544. Each D/S converter channel on the Synchro Converter Assemblies converts the digital input to a two-wire AC output, which is scaled to the amplitude sine and cosine of the angle represented by the digital data from the Nav Processor. These sine/cosine outputs are applied to the SBAs, where power ampliﬁers and Scott-T transformers convert the signals to three-wire synchro format for driving

external synchro loads. Each sine/cosine signal is also applied directly to a Scott-T transformer on the Synchro Converter Assembly. These transformers convert the sine/cosine signal directly to three-wire synchro data format for low output load applications.
The low power synchro outputs from channels 3 and 4 on Synchro Converter CCA (1A1A38) are used to provide 1X and 10X total velocity (Vt) synchro format data. The low power synchro outputs from channels 1 through 4 on Synchro Converter CCA (1A1A40) are used to provide 1X and 10X synchro format north-south velocity (Vn), and 1X and 10X east-west velocity (Ve). The data type output from each channel (heading, roll, pitch, or velocity) and the scaling (1X or 2X and 10X or 36X) from each channel is determined by the Nav Processor and is represented in the digital value applied to the D/S converter.
In addition to sine/cosine to three-wire synchro format conversion and power ampliﬁcation, the SBAs contain switching relays in the output circuits. These relays are normally deactivated and are set by control signals from Vital Bus CCA (1A1A3) if a fault is detected in the system’s primary power input. Whenever a primary power fault is detected and the AN/WSN-7(V) switches to internal battery power, Power Alarm 1 through 4 lines are set high, and the relays on each SBA are energized. This action opens the non-vital heading, roll, and pitch outputs to reduce system power requirements during the time when the AN/WSN-7(V) is operating from the battery.
A comparator circuit on each SBA provides BIT monitoring for the ampliﬁers function. If the output from any operational ampliﬁer is outside a predetermined limit, the comparator circuit sets a solid state relay (two relays on SBAs (1A1A41) and (1A1A42)), which opens the input circuits and applies a ground to the ampliﬁers. This action prevents false data from being output from the AN/WSN-7(V) in the event of a failure in a SBA. Opening of one set of normally closed contacts on solid state relay 1A1A41U2 / 1A1A42U2 turns on a transistor 1A1A41Q2 / 1A1A42Q2, which activates a fault Light Emitting Diode (LED) on the SBA, and also sets the SBA Fail output line to Status and Command CCA (1A1A15) low, indicating to the BIT function that the SBA has failed.

3.4.8 HARDWARE

MONITORING

AND

FAULT/STATUS OUTPUT. (Refer to Figure

3-30). In addition to monitoring the status of the IMU

circuits and RS-422 I/O circuits via data generated

by the IMU Processor and I/O Processor functions,

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S9427-AN-OMP-010/WSN-7

the Nav Processor monitors the operation of certain power and control functions via a status data word which is generated by Status and Command CCA (1A1A15). This status information is processed along with all other BIT-related functions and software-generated ﬂags to determine the operational and fault status condition of the AN/WSN-7(V). The Nav Processor, in addition to generating displayed Fault Codes, controls setting of relay contacts and switching of power for external status and alarm functions via the parallel bus and circuits on the Status and Command Assembly.
3.4.9 BUILT-IN TEST (BIT) AND STATUS. (Refer to Figure 3-31.) The BIT functions consist of software analysis of operational parameters, I/O transmission monitoring (message checksum, overrun, and time out errors), and comparison of signals, voltages, and status conditions with reasonableness limits. This combination of test functions consists of tests and monitoring, which are performed on-line at system power turn-on and during normal operation, and off-line tests, which are performed only in the Test mode. In addition, the system processors can be set to select wrap-around loops in an off-line Test mode, which checks I/O functions and synchro data output channels by comparing data output by the processor with data output by the function being tested.
During normal operation, the combination of information from the BIT functions is processed by the Nav Processor, which sets fault bits in error words in response to detection of fault conditions. These error words (FERRxx) are used to generate fault codes, which are presented in the upper-right corner of the display. In addition to generating fault codes, the Nav Processor controls the setting of fault status relays, which can be used to control external alarms or provide fault status to external equipment.
Basically, the BIT consists of test and monitoring functions from ﬁve sources:
1. Faults Detected by the I/O Processor.
2. Faults Detected by the IMU Processor.
3. Faults Detected by the Nav Processor.
4. Faults Detected by the ATM Processor.
5. Hardware-detected faults from the Status and Command Assembly .
3.4.9.1 Off-Line Tests. Whether selected by the System Conﬁdence Test or selected manually from the Select Tests menus, each off-line test performed

