3889 lines
171 KiB
Plaintext
3889 lines
171 KiB
Plaintext
FM 6-40 MCWP 3-16.4
|
||
Tactics, Techniques, and Procedures for the Field Artillery
|
||
Manual Cannon Gunnery
|
||
U.S. Marine Corps
|
||
PCN 143 000003 00
|
||
|
||
FOREWARD This publication may be used by the US Army and US Marine Corps forces during training, exercises, and contingency operations.
|
||
|
||
General, USA Commanding Training and Doctrine Command
|
||
|
||
Lieutenant General, USMC Commanding General Marine Corps Combat Development Command
|
||
|
||
FM 6-40/MCWP 3-1.6.19
|
||
|
||
PREFACE
|
||
|
||
This field manual (FM) explains all aspects of the cannon gunnery problem and presents a practical application of the science of ballistics. It includes step-by-step instructions for manually solving the gunnery problem and applies to units organized under tables of organization and equipment (TOE) of the L series. The material concerns nonnuclear solutions to the gunnery problem. Automated procedures are covered in ST 6-40-2, ST 6-40-31, and ST 6-50-60. This publication is a guide for field artillery (FA) officers (commanders and fire direction officers [FDOs]), FA noncommissioned officers (NCOs), and enlisted personnel in the military occupational specialty (MOS) of cannon gunnery (MOS 13E; United States Marine Corps [USMC] MOS 0844/48). This publication implements the following North Atlantic Treaty Organization (NATO) Standardization Agreements (STANAGs)/Quadripartite Standardization Agreements (QSTAGs):
|
||
|
||
STANAG 2934 (Chap 10) (Ed 1) 2934 (Chap 6) (Ed 1) 2934 (Chap 7) (Ed 1) 2934 (Chap 5) (Ed 1) 2934 (Chap 3) (Ed 1) 2963 (Ed 1) 4119 (Ed 1) none 4425 (Ed 1)
|
||
|
||
QSTAG 182 (Ed 2) 255 (Ed 3) 221 (Ed 2) 246 (Ed 3) 217 (Ed 2) 802 (Ed 1) 220 (Ed 2) 224 (Ed 2) none
|
||
|
||
TITE Artillery Procedures, Battlefield Illumination Artillery Procedures, Call for Fire Procedures Artillery Procedures, Target Numbering System (Nonnuclear) Artillery Procedures, Radio Telephone Procedures for the Conduct of Artillery Fire Artillery Procedures, Tactical Tasks and Responsibilities for Control of Artillery Coordination of Field Artillery Delivered Scatterable Mines Adoption of a Standard (Cannon) Artillery Firing Table Format Manual Fire Direction Equipment, Target Classification, and Methods of Engagement for Post-1970 Procedure to Determine the Degree of Interchangeability of NATO Indirect Fire Ammunition-APO-29
|
||
|
||
The proponent of this publication is Headquarters (I-IQ), US Army Training and Doctrine Command (TRADOC). Send comments and recommendations on DA Form 2028 (Recommended Changes to Publications and Blank Forms) directly to Commandant, US Army Field Artillery School (USAFAS), ATTN: ATSF-GD, Fort Sill, OK 73503-5600.
|
||
|
||
Unless this publication states otherwise, masculine nouns and pronouns do not refer exclusively to men.
|
||
|
||
xviii
|
||
|
||
C1, FM 6-40/MCWP 3-16.4
|
||
|
||
Change No.1
|
||
|
||
HEADQUARTERS DEPARTMENT OF THE ARMY
|
||
Washington, DC, 1 October 1999
|
||
|
||
Tactics, Techniques, and Procedures for
|
||
FIELD ARTILLERY MANUAL CANNON GUNNERY
|
||
|
||
FM 6-40/MCWP 3-16.4, April 1996, is changed as follows:
|
||
|
||
1. Change the following paragraphs or sections (changes are in bold type):
|
||
|
||
Replace Paragraph 6-1, Page 6-1 with the following:
|
||
|
||
6-1. Description
|
||
|
||
A firing chart is a graphic representation of a portion of the earth's surface used for determining
|
||
distance (or range) and direction (azimuth or deflection). The chart may be constructed by using a map, a photomap, a gridsheet, or other material on which the relative locations of batteries, known points, targets, and observers can be plotted. Additional positions, fire support coordinating measures, and other data needed for the safe and accurate conduct of fire may also be recorded.
|
||
|
||
Replace Step 5, Table 6-6, Page 6-19 with the following:
|
||
|
||
5 Place a plotting pin opposite the number on the azimuth scale (blue numbers) on the arc of the RDP corresponding to the last three digits of the azimuth in which the arm of the RDP is oriented. The location of the pin represents a temporary index and will not be replaced with a permanent index. The value of the pin is the value of the first digit of the azimuth in which the arm o f the RDP is oriented. Use the rules outlined in step 4 of Table 6-5 to determine where the pin should be placed. In Figure 6-15, the azimuth of lay is 1850, so the RDP has been oriented east (1600 mils).
|
||
|
||
Replace Figure 7-1, Page 7-1 with the following:
|
||
|
||
STANDARD CONDITIONS WEATHER
|
||
1 AIR TEMPERATURE 100 PERCENT (59° F) 2 AIR DENSITY 100 PERCENT (1,225 gm/m3) 3 NO WIND
|
||
POSITION
|
||
1 GUN, TARGET AND MDP AT SAME ALTITUDE 2 ACCURATE RANGE 3 NO ROTATION OF THE EARTH
|
||
MATERIAL
|
||
1 STANDARD WEAPON, PROJECTILE, AND FUZE 2 PROPELLANT TEMPERATURE (70° F) 3 LEVEL TRUNNIONS AND PRECISION SETTINGS 4 FIRING TABLE MUZZLE VELOCITY 5 NO DRIFT
|
||
LEGEND: gm/m3 - grams per cubic meter
|
||
|
||
Replace Table C-6, page C-18, with the following
|
||
|
||
Table C-6. Target Acquisition Method.
|
||
|
||
TLE = 0 Meters (CEP)
|
||
Forward observer with laser Target area base Photointerpretation Airborne target location
|
||
|
||
TLE = 75 Meters (CEP)
|
||
Counterbattery Radar Airborne infrared system Flash ranging Countermortar radar
|
||
|
||
TLE = 150 Meters (CEP) Sound ranging
|
||
|
||
TLE = 250 Meters (CEP)
|
||
Forward observer w/o laser Air observer Tactical air Forward observer (non FA) Long-range patrol Side-looking airborne radar Communications intel Shell reports
|
||
|
||
2.
|
||
|
||
Remove old pages and insert new pages indicated below:
|
||
|
||
REMOVE PAGES
|
||
|
||
INSERT PAGES
|
||
|
||
8-16
|
||
|
||
8-16
|
||
|
||
15-7 TO 15-25
|
||
(Including Figure 15-22 on page 15-26)
|
||
|
||
15-7 TO 15-45
|
||
|
||
3.
|
||
|
||
Insert new pages as indicated below:
|
||
|
||
INSERT PAGES
|
||
|
||
13-77 to 13-82
|
||
|
||
4.
|
||
|
||
File this transmittal sheet in the front of the publication for reference.
|
||
|
||
DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited.
|
||
|
||
FM 6-40 MCWP 3-16.4
|
||
1 October 1999
|
||
|
||
By Order of the Secretary of the Army:
|
||
Official:
|
||
JOEL B. HUDSON Administrative Assistant to the
|
||
Secretary of the Army 0011015
|
||
By Direction of the Commandant of the Marine Corps:
|
||
|
||
ERIK K. SHINSEKI General, United States Army
|
||
Chief of Staff
|
||
|
||
J. E. RHODES Lieutenant General, US Marine Corps
|
||
Commanding General Marine Corps Combat Development Command
|
||
|
||
DISTRIBUTION:
|
||
Active Army, Army National Guard, and U.S. Army Reserve: To be distributed in accordance with initial distribution number 110044, requirements for FM 6-40/MCWP 3-16.4.
|
||
|
||
FM 6-40 ______________________________________________________________________ 8-15. Determination of 10-Mil Site Factor Without a High-Angle GFT
|
||
The 10-mil site factor is the value of high angle site for every 10 mils of angle of site. The 10-mil site factor can be determined manually by solving two equal equations for the 10-mil site factor.
|
||
SI = < SI + CAS (FOR LOW AND HIGH ANGLE) SI = < SI + ( | < SI | X CSF) FOR POSITIVE ANGLES OF SITE: HIGH ANGLE SITE = < SI ( 1 + CSF ) FOR NEGATIVE ANGLES OF SITE: HIGH ANGLE SITE = < SI ( 1 - CSF ) USING THE HIGH ANGLE GFT: HIGH ANGLE SITE = (< SI / 10) X 10-MIL SI FACTOR HOW TO DETERMINE 10-MIL SI FACTOR WITHOUT A GFT: FOR POSITIVE ANGLES OF SITE: 10-MIL SI FACTOR = 10 ( 1 + CSF ) FOR NEGATIVE ANGLES OF SITE: 10-MIL SI FACTOR = 10 ( 1 - CSF ) NOTE: If the 10-mil site factor is not listed on the high angle GFT, use the last listed value or change charges
|
||
The FDC can compute high angle site by manually determining the 10-mil site factor for those situations when a high angle GFT is not available. The 10-mil site factor from the GFT actually reflects the complementary angle of site for a positive VI. Therefore, this method will introduce a slight inaccuracy when estimating for negative VI's
|
||
8-16
|
||
|
||
______________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
13-42.
|
||
|
||
Sense And Destroy Armor (SADARM M898)
|
||
|
||
The M898 SADARM projectile is a base ejecting munition carrying a payload of two target sensing submunitions. The projectile is a member of the DPICM family, and is ballistically similar to the M483A1. The technical fire direction computations are similar to those used for the ADAM projectile, in that low level wind corrections must be applied to the firing solution (because of the high Height of Burst) in order to place the payload at the optimal location over the target area.
|
||
|
||
13-43.
|
||
|
||
M898 Firing Data Computations
|
||
|
||
Firing data are computed for SADARM by using the FT 155 ADD-W-0 or FT 155 ADDW-1 in conjunction with the FT 155 AN-2. The difference between the ADD-W-0 and ADDW-1 is the Height of Burst of the projectile. The ADD-W-1 increases the HOB to correct for changes in the operational parameters of the projectile. The ADD-W-1 is the preferred method of producing data, although the ADD-W-0 procedure may be used in lieu of the FT ADD 155W-1 if it is unavailable. (Note: BCS Version 11 will incorporate the ADD-W-1 solution. BCS Version 10 has the incorrect HOB, and automated firings must also incorporate the change in HOB discussed in the ADD-W-0 method).
|
||
|
||
13-44.
|
||
|
||
Technical Fire Direction Procedures
|
||
|
||
Technical fire direction procedures consist of four steps (following the Fire Order):
|
||
|
||
a. Determine chart data to the target location. Chart range, chart deflection, and angle "T" are recorded on the DA-4504 (Record of Fire) in the Initial Fire Commands portion of the form. AN-2 site, elevation, QE, and angle "T" are determined to this target location. Fire commands are not determined from this data! (See Figures 13-33 and 13-34, Sample Records of Fire for SADARM)
|
||
|
||
b. Offset aimpoint for low level winds. The HCO places a target grid over the target location from step 1. He then applies the Direction of Wind from the Meteorological Message (Extracted from Line 3) and offsets the aimpoint by the distance determined by multiplying the Wind Speed (Extracted from Line 3) times the correction factor from Table "A", Column 5, expressed to the nearest 10 meters. This is the offset aimpoint which is used to determine firing data for SADARM.
|
||
|
||
c. Determine AN-2 graze burst data to the corrected aimpoint. The HCO announces chart range and deflection to the corrected aimpoint from step 2. These values are recorded in the Subsequent Fire Commands portion of the DA-4504. AN-2 graze burst data are determined to this offset aimpoint, to include Fuze Setting, Deflection to fire, and Quadrant Elevation (Site and angle "T" were determined in step (a.)).
|
||
|
||
d. Determine SADARM firing data from the ADD-W-0 or ADD-W-1. If data are being determined with the ADD-W-0, use paragraph (1.) below. If data are being determined with the ADD-W-1, then use paragraph (2.) below.
|
||
|
||
13-77
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4______________________________________________
|
||
|
||
(1) ADD-W-0. First determine SADARM firing data from the ADD-W0. Then the Height of Burst correction must be applied. Table 13-33 contains the HOB corrections by charge and AN-2 Quadrant Elevation. To extract values from the table, enter with Charge on the left, and with the AN-2 graze burst Quadrant Elevation on the top. If your Quadrant Elevation is less than or equal to the QE listed in Column 2, then use the up correction in Column 2. If it is greater than the value listed in column 3 and less than 800 mils, apply the up correction from column 3. If it is greater than 800 mils, apply the up correction from column 4. The extracted up correction is used to determine the change in Quadrant Elevation (from Table "A", Column 3) and change in Fuze Setting (from Table "B", Column 3) for the change in HOB. These values are then algebraically added to the ADD-W-0 data to determine the data to fire. The FT 155 ADD-W-0 use the following formulas:
|
||
|
||
DEFLECTION TO FIRE
|
||
|
||
AIMPT CHT DF+ADD-W-0 DF CORR+GFT DF CORR+AN-2 DFT=M898 DF
|
||
|
||
FUZE SETTING TO FIRE
|
||
|
||
AN-2 FS+ADD-W-0 FS CORRECTION+HOB FS CORRECTION=M898 FS
|
||
|
||
QUADRANT ELEVATION TO FIRE
|
||
|
||
AN-2 QE+ADD-W-0 QE CORRECTION+HOB QE CORRECTION=M898 QE
|
||
|
||
Table 13-33, FT 155 ADD-W-0 HOB Corrections
|
||
|
||
Column 1
|
||
CHARGE 3G (M3A1) 4G (M3A1) 5G (M3A1) 3W (M4A2) 4W (M4A2) 5W (M4A2) 6W (M4A2) 7W (M4A2) 7R/8W (M119/A1/A2) 8S (M203/A1)
|
||
|
||
Column 2
|
||
AN-2 QE <= QE<=498, U200 QE<=430, U100 QE<=366, U100 QE<=434, U100 QE<=388, U150 QE<=343, U150 QE<=305, U100 QE<=251, U100 QE<=205, U100 QE<=173, U100
|
||
|
||
Column 3
|
||
AN-2 QE> and <800 QE>498, U200 QE>430, U150 QE>366, U150 QE>434, U200 QE>388, U150 QE>343, U150 QE>305, U200 QE>251, U200 QE>205, U200 QE>173, U200
|
||
|
||
Column 4
|
||
AN-2 QE >800 U250 U250 U250 U250 U250 U250 U300 U300 U300 U300
|
||
|
||
Table 13-34 contains the specific step action drill required to compute SADARM firing data using the ADD-W-0 method.
|
||
|
||
13-78
|
||
|
||
______________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
Table 13-34. SADARM employment procedures (FT 155 ADD-W-0)
|
||
|
||
STEP 1 2 3 4 5 6
|
||
7
|
||
8
|
||
9 10 11
|
||
12 13 14
|
||
15
|
||
|
||
ACTION The call for fire is received FDO issues Fire Order The computer records the target information on the Record of Fire. (Note: All fire commands are announced as they are determined) The HCO plots the target location on the firing chart and determines chart range, chart deflection, and angle "T" to the target. The VCO determines and announces AN-2 site to the target location. The Computer determines and announces the data for the offset aimpoint by extracting the Wind Direction and Wind Speed from line 3 of the meteorological message. The Wind Direction is announced in hundreds of mils. The aimpoint shift correction is determined by multiplying the windspeed times the value from column 5, Table "A" of the Firing Table Addendum. (Note, the entry argument for the addendum is the AN-2 data determined to the target location) The HCO places a target grid over the target location and applies the Wind Direction announced by the Computer in step 5. The aimpoint shift correction is applied into the wind. (Note: the Wind Direction from the MET MSG is the direction the wind is blowing from.) The HCO determines and announces chart range and chart deflection to the offset aimpoint. The target grid is then reoriented to the OT direction announced by the observer, as all corrections will be based on this aimpoint. Angle "T", however, is determined to the actual target location in step 4. The computer determines AN-2 data to the corrected aimpoint. The computer uses the data from step 9 to determine SADARM data. The computer determines the FS HOB correction necessary by dividing the HOB correction from table 13-33 by 50. This value is then multiplied times the correction factor from Table "B", Column 3 of the ADD-W-0 addendum to determine the HOB FS CORRECTION. The computer determines fuze setting to fire. The fuze setting to fire is determined with the following formula: AN-2 FS+ADD-W-0 FS CORR+HOB FS CORR=M898 FS The computer determines the deflection to fire. The deflection to fire is determined with the following formula: AIMPT CHT DF+ADD-W-0 DF CORR+GFT DF CORR+AN-2 DFT=M898 DF The computer determines the QE HOB correction necessary by dividing the HOB correction from table 13-33 by 50. This value is then multiplied times the correction factor from Table "A", Column 3 of the ADD-W-0 addendum to determine the HOB QE CORRECTION. The computer determines the Quadrant Elevation to fire. The QE to fire is determined with the following formula: AN-2 QE+ADD-W-0 QE CORR+HOB QE CORR =M898 QE
|
||
|
||
13-79
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4______________________________________________ Figure 13-33. Sample Record of Fire for SADARM, FT 155 ADD-W-0 Method
|
||
:
|
||
13-80
|
||
|
||
FDC: K36
|
||
H42 442 783
|
||
|
||
LAST TGT # AA72Ø1
|
||
|
||
T-72 Platoon i/o, SADARM 2
|
||
|
||
K, 2 TGT # AA72Ø2
|
||
|
||
BTRY 2
|
||
|
||
SAD
|
||
|
||
S/G
|
||
|
||
(2ØØ)
|
||
|
||
SADARM FT 155 ADD-W-0
|
||
|
||
TGT ALT 445
|
||
|
||
-BTRT ALT 4Ø5
|
||
|
||
VI
|
||
|
||
+4Ø
|
||
|
||
BTRY ALT 4Ø5
|
||
23 5
|
||
|
||
45ØØ
|
||
|
||
5
|
||
|
||
(< 38)
|
||
|
||
(15)
|
||
|
||
327Ø
|
||
|
||
+ 9 232
|
||
(241)
|
||
|
||
AN-2 AIMPOINT DATA SADARM AIMPOINT DATA
|
||
|
||
(15.3) 326Ø
|
||
DRIFT (L4) + GFT (L5) =
|
||
-2.Ø (13.3)
|
||
|
||
L9 (3269)
|
||
LØ (3269)
|
||
|
||
464Ø
|
||
|
||
+9 +9 241
|
||
+ 129
|
||
|
||
ADD-W-Ø, TBL B, COL 2
|
||
|
||
TBL A, COL 8
|
||
|
||
HOB CORRECTION DATA (U1ØØ/5Ø =2 INC) +Ø.2 13.5
|
||
|
||
3269
|
||
|
||
TBL A, COL 2 +32
|
||
|
||
ADD-W- Ø TBL B, COL 3 X INC (Ø.1 X 2) = EOM EOM
|
||
|
||
TBL A COL 3 X INC (16.1 X 2) =
|
||
|
||
(250) (379) 411
|
||
|
||
12 SAD
|
||
|
||
MET MSG LINE Ø3 19 KTS (From Met Msg) Wind Dir 24ØØ Mils X 9.9 M/KT (TBL A, Col 5)
|
||
Wind Speed 19 Knots = 188.1~19Ø Meter Aimpt shift
|
||
|
||
AN-2 GFT SETTING: GFT B, CHG5, LOT D/G, RG 5ØØØ, EL 264, TI 16.7 (M577) GFT DF CORR L5
|
||
|
||
B
|
||
|
||
241022SFEB98
|
||
|
||
AA72Ø2
|
||
|
||
______________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
(2) ADD-W-1. No corrections to the Height of Burst are required. The AN-2 graze burst data are used as entry arguments into the ADD-W-1 and the corrections to DF, FS, and QE are and applied. The FT 155 ADD-W-1 use the following formulas:
|
||
|
||
FUZE SETTING TO FIRE AN-2 FS+ADD-W-1 FS CORRECTION=M898 FS
|
||
DEFLECTION TO FIRE AIMPT CHT DF+ADD-W-1 DF CORR+GFT DF CORR+AN-2 DFT=M898 DF
|
||
QUADRANT ELEVATION TO FIRE AN-2 QE+ADD-W-1 QE CORRECTION=M898 QE
|
||
|
||
Table 13-35. SADARM employment procedures (FT 155 ADD-W-1)
|
||
|
||
STEP 1 2 3 4 5 6
|
||
7
|
||
8
|
||
9 10 11
|
||
|
||
ACTION The call for fire is received FDO issues Fire Order The computer records the target information on the Record of Fire. (Note: All fire commands are announced as they are determined) The HCO plots the target location on the firing chart and determines chart range, chart deflection, and angle "T" to the target. The VCO determines and announces AN-2 site to the target location. The Computer determines and announces the data for the offset aimpoint by extracting the Wind Direction and Wind Speed from line 3 of the meteorological message. The Wind Direction is announced in hundreds of mils. The aimpoint shift correction is determined by multiplying the windspeed times the value from column 5, Table "A" of the Firing Table Addendum. (Note, the entry argument for the addendum is the AN-2 data determined to the target location) The HCO places a target grid over the target location and applies the Wind Direction announced by the Computer in step 5. The aimpoint shift correction is applied into the wind. (Remember, the Wind Direction from the Meteorological Message is the direction the wind is blowing from.) The HCO determines and announces chart range and chart deflection to the offset aimpoint. The target grid is then reoriented to the OT direction announced by the observer, as all corrections will be based on this aimpoint. Angle "T", however, is determined to the actual target location in step 4. The computer determines the FS to fire. The FS to fire is determined with the following formula: AN-2 FS+ADD-W-1 FS CORR = M898 FS The computer determines the DF to fire. The DF to fire is determined with the following formula: AIMPT CHT DF+ADD-W-1 DF CORR+GFT DF CORR+AN-2 DFT=M898 DF The computer determines the QE to fire. The QE to fire is determined with the following formula: AN-2 QE+ADD-W-1 QE CORR=M898 QE
|
||
|
||
13-81
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4______________________________________________ Figure 13-34. Sample Record of Fire for SADARM, FT 155 ADD-W-1 Method
|
||
:
|
||
13-82
|
||
|
||
FDC: K36
|
||
H42 442 783
|
||
|
||
LAST TGT # AA72Ø1
|
||
|
||
T-72 Platoon i/o, SADARM 2
|
||
K, 2 TGT # AA72Ø2
|
||
|
||
BTRY 2
|
||
|
||
SAD
|
||
|
||
S/G
|
||
|
||
(2ØØ)
|
||
|
||
SADARM FT 155 ADD-W-1 METHOD
|
||
|
||
TGT ALT 445
|
||
|
||
-BTRT ALT 4Ø5
|
||
|
||
VI
|
||
|
||
+4Ø
|
||
|
||
BTRY ALT 4Ø5
|
||
23 5
|
||
|
||
45ØØ
|
||
|
||
5
|
||
|
||
(< 38)
|
||
|
||
(15)
|
||
|
||
327Ø
|
||
|
||
+ 9 232
|
||
(241)
|
||
|
||
AN-2 AIMPOINT DATA
|
||
|
||
(15.3) 326Ø L9 (3269)
|
||
|
||
DRIFT (L4) + GFT (L5) =
|
||
|
||
SADARM AIMPOINT DATA
|
||
|
||
-1.8 13.5
|
||
|
||
LØ 3269
|
||
|
||
ADD-W-1, TBL B, COL 2 EOM EOM
|
||
|
||
TBL A, COL 8
|
||
|
||
464Ø
|
||
|
||
+9 +9 241
|
||
|
||
+ 161 TBL A, COL 2
|
||
|
||
(250)
|
||
411
|
||
|
||
12 SAD
|
||
|
||
MET MSG LINE Ø3 19 KTS (From Met Msg) Wind Dir 24ØØ Mils X 9.9 M/KT (TBL A, Col 5)
|
||
Wind Speed 19 Knots = 188.1~19Ø Meter Aimpt shift
|
||
|
||
AN-2 GFT SETTING: GFT B, CHG5, LOT D/G, RG 5ØØØ, EL 264, TI 16.7 (M577) GFT DF CORR L5
|
||
|
||
B
|
||
|
||
241022SFEB98
|
||
|
||
AA72Ø2
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
Section II
|
||
Manual Computation of Safety Data
|
||
|
||
Minimum and maximum quadrant elevations, deflection limits, and minimum fuze settings must be computed to ensure that all rounds fired impact or function in the target area. These data are presented and arranged in a logical manner on a safety T. This section describes the manual computation of safety data by use of tabular and graphical equipment. As stated earlier, the range officer gives the OIC the lateral safety limits and the minimum and maximum ranges of the target areas. These data must be converted to fuze settings, deflections, and quadrants. The computations discussed in this section should be done by two safety-certified personnel working independently.
|
||
|
||
15-4. Manual Computational Procedures
|
||
|
||
Manual safety computations are accomplished in four steps, beginning with receipt of the range safety card and ultimately ending with the production of the safety T. These steps are listed in Table 15-1.
|
||
|
||
STEP 1 2 3
|
||
4
|
||
|
||
Table 15-1. Four Steps of Manual Safety Production.
|
||
ACTION Receive the Range Safety Card (Produced by unit or from Range Control). Construct the Safety Diagram in accordance with Table 15-2. Construct and complete the computation matrix using Figure 15-3 for Low Angle Safety and Figure 15-12 for High Angle Safety. Construct the Safety T and disseminate in accordance with unit SOP
|
||
|
||
NOTE: Figures 15-16 and 15-17 are reproducible safety computation forms
|
||
|
||
15-5. Safety Card
|
||
A Range Safety Card (Figure 15-1), which prescribes the hours of firing, the area where the firing will take place, the location of the firing position, limits of the target area (in accordance with AR 385-63/MCO P3570) and other pertinent data is approved by the range officer and sent to the OIC of firing. The OIC of firing gives a copy of the safety card to the position safety officer, who constructs the safety diagram based on the prescribed limits.
|
||
|
||
15-7
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
NOTE: The range safety card depicted in Figure 15-1 is used for all safety computation examples in this chapter.
|
||
Range Safety Card
|
||
|
||
Unit/STR K 3/11
|
||
|
||
ScheduledDateIn Ø5/30/98
|
||
|
||
TimeIn
|
||
|
||
Ø7:ØØ
|
||
|
||
ScheduledDate Out Ø5/30/98
|
||
|
||
TimeOut
|
||
|
||
23:59
|
||
|
||
Firing Point 185 (6Ø26 411Ø) HT 37Ø.Ø Impact Area S. CARLTON AREA Weapon M198 (155) Ammunition M1Ø7, M11Ø, M116, M825, M485, M557, M582, M732,M577
|
||
|
||
Type of Fire LOW ANGLE: HE, WP, M825, ILA, M116
|
||
|
||
Type of Fire HIGH ANGLE: HE, M825, ILA
|
||
|
||
Direction Limits: (Ref GN):
|
||
|
||
Left 134Ø MILS Right 19ØØ MILS
|
||
|
||
Low Angle PD Minimum Range
|
||
|
||
39ØØ METERS
|
||
|
||
Min Charge 3GB
|
||
|
||
Fuze TI and High Angle Minimum Range
|
||
|
||
4ØØØ METERS
|
||
|
||
Min Charge 3GB
|
||
|
||
To Establish MIN Time for Fuze VT Apply +5.5 seconds to the Low Angle PD Min Rg
|
||
|
||
Maximum Range to Impact
|
||
|
||
62ØØ METERS
|
||
|
||
Max Charge 4GB
|
||
|
||
COMMENTS
|
||
From AZ 134Ø TO AZ 15ØØ MAXIMUM RANGE IS 57ØØ
|
||
|
||
SPECIAL INSTRUCTIONS
|
||
1. SHELL ILLUMINATION (ALL CALIBERS)
|
||
A. MAX QE WILL NOT EXCEED QE FOR MAXIMUM RANGE TO IMPACT B. ONE INITIAL ILLUMINATION CHECK ROUND WILL BE FIRED TO INSURE
|
||
ILLUMINATION FLARE REMAINS IN IMPACT AREA C. IF INITIAL ILLUMINATION FLARE DOES NOT LAND IN IMPACT AREA, NO
|
||
FURTHER ILLUMINATION WILL BE FIRED AT THAT DF AND QE. D. INSURE THAT ALL SUCCEEDING ROUNDS ARE FIRED AT A HOB
|
||
SUFFICIENT TO PROVIDE COMPLETE BURNOUT BEFORE REACHING THE GROUND. E. FOR 155MM HOWITZER, CHARGE 7 NOT AUTHORIZED WHEN FIRING PROJ ILLUM , M485.
|
||
UNCLEARED AMMUNITION(FUZES, PROJECTILES, POWDER) WILL NOT BE USED
|
||
Figure 15-1. Example of a Range Safety Card
|
||
|
||
15-6. Basic Safety Diagram
|
||
|
||
a. The FDO, on receipt of the safety card, constructs a basic safety diagram. The basic safety diagram is a graphical portrayal of the data on the safety card or is determined from the surface danger zone (AR 385-63, Chapter 11) and need not be drawn to scale. Shown on the basic safety diagram are the minimum and maximum range lines; the left, right, and intermediate (if any) azimuth limits; the deflections corresponding to the azimuth limits; and the azimuth of lay.
|
||
|
||
b. The steps for constructing a basic safety diagram are shown in table 15-2. An example of a completed safety diagram is shown in Figure 15-2.
|
||
15-8
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
STEP 1
|
||
2 3
|
||
4 5
|
||
6
|
||
|
||
Table 15-2. Construction of a Basic Safety Diagram.
|
||
ACTION On the top third of a sheet of paper, draw a line representing the AOL for the firing unit. Label this line with its azimuth and the common deflection for the weapon system. NOTE: If the AOL is not provided, use the following procedures to determine it: Subtract the maximum left azimuth limit from the maximum right azimuth limit. Divide this value by two, add the result to the maximum left azimuth limit, and express the result to the nearest 100 mils. Expressing to the nearest 100 mils makes it easier for the aiming circle operator to lay the howitzers. Draw lines representing the lateral limits in proper relation to the AOL. Label these lines with the corresponding azimuth from the range safety card. Draw lines between these lateral limits to represent the minimum and maximum ranges. Label these lines with the corresponding ranges from the range safety card. These are the Diagram Ranges. NOTE: If the minimum range for fuze time is different from the minimum range, draw a dashed line between the lateral limits to represent the minimum range for fuze time. Label this line with the corresponding range from the range safety card. This is the minimum time Diagram Range. Compute the angular measurements from the AOL to each lateral limit. On the diagram, draw arrows indicating the angular measurements and label them. Apply the angular measurements to the deflection corresponding to the AOL (Common Deflection) and record the result. This will be added to the Drift and GFT Deflection Correction determined in the Safety Matrices to produce the Deflection Limits on the Safety T. (Note: If no GFT Deflection Correction has been determined, then the Deflection Limits = Drift + Diagram Deflection. If a GFT setting has been determined, then the Deflection Limits = Drift + GFT Deflection Correction + Diagram Deflection). Drift is applied to the Basic Safety Diagram by following the "least left, most right" rule. The lowest (least) drift is applied to all left deflection limits, and the highest (greatest) drift is applied to all right deflection limits. Label the diagram with the following information from the range safety card: firing point location (grid and altitude), charge, shell, fuze, angle of fire, and azimuth of lay.
|
||
|
||
c. When the basic safety diagram is complete, it will be constructed to scale, in red, on the firing chart. Plot the firing point location as listed on the range safety card. Using temporary azimuth indexes, an RDP, and a red pencil to draw the outline of the basic safety diagram. To do this, first draw the azimuth limits to include doglegs. Then, by holding the red pencil firmly against the RDP at the appropriate ranges, connect the azimuth lines.
|
||
|
||
d. Only after drawing the basic safety diagram on the firing chart may the base piece location be plotted and deflection indexes be constructed. Should the diagram be drawn from the base piece location, it would be invalid unless the base piece was located over the firing point marker.
|
||
|
||
e. After the basic safety diagram has been drawn on a sheet of paper and on the firing chart, it is drawn on a map of the impact area using an RDP and a pencil. These limits must be drawn accurately, because they will be used to determine altitudes for vertical intervals. Determine the maximum altitude along the minimum range line. This is used to ensure that the quadrant fired will cause the round to clear the highest point along the minimum range line and impact (function) within the impact area. At the maximum range, select the minimum altitude to
|
||
|
||
15-9
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
ensure that the round will not clear the lowest point along the maximum range. Once the altitudes have been selected, label the basic safety diagram with the altitudes for the given ranges.
|
||
NOTE: The rule for determining the correct altitude for safety purposes is called the mini-max rule. At the minimum range, select the maximum altitude; at the maximum range, select the minimum altitude. If the contour interval is in feet, use either the GST or divide feet by 3.28 to determine the altitude in meters. (Feet ÷ 3.28 = Meters) This rule applies to both manual and automated procedures.
|
||
FP 185 (GRID 6026 4110 ALT 370) LOW ANGLE, HE/WP/SMK, CHG 4GB, AOF 1600
|
||
|
||
AZ 1340 DF 3460 + L4 = 3464
|
||
|
||
AZ 1500 DF 3300 + L4 = 3304 Max Rg 5700 Min Alt 355
|
||
L 260
|
||
|
||
Max Rg 6200 Min Alt 345
|
||
|
||
L 100
|
||
AOF 1600 DF 3200
|
||
|
||
R 300
|
||
|
||
Min TI Rg 4000
|
||
|
||
AZ 1900 DF 2900 + L9 = 2909
|
||
|
||
Min Rg 3900 Max Alt 393
|
||
|
||
Figure 15-2. Example of a Completed Safety Diagram, HE/WP/SMK
|
||
|
||
15-7. Computation of Low Angle Safety Data
|
||
|
||
Use the steps outlined in Table 15-3 and in the matrix in Figure 15-3 as examples for organizing computations. The Low Angle Safety Matrix is used for all munitions except M712 CLGP (Copperhead). Paragraph 15-13 describes M712 safety computations. The data are determined by either graphical or tabular firing tables. In the case of expelling charge munitions, the Safety Table located in the Firing Tables or Firing Table Addendums is utilized to determine Elevation, Time of Flight, Fuze Setting, and Drift. (Note: the Safey Tables used for computing the examples in this chapter are located after the Illum and M825 Low Angle examples). Use artillery expression for all computations except where noted.