by BIT automatically sets up an off-line test loop, which exercises a speciﬁc function or circuit and checks for an expected result. Some tests require manual operations such as setting circuit breakers, disconnecting cables, connecting test cables, and setting of a CCA-mounted switch during performance of the test. Wherever manual procedures are required, the display prompts the operator to perform the procedure, and the test pauses until completion of the procedure is detected.
If the test passes, the message TEST COMPLETE - TEST PASSED is displayed. If the test fails, the message TEST COMPLETE - FAILURE xxx is displayed (where xxx is a three-digit code which indicates the type of fault detected). Generally, the failure code provides more detailed information than is necessary to correct the fault, as the AN/WSN-7(V) is repaired by replacement of the faulty subassembly. The off-line tests are described in Table 5-1.
3.4.9.2 System Conﬁdence Test. The System Conﬁdence Test is an automatic battery of off-line, Test mode tests. Only one test, Display Test 201, requires operator intervention. The System Conﬁdence Test conducts the following tests in the order shown over 12 minutes:
201 (Display, approx. 1 minute), 203, 204, 106, 209, 210, 212, 314, 315, 316, 117, 318, 220 (approx. 1 minute. If test 220 fails perform test 221), 322, 323, 424, 425 426, 427, 458, 459, 460, 461, 484, 485, 329 (approx. 3 minutes), 330 (approx. 4 minutes), 331 (approx. 1 minute), 533, 534, 535, 536, 537, 538, 539, 540, 541, 542, 543, 544, 546, 547, 548, 549, 591, 592. (Tests 424 through 485 are I/O port short loop tests. Test is performed for applicable I/O port only if the port is enabled and the IDS code is not 00.)
The System Conﬁdence Test can only be selected and conducted when the AN/WSN-7(V) is operating in the off-line Test mode. The System Conﬁdence Test is necessary because on-line Fault Codes do not always provide sufﬁcient guidance for selecting individual off-line tests, which are necessary to verify a fault condition and isolate a faulty component. The System Conﬁdence Test should be the ﬁrst test performed when troubleshooting. Additionally, this test should always be selected and run after a suspect, faulty assembly has been replaced with a known good assembly. The AN/WSN-7(V) should be turned on in normal mode only after the System Conﬁdence Test passes and conﬁrms successful assembly replacement.
The System Conﬁdence Test progresses through the off-line test battery until aborted by the operator. If in-

dividually selected, each test is performed for a time period of one second, and then the next test in the sequence is selected. If a fault is detected during the System Conﬁdence Test, the fault is announced and the test procedure pauses to allow the operator to observe the Fault Code. Detecting a fault does not abort the test series, and the sequence resumes when the operator presses the <ENTER> key.
The System Conﬁdence Test can be run by pressing the <1> key to select Run Sys Conf Test listed on the Main Menu. It can also be selected from the System Tests Menu by pressing the 00 on the keypad and then pressing the <ENTER> key.
3.4.9.3 Operator Response to Advisories and Faults. During on-line operation of the AN/WSN7(V), interfering conditions such as fault conditions associated with hardware and software functions, I/O bus data input checks, I/O bus wraparound testing, and IMU functions may occur that require certain actions to be performed.
At startup and during operation, the AN/WSN-7(V) BIT function continually monitors hardware and software functions and checks calculation results for reasonableness. In addition, the AN/WSN-7(V) checks data input on the I/O bus and performs wraparound testing of I/O outputs. Any fault condition detected by BIT is announced by a visual alarm. Each detected condition results in the generation of a fault code, which is stored in battery-backed RAM if still active when acknowledged for display and review. Based on the type of fault code displayed, the operator may acknowledge the fault by pressing the <ALARM ACK> key and choose to continue system operation, or may take the AN/WSN-7(V) out of service for navigation. Certain faults automatically shut down the AN/WSN-7(V) and cannot be overridden by the operator.
Table B-1, Fault Code Descriptions and Fault Isolation, lists all of the possible BIT fault codes and associated fault/status relay settings. It indicates the source of the fault and the classiﬁcation(s) of the fault. This Fault Code table also provides diagnostic information and references off-line BIT to be performed to verify and troubleshoot the fault condition. In addition to the valid fault codes, several spare code numbers are listed. Spare codes are reserved for future expansion and will not be announced for fault conditions.
Fault and status indicators may also be installed external to the system. These can be controlled by fault and status relays (K1, K2, K3, and K7) to either illuminate or extinguish upon detection of the fault or status condition. (Refer to Figure 5-5, sheet 1.) Re-