|
||
|
||
STEP 1 2 3 4
|
||
|
||
Table 15-3: Low Angle Procedures
|
||
ACTION On the top third of a blank sheet of paper, construct the basic safety diagram In the middle third of the sheet of paper, construct the Low Angle Safety Matrix Record the Diagram Ranges from the basic safety diagram. Record the Charge from the range safety card.
|
||
|
||
15-10
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
5
|
||
|
||
Enter the Range Correction, if required. This range correction is only necessary if a
|
||
|
||
nonstandard condition exists and is not already accounted for in a GFT setting, such
|
||
|
||
as correcting for the always heavier than standard White Phosphorous projectile.
|
||
|
||
See figure 2, paragraph (b) to determine range correction. If a range correction is
|
||
|
||
required, it is expressed to the nearest 10 meters. If no range correction is
|
||
|
||
required, enter 0 (zero).
|
||
|
||
6
|
||
|
||
Determine the Total Range. Total range is the sum of the Diagram Range and the
|
||
|
||
Range Correction. Total Range is expressed to the nearest 10 meters.
|
||
|
||
7
|
||
|
||
Enter the Range K. Range K is only required if a GFT setting has been obtained but
|
||
|
||
cannot be applied to a GFT (i.e., determining Illumination safety with a HE GFT
|
||
|
||
setting). Range K is simply the Total Range Correction from the GFT setting
|
||
|
||
expressed as a percentage. This percentage, when multiplied by the Total Range,
|
||
|
||
produces the Entry Range. If no GFT setting is available (i.e., pre-occupation
|
||
|
||
safety), then enter 1.0000 as the Range K. If a GFT setting is available, (i.e., post
|
||
|
||
occupation safety), then enter the Range K expressed to four decimal places
|
||
|
||
(i.e., 1.1234). Step 7a demonstrates how to compute Range K.
|
||
|
||
7a Divide Range ~ Adjusted Elevation by the Achieved Range from the GFT setting to
|
||
|
||
determine Range K:
|
||
|
||
Range ~ Adjusted Elevation = Range K, expressed to four decimal places.
|
||
|
||
Achieved Range
|
||
|
||
8
|
||
|
||
Determine the Entry Range. Multiply the Total Range times Range K to determine the
|
||
|
||
Entry Range. If Range K is 1.0000, then the Entry Range will be identical to the Total
|
||
|
||
Range. Entry Range is expressed to the nearest 10 meters.
|
||
|
||
9
|
||
|
||
Following the Mini-Max rule, determine the Vertical Interval by subtracting the unit
|
||
|
||
altitude from the altitude corresponding to the Diagram Range, and record it. (Note:
|
||
|
||
Diagram Range is used for computations of VI and Site because this is the actual
|
||
|
||
location of the minimum range line. VI is not computed for minimum time range lines.
|
||
|
||
The Range Correction, Total Range, and Range K are used to compensate for
|
||
|
||
nonstandard conditions, and represent the aimpoint which must be used to cause the
|
||
|
||
round to cross the Diagram Range.) VI is expressed to the nearest whole meter.
|
||
|
||
10 Compute and record Site to the Diagram Range. Use the GST from the head of the
|
||
|
||
projectile family whenever possible. Site is expressed to the nearest whole mil.
|
||
|
||
11 Determine the Elevation from Table C (base ejecting) or TFT/GFT (bursting), and
|
||
|
||
record it. (Note: GFT Settings are not used to determine Elevation, as Range K
|
||
|
||
represents total corrections, and to use a GFT setting would double the effects of
|
||
|
||
those corrections). Elevation is expressed to the nearest whole mil.
|
||
|
||
12 Compute the Quadrant Elevation and record it. Quadrant Elevation is the sum of
|
||
|
||
Elevation and Site. Quadrant Elevation is expressed to the nearest whole mil.
|
||
|
||
13 Determine and record the minimum fuze setting for M564/M565 fuzes. These fuze
|
||
|
||
settings correspond to the Entry Range and are extracted from Table C (base ejecting)
|
||
|
||
or TFT/GFT. (Note: Minimum Fuze Settings are only determined for minimum range
|
||
|
||
lines, and may be computed for separate minimum fuze range lines). Fuze Settings
|
||
|
||
are expressed to the nearest tenth of a fuze setting increment.
|
||
|
||
14 Determine and record the minimum fuze setting for M582/M577 fuzes. These fuze
|
||
|
||
settings correspond to the Entry Range and are extracted from Table C (base ejecting)
|
||
|
||
or TFT/GFT. (Note: Minimum Fuze Settings are only determined for minimum range
|
||
|
||
lines, and may be computed for separate minimum fuze range lines). Fuze Settings
|
||
|
||
are expressed to the nearest tenth of a second.
|
||
|
||
15 Determine and record the Time of Flight corresponding to the entry range from Table
|
||
|
||
C, (base ejecting) or TFT/GFT. Time of Flight is expressed to the nearest tenth of
|
||
|
||
a second.
|
||
|
||
16 Determine the minimum fuze setting for M728/M732 fuzes. Add 5.5 seconds to the
|
||
|
||
time of flight, and express to the next higher whole second. The VT fuze is designed to
|
||
|
||
arm 3.0 seconds before the time set. They have been known to arm up to 5.5
|
||
|
||
seconds before the time set. That is why this value is added and always expressed up
|
||
|
||
to the next whole second. (Note: Minimum Fuze Settings are only determined for
|
||
|
||
15-11
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
minimum range lines, and may be computed for separate minimum fuze range lines). VT Fuze Settings are expressed up to the next higher whole second. 17 Determine and record Drift corresponding to the Entry Range from Table C (base ejecting) or TFT/GFT. Drift is applied to the Basic Safety Diagram by following the "least left, most right" rule. The lowest (least) drift is applied to all left deflection limits, and the highest (greatest) drift is applied to all right deflection limits. Drift is expressed to the nearest whole mil. 18 Ensure computations are verified by a second safety-certified person. 19 On the bottom third of the sheet of paper, record the data on the safety T.
|
||
|
||
(a)
|
||
|
||
(b)
|
||
|
||
(c) (d)
|
||
|
||
(e) (f) (g) (h) (i) (j)
|
||
|
||
DIAGRAM
|
||
|
||
RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE
|
||
|
||
(k)
|
||
|
||
(l)
|
||
|
||
M564/ M582
|
||
|
||
M565 M577
|
||
|
||
(m) (n) (o) (p) M728/
|
||
TOF + 5.5 = M732 DFT
|
||
|
||
(a) This is the minimum or maximum range from the range safety diagram.
|
||
|
||
(b) This is the range correction for nonstandard conditions from Table F, if required. This is typically for preoccupation safety or
|
||
|
||
corrections for nonstandard conditions not included in the Range K factor in column (d), such as WP [] weight. Examples of
|
||
|
||
nonstandard conditions accounted for in (b) include, but are not limited to, difference in projectile square weight, difference in
|
||
|
||
muzzle velocity, or any nonstandard condition accounted for prior to determining a Range K factor. If there is no change from
|
||
|
||
standard, or all nonstandard conditions are accounted for in the Range K factor, this value is zero (0).
|
||
|
||
To determine a range correction from Table F, use the following formula:
|
||
|
||
NONSTANDARD STANDARD CHANGE IN RG CORR RANGE
|
||
|
||
RANGE CHG CONDITION
|
||
|
||
- CONDITION = STANDARD x FACTOR = CORRECTION
|
||
|
||
(c) This is the sum of the Diagram Range and the Range Correction. If there is no range correction, then the Total Range will be the same as the Diagram Range.
|
||
|
||
(d) This is the Range K factor determined by using Technique 2, Appendix F, Page F-5 in the FM 6-40/MCWP 3-16.4. This is for post occupation safety.
|
||
It represents total corrections for a registration, MET + VE, or other subsequent MET technique. It represents all nonstandard conditions (unless a separate nonstandard condition such as change in square weight for WP is listed separately in column (b)). It is multiplied times the Total Range to determine Entry Range. If there is no Range K, enter 1.0000.
|
||
|
||
(e) This is the sum of the Total Range times the Range K factor. If there is no Range K factor, then the Entry Range will be the same as the Total Range. Entry Range is the range to which Elevation is determined.
|
||
|
||
(f) This is the charge from the range safety card for this set of safety computations.
|
||
|
||
(g) This is the Vertical Interval from the range safety diagram.
|
||
|
||
(h) This is the site determined to the Diagram Range by using the GST or TFT from the head of the projectile family; e.g., site for the M110 WP projectile is determined with the AM-2, M825 site is computed using the AN-2. Site is computed to the Diagram Range, as that is where the Vertical Intervals are determined.*
|
||
|
||
(i) This is the elevation from Table C (base ejecting), or GFT/TFT (bursting).*
|
||
|
||
(j) This is the sum of Elevation and Site. It is the minimum or maximum Quadrant Elevation corresponding to the Minimum or Maximum Range.
|
||
|
||
(k) This is the Minimum Fuze Setting for the M564/565 fuze from Table C (base ejecting), or GFT/TFT (bursting), corresponding to the Entry Range. */**
|
||
|
||
(l) This is the Minimum Fuze Setting for the M582/M577 fuze from Table C (base ejecting), or GFT/TFT (bursting), corresponding to the Entry range. */** (Note, this also applies to the M762, M767, and MOFA fuzes)
|
||
|
||
(m) This is the Time Of Flight from Table C (base ejecting), or GFT/TFT (bursting), corresponding to the Entry Range. */**
|
||
|
||
(n) This is the safety factor applied to the Time of Flight to determine VT fuze data. **
|
||
|
||
(o) This is the sum of TOF + 5.5. It is the Minimum Fuze Setting for M728/M732 VT fuzes. **
|
||
|
||
(p) This is the Drift corresponding to the Entry Range from Table C (base ejecting), or GFT/TFT (bursting). Drift is applied to the range safety diagram by using the "Least, Left; Most Right, “ rule. The "least" or lowest drift is applied to all left deflection limits, and the "Most" or greatest drift is applied to all right deflection limits.
|
||
|
||
15-12
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
* - See Table 15-4 to determine the correct source table or addendum for computations. ** - Computed only for minimum Entry Ranges, and only if applicable to the ammunition and the range safety card.
|
||
Figure 15-3. Low Angle Safety Matrix
|
||
|
||
4[] HE/SMK (M116) LOW ANGLE CHG 4GB
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732 DFT
|
||
|
||
3900
|
||
|
||
+ 0 = 3900 x 1.0000 = 3900 4GB +23 +6 + 225 = 231 --
|
||
|
||
13.7 / 19.2 ~ 20.0 L4
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0000 = 4000 4GB -- --
|
||
|
||
-- --
|
||
|
||
--
|
||
|
||
14.1
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0000 = 5700 4GB -15 -3 + 362 = 359 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0000 = 6200 4GB -25 -5 + 408 = 403 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
-- L9
|
||
|
||
WP (M110, Weight Unknown) Low Angle Chg 4GB
|
||
|
||
Determining Range Correction for [] Weight Unknown Projectile
|
||
|
||
RANGE CHG 3900 4GB 4000 4GB
|
||
|
||
NONSTANDARD STANDARD CHANGE IN
|
||
|
||
CONDITION - CONDITION = STANDARD
|
||
|
||
8[]
|
||
|
||
- 4[]
|
||
|
||
= I 4[]
|
||
|
||
8[]
|
||
|
||
- 4[]
|
||
|
||
= I 4[]
|
||
|
||
RG CORR RANGE
|
||
|
||
x FACTOR = CORRECTION
|
||
|
||
x
|
||
|
||
+28 = +112 ~ +110
|
||
|
||
x
|
||
|
||
+28 = +112 ~ +110
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732 DFT
|
||
|
||
3900
|
||
|
||
+ (+110) = 4010 x 1.0000 = 4010 4GB +23 (+6) + 232 = 238 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
4000
|
||
|
||
+ (+110) = 4110 x 1.0000 = 4110 4GB -- -- -- --
|
||
|
||
-- 14.6
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
Figure 15-4. Completed Low Angle Safety Matrix, HE/WP/SMK
|
||
|
||
15-8. Safety T
|
||
|
||
a. The safety T is a convenient method of arranging safety data and is used to verify the safety of fire commands (Figure 15-5). The information needed by the FDO, XO, or platoon leader, and section chief is organized in an easy to read format. The safety T is labeled with a minimum of firing point location, charge, projectiles(s), fuze(s), angle of fire, and AOL. Other optional entries are subject to unit SOP. Any time new safety data are determined, new safety Ts are constructed and issued only after the old safety Ts have been collected (that is, after a move or after a registration or MET + VE). Use only one charge per Safety T. (Note: The examples in this demonstrate which data is transferred from the Safety Matrix to the Safety Tee. This data is in bold type in the matrix and the associated safety T).
|
||
|
||
b. It is the FDO’s responsibility to ensure that all data transmitted from the FDC is within the limits of the safety T. It is the section chief’s responsibility to ensure that all data applied to the ammunition or howitzer is within the limits of the safety T. The FDO must ensure that deflection to fire is between the deflections listed on the safety T. He then must determine if the quadrant elevation corresponding to that deflection is between the minimum and maximum QE on the safety T. Finally, he must ensure that the fuze setting is equal to or greater than the minimum fuze setting listed on the safety T for the specific fuze type.
|
||
|
||
15-13
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
NOTE: A reproducible copy of DA Form 7353-R (Universal Safety T) is included at the end of this manual, in the reproducible forms section.
|
||
|
||
FP 185, HE/WP/SMK LOW ANGLE, CHG 4GB, AOL 1600
|
||
|
||
359
|
||
|
||
403
|
||
|
||
3464
|
||
|
||
3304
|
||
|
||
231
|
||
|
||
238
|
||
|
||
14.1
|
||
|
||
14.6
|
||
|
||
20.0
|
||
|
||
MAX QE
|
||
|
||
2909
|
||
|
||
DF
|
||
|
||
MIN QE HE
|
||
|
||
MIN QE WP
|
||
|
||
MIN HE TI M582
|
||
|
||
MIN WP TI M582 MIN VT M732
|
||
|
||
Figure 15-5. Example of a Completed Safety T.
|
||
|
||
Table 15-4. Tables and Addendums required for Safety Computations
|
||
|
||
Weapon System
|
||
|
||
Safety
|
||
|
||
Base
|
||
|
||
Required for: Projectile
|
||
|
||
M101A1
|
||
M102/ M119 M198 or M109A3/A5/A6
|
||
|
||
M314 M444 M314 M444 M485 M449 M483A1 M483A1 M825 M825 M825A1 M825A1 M692/M731 M718/M741 M898
|
||
|
||
HE HE HE HE HE HE HE DPICM HE DPICM HE DPICM DPICM DPICM DPICM
|
||
|
||
Firing Table for Base Projectile 105-H-7 105-H-7 105-AS-3 105-AS-3 155-AM-2 155-AM-2 155-AM-2 155-AN-2 155-AM-2 155-AN-2 155-AN-2 155-AN-2 155-AN-2 155-AN-2 155-AN-2
|
||
|
||
Firing Table Addendum
|
||
N/A ADD-B-2 N/A ADD-F-1 N/A ADD-I-2 ADD-R-1 ADD-J-2 ADD-T-0 w/ch1 ADD-Q-O w/ch1,2 ADD-T-0 w/ch1 ADD-Q-0 w/ch1,2 ADD-L-1 w/ch1,2 ADD-N-1 w/ch1 ADD-W-0
|
||
|
||
15-9. Updating Safety Data after Determining a GFT Setting
|
||
|
||
a. After a GFT setting is determined (result of registration or MET + VE technique), the FDO must compute new safety data. The GFT setting represents all nonstandard conditions in effect at the time the GFT setting was determined (Chapter 10 and 11 discuss Total Corrections in detail). The effect on safety is that the data determined before the GFT setting was determined no longer represent the safety box, and could result in an unsafe condition if not applied to safety
|
||
|
||
15-14
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
computations. In order to update safety, new elevations are determined which correspond to the minimum and maximum ranges. Deflections are modified by applying the GFT deflection correction to each lateral limit. Minimum fuze settings are also recomputed. The basic safety diagram drawn in red on the firing chart does not change. It was drawn on the basis of azimuths and ranges, and it represents the actual limits.
|
||
|
||
b. There are two techniques which can be used to update safety computations: The Range K Method and Applying a GFT setting to a GFT. Both methods use the same safety matrices, and apply to both low and high angle fire. The preferred technique for updating safety is to apply a GFT setting to the appropriate GFT. Unfortunately, not all munitions have associated GFTs. Application of Total Corrections is the same as for normal mission processing. The Total Corrections, in the form of a GFT setting or Range K, must be applied in accordance with the data on which they were determined (i.e., the GFT setting for a HE registration applies to all projectiles in the HE family, while a MET + VE for DPICM would apply to all projectiles in the DPICM family). If automation is available a false registration with M795 graze burst data may be used to determine total corrections for all projectiles in the DPICM family (see ST 6-40-2 for procedures). The principle difference between the two techniques is the manner in which minimum fuze setting is determined.
|
||
|
||
(1) Determining Minimum Fuze Setting with a GFT with a GFT Setting Applied: When a GFT setting is applied and a fuze setting is to be determined, it is extracted opposite the Time Gage Line (if it is the fuze listed on the GFT setting) or as a function of elevation (for all others). Use the procedures in Table 15-5 to update safety using a GFT with a GFT setting applied.