lay K1 functions as both a status and a fault relay. This relay initially remains reset when the system is in STANDBY to provide an external indication that the system is not ready, and then sets when the system enters the Align mode. The relay remains set unless a fault condition occurs.
3.4.9.4 Source AC Power or Synchro Reference Fault. The AN/WSN-7(V) contains an internal Power Supply (1A1A6), which provides an output of +25 VDC power during normal operation from the ship’s AC power source. The +25 VDC is distributed via the Terminal Junction System (TJS) to all end users. The Battery Charger (1A1A7) produces -25 VDC power using the +25 VDC as its input power under all conditions. The -25 VDC is also distributed via the TJS to all users on the bus.
The Battery Charger also maintains the charge on the Battery Assembly (1A1A5) using the +25 VDC output from the Power Supply. The Inverter Assembly (1A1A2), which operates from the +25 VDC bus, generates 115 VAC, 400 Hz for the components on the vital synchro reference circuit as long as the AN/WSN-7(V) is energized. In the event that the ship’s main power bus is interrupted or out of tolerance, the Battery Assembly, working through the Battery Charger, provides emergency ±25 VDC power for continuous operation. BIT functions on the Vital Bus CCA (1A1A3) monitor main AC power and non-vital reference supplied to the AN/WSN-7(V), and provide control to automatically turn off all non-vital synchro outputs in the event that a source power or non-vital synchro reference fault is detected. When the external power is reestablished within the correct limits, the AN/WSN-7(V) automatically switches back to AC operation and restores non-vital synchro outputs.
3.4.10 NAV AND I/O PROCESSORS. The I/O Processor continuously monitors the operation of the RLGN-RLGN interface, the installed NTDS I/O boards, and the I/O messages being received or transmitted via the conﬁgured NTDS interface ports. The I/O Processor sets error bits in fault error words and then transmits the error words to the Nav Processor via the processor’s data interface.
The I/O Processor provides two categories of fault indications. One category consists of faults that are directly related to the I/O boards or processor-I/O interface (FERR14 through FERR21). The second category consists of faults that are detected in input or output data message transfer or transfer timing protocol (FERR27 through FERR42). These faults may be related to the I/O board, external cabling, external

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S9427-AN-OMP-010/WSN-7

equipment, or incorrect message format selection for the conﬁgured port(s).
If the I/O Processor detects a message-related error, it sets up and executes a short loop wraparound test of the I/O port to determine if the fault is port- or message-related. Further testing of I/O ports can be performed off-line by selecting a long loop test, which utilizes test wraparound cables. These off-line tests verify operation of the interface ports and all I/O cabling internal to the AN/WSN-7(V) cabinet.
The IMU BIT monitors IMU processor operation, IMU data interface, timing, and the function of IMU Electronics boards. Circuits on the boards in the IMU Electronics continuously monitor the analog signals associated with operation of the platform gimbal indexers and sensor elements via the A/D Multiplex board. Monitored signals include those associated with the RLGs, accelerometers, and High Voltage Power Supply. The IMU Processor sets error words FERR06 through FERR10 and then transmits the error words to the Nav Processor via the serial data interface.
In addition to the faults detected directly by the I/O Processor and IMU functions, the Nav Processor also monitors the data and data interface associated with the I/O and IMU, and sets faults associated with strapdown control, gyro and accelerometer rate limits, and IMU Processor and interface faults (FERR03, FERR04, and FERR05). I/O monitoring performed by the Nav Processor consists of GPS message and comparison of position and attitude data with that received from the other AN/WSN-7(V) (FERR22 and FERR23). In addition to the I/O and IMU functions monitored, the Nav Processor also monitors the reasonableness of navigation data and of position and velocity input data (FERR02).
The hardware status faults detected by various circuits are latched in a buffer in the Status and Command Assembly and are read as FERR01 by the Nav Processor. These faults are associated with operation of internal power supply functions, synchro output circuits, speed log input, and platform indexing control. Detection of loss of ship’s main power and switching to battery operation is automatic and is controlled by circuits on the Vital Bus board without intervention by the Nav Processor.
After the Nav Processor CCA (1A1A13) has successfully completed the power-up self-tests, further monitoring of CPU operation is performed by a heartbeat detector function on Status and Command CCA (1A1A15). Nav Processor CCA (1A1A13) periodically addresses the heartbeat detector on (1A1A15), performing a reset which causes the associated