|
||
(2) Determining Fuze Setting using the Range K Technique: In order to simplify updating safety, the Range K technique determines all fuze settings as a function of elevation. The difference between registered fuze settings and fuze settings determined using the Range K technique in actual firings and computer simulations varies by only zero to two tenths (0.0 – 0.2) of a Fuze Setting Increment/Second. The safety requirements in the AR 385-63 and incorporation of Minimum Fuze Setting Range Lines adequately compensate for the difference in computational techniques. Figure 15-7 demonstrates how to update safety when no GFT is available, utilizing the Range K technique. Use the procedures in Table 15-3 (Low Angle) or Table 15-8 (High Angle) to update safety using the Range K method.
|
||
|
||
Table 15-5: Low Angle Procedures using a GFT with GFT Setting applied
|
||
|
||
STEP 1
|
||
2
|
||
3 4 5
|
||
|
||
ACTION On the top third of a blank sheet of paper, construct the basic safety diagram in accordance with the range safety card. (See Table 15-1 for procedures) In the middle third of the sheet of paper, construct the Low Angle Safety Matrix (Figure 1). Record the Diagram Ranges from the basic safety diagram. Record the Charge from the range safety card. Enter the Range Correction, if required. This range correction is only necessary if a nonstandard condition exists which requires a change in aimpoint and is not already accounted for in a GFT setting, such as correcting for the always heavier than standard White Phosphorous projectile. See figure 2, paragraph (b) to determine range correction. If a range correction is required, it is artillery expressed to the nearest 10 meters. If no range correction is required, enter 0 (zero).
|
||
15-15
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
6
|
||
|
||
Determine the Total Range. Total range is the sum of the Diagram Range and the
|
||
|
||
Range Correction. Total Range is expressed to the nearest 10 meters.
|
||
|
||
7
|
||
|
||
Range K. This is not used when determining data with a GFT with a GFT setting
|
||
|
||
applied, as the Elevation Gage line represents Range K.
|
||
|
||
8
|
||
|
||
Entry Range. This value is the same as the Total Range. Entry Range is artillery
|
||
|
||
expressed to the nearest 10 meters.
|
||
|
||
9
|
||
|
||
Following the Mini-Max rule, determine the Vertical Interval by subtracting the unit
|
||
|
||
altitude from the altitude corresponding to the Diagram Range, and record it. (Note:
|
||
|
||
Diagram Range is used for computations of VI and Site because this is the actual
|
||
|
||
location of the minimum range line. VI is not determined for minimum fuze range
|
||
|
||
lines. The Range Correction, Total Range, and Range K are used to compensate for
|
||
|
||
nonstandard conditions, and represent the aimpoint which must be used to cause the
|
||
|
||
round to cross the Diagram Range). VI is artillery expressed to the nearest whole
|
||
|
||
meter.
|
||
|
||
10 Compute and record Site to the Diagram Range. Use the GST from the head of the
|
||
|
||
projectile family whenever possible. Site is artillery expressed to the nearest whole
|
||
|
||
mil.
|
||
|
||
11 Place the MHL on the Entry Range and determine the Elevation from the Elevation
|
||
|
||
Gage Line on the GFT and record it. Elevation is artillery expressed to the
|
||
|
||
nearest whole mil.
|
||
|
||
12 Compute the Quadrant Elevation and record it. Quadrant Elevation is the sum of
|
||
|
||
Elevation and Site. Quadrant Elevation is artillery expressed to the nearest whole
|
||
|
||
mil.
|
||
|
||
13 Using the procedures from Appendix G, determine and record the minimum fuze
|
||
|
||
setting for M564/M565 fuzes. These fuze settings correspond to the Entry Range. If
|
||
|
||
the GFT Setting was determined using the M564/M565 fuze, then determine the fuze
|
||
|
||
setting opposite the Time Gage Line. If the GFT setting was not determined using the
|
||
|
||
M564/M565 fuze, then extract the fuze setting corresponding to adjusted elevation.
|
||
|
||
(Note: Minimum Fuze Settings are only determined for minimum range lines, and may
|
||
|
||
be computed for separate minimum fuze range lines). Fuze Settings are artillery
|
||
|
||
expressed to the nearest tenth of a fuze setting increment.
|
||
|
||
14 Using the procedures from Appendix G, determine and record the minimum fuze
|
||
|
||
setting for M582/M577 fuzes. These fuze settings correspond to the Entry Range. If
|
||
|
||
the GFT Setting was determined using the M582/M577 fuze, then determine the fuze
|
||
|
||
setting opposite the Time Gage Line. If the GFT setting was not determined using the
|
||
|
||
M582/M577 fuze, then extract the fuze setting corresponding to adjusted elevation.
|
||
|
||
(Note: Minimum Fuze Settings are only determined for minimum range lines, and may
|
||
|
||
be computed for separate minimum fuze range lines). Fuze Settings are artillery
|
||
|
||
expressed to the nearest tenth of a second.
|
||
|
||
15 Using the procedures from Appendix G, determine and record the Time of Flight
|
||
|
||
corresponding to the Entry Range. Extract the Time of Flight corresponding to
|
||
|
||
adjusted elevation from the TOF scale. Time of Flight is artillery expressed to the
|
||
|
||
nearest tenth of a second.
|
||
|
||
16 Using the procedures in Appendix G, determine the minimum fuze setting for
|
||
|
||
M728/M732 fuzes. Add 5.5 seconds to the time of flight, and express to the next
|
||
|
||
higher whole second. (Note: Minimum Fuze Settings are only determined for
|
||
|
||
minimum range lines, and may be computed for separate minimum fuze range lines).
|
||
|
||
VT Fuze Settings are expressed up to the next higher whole second.
|
||
|
||
17 Determine and record Drift corresponding to adjusted elevation. Drift is applied to the
|
||
|
||
Basic Safety Diagram by following the "least left, most right" rule. The smallest (least)
|
||
|
||
drift is applied to all left deflection limits, and the greatest (most) drift is applied to all
|
||
|
||
right deflection limits. Drift is artillery expressed to the nearest whole mil.
|
||
|
||
18 Ensure computations are verified by a second safety-certified person.
|
||
|
||
19 On the bottom third of the sheet of paper, record the data on the safety T.
|
||
|
||
15-16
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
Max Rg 6200 Min Alt 345
|
||
|
||
FP 185 (GRID 6026 4110 ALT 370) LOW ANGLE, HE/WP/SMK, CHG 4GB, AOF 1600
|
||
|
||
AZ 1340 DF 3460 + L9 = 3469
|
||
|
||
AZ 1500 DF 3300 + L9 = 3309 Max Rg 5700 Min Alt 355
|
||
L 260
|
||
|
||
L 100
|
||
AOF DF
|
||
|
||
1600 3200
|
||
R 300
|
||
|
||
Min TI Rg 4000
|
||
|
||
4650
|
||
|
||
GFT K, CHG 4GB, LOT A/G, RG 4450, EL 278, TI 16.3 (M582) TOT DF CORR L10 GFT DF CORR L5
|
||
|
||
AZ 1900 DF 2900 + AZL115900 = D2F9219500
|
||
+ L15 = 2915
|
||
|
||
16.8
|
||
RG K = 4650/4450 ~ 1.0449
|
||
|
||
Min Rg 3900 Max Alt 393
|
||
|
||
4[] HE/SMK (M116) Low Angle Chg 4GB
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732 DFT
|
||
|
||
3900
|
||
|
||
+ 0 = 3900 x 1.0449 = 4080 4GB +23 +6 + 238 = 244 -- 14.5
|
||
|
||
/ 20.0 ~ 20.0 L4
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0449 = 4180 4GB -- -- --
|
||
|
||
--
|
||
|
||
-- 14.8
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0449 = 5960 4GB -15 -3 + 386 = 383 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0449 = 6480 4GB -25 -5 + 436 = 431 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
-- L10
|
||
|
||
WP (M110, Weight Unknown) LOW ANGLE CHG 4GB
|
||
|
||
Determining Range Correction for [] Weight Unknown Projectile
|
||
|
||
RANGE CHG 3900 4GB 4000 4GB
|
||
|
||
NONSTANDARD STANDARD CHANGE IN
|
||
|
||
CONDITION - CONDITION = STANDARD x
|
||
|
||
8[]
|
||
|
||
- 4[]
|
||
|
||
= I 4[]
|
||
|
||
x
|
||
|
||
8[]
|
||
|
||
- 4[]
|
||
|
||
= I 4[]
|
||
|
||
x
|
||
|
||
RG CORR RANGE FACTOR = CORRECTION
|
||
+28 = +112 ~ +110 +28 = +112 ~ +110
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732 DFT
|
||
|
||
3900
|
||
|
||
+ (+110) = 4010 x 1.0449 = 4190 4GB +23 (+6) + 245 = 251 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
4000
|
||
|
||
+ (+110) = 4110 x 1.0449 = 4290 4GB -- -- -- -- -- 15.3
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
FP 185, HE/WP/SMK LOW ANGLE, CHG 4GB, AOL 1600 GFT K, CHG 4GB, LOT A/G, RG 4450, EL 278, TI 16.3 (M582) TOT DF CORR L10 GFT DF CORR L5
|
||
|
||
383
|
||
|
||
431
|
||
|
||
MAX QE
|
||
|
||
3469
|
||
|
||
3309
|
||
|
||
2915
|
||
|
||
DF
|
||
|
||
244
|
||
|
||
MIN QE HE
|
||
|
||
251
|
||
|
||
MIN QE WP
|
||
|
||
14.8
|
||
|
||
MIN HE TI (M582)
|
||
|
||
15.3
|
||
|
||
MIN WP TI (M582)
|
||
|
||
20.0
|
||
|
||
MIN VT (M732)
|
||
|
||
Figure 15-6. Post Occupation Low Angle Safety, Range K Method, HE/WP/SMK
|
||
|
||
15-17
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
FP 185 (GRID 6026 4110 ALT 370) LOW ANGLE, M825, CHG 4GB, AOF 1600
|
||
|
||
AZ 1340 DF 3460 + L4 = 3464
|
||
|
||
AZ 1500 DF 3300 + L4 = 3304 Max Rg 5700 Min Alt 355
|
||
L 260
|
||
|
||
Max Rg 6200 Min Alt 345
|
||
L 100
|
||
AOF 1600 DF 3200
|
||
R 300
|
||
|
||
Min TI Rg 4000
|
||
|
||
AZ 1900 DF 2900 + L9 = 2909
|
||
|
||
M825 LOW ANGLE CHG 4GB
|
||
|
||
Min Rg 3900 Max Alt 393
|
||
|
||
DIAGRAM
|
||
|
||
RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732 DFT
|
||
|
||
3900
|
||
|
||
+ 0 = 3900 x 1.0000 = 3900 4GB +23 +6 + 254 = 260 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
L4
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0000 = 4000 4GB -- -- --
|
||
|
||
-- -- 15.1
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0000 = 5700 4GB -15 -3 + 423 = 420 -- --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0000 = 6200 4GB -25 -6 + 486 = 480 -- --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
L9
|
||
|
||
FP 185, M825 LOW ANGLE, CHG 4GB, AOL 1600
|
||
|
||
420
|
||
|
||
480
|
||
|
||
MAX QE
|
||
|
||
3464
|
||
|
||
3304
|
||
|
||
2909
|
||
|
||
DF
|
||
|
||
260
|
||
|
||
MIN QE M825
|
||
|
||
15.1
|
||
|
||
MIN M825 TI (M577)
|
||
|
||
Figure 15-7. Example of Low Angle Safety Shell M825 15-18
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
EXPLANATION:
|
||
|
||
Ballistic Data for Safety Computations FT ADD-T-0 Projectile Improved Smoke M825
|
||
Projectile Family = DPICM
|
||
|
||
These tables contain ballistic data for safety computations. They are not to be used for computation of firing data, as they do not account for submunition/payload delivery. These tables are to be used in conjunction with Chapter 15 of the FM 6-40 for safety computations only.
|
||
|
||
TABLE DATA:
|
||
|
||
The tables are arranged by charge, as follows:
|
||
|
||
CHARGE: 3G = Charge 3, M3A1 4G = Charge 4, M3A1 5G = Charge 5, M3A1 3W = Charge 3, M4A2 4W = Charge 4, M4A2 5W = Charge 5, M4A2 6W = Charge 6, M4A2 7W = Charge 7, M4A2 7R = Charge 7, M119A2
|
||
|
||
PAGE: 2 5 8 12 15 19 23 28 34
|
||
|
||
COLUMNAR DATA:
|
||
|
||
COLUMN:
|
||
|
||
1.
|
||
|
||
Range - The distance, measured on the surface of a sphere concentric with the earth, from
|
||
|
||
the muzzle to a target at the level point.
|
||
|
||
2.
|
||
|
||
Elevation - The angle of the gun in the vertical plane required to reach the range
|
||
|
||
tabulated in column 1. The maximum elevation shown represents the highest angle at
|
||
|
||
which predictable projectile flight is possible under standard conditions of met and
|
||
|
||
material.
|
||
|
||
3.
|
||
|
||
Fuze Setting M577 - Fuze setting for a graze burst - numbers to be set on the fuze,
|
||
|
||
MTSQ, M577 or ET, M762 that will produce a graze burst at the level point when firing
|
||
|
||
under standard conditions. This setting will produce a graze burst at the time of flight
|
||
|
||
listed in column 4.
|
||
|
||
4.
|
||
|
||
Time of Flight - The projectile travel time, under standard conditions, from the muzzle to
|
||
|
||
the level point at the range in column 1. Time of flight is used as fuze setting for fuze
|
||
|
||
MTSQ M577 and fuze ET M762.
|
||
|
||
5.
|
||
|
||
Azimuth correction to compensate for Drift - Because of the right hand twist of the
|
||
|
||
tube, the drift of the projectile is to the right of the vertical plane of fire. This drift must
|
||
|
||
be compensated for by a correction to the left.