heartbeat fault LED (1A1A15-DS2) on the board to remain turned off. If the CPU fails and is unable to address the heartbeat detector within a reasonable time limit, the detector circuit will time-out, causing the heartbeat fault LED to illuminate and a status bit to be set indicating a probable fault in Nav Processor CCA (1A1A13). If the fault is in the CPU, system operation will shut down and the LED will remain illuminated. If the fault is in the detector logic and not in the CPU, the system will continue to operate and Fault Code 042 will be displayed.
The Nav Processor and the I/O Processor periodically perform a test pattern write/read test on the common RAM (dual port memory) on Dual Port Memory CCA (1A1A23). This consists of the Nav Processor writing data into the common RAM, which is read by the I/O Processor and then written back into common RAM by the I/O Processor. The reﬂected data from the I/O processor is read by the Nav Processor and is then compared with the original pattern data to verify memory and data transfer integrity. The test is repeated in reverse order with the test pattern data originating from and compared by the I/O Processor. If the test initiated by the Nav Processor fails twice in a row, Fault Code 019 will be displayed. If the test initiated by the I/O Processor fails twice in a row, Fault Code 252 will be displayed.
3.4.11 SYNCHRO DATA CONVERSION AND SBA DESCRIPTIONS.
3.4.11.1 Synchro Converter CCAs (1A1A38), (1A1A39), and (1A1A40). The digital-to-synchro converters convert digital angle values from the Central Processor to an analog output proportional to the sine and cosine of the synchro angle. The output (heading, pitch, or roll) data type is dependent on the rack location of the CCA. The Synchro Converter CCA in rack location (1A1A38) provides 1X and 36X (sine/cos) heading to SBAs 32 VA (1A1A43) and (1A1A44), respectively. The Synchro Converter CCA in rack location (1A1A39) provides 1X (or 2X) and 36X (sine/cos) roll output to SBA (1A1A41) and 1X (or 2X) and 36X (sine/cos) pitch output to SBA (1A1A42).
The coarse output is either 1X or 2X depending on the Synchro Output Function selections made on the System Conﬁguration menu at installation. 2X output is selected for the AN/WSN-7(V).
Two of the digital-to-synchro converter channels on Synchro Converter CCA (1A1A38) are used to convert digital values from the Central Processor to provide direct output of ship’s total velocity vectors formatted as 1X and 10X scaled synchro. All four of

the digital-to-synchro converter channels on Synchro Converter CCA (1A1A40) are used to convert digital values from the Central Processor to provide direct output of ship’s north-south and east-west velocity vectors formatted as 1X and 10X scaled synchro. Depending on the INS installation requirements, the synchro-to-digital input channels on each card can be used to convert any single-speed synchro input to a digital value for input to the Central Processor. In a standard AN/WSN-7(V) installation, the input to Synchro Converter CCA (1A1A38) is reserved for input of 1X speed data (fore-aft) and the input to Synchro Converter CCA (1A1A39) is reserved for input of 1X speed data (athwartships) from the ship’s dual-axis speed log. The synchro-to-digital input channels on card (1A1A40) are not used.
3.4.11.2 Synchro Buffer Ampliﬁers (SBAs) 8 VA (1A1A41) and (1A1A42). SBAs 8 VA (1A1A41) and (1A1A42) are identical (8 volt-amp) output subassemblies and can be interchanged in the AN/WSN-7(V). SBAs amplify and convert the sine and cosine signals from the Synchro Converter Assemblies to three-wire synchro format for driving external synchro loads. The ampliﬁers contain two identical circuits, each comprising two solid-state ampliﬁers, a Scott-T output transformer, and output switching relays. The sine and cosine analog input signals from the associated converter channels on Synchro Converter CCA (1A1A39) are ampliﬁed and applied to the input windings of the channel’s transformer. The output from each transformer is three-line synchro format signal. SBA (1A1A41) is used to output synchro format roll and SBA (1A1A42) is used to output synchro format pitch. Each synchro output line is applied to the contacts of switching relays in the SBA. During normal operation, the relays switch the synchro outputs to the system’s external output connector.
In the event of a power failure (or during off-line tests), the relays are deenergized and all AN/WSN-7(V) external pitch and roll outputs from the SBAs are opened. The open circuit relay contacts switch the synchro roll and pitch outputs back to multiplexed inputs on Synchro Converter CCA (1A1A39), where they can be selected to provide wraparound of the synchro outputs during performance of off-line testing of the SBAs.
3.4.11.3 Synchro Buffer Ampliﬁers (SBAs) 32 VA (1A1A43) and (1A1A44). SBAs 32 VA (1A1A43) and (1A1A44) are identical (32 volt-amp) subassemblies and can be interchanged in the AN/WSN-7(V). These SBAs are similar in function to SBA 8 VA (1A1A41) and (1A1A42) but, because of differences