|
||
|
||
Figure 15-8. Safety Table Data for M825 Example
|
||
|
||
15-19
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
Ballistic Data for Safety Computations FT ADD-T-0 Projectile Improved Smoke M825
|
||
Projectile Family = DPICM Charge 4G
|
||
|
||
Range Elevation Fuze Setting Time of Flight Drift
|
||
|
||
m
|
||
|
||
mil
|
||
|
||
M577
|
||
|
||
sec
|
||
|
||
mil
|
||
|
||
0
|
||
|
||
0.0
|
||
|
||
0.0
|
||
|
||
0.0
|
||
|
||
3800
|
||
|
||
246.4
|
||
|
||
14.2
|
||
|
||
3900
|
||
|
||
254.3
|
||
|
||
14.6
|
||
|
||
4000
|
||
|
||
262.3
|
||
|
||
15.1
|
||
|
||
4100
|
||
|
||
270.4
|
||
|
||
15.5
|
||
|
||
4200
|
||
|
||
278.6
|
||
|
||
16.0
|
||
|
||
4300
|
||
|
||
287.0
|
||
|
||
16.4
|
||
|
||
4400
|
||
|
||
295.5
|
||
|
||
16.9
|
||
|
||
4500
|
||
|
||
304.1
|
||
|
||
17.3
|
||
|
||
4600
|
||
|
||
312.9
|
||
|
||
17.8
|
||
|
||
4700
|
||
|
||
321.8
|
||
|
||
18.3
|
||
|
||
4800
|
||
|
||
330.9
|
||
|
||
18.8
|
||
|
||
4900
|
||
|
||
340.2
|
||
|
||
19.3
|
||
|
||
5000
|
||
|
||
349.7
|
||
|
||
19.8
|
||
|
||
5100
|
||
|
||
359.4
|
||
|
||
20.3
|
||
|
||
5200
|
||
|
||
369.3
|
||
|
||
20.8
|
||
|
||
5300
|
||
|
||
379.5
|
||
|
||
21.3
|
||
|
||
5400
|
||
|
||
389.9
|
||
|
||
21.9
|
||
|
||
5500
|
||
|
||
400.5
|
||
|
||
22.4
|
||
|
||
5600
|
||
|
||
411.5
|
||
|
||
23.0
|
||
|
||
5700
|
||
|
||
422.8
|
||
|
||
23.5
|
||
|
||
5800
|
||
|
||
434.5
|
||
|
||
24.1
|
||
|
||
5900
|
||
|
||
446.5
|
||
|
||
24.7
|
||
|
||
6000
|
||
|
||
459.0
|
||
|
||
25.4
|
||
|
||
6100
|
||
|
||
472.0
|
||
|
||
26.0
|
||
|
||
6200
|
||
|
||
485.5
|
||
|
||
26.7
|
||
|
||
6300
|
||
|
||
499.7
|
||
|
||
27.3
|
||
|
||
6400
|
||
|
||
514.6
|
||
|
||
28.1
|
||
|
||
6500
|
||
|
||
530.4
|
||
|
||
28.8
|
||
|
||
6600
|
||
|
||
547.3
|
||
|
||
29.6
|
||
|
||
6700
|
||
|
||
565.4
|
||
|
||
30.5
|
||
|
||
6800
|
||
|
||
585.2
|
||
|
||
31.4
|
||
|
||
6900
|
||
|
||
607.3
|
||
|
||
32.4
|
||
|
||
14.2
|
||
|
||
3.9
|
||
|
||
14.6
|
||
|
||
4.0
|
||
|
||
15.1
|
||
|
||
4.2
|
||
|
||
15.5
|
||
|
||
4.3
|
||
|
||
16.0
|
||
|
||
4.4
|
||
|
||
16.4
|
||
|
||
4.6
|
||
|
||
16.9
|
||
|
||
4.8
|
||
|
||
17.3
|
||
|
||
4.9
|
||
|
||
17.8
|
||
|
||
5.1
|
||
|
||
18.3
|
||
|
||
5.2
|
||
|
||
18.8
|
||
|
||
5.4
|
||
|
||
19.3
|
||
|
||
5.6
|
||
|
||
19.8
|
||
|
||
5.8
|
||
|
||
20.3
|
||
|
||
6.0
|
||
|
||
20.8
|
||
|
||
6.2
|
||
|
||
21.3
|
||
|
||
6.4
|
||
|
||
21.9
|
||
|
||
6.6
|
||
|
||
22.4
|
||
|
||
6.8
|
||
|
||
23.0
|
||
|
||
7.0
|
||
|
||
23.5
|
||
|
||
7.3
|
||
|
||
24.1
|
||
|
||
7.5
|
||
|
||
24.7
|
||
|
||
7.8
|
||
|
||
25.4
|
||
|
||
8.1
|
||
|
||
26.0
|
||
|
||
8.4
|
||
|
||
26.7
|
||
|
||
8.7
|
||
|
||
27.3
|
||
|
||
9.0
|
||
|
||
28.1
|
||
|
||
9.4
|
||
|
||
28.8
|
||
|
||
9.8
|
||
|
||
29.6
|
||
|
||
10.2
|
||
|
||
30.5
|
||
|
||
10.7
|
||
|
||
31.4
|
||
|
||
11.2
|
||
|
||
32.4
|
||
|
||
11.8
|
||
|
||
Figure 15-8. Safety Table Data for M825 Example (Cont’d)
|
||
|
||
15-20
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
Ballistic Data for Safety Computations FT ADD-T-0 Projectile Improved Smoke M825
|
||
Projectile Family = DPICM
|
||
|
||
7000 7100 7200 ************** 7200 7100 7000 6900 6800 6700 6600 6500 6400 6300 6200 6100 6000 5900 5800 5700 5600 5500 5400 5300 5200 5100 5000 4900 4800 4700 4600 4500 4400 4300 4200 4100 4000 3900 3800 3700 3669
|
||
|
||
632.5 663.2 705.5 ************ 852.1 894.3 924.8 950.0 971.9 991.6 1009.7 1026.4 1042.1 1056.9 1071.0 1084.4 1097.3 1109.7 1121.6 1133.2 1144.3 1155.2 1165.7 1175.9 1185.9 1195.6 1205.1 1214.3 1223.3 1232.1 1240.7 1249.1 1257.2 1265.2 1272.9 1280.4 1287.7 1294.7 1301.5 1308.0 1310.0
|
||
|
||
33.5 34.9 36.7 *************** 42.4 44.0 45.0 45.9 46.6 47.2 47.8 48.3 48.7 49.2 49.6 49.9 50.3 50.6 50.9 51.2 51.5 51.8 52.1 52.3 52.5 52.8 53.0 53.2 53.4 53.6 53.8 54.0 54.2 54.4 54.6 54.8 55.0 55.2 55.4 55.6
|
||
|
||
33.5 34.9 36.7 **************** 42.4 44.0 45.0 45.9 46.6 47.2 47.8 48.3 48.7 49.2 49.6 49.9 50.3 50.6 50.9 51.2 51.5 51.8 52.1 52.3 52.5 52.8 53.0 53.2 53.4 53.6 53.8 54.0 54.2 54.4 54.6 54.8 55.0 55.2 55.4 55.6
|
||
|
||
12.5 13.5 14.9 ************ 21.0 23.2 25.0 26.6 28.2 29.7 31.2 32.6 34.1 35.6 37.2 38.7 40.3 42.0 43.7 45.6 47.5 49.5 51.7 54.0 56.6 59.3 62.3 65.6 69.3 73.4 78.1 83.4 89.4 96.4 104.5 113.9 124.9 138.0 153.3 171.2
|
||
|
||
Figure 15-8. Safety Table Data for M825 Example (Cont’d)
|
||
|
||
15-21
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
FP 185 (GRID 6026 4110 ALT 370) LOW ANGLE, M825, CHG 4GB, AOF 1600
|
||
|
||
AZ 1340 DF 3460 + L9 = 3469
|
||
|
||
AZ 1500 DF 3300 + L9 = 3309 Max Rg 5700 Min Alt 355
|
||
|
||
Max Rg 6200 Min Alt 345
|
||
L 100
|
||
AOF 1600 DF 3200
|
||
|
||
L 260 Min TI Rg 4000
|
||
|
||
R 300
|
||
|
||
Min Rg 3900 Max Alt 393
|
||
|
||
4650
|
||
|
||
GFT K, CHG 4GB, LOT A/G, RG 4450, EL 278, TI 16.3 (M582)
|
||
|
||
ADZFTG2O1F99TT000D0DFF
|
||
|
||
CORR CORR
|
||
|
||
L10 L5
|
||
|
||
+ L15 = A2Z9119500
|
||
|
||
16.8
|
||
|
||
DF 2900
|
||
|
||
RG K = 4650/4450
|
||
|
||
+ L15
|
||
|
||
~ 1.0449
|
||
|
||
= 2915
|
||
|
||
M825 LOW ANGLE CHG 4GB
|
||
|
||
DIAGRAM
|
||
|
||
RG
|
||
|
||
TOT RG
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K
|
||
|
||
DFT
|
||
|
||
ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
= RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732
|
||
|
||
3900
|
||
|
||
+ 0 = 3900 x 1.0449 = 4080 4GB +23 +6 + 269 = 275 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
L4
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0449 = 4180 4GB -- -- -- --
|
||
|
||
-- 15.9
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0449 = 5960 4GB -15 -3 + 454 = 451 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
--
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0449 = 6480 4GB -25 -6 + 527 = 521 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
-- L10
|
||
|
||
FP 185, M825 LOW ANGLE, CHG 4GB, AOL 1600
|
||
|
||
451
|
||
|
||
521
|
||
|
||
3469
|
||
|
||
3309
|
||
|
||
275
|
||
|
||
MAX QE
|
||
|
||
2915
|
||
|
||
DF
|
||
|
||
MIN QE M825
|
||
|
||
15.9
|
||
|
||
MIN M825 TI (M577)
|
||
|
||
Figure 15-9. Example of Post Occupation Low Angle Safety with Range K applied, Shell M825
|
||
|
||
15-22
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
AZ 1340 DF 3460 + L7 = 3467
|
||
|
||
FP 185 (GRID 6026 4110 ALT 370) LOW ANGLE, ILLUM, CHG 3GB, AOF 1600
|
||
|
||
AZ 1500 DF 3300 + L7 = 3307
|
||
Max Rg 5700 Min Alt 355
|
||
|
||
Max Rg 6200 Min Alt 345
|
||
L 100 AOF 1600 DF 3200
|
||
|
||
L 260 Min TI Rg 4000
|
||
|
||
R 300
|
||
|
||
AZ 1900 DF 2900 + L16 = 2916
|
||
|
||
Min Rg 3900 Max Alt 393
|
||
|
||
ILLUM LOW ANGLE CHG 3GB
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732 DFT
|
||
|
||
3900
|
||
|
||
+ 0 = 3900 x 1.0000 = 3900 3GB +23 +7 + 290 = 297 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
-- L7
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0000 = 4000 3GB -- -- + -- = -- -- 16.2
|
||
|
||
--
|
||
|
||
-- --
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0000 = 5700 3GB -15 -4 + 497 = 493 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
-- --
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0000 = 6200 3GB -25 -7 + 587 = 580 --
|
||
|
||
--
|
||
|
||
--
|
||
|
||
-- L16
|
||
|
||
FP 185, ILLUM LOW ANGLE, CHG 3GB AOL 1600
|
||
|
||
493
|
||
|
||
580
|
||
|
||
MAX QE
|
||
|
||
3467
|
||
|
||
3307
|
||
|
||
2916
|
||
|
||
DF
|
||
|
||
297
|
||
|
||
MIN QE HE
|
||
|
||
----
|
||
|
||
16.2
|
||
|
||
MIN Illum TI M577
|
||
|
||
----
|
||
|
||
----
|
||
|
||
Rg 4800 Col 7 (Max Rg) RTI ~ 6196
|
||
EFFECTIVE ILLUMINATION BOX
|
||
Col 3 (FS) 16.0 M565 ~ RTI 4120
|
||
Entry for Col 3 is really 16.0 after converting to M565. FDOs Call!
|
||
|
||
Figure 15-10. Example of Low Angle Safety, Shell Illum
|
||
|
||
15-23
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
Ballistic Data for Safety Computations FT 155-AM-2 Projectile Illumination M485/M485A1/M485A2
|
||
Projectile Family = HE
|
||
|
||
EXPLANATION:
|
||
|
||
These tables contain ballistic data for safety computations. They are not to be used for computation of firing data, as they do not account for submunition/payload delivery. These tables are to be used in conjunction with Chapter 15 of the FM 6-40 for safety computations only.
|
||
|
||
TABLE DATA:
|
||
|
||
The tables are arranged by charge, as follows:
|
||
|
||
CHARGE: 1G = Charge 1, M3A1 2G = Charge 2, M3A1 3G = Charge 3, M3A1 4G = Charge 4, M3A1 5G = Charge 5, M3A1 3W = Charge 3, M4A2 4W = Charge 4, M4A2 5W = Charge 5, M4A2 6W = Charge 6, M4A2 7W = Charge 7, M4A2 8 = Charge 8, M119, M119A1
|
||
|
||
PAGE: 2 (Not applicable M198 howitzer) 4 6 9 12 16 19 23 27 32 38
|
||
|
||
COLUMNAR DATA:
|
||
|
||
COLUMN:
|
||
|
||
1.
|
||
|
||
Range - The distance, measured on the surface of a sphere concentric with the earth, from
|
||
|
||
the muzzle to a target at the level point.
|
||
|
||
2.
|
||
|
||
Elevation - The angle of the gun in the vertical plane required to reach the range
|
||
|
||
tabulated in column 1. The maximum elevation shown represents the highest angle at
|
||
|
||
which predictable projectile flight is possible under standard conditions of met and
|
||
|
||
material.
|
||
|
||
3.
|
||
|
||
Fuze Setting M565 - Fuze setting for a graze burst - numbers to be set on the fuze MT,
|
||
|
||
M565 that will produce a graze burst at the level point when firing under standard
|
||
|
||
conditions. This setting will produce a graze burst at the time of flight listed in column 4.
|
||
|
||
4.
|
||
|
||
Time of Flight - The projectile travel time, under standard conditions, from the muzzle to
|
||
|
||
the level point at the range in column 1. Time of flight is used as fuze setting for fuzes
|
||
|
||
MTSQ M577 and fuze ET M762.
|
||
|
||
5.
|
||
|
||
Azimuth correction to compensate for Drift - Because of the right hand twist of the
|
||
|
||
tube, the drift of the projectile is to the right of the vertical plane of fire. This drift must
|
||
|
||
be compensated for by a correction to the left.
|
||
|
||
Figure 15-11. Safety Table Data for M485 Illumination Example 15-24
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4 15-25
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
Ballistic Data for Safety Computations FT 155-AM-2 Projectile Illumination M485/M485A1/M485A2
|
||
Projectile Family = HE
|
||
Charge 3G
|
||
|
||
Range Elevation Fuze Setting Time of Flight Drift
|
||
|
||
m
|
||
|
||
mil
|
||
|
||
M565
|
||
|
||
sec
|
||
|
||
mil
|
||
|
||
0
|
||
|
||
0.0
|
||
|
||
100
|
||
|
||
6.4
|
||
|
||
0.0
|
||
|
||
0.0
|
||
|
||
0.4
|
||
|
||
0.1
|
||
|
||
3800
|
||
|
||
280.9
|
||
|
||
15.1
|
||
|
||
3900
|
||
|
||
290.0
|
||
|
||
15.5
|
||
|
||
4000
|
||
|
||
299.4
|
||
|
||
16.0
|
||
|
||
4100
|
||
|
||
308.8
|
||
|
||
16.5
|
||
|
||
4200
|
||
|
||
318.5
|
||
|
||
17.0
|
||
|
||
4300
|
||
|
||
328.3
|
||
|
||
17.5
|
||
|
||
4400
|
||
|
||
338.4
|
||
|
||
18.0
|
||
|
||
4500
|
||
|
||
348.6
|
||
|
||
18.5
|
||
|
||
4600
|
||
|
||
359.1
|
||
|
||
19.0
|
||
|
||
4700
|
||
|
||
369.8
|
||
|
||
19.5
|
||
|
||
4800
|
||
|
||
380.8
|
||
|
||
20.1
|
||
|
||
4900
|
||
|
||
392.0
|
||
|
||
20.6
|
||
|
||
5000
|
||
|
||
403.6
|
||
|
||
21.2
|
||
|
||
5100
|
||
|
||
415.5
|
||
|
||
21.8
|
||
|
||
5200
|
||
|
||
427.8
|
||
|
||
22.3
|
||
|
||
5300
|
||
|
||
440.5
|
||
|
||
23.0
|
||
|
||
5400
|
||
|
||
453.7
|
||
|
||
23.6
|
||
|
||
5500
|
||
|
||
467.4
|
||
|
||
24.2
|
||
|
||
5600
|
||
|
||
481.7
|
||
|
||
24.9
|
||
|
||
5700
|
||
|
||
496.7
|
||
|
||
25.6
|
||
|
||
5800
|
||
|
||
512.4
|
||
|
||
26.3
|
||
|
||
5900
|
||
|
||
529.1
|
||
|
||
27.1
|
||
|
||
6000
|
||
|
||
547.0
|
||
|
||
27.9
|
||
|
||
6100
|
||
|
||
566.2
|
||
|
||
28.7
|
||
|
||
6200
|
||
|
||
587.3
|
||
|
||
29.6
|
||
|
||
6300
|
||
|
||
610.9
|
||
|
||
30.6
|
||
|
||
6400
|
||
|
||
638.3
|
||
|
||
31.8
|
||
|
||
15.2
|
||
|
||
6.5
|
||
|
||
15.7
|
||
|
||
6.7
|
||
|
||
16.2
|
||
|
||
7.0
|
||
|
||
16.6
|
||
|
||
7.2
|
||
|
||
17.1
|
||
|
||
7.5
|
||
|
||
17.6
|
||
|
||
7.7
|
||
|
||
18.1
|
||
|
||
8.0
|
||
|
||
18.7
|
||
|
||
8.3
|
||
|
||
19.2
|
||
|
||
8.6
|
||
|
||
19.7
|
||
|
||
8.9
|
||
|
||
20.3
|
||
|
||
9.2
|
||
|
||
20.8
|
||
|
||
9.5
|
||
|
||
21.4
|
||
|
||
9.8
|
||
|
||
21.9
|
||
|
||
10.1
|
||
|
||
22.5
|
||
|
||
10.5
|
||
|
||
23.2
|
||
|
||
10.9
|
||
|
||
23.8
|
||
|
||
11.3
|
||
|
||
24.4
|
||
|
||
11.7
|
||
|
||
25.1
|
||
|
||
12.1
|
||
|
||
25.8
|
||
|
||
12.6
|
||
|
||
26.5
|
||
|
||
13.1
|
||
|
||
27.3
|
||
|
||
13.6
|
||
|
||
28.1
|
||
|
||
14.2
|
||
|
||
28.9
|
||
|
||
14.9
|
||
|
||
29.9
|
||
|
||
15.6
|
||
|
||
30.9
|
||
|
||
16.5
|
||
|
||
32.1
|
||
|
||
17.5
|
||
|
||
Figure 15-11. Safety Table Data for M485 Illumination Example (Cont’d) 15-26
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
Ballistic Data for Safety Computations FT 155-AM-2 Projectile Illumination M485/M485A1/M485A2
|
||
Projectile Family = HE
|
||
Charge 3G
|
||
|
||
Range Elevation Fuze Setting Time of Flight Drift
|
||
|
||
m
|
||
|
||
mil
|
||
|
||
M565
|
||
|
||
sec
|
||
|
||
mil
|
||
|
||
6500
|
||
|
||
672.1
|
||
|
||
33.2
|
||
|
||
33.5
|
||
|
||
18.8
|
||
|
||
6600
|
||
|
||
722.3
|
||
|
||
35.2
|
||
|
||
35.5
|
||
|
||
21.0
|
||
|
||
************* ************ ***************** **************** ************
|
||
|
||
6600
|
||
|
||
842.7
|
||
|
||
39.7
|
||
|
||
40.0
|
||
|
||
27.1
|
||
|
||
6500
|
||
|
||
892.6
|
||
|
||
41.4
|
||
|
||
41.7
|
||
|
||
30.2
|
||
|
||
6400
|
||
|
||
926.2
|
||
|
||
42.5
|
||
|
||
42.8
|
||
|
||
32.5
|
||
|
||
6300
|
||
|
||
953.2
|
||
|
||
43.4
|
||
|
||
43.7
|
||
|
||
34.5
|
||
|
||
6200
|
||
|
||
976.6
|
||
|
||
44.1
|
||
|
||
44.4
|
||
|
||
36.5
|
||
|
||
6100
|
||
|
||
997.4
|
||
|
||
44.7
|
||
|
||
45.0
|
||
|
||
38.3
|
||
|
||
6000
|
||
|
||
1016.4
|
||
|
||
45.2
|
||
|
||
45.6
|
||
|
||
40.1
|
||
|
||
5900
|
||
|
||
1033.9
|
||
|
||
45.7
|
||
|
||
46.1
|
||
|
||
42.0
|
||
|
||
5800
|
||
|
||
1050.3
|
||
|
||
46.2
|
||
|
||
46.5
|
||
|
||
43.8
|
||
|
||
5700
|
||
|
||
1065.8
|
||
|
||
46.6
|
||
|
||
47.0
|
||
|
||
45.6
|
||
|
||
5600
|
||
|
||
1080.4
|
||
|
||
47.0
|
||
|
||
47.3
|
||
|
||
47.5
|
||
|
||
5500
|
||
|
||
1094.4
|
||
|
||
47.4
|
||
|
||
47.7
|
||
|
||
49.5
|
||
|
||
5400
|
||
|
||
1107.7
|
||
|
||
47.7
|
||
|
||
48.0
|
||
|
||
51.5
|
||
|
||
5300
|
||
|
||
1120.6
|
||
|
||
48.0
|
||
|
||
48.4
|
||
|
||
53.6
|
||
|
||
5200
|
||
|
||
1132.9
|
||
|
||
48.3
|
||
|
||
48.7
|
||
|
||
55.8
|
||
|
||
5100
|
||
|
||
1144.8
|
||
|
||
48.6
|
||
|
||
48.9
|
||
|
||
58.2
|
||
|
||
5000
|
||
|
||
1156.2
|
||
|
||
48.9
|
||
|
||
49.2
|
||
|
||
60.7
|
||
|
||
4900
|
||
|
||
1167.3
|
||
|
||
49.1
|
||
|
||
49.5
|
||
|
||
63.4
|
||
|
||
4800
|
||
|
||
1178.1
|
||
|
||
49.3
|
||
|
||
49.7
|
||
|
||
66.3
|
||
|
||
4700
|
||
|
||
1188.5
|
||
|
||
49.6
|
||
|
||
49.9
|
||
|
||
69.4
|
||
|
||
4600
|
||
|
||
1198.6
|
||
|
||
49.8
|
||
|
||
50.2
|
||
|
||
72.9
|
||
|
||
4500
|
||
|
||
1208.4
|
||
|
||
50.0
|
||
|
||
50.4
|
||
|
||
76.7
|
||
|
||
4400
|
||
|
||
1217.9
|
||
|
||
50.2
|
||
|
||
50.6
|
||
|
||
81.0
|
||
|
||
4300
|
||
|
||
1227.1
|
||
|
||
50.4
|
||
|
||
50.8
|
||
|
||
85.8
|
||
|
||
4200
|
||
|
||
1236.0
|
||
|
||
50.6
|
||
|
||
51.0
|
||
|
||
91.3
|
||
|
||
4100
|
||
|
||
1244.7
|
||
|
||
50.8
|
||
|
||
51.2
|
||
|
||
97.5
|
||
|
||
4000
|
||
|
||
1253.0
|
||
|
||
51.0
|
||
|
||
51.3
|
||
|
||
104.8
|
||
|
||
3900
|
||
|
||
1261.1
|
||
|
||
51.2
|
||
|
||
51.5
|
||
|
||
113.1
|
||
|
||
3800
|
||
|
||
1268.8
|
||
|
||
51.3
|
||
|
||
51.7
|
||
|
||
123.0
|
||
|
||
Figure 15-11. Safety Table Data for M485 Illumination Example (Cont’d) 15-27
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
15-10. Determination of Maximum Effective Illumination Area
|
||
|
||
All illumination safety data are for graze burst. Therefore, when illumination fire mission data are computed, the QE determined includes the appropriate HOB. This will prevent achieving a 600 meter HOB (750 meter HOB for 105 mm) at the minimum and maximum range lines. Before processing illumination fire mission, it is beneficial to determine the maximum effective illumination area for the current range safety card. This area should be plotted on the firing chart to help determine if illumination can be fired and to let the Forward Observers know where they can fire illumination effectively. This area will always be significantly smaller than the HE safety area. See Table 15-6 for steps outlining the general procedure. This area can be increased by computing High Angle data.