in the conﬁguration of the output switching circuits and power speciﬁcations, cannot be interchanged with them. The primary difference in output switching is that one synchro channel (designated for vital heading reference) is hard-wired to the ampliﬁer output rather than being switched through relay contacts. In the event of a power failure, one channel from SBA (1A1A43) continues to output 1X vital heading and one channel from SBA (1A1A44) continues to output 36X vital heading to the system external output connector. The output from the second (non-vital) channel in each ampliﬁer is switched off-line and wrapped back to Synchro Converter CCA (1A1A38) in the same manner as the synchro roll and pitch outputs.

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S9427-AN-OMP-010/WSN-7

Table 3-1. Trigonometric Functions

FUNCTION RATIO OF

FUNCTION APPROXIMATE VALUE AT SELECTED ANGLES

0.0°

15°

30°

45°

60°

75°

90°

Sin θ

Y/r

0.00

0.259

0.5 0.707 0.866

0.966

1

Table 3-2. Sample Data Calculations Illustrating Concept of Variance

MEASUREMENT REVOLUTIONS PER
MINUTE (RPM) (Column 1)

I

Xi

1

103.0

2

101.2

3

98.0

4

96.0

5

101.0

6

101.2

7

99.8

8

100.0

9

97.5

10

95.3

X = 99.3 rpm

VARIANCE FROM AVERAGE X (Column 2)
∆σi = Xi - X +3.7 +1.9 -1.3 -3.3 +1.7 =1.9 +0.5 +0.7 -1.8 -4.0
∆σavg = 0.00 rpm

SQUARED VARIATION (Column 3)
(∆σi)2 = (Xi - X)2 13.69 3.61 1.69 10.89 2.89 3.61 0.25 0.49 3.24 16.00
(∆σ)2avg = 5.636 rpm2

10

Xi

where: X =

Σ

___

I=1

10′

the sample average

∆σavg = (∆σ)2avg =

10 Σ I=1
10 Σ I=1

∆σi ___ 10’
(∆σi)2 ___ 10’

the average variation the average variation σ2

FUNCTION
Cos θ Tan θ

Table 3-1. Trigonometric Functions - Continued

RATIO OF

FUNCTION APPROXIMATE VALUE AT SELECTED ANGLES

X/r

1

0.966 0.866 0.707

0.5

0.259

Y/X

0.00 0.268 0.577 1.0

1.732

3.732

0.00 INFINITY

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S9427-AN-OMP-010/WSN-7

Figure 3-1. Simple Strapdown System

Figure 3-2. Simple Gimbal Stabilization of the Accelerometer

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S9427-AN-OMP-010/WSN-7

3-20

Figure 3-3. Single-Axis Schuler-Tuned Gimbaled System

Figure 3-4. Single-Axis Schuler-Tuned Strapdown System

S9427-AN-OMP-010/WSN-7

Figure 3-5. Schuler Oscillations in an Undamped Inertial Navigator

Figure 3-6. Effect of Earth’s Rotation on Local Vertical

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S9427-AN-OMP-010/WSN-7

3-22

Figure 3-7. Earth Rate Components

Figure 3-8. North Position Error