|
||
|
||
NOTE: The procedures used to determine the Maximum Effective Illumination Area can be used to for all expelling charge munitions to depict their Maximum Effective Engagement Area.
|
||
|
||
Table 15-6. Procedures to Determine Maximum Effective Illumination Area
|
||
|
||
STEP 1 2 3
|
||
4
|
||
|
||
ACTION Enter the TFT, Part 2, Column 7 (RTI) with the nearest range listed without exceeding the maximum range. Determine the corresponding range to target in column 1. This is the maximum range the unit can achieve a 600 meter (155mm) HOB and keep the projectile in the safety box if the fuze fails to function. Determine the minimum range for which a 600 meter (155 mm) HOB is achieved and have the fuze function no earlier than the minimum range line. Enter the TFT, Part 2, Column 3, with the nearest listed FS that is not less than the determined minimum FS. Column 3 is the Fuze Setting for the M565 Fuze, so if M577 is to be used, the fuze setting must be corrected by using Table B. Determine the corresponding range to target in Column 1. The area between these two lines is the maximum effective illumination area where a 600 meter HOB (155mm) is achieved, the fuze functions no earlier than the minimum range line, and the round does not exceed the maximum range line if the fuze fails to function. Note: High Angle fire produces a much greater effective illumination area. The FDO must use Column 6, Range to Fuze Function, to determine the minimum effective illumination range line. The maximum effective illumination range line is determined by using fuze setting corresponding to Column 7, Range to Impact.
|
||
|
||
15-11. Safety Considerations for M549/M549A1 RAP
|
||
|
||
RAP safety data are computed using the Low Angle Safety or High Angle Safety matrix, as appropriate. The only difference is that a safety buffer must be incorporated for rocket failure or rocket cap burn through. For firing in the Rocket-Off Mode, a 6000 meter buffer must be constructed beyond the maximum range line to preclude the projectile exceeding the maximum range line. For firing in the Rocket-On Mode, a 6000 meter buffer must be constructed short of the minimum range line to preclude the projectile falling short of the minimum range line.
|
||
|
||
15-28
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
15-12. Safety Considerations for M864 Base Burn DPICM/M795A1 Base Burn HE
|
||
|
||
Base Burn safety data are computed using the Low Angle Safety or High Angle Safety matrix, as appropriate. The only difference is that a safety buffer must be incorporated for Base Burn Element Failure. A 5000 meter buffer must be constructed short of the minimum range line to preclude the projectile falling short of the minimum range line.
|
||
|
||
15-13. Safety Procedures for M712 Copperhead
|
||
|
||
a. Copperhead safety data are determined from ballistic data developed specifically for the Copperhead projectile. Computations are much like those for normal projectiles. The Copperhead round should never be fired with standard data. Therefore, the computation of safety data requires the solving of a Copperhead Met to Target technique for each listed range using the FT 155-AS-1, as covered in Chapter 13, Section 1. See Table 15-7 for steps to compute Copperhead safety. Surface Danger Zones (SDZs) for shell Copperhead are significantly different than normal indirect fire SDZs. AR 385-63 (MCO P3570), chapter 11, contains the SDZs for Copperhead.
|
||
|
||
b. All ranges listed on the range safety card may not fall within the ranges listed in the TFT charge selection table for that charge and mode. Therefore, additional safety computations may be required for additional charge(s) and mode(s) to adequately cover the impact area. If ranges listed on the range safety card overlap charge and mode range limitations in the charge selection table, then safety for both affected charges and modes must be computed.
|
||
|
||
Table 15-7. Copperhead Safety Data Procedures
|
||
|
||
STEP 1 2
|
||
3
|
||
|
||
Construct the basic safety diagram.
|
||
|
||
ACTION
|
||
|
||
For low angle, circle the lower left hand corner of the safety diagram. Proceed in a clockwise manner, and circle every other corner. For high angle, start in the lower right hand corner and circle every other corner in a clockwise manner. Complete a Copperhead Met to Target technique for each circled corner. Record the FS, deflection, and QE in the safety T. The lower left hand corner will provide the minimum FS, maximum left deflection, and minimum QE. The upper right hand corner will provide the maximum right deflection and maximum QE. Intermediate deflections and ranges will provide intermediate deflection limits.
|
||
|
||
15-14. Computation of High Angle Safety
|
||
|
||
a. The safety data for high angle fire is computed in much the same manner as that for low angle fire except for the ballistic variations caused by the high trajectory. Site is computed differently (by using the 10 mil Site Factor and the Angle of Site/10), and mechanical or electronic fuze settings are not determined. (Note: It is the FDO’s responsibility to ensure that all High Angle Fuze Settings will cause the fuze to function within the safety box). Table 15-8 contains the steps required for computation of High Angle Safety.
|
||
|
||
b. Use the steps outlined in Table 15-8 and in the matrix in Figure 15-12 as examples for organizing computations. The High Angle Safety Matrix is used for all munitions except M712
|
||
15-29
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
CLGP (Copperhead). The data are determined by either graphical or tabular firing tables. In the case of expelling charge munitions, the Safety Table located in the Firing Tables or Firing Table Addendums is utilized to determine Elevation, Time of Flight, Fuze Setting, and Drift. (Note: The Safety Tables which are used to compute the High Angle examples are located after the Low Angle Safety examples). Use artillery expression for all computations except where noted.
|
||
|
||
STEP 1 2 3 4 5
|
||
6 7
|
||
7a
|
||
8 9
|
||
10
|
||
11 12 13
|
||
|
||
Table 15-8. High Angle Procedures
|
||
ACTION On the top third of a blank sheet of paper, construct the basic safety diagram in accordance with the range safety card. (See Table 15-1 for procedures) In the middle third of the sheet of paper, construct the High Angle Safety Matrix (Figure 2) Record the Diagram Ranges from the basic safety diagram. Record the Charge from the range safety card. Enter the Range Correction, if required. This range correction is only necessary if a nonstandard condition exists which requires a change in aimpoint and is not already accounted for in a GFT setting, such as correcting for the always heavier than standard White Phosphorous projectile. See figure 2, paragraph (b) to determine range correction. If a range correction is required, it is artillery expressed to the nearest 10 meters. If no range correction is required, enter 0 (zero). Determine the Total Range. Total range is the sum of the Diagram Range and the Range Correction. Total Range is expressed to the nearest 10 meters. Enter the Range K. Range K is only required if a GFT setting has been obtained but cannot be applied to a GFT (i.e., determining Illumination safety with a HE GFT setting). Range K is simply the Total Range Correction from the GFT setting expressed as a percentage. This percentage, when multiplied by the Total Range, produces the Entry Range. If no GFT setting is available (i.e., pre-occupation safety), then enter 1.000 as the Range K. If a GFT setting is available, (i.e., post occupation safety), then enter the Range K expressed to four decimal places (i.e., 1.1234). Step 7a demonstrates how to compute Range K. Divide Range ~ Adjusted Elevation by the Achieved Range from the GFT setting to determine Range K:
|
||
Range ~ Adjusted Elevation = Range K, expressed to four decimal places. Achieved Range Determine the Entry Range. Multiply the Total Range times Range K to determine the Entry Range. If Range K is 1.0000, then the Entry Range will be identical to the Total Range. Entry Range is artillery expressed to the nearest 10 meters. Following the Mini-Max rule, determine the Vertical Interval by subtracting the unit altitude from the altitude corresponding to the Diagram Range, and record it. (Note: Diagram Range is used for computations of VI and Site because this is the actual location of the minimum range line. The Range Correction, Total Range, and Range K are used to compensate for nonstandard conditions, and represent the aimpoint which must be used to cause the round to cross the Diagram Range). VI is artillery expressed to the nearest whole meter. Determine and record the Angle of Site divided by 10 to the Diagram Range. This is performed by dividing the Angle of Site (use the appropriate GST, if possible) by 10. <SI/10 is artillery expressed to the nearest tenth of a mil, and has the same sign as the VI. Determine and record the 10 mil Site Factor from the GFT or TFT which heads the projectile family. (Note: Remember to use the Diagram Range to compute 10 mil Si Fac). 10 mil Si Fac is artillery expressed to the nearest tenth of a mil and is always negative. Compute and record Site. Site is the product of <SI/10 times 10 mil Si Fac. Site is artillery expressed to the nearest whole mil. Determine the Elevation from Table C (base ejecting) or TFT/GFT (bursting), and
|
||
|
||
15-30
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
record it. (Note: GFT Settings are not used to determine Elevation, as Range K represents total corrections, and to use a GFT setting would double the effects of those corrections). Elevation is artillery expressed to the nearest whole mil. 14 Compute the Quadrant Elevation and record it. Quadrant Elevation is the sum of Elevation and Site. Quadrant Elevation is artillery expressed to the nearest whole mil. 15 Determine and record Drift corresponding to the Entry Range from Table C (base ejecting) or TFT/GFT. Drift is applied to the Basic Safety Diagram by following the "left least, right most" rule. The lowest (least) drift is applied to all left deflection limits, and the highest (greatest) drift is applied to all right deflection limits. Drift is artillery expressed to the nearest whole mil. 16 Ensure computations are verified by a second safety-certified person. 17 On the bottom third of the sheet of paper, record the data on the safety T.
|
||
|
||
NOTE: Minimum fuze settings are not computed for High Angle safety. It is the FDO's responsibility to ensure that all fuze settings will cause the projectile to function in the impact area.
|
||
|
||
(a)
|
||
|
||
(b)
|
||
|
||
(c) (d)
|
||
|
||
(e)
|
||
|
||
(f) (g) (h)
|
||
|
||
(I)
|
||
|
||
(j) (k) (l)
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG
|
||
|
||
CHG VI <SI/10 X10mil Si Fac = SI + EL = QE
|
||
|
||
(m) DRIFT
|
||
|
||
(a) This is the minimum or maximum range from the range safety diagram.
|
||
|
||
(b) This is the range correction for nonstandard conditions from Table F, if required. This is typically for reoccupation
|
||
|
||
safety or corrections for nonstandard conditions not included in the Range K factor in column (d), such as WP []
|
||
|
||
weight. Examples of nonstandard conditions accounted for in (b) include, but are not limited to, difference in
|
||
|
||
projectile square weight, difference in muzzle velocity, or any nonstandard condition accounted for prior to
|
||
|
||
determining a Range K factor. If there is no change from standard, or all nonstandard conditions are accounted
|
||
|
||
for in the Range K factor, this value is zero (0).
|
||
|
||
To determine a range correction from Table F, use the following formula:
|
||
|
||
NONSTANDARD STANDARD CHANGE IN RG CORR RANGE
|
||
|
||
RANGE CHG CONDITION
|
||
|
||
- CONDITION = STANDARD x FACTOR = CORRECTION
|
||
|
||
(c) This is the sum of the Diagram Range and the Range Correction. If there is no range correction, then the Total Range will be the same as the Diagram Range.
|
||
|
||
(d) This is the Range K factor determined by using technique 2 in the FM 6-40/MCWP 3-16.6. This is for post occupation safety. It represents total corrections for a registration, MET + VE, or other subsequent MET technique. It represents all nonstandard conditions (unless a separate nonstandard condition such as change in square weight for WP is listed separately in column (b)). It is multiplied times the Total Range to determine Entry Range. If there is no Range K, enter 1.0000
|
||
|
||
(e) This is the sum of the Total Range times the Range K factor. If there is no Range K factor, then the Entry Range will be the same as the Total Range. Entry Range is the range to which Elevation is determined.
|
||
|
||
(f) This is the charge from the range safety card for this set of safety computations.
|
||
|
||
(g). This is the Vertical Interval from the range safety diagram.
|
||
|
||
(h). This is the Angle of Site divided by 10, determined by dividing Vertical Interval by Entry Range in Thousands. (i). This is the 10 mil Site Factor, determined from the GFT or TFT from the head of the projectile family; e.g., 10 mil
|
||
Site Factor for the M110 WP projectile would be determined with the AM-2, M825 10 mil Site Factor would be computed using the AN-2. *
|
||
|
||
(j). This is Site, the product of <Site/10 X 10 Mil Site Factor (Note: Site is determined for the Diagram Range). *
|
||
|
||
(k). This is the elevation to impact from Table C (base ejecting), or GFT/TFT (bursting). *
|
||
|
||
(l). This is the sum of Elevation and Site. It is the minimum or maximum Quadrant Elevation corresponding to
|
||
15-31
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
maximum or minimum range. (m). This is the Drift corresponding to Table C (base ejecting), or GFT/TFT (bursting), Drift is applied to the range
|
||
safety diagram by using the "Least, Left; Most, Right;" rule. The "least" or lowest drift is applied to all left deflection limits, and the "most" or greatest drift is applied to all right deflection limits.
|
||
* - see Table 15-8 to determine the correct source table or addendum for computations/
|
||
Figure 15-12. High Angle Safety Matrix
|
||
|
||
FP 185 (GRID 6026 4110 ALT 370) HIGH ANGLE, HE, CHG 3GB, AOF 1600
|
||
|
||
AZ 1340 DF 3460 + L34 = 3494
|
||
|
||
AZ 1500 DF 3300 + L34 = 3334 Max Rg 5700 Min Alt 355
|
||
L 260
|
||
|
||
Max Rg 6200 Min Alt 345 L 100
|
||
AOF 1600 DF 3200
|
||
R 300
|
||
|
||
AZ 1900 DF 2900 + L101 = 3001
|
||
|
||
4[] HE HIGH ANGLE CHG 3GB
|
||
|
||
Min Rg 4000 Max Alt 393
|
||
|
||
DIAGRAM RANGE TOTAL RANGE ENTRY RANGE + CORR = RANGE X k__ = RANGE CHG VI <SI/10 X 10mil Si Fac = SI + EL = QE DRIFT
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0000 = 4000 3GB +23 +0.6 x -1.0
|
||
|
||
= -1 + 1247 = 1246 L101
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0000 = 5700 3GB -15 -0.3 x -5.2
|
||
|
||
= +2 + 1052 = 1054 --
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0000 = 6200 3GB -25 -0.4 x -15.0 = +6 + 954 = 960 L34
|
||
|
||
FP 185, HE HIGH ANGLE, CHG 3GB, AOL 1600
|
||
|
||
1246
|
||
|
||
MMAAXX QQEE
|
||
|
||
3494
|
||
|
||
3334 3001
|
||
|
||
DF
|
||
|
||
1054 960
|
||
|
||
MMININQQEE
|
||
|
||
Figure 15-13. Example of High Angle Safety, Shell HE
|
||
|
||
15-32
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
AZ 1340 DF 3460 + L37 = 3497
|
||
|
||
FP 185 (GRID 6026 4110 ALT 370) HIGH ANGLE, M825, CHG 4GB, AOF 1600
|
||
|
||
AZ 1500 DF 3300 + L37
|
||
|
||
Max Rg 6200 Min Alt 345
|
||
|
||
= 3337
|
||
|
||
Max Rg 5700
|
||
|
||
L 100
|
||
|
||
Min Alt 355
|
||
|
||
AOF 1600 DF 3200
|
||
|
||
L 260
|
||
|
||
R 300 R 300
|
||
|
||
Min TI Rg 4000
|
||
|
||
Min Rg 3900 Max Alt 393
|
||
|
||
AZ 1900 DF 2900 + L125 = 3025
|
||
|
||
M825 HIGH ANGLE CHG 4GB
|
||
|
||
DIAGRAM RANGE TOTAL RANGE ENTRY RANGE + CORR = RANGE X __k__ = RANGE CHG
|
||
|
||
VI <SI/10 X 10mil Si Fac = SI + EL = QE DRIFT
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0000 = 4000 4GB +23 +0.6 x -0.7
|
||
|
||
= 0 + 1288 = 1288 L125
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0000 = 5700 4GB -15 -0.3 x -2.8
|
||
|
||
= +1 + 1133 = 1134 --
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0000 = 6200 4GB -25 -0.4 x -4.4
|
||
|
||
= +2 + 1071 = 1073 L37
|
||
|
||
FP 185, M825 HIGH ANGLE, CHG 4GB, AOL 1600
|
||
|
||
1288
|
||
|
||
MAMXMAQAEXXQQEE
|
||
|
||
3497
|
||
|
||
3337 3025
|
||
|
||
DF
|
||
|
||
1134 1073 MIMNMIQNINEQQEE
|
||
|
||
Figure 15-14. Example of High Angle Safety, Shell M825
|
||
|
||
15-33
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
FP 185 (GRID 6026 4110 ALT 370) HIGH ANGLE, ILLUM, CHG 3GB, AOF 1600
|
||
|
||
AZ 1340 DF 3460 + L36 = 3496
|
||
|
||
AZ 1500 DF 3300 + L36 = 3336
|
||
Max Rg 5700 Min Alt 355
|
||
|
||
Max Rg 6200 Min Alt 345
|
||
L 100
|
||
|
||
L 260
|
||
|
||
AOF 1600 DF 3200 R 300
|
||
|
||
R 300 Min TI Rg 4000
|
||
|
||
AZ 1900 DF 2900 + L105 = 3005
|
||
|
||
ILLUM HIGH ANGLE CHG 3GB
|
||
|
||
Min Rg 3900 Max Alt 393
|
||
|
||
DIAGRAM RANGE TOTAL RANGE ENTRY RANGE + CORR = RANGE X __k__ = RANGE CHG VI <SI/10 X 10mil Si Fac = SI + EL = QE DRIFT
|
||
|
||
4000
|
||
|
||
+ 0 = 4000 x 1.0000 = 4000 3GB +23 +0.6 x -1.0
|
||
|
||
= -1 + 1253 = 1252 L105
|
||
|
||
5700
|
||
|
||
+ 0 = 5700 x 1.0000 = 5700 3GB -15 -0.3 x -5.3
|
||
|
||
= +2 + 1066 = 1068
|
||
|
||
--
|
||
|
||
6200
|
||
|
||
+ 0 = 6200 x 1.0000 = 6200 3GB -25 -0.4 x -15.0
|
||
|
||
= +6 + 977 = 983
|
||
|
||
L36
|
||
|
||
FP 185, ILLUM HIGH ANGLE, CHG 3GB, AOL 1600
|
||
|
||
1252 MAX QME AX QE
|
||
|
||
3496
|
||
|
||
3336 3005
|
||
|
||
DF
|
||
|
||
1068 983 MIN QMEIN QE
|
||
|
||
EFFECTIVE ILLUMINATION BOX
|
||
|
||
40.8
|
||
|
||
4+0.83
|
||
|
||
+410.13
|
||
|
||
41.1
|
||
|
||
5200
|
||
|
||
5600 4200
|
||
|
||
38.3 M565 +0.3 CORR for M577 38.6 SEC
|
||
Range to Fuze Function 44.2 +0.3 44.5 SEC
|
||
|
||
15-34
|
||
|
||
Figure 15-15. Example of High Angle Safety, Shell Illum
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
FIGURE 15-16: LOW ANGLE SAFETY COMPUTATIONS
|
||
|
||
Location (Grid/Alt):
|
||
|
||
Safety Diagram Charge: Shell(s):
|
||
AOL:
|
||
|
||
Fuze(s):
|
||
|
||
Angle of Fire:
|
||
|
||
AOF
|
||
|
||
DF
|
||
|
||
Low Angle Safety Matrix
|
||
|
||
Chg:_____ Shell(s):__________ Fuze(s):__________ Projectile Family:__________
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT RG ENTRY
|
||
|
||
M564/ M582
|
||
|
||
M728/
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG CHG VI SI + EL = QE M565 M577 TOF + 5.5 = M732 DFT
|
||
|
||
Safety T Location:____________Charge: _____Shell(s):___________Fuze(s):__________Angle of Fire:___ AOL: ____
|
||
|
||
15-35
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
FIGURE 15-17: HIGH ANGLE SAFETY COMPUTATIONS
|
||
|
||
Location (Grid/Alt):
|
||
|
||
Safety Diagram Charge: Shell(s): AOL:
|
||
|
||
Angle of Fire:
|
||
|
||
AOF
|
||
|
||
DF
|
||
|
||
High Angle Safety Matrix
|
||
|
||
Chg:_____ Shell(s):__________ Projectile Family:__________
|
||
|
||
DIAGRAM RG
|
||
|
||
TOT
|
||
|
||
RG
|
||
|
||
ENTRY
|
||
|
||
RG
|
||
|
||
+ CORR = RG x K = RG
|
||
|
||
CHG VI <SI/10 x 10 mil Si Fac = SI + EL = QE DFT
|
||
|
||
Safety T Location:_________________Charge: _____Shell(s):__________Angle of Fire:_____AOL:________
|
||
|
||
15-36
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
Section III
|
||
Minimum Quadrant Elevation
|
||
The XO or platoon leader is responsible for determining the lowest QE that can be safely fired from his position that will ensure projectiles clear all visible crests (minimum QE).
|
||
15-15. Elements of Computation
|
||
A minimum quadrant for EACH howitzer is ALWAYS determined. The maximum of these minimum quadrants is the XO’s minimum quadrant. Use of the rapid fire tables in ST 6-50-20 is the fastest method of computing minimum QE. The QE determined from ST 6-5020 is always equal to or greater than (more safe) than manual computations. Manual computations are more accurate than the rapid fire tables and are used if the sum of the site to crest and the angle needed for a 5-meter vertical clearance is greater than 300 mils. Figure 15-18 shows the elements of minimum QE.
|
||
a. Piece-to-crest range (PCR) is the horizontal distance between the piece and the crest, expressed to the nearest 100 meters. Procedures for measurement are discussed in paragraph 15-16.
|
||
NOTE: All angles are determined and expressed to the next higher mil.
|
||
b. Angle 1 (Figure 15-18) is the angle of site to crest measured by the weapons. See paragraph 15-16 for procedures.
|
||
c. Angle 2 (Figure 15-18) is the vertical angle required to clear the top of the crest. For quick, time, and unarmed proximity (VT) fuzes, a vertical clearance of 5 meters is used. For armed VT fuzes, see paragraph 15-19.
|
||
d. Angle 3 (Figure 15-18) is the complementary angle of site. It is the complementary site factor (TFT, Table G) for the appropriate charge at the piece to crest range mulitiplied by the sum of angles 1 and 2. Site is the sum of angles 1, 2, and 3.
|
||
NOTE: The entry argument for Table G is PCR. If it is not listed, do not interpolate, use the next higher listed value.
|
||
e. Angle 4 (Figure 15-18) is the elevation (TFT, Table F) for the appropriate charge corresponding to the PCR.
|
||
f. Angle 5 (Figure 15-18) is a safety factor equivalent to the value of 2 forks (TFT, Table F) for the appropriate charge at the PCR.
|
||
15-37
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
g. The sum of angles 1 through 5 (Figure 15-18) is the minimum QE for the weapon and the charge computed.
|
||
Figure 15-18. Angles of Minimum QE 15-16. Measuring Angle of Site to Crest
|
||
As soon as the piece is “safed”, prefire checks conducted, and ammunition prepared , position improvement begins with verification of site to crest as measured by the advance party. The advance party measures site to crest with an M2 compass or aiming circle. The section chief measures the angle of site to crest and reports it to the XO or platoon leader. To measure the angle of site to crest, the section chief sights along the bottom edge of the bore, has the tube traversed across the probable field of fire, and has the tube elevated until the line of sight clears the crest at the highest point. He then centers all bubbles on the elevation mount and reads the angle of site to the crest from the elevation counter. This angle of site and the PCR are reported as part of the section chief’s report. 15-17. Measuring Piece-To-Crest Range
|
||
a. There are five methods that can be used to measure piece-to-crest range: (1) Taping. This is the most accurate method; however, it is normally too time-
|
||
consuming. (2) Subtense. This method is fast and accurate. (3) Map Measurement. This method is fast and accurate if the obstacle can be
|
||
accurately located (for example, a lone tree will not appear on a map). (4) Pacing. This method is time-consuming and depends on the distance and
|
||
accessibility to the crest. 15-38
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
(5) Estimation. This method is least accurate, but it is used when other methods are not feasible.
|
||
b. Regarless of the method used to measure PCR, the XO or platoon leader must verify PCR before he computes QE. He can do this by using any of the five methods.
|
||
|
||
15-18. Computation of Fuzes Other Than Armed VT
|
||
|
||
a. The XO or platoon leader does the computations indicated in this section if the sum of angles 1 and 2 (Figure 15-18) exceeds 300 mils or if the rapid firing tables (RFTs) are not available. All angles are determined and expressed to the next higher mil. Table 15-9 lists the steps and solves an example of an XO’s or platoon leader’s manual computations.
|
||
|
||
STEP
|
||
1 2 3
|
||
4
|
||
5 6 7
|
||
|
||
Table 15-9. Manual Minimum QE Computations.
|
||
ACTION
|
||
Howitzer 1 (M109A3) reports a site to crest of 16 mils at a PCR of 1,100 meters. Charge 3GB is used.
|
||
∋1 = site to crest = 16 mils ∋2 = (VI x 1.0186) + PCR (in 1,000s)
|
||
= (5 x 1.0186) + 1.1 = 4.6 λ 5 mils This VI is a 5-meter vertical clearance safety factor. It can also be computed using one of the following methods: • Use the GST. Solve in the same way as angle of site (4.6 λ 5). • Use ST 6-50-20, page 2-7 (5). ∋3 = (∋1 + ∋2) x CSF = (16 + 5) x 0.010 = (0.210) λ 1 mil ∋4 = EL = 74.1 λ 75 mils ∋5 = 2 Forks (TFT, Table F, Column 6) = 2 x 2 = 4 mils
|
||
Min QE = ∋1 + ∋2 + ∋3 + ∋4 + ∋5 = 16 + 5 + 1 + 75 + 4 = 101 mils
|
||
|
||
b. The same example is solved in Table 15-10 by using RFTs in the ST 6-50-20, Appendix B.
|
||
|
||
15-39
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
STEP
|
||
1 2
|
||
3
|
||
|
||
Table 15-10. RFT Minimum QE Computations.
|
||
ACTION
|
||
Determine if the RFT can be used (∋1 + ∋2 [ 300 mils). Use the ST 6-50-20, page A-1. Since the sum of angles 1 and 2 is less than or equal to 300 (16 +5 = 21), the RFT can be used. Determine RFT value. Enter the appropriate RFT. The entry arguments are howitzer (M109A3), propellant (M3A1, GB), fuze (PD), PCR (1100), and charge (3). The correct table is on page A-7. The RFT value is 86. This value equals the sum of angles 2, 3, 4, and 5 (∋2 + ∋3 + ∋4 + ∋5). NOTE: Use the RFT labeled “M557, M564” for all minimum QE computations except armed VT. For armed VT, use the RFT labeled “M728.” Determine the RFT minimum QE. This value equals the sum of angle 1 and the RFT value (16 + 86 = 102).
|
||
|
||
c. One howitzer section may report a site to crest that is unusually high. If the XO or platoon leader determines that it is the result of a single narrow obstruction (such as a tree), the piece can be called out of action when firing a deflection that would engage the obstruction. This would enable the platoon to use the next lower site to crest. Other alternatives are to remove the obstruction or move the weapon.
|
||
|
||
d. Table 15-11 illustrates why minimum QE is computed for all guns, regardless of which has the largest site to crest.
|
||
|
||
GUN 1 2 3 4
|
||
|
||
Table 15-11. RFT Example for Howitzer Platoon.
|
||
|
||
SITE TO
|
||
|
||
CHG
|
||
|
||
PCR CREST
|
||
|
||
+
|
||
|
||
RFT
|
||
|
||
=
|
||
|
||
3GB
|
||
|
||
800
|
||
|
||
128
|
||
|
||
64
|
||
|
||
3GB
|
||
|
||
1000
|
||
|
||
105
|
||
|
||
80
|
||
|
||
3GB
|
||
|
||
1500
|
||
|
||
92
|
||
|
||
116
|
||
|
||
3GB
|
||
|
||
1200
|
||
|
||
115
|
||
|
||
93
|
||
|
||
MIN QE 192 185 208 208
|
||
|
||
15-19. Computations for Armed VT Fuze (Low-Angle Fire)
|
||
|
||
a. The method of computing the XO’s minimum QE for firing a projectile fuzed with an M728 or M732 fuze depends on the method in which the fuze is used. The proximity (VT) fuze is designed to arm 3 seconds before the time set on the fuze; however, some VT fuzes have armed as early as 5.5 seconds before the time set on the fuze. Because of the probability of premature arming, a safety factor of 5.5 seconds is added to the time of flight to the PCR. Since time on the setting ring is set to the whole second, the time determined in computing minimum safe time is expressed up to the nearest whole second. A VT fuze is designed so that it will not arm earlier than 2 seconds into its time of flight, which makes it a bore-safe fuze.
|
||
|
||
b. In noncombat situations, the XO or platoon leader determines the minimum safe time by adding 5.5 seconds to the time of flight to the minimum range line as shown on the range safety card. The minimum QE determined for fuzes quick and time is also valid for fuze VT.
|
||
|
||
c. In combat situations, the XO or platoon leader determines the minimum QE and a minimum safe time for fuze VT. The minimum QE determined for PD fuzes is safe for VT fuzes
|
||
15-40
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
if the fuze setting to be fired equals or is greater than the minimum safe time determined in paragraph a above. If the XO or platoon leader finds it necessary to fire a VT fuze with a time less than the minimum safe time, he must modify the minimum QE. He does this by increasing the vertical clearance to ensure that the fuze will not function as it passes over the crest. In addition, he must ensure the fuze will not function over any intervening crests along the guntarget line (See paragraph 15-21).
|
||
d. If the projectile is to be fired with the VT fuze set at a time less than the minimum safe time, allowance must be made for vertical clearance of the crest. Vertical crest clearances for armed M728 and M732 VT fuzes fired over ordinary terrain for all howitzer systems is 70 meters.
|
||
e. If the projectile is to be fired over marshy or wet terrain, the average height of burst will increase. The vertical clearance is increased to 105 meters. If the projectile is fired over water, snow, or ice, the vertical clearance is 140 meters.
|
||
f. The minimum QE for armed fuze VT when a fuze setting less than the minimum safe time is fired is based on the piece-to-crest range and a vertical clearance as indicated in paragraphs d and e above.
|
||
g. Figure 15-19 shows a decision tree for application of armed VT minimum QE.
|
||
|
||
In combat, you have a VT mission with a time setting of ________ and a QE of ________. Ask the following questions:
|
||
|
||
Begin
|
||
|
||
Is QE > XO’s min QE?
|
||
|
||
No Decrease charge or fire HA
|
||
|
||
No VT FS > min VT FS to the FLOT?
|
||
|
||
No
|
||
|
||
Is VT QE > min QE for armed VT?
|
||
|
||
Decrease Chg,
|
||
|
||
fire HA, or
|
||
|
||
change fuze
|
||
|
||
Safe; fire it.
|
||
|
||
15-41
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________ Figure 15-19. Armed VT Decision Tree.
|
||
h. Table 15-12 is an example of computations to determine minimum QE for an armed VT fuze.
|
||
15-42
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
STEP
|
||
1 2 3
|
||
4
|
||
5 6 7
|
||
8
|
||
|
||
Table 15-12. Manual Armed VT Minimum QE Computations.
|
||
ACTION
|
||
Howitzer 1 (M109A3) reports a site to crest of 16 mils at a PCR of 1,100 meters. Charge 3GB is used.
|
||
∋1 = site to crest = 16 mils ∋2 = (VI x 1.0186) + PCR (in 1,000s)
|
||
=(70 x 1.0186) + 1.1 = 64.8 λ 65 mils This VI is a 70-meter vertical clearance safety factor. It can also be computed by using the GST. Solve in the same way as angle of site (64.7 λ 65). ∋3 = (∋1 + ∋2) x CSF (TFT, Table G) = (16 + 65) x 0.010 = 0.710 λ 1 mil ∋4 = EL = 74.1 λ 75 mils ∋5 = 2 Forks (TFT, Table F, Column 6) = 2 x 2 = 4 mils
|
||
Min QE = ∋1 + ∋2 + ∋3 + ∋4 + ∋5 = 16 + 65 + 1 + 75 + 4 = 161 mils
|
||
Determine minimum safe time. This value is the sum of TOF to PCR and 5.5 expressed up to the next higher second (4.1 + 5.5 = 9.6 λ 10.0 sec).
|
||
|
||
i. The same example is solved in Table 15-13 by using the RFT in the ST 6-50-20, Appendix A.
|
||
|
||
STEP
|
||
1 2
|
||
3 4
|
||
|
||
Table 15-13 RFT Minimum QE Computations.
|
||
ACTION
|
||
Determine if the RFT can be used (∋1 + ∋3 [ 300 mils). This is done manually, since page A1 uses a vertical clearance of 5 meters. See step 3 in table 15-12 for ∋2. Since the sum of angles 1 and 2 is less than or equal to 300 (16 +65 = 81), the RFT can be used. Determine RFT value. Enter the appropriate RFT. The entry arguments are howitzer (M109A3), propellant (M3A1, GB), fuze (M728 or M732), PCR (1100) and charge (3). The correct table is on page A-13. The RFT value is 147. This value equals the sum of angles 2, 3, 4, and 5. NOTE: Use the RFT labeled “M557, M564” for all minimum QE computations except armed VT. For armed VT, use the RFT labeled “M728.” Determine the RFT minimum QE. This value equals the sum of angle 1 and the RFT value (16 + 147 = 163). Determine the minimum safe time. Use the same entry arguments as in step 2. The minimum safe time is 10.0.
|
||
|
||
j. If the VT fuze setting to be fired is equal to or greater than the minimum safe VT time, the minimum QE for fuzes quick and time applies. If the VT fuze setting to be fired is less than the minimum safe VT time, the minimum QE determined for armed VT applies.
|
||
15-20. Using Minimum Quadrant Elevation
|
||
|
||
After computing minimum QE for each charge authorized, the XO or platoon leader must compare the minimum QE to the QE required to clear the minimum range line. The XO must then select the highest quadrant for each charge to be used as the minimum QE to be fired from that position.
|
||
15-43
|
||
|
||
Chg 1 FM 6-40/MCWP 3-16.4_____________________________________________
|
||
|
||
15-21. Intervening Crest
|
||
|
||
a. FDOs must ensure that artillery fires clear intervening crests. Intervening crests are defined as any obstruction between the firing unit and the target not visible from the firing unit. The following are the possible options, listed in order of preference.
|
||
|
||
(1) Determine firing data to the crest (include all nonstandard conditions) and add 2 forks (Table 15-12).
|
||
|
||
(2) Determine a minimum QE in a similar manner as XO’s minimum QE (Table 15-13).
|
||
|
||
(3) Use the trajectory tables in the appendix of the TFT.
|
||
|
||
b. Option 1 is preferred because it incorporates all current nonstandard conditions that will affect the projectile along the trajectory. The FDO has the responsibility to determine on the basis of availability of corrections for nonstandard conditions if this really is the best option. Table 15-12 lists the steps.
|
||
|
||
STEP
|
||
1 2
|
||
3 4 5
|
||
|
||
Table 15-14. Intervening Crest, Option 1.
|
||
ACTION
|
||
Upon occupation, the FDO analyzes the terrain for intervening crests. Upon determining the altitude of this crest, he computes firing data to this point (QE). The best solution includes all available corrections for nonstandard conditions (current and valid GFT setting). Add the value of 2 forks (TFT, Table F, Column 6) to the QE determined in step 2 to ensure that round-to-round variations (probable errors) will clear the crest. The FDO then records this QE and charge on his situation map as a check to ensure that rounds will clear the intervening crest. Upon receipt of a fire mission, the FDO will compare his intervening crest QE to his fire mission quadrant. One of the three following situations will occur:
|
||
|
||
1) The target is located short of the intervening crest. The FDO does not consider the effects of the crest at this time.
|
||
|
||
2) The mission QE exceeds intervening crest QE by a significant margin, indicating the rounds will clear the crest.
|
||
|
||
3) Fire mission QE exceeds intervening crest QE by only a small margin or is less than intervening crest QE, indicating the round may or may not clear the crest. The FDO must determine if the round will clear after considering the following:
|
||
|
||
15-44
|
||
|
||
_____________________________________________Chg 1 FM 6-40/MCWP 3-16.4
|
||
|
||
STEP
|
||
6
|
||
|
||
Table 15-14. Intervening Crest, Option 1 (Continued).
|
||
ACTION
|
||
• Have all nonstandard conditions been accounted for? • How old is the current met message? • Are registration corrections being applied to this mission?
|
||
Upon realizing that the round may not or will not clear the crest, the FDO can either fire high angle or a reduced charge. The quickest choice would be to fire high angle, but tactical situations may prevent this. Firing a lower charge will increase dispersion more than high angle. For example, at a range of 6,000 meters, the following applies:
|
||
• Low angle, charge 5: Probable error in range = 15 meters. • High angle, charge 5: Probable error in range = 17 meters. • Low angle, charge 4: Probable error in range = 23 meters.
|
||
If a lower charge is selected, steps 2 through 5 must be repeated. If VT fuzes are to be fired (M700 series), the FDO must take additional steps to ensure that the VT fuze does not arm before passing over the crest. Follow the steps for determining armed VT minimum QE and FS in paragraph 15-15.
|
||
|
||
c. Option 2 does not include current conditions for all nonstandard conditions. Table 1520 lists the steps.
|
||
|
||
STEP
|
||
1 2 3 4 5
|
||
6
|
||
7 8 9
|
||
|
||
Table 15-15. Intervening Crest, Option 2.
|
||
ACTION
|
||
Upon occupation, the FDO analyzes the terrain for intervening crests. The FDO determines and announces the grid and map spot altitude to the crest. The HCO plots the grid and determines and announces range to crest. The VCO computes angle of site to the crest. This is the same as determining site to crest with a howitzer
|
||
Determine if RFT can be used (∋1 + ∋2 [ 300 mils). Angle 1 equals angle of site to the crest. Refer to ST 6-50-20, page A-1. Since ∋1 and ∋2 decrease with range, this should not be a problem. Determine RFT value. Enter the appropriate RFT. The entry arguments are howitzer, propellant, fuze, PCR (chart range to the crest), and charge. This value equals the sum of angles 2, 3, 4, and 5. NOTE: Use the RFT labeled “M557, M564” for all minimum QE computations except armed VT. For armed VT, use the RFT labeled “M728.” Determine RFT intervening crest QE. This value is the sum of the angle of site to the crest and the RFT value. If VT is fired, enter the appropriate table and extract the correct information. Follow steps 4 and 5 of table 15-14.
|
||
|
||
d. The least preferred option is using the trajectory charts in the appendix of the TFT. This offers a quicker but less accurate method to clear the intervening crest since it is based off of standard conditions. The FDO must make a judgment call when to use these charts. The FDO must use caution when making this decision.
|
||
|
||
15-45
|
||
|
||
*FM 6-40/MCWP 3-1.6.19 i
|
||
|
||
FM 6-40/MCWP 3-1.6.19 ii
|
||
|
||
FM 6-40/MCWP 3-1.6.19 iii
|
||
|
||
FM 6-40/MCWP 3-1.6.19 iv
|
||
|
||
FM 6-40/MCWP 3-1.6.19 v
|
||
|
||
FM 6-40/MCWP 3-1.6.19 vi
|
||
|
||
FM 6-40/MCWP 3-1.6.19 vii
|
||
|
||
FM 6-40/MCWP 3-1.6.19 viii
|
||
|
||
FM 6-40/MCWP 3-1.6.19 ix
|
||
|
||
FM 6-40/MCWP 3-1.6.19 x
|
||
|
||
FM 6-40/MCWP 3-1.6.19 xi
|
||
|
||
FM 6-40/MCWP 3-1.6.19 xii
|
||
|
||
FM 6-40/MCWP 3-1.6.19 xiii
|
||
|
||
FM 6-40/MCWP 3-1.6.19 xiv
|
||
|
||
FM 6-40/MCWP 3-1.6.19 xv
|
||
|
||
FM 6-40/MCWP 3-1.6.19 xvi
|
||
|
||
FM 6-40/MCWP 3-1.6.19 xvii
|
||
|
||
FM 6-40
|
||
Chapter 1
|
||
THE GUNNERY PROBLEM AND THE GUNNERY TEAM
|
||
The mission of the Field Artillery is to destroy, neutralize, or suppress the enemy by cannon, rocket, and missile fires and to help integrate all fire support assets into combined arms operations. Field artillery weapons are normally employed in masked or defilade positions to conceal them from the enemy. Placing the firing platoon in defilade precludes direct fire on most targets. Consequently, indirect fire must be used when FA weapons fire on targets that are not visible from the weapons. The gunnery problem is an indirect fire problem. Solving the problem requires weapon and ammunition settings that, when applied to the weapon and ammunition, will cause the projectile to achieve the desired effects on the target.
|
||
1-1. Gunnery Problem Solution a. The steps in solving the gunnery problem areas follows: (1) Know the location of the firing unit, and determine the location of the target. (2) Determine chart (map) data (deflection, range from the weapons to the target,
|
||
and altitude of the target). (3) Determine vertical interval (VI) and site (si). (4) Compensate for nonstandard conditions that would affect firing data
|
||
(meteorological [met] procedures). (5) Convert chart data to firing data (shell, charge, fuze, fuze setting, deflection, and
|
||
quadrant elevation). (6) Apply the firing data to the weapon and ammunition.
|
||
b. The solution to the problem provides weapon and ammunition settings that will cause the projectile to function on or at a predetermined height above the target. This is necessary so the desired effects will be achieved.
|
||
1-2. Field Artillery Gunnery Team The coordinated efforts of the field artillery gunnery team are required to accomplish the
|
||
solution of the gunnery problem outlined in paragraph 1-2. The elements of the team must be linked by an adequate communications system.
|
||
NOTE: The terms battery and platoon used throughout this manual are synonymous, unless otherwise stated.
|
||
1-1
|
||
|
||
FM 6-40
|
||
a. Observer. The observer and/or target acquisition assets serve as the “eyes and ears” of all indirect fire systems. The mission of the forward observer is to detect and locate suitable indirect fire targets within his zone of observation and bring fires on them. When a target (tgt) is to be attacked, the observer transmits a call for fire and adjusts the fires onto the target as necessary. An observer provides surveillance data of his own fires and any other fires in his zone of observation. Field artillery observers include the following:
|
||
Aerial observers (AOs).
|
||
Forward observers (F0s).
|
||
Fire support teams (FISTs).
|
||
Combat observation/lasing teams (COLTs).
|
||
Air and naval gunfire liaison company (ANGLICO).
|
||
Firepower control teams (FCTs).
|
||
Any other friendly battlefield personnel.
|
||
b. Target Acquisition. Target acquisition assets also function as observers. They provide accurate and timely detection, identification, and location of ground targets, collect combat and/or target information, orient and/or cue intelligence sources, and permit immediate attack on specific areas. Field artillery target acquisition (TA) assets include the following:
|
||
Weapons-locating radar sections.
|
||
Aircraft radar systems.
|
||
NOTE: See FM 6-121 for a discussion of TA assets. See FMs 100-2-1, 100-2-2, and 100-2-3 for information on target characteristics.
|
||
c. Fire Direction Center. The fire direction center (FDC) serves as the “brains” of the gunnery team. It is the control center for the gunnery team and is part of the firing battery headquarters. The FDC personnel receive calls for fire directly from an observer or they maybe relayed through the initial fire support automated system (IFSAS) at battalion level. The FDC will then process that information by using tactical and technical fire direction procedures.
|
||
(1) Tactical fire direction includes processing calls for fire and determining appropriate method of fire, ammunition expenditure, unit(s) to fire, and time of attack. The fire direction officer’s decision on how to engage the target is concisely stated as a FIRE ORDER.
|
||
(2) Technical fire direction is the process of converting weapon and ammunition characteristics (muzzle velocity, propellant temperature, and projectile weight), weapon and target locations, and met information into firing data. Firing data consist of shell (sh), charge (chg), fuze (fz), fuze setting (FS), deflection (df), and quadrant elevation (QE). The FDC transmits firing data to the guns as fire commands.
|
||
1-2
|
||
|
||
FM 6-40
|
||
d. Firing Battery. The firing battery serves as the “muscle” of the gunnery team. The firing battery includes the battery HQ, the howitzer sections, the ammunition section, and the FDC. The howitzer sections apply the technical firing data to the weapon and ammunition. Organization and employment considerations of the firing sections are discussed in FM 6-50.
|
||
1-3. Five Requirement for Accurate Predicted Fire
|
||
To achieve accurate first-round fire for effect (FFE) on a target, an artillery unit must compensate for nonstandard conditions as completely as time and the tactical situation permit. There are five requirements for achieving accurate first-round fire for effect. These requirements are accurate target location and size, firing unit location, weapon and ammunition information, met information, and computational procedures. If these requirements are met, the firing unit will be able to deliver accurate and timely fires in support of the ground-gaining arms. If the requirements for accurate predicted fire cannot be met completely, the firing unit maybe required to use adjust-fire missions to engage targets. Adjust-fire missions can result in less effect on the target, increased ammunition expenditure, and greater possibility that the firing unit will be detected by hostile TA assets.
|
||
a. Target Location and Size. Establishing the range (rg) from the weapons to the target requires accurate and timely detection, identification, and location of ground targets. Determining their size and disposition on the ground is also necessary so that accurate firing data can be computed. Determining the appropriate time and type of attack requires that the target size (radius or other dimensions) and the direction and speed of movement be considered. Target location is determined by using the TA assets mentioned in paragraph 1-2.
|
||
b. Firing Unit Location. Accurate range and deflection from the firing unit to the target requires accurate weapon locations and that the FDC knows this location. The battalion survey section uses the position and azimuth determining system (PADS) to provide accurate survey information for the battery location. Survey techniques available to the firing battery may also help in determining the location of each weapon. The FDC can determine the grid location of each piece by using the reported direction, distance, and vertical angle for each piece from the aiming circle used to lay the battery.
|
||
c. Weapon and Ammunition Information. The actual performance of the weapon is measured by the weapon muzzle velocity (velocity with which the projectile leaves the muzzle of the tube) for a projectile-propellant combination. The firing battery can measure the achieved muzzle velocity of a weapon and correct it for nonstandard projectile weight and propellant temperature. This is done by using the M90 velocimeter and muzzle velocity correction tables (MVCT M90-2) for each type of charge and projectile family. Calibration should be conducted continuously by using the M90 velocimeter. Firing tables and technical gunnery procedures allow the unit to consider specific ammunition information (weight, fuze type, and propellant temperature); thus, accurate firing data are possible.
|
||
d. Meteorological Information. The effects of weather on the projectile in flight must be considered, and firing data must compensate for those effects. Firing tables and technical gunnery procedures allow the unit to consider specific met information (air temperature, air density, wind direction, and wind speed) in determining accurate firing data.
|
||
1-3
|
||
|
||
FM 6-40 e. Computational Procedures. The computation of firing data must be accurate.
|
||
Manual and automated techniques are designed to achieve accurate and timely delivery of fire. The balance between accuracy, speed, and the other requirements discussed in this chapter should be included in the computational procedures.
|
||
f . Nonstandard Conditions. If the five requirements for accurate predicted fire cannot be met, registrations can be conducted or a met + VE technique can be completed to compute data that will compensate for nonstandard conditions. Applying these corrections to subsequent fire missions will allow the unit to determine accurate firing data. Accuracy of these fires will be a direct function of the observer’s target location.
|
||
1-4
|
||
|
||
FM 6-40
|
||
Chapter 2
|
||
FIRING BATTERY AND BATTERY FDC ORGANIZATION
|
||
The FA cannon battery is firing unit within the cannon battalion and is organized in one of two ways: a battery-based unit (3 x 6 organization) or a platoon-based unit (3 x 8 organization). In either case, they have the personnel and equipment needed to shoot, move, and communicate. This chapter describes the organization of the firing battery and the battery FDC.
|
||
2-1. Firing Battery Organization a. The organization of all cannon batteries is basically the same. Differences in
|
||
organization stem from differences in weapon caliber, whether the weapon is towed or self-propelled (SP), and whether the battery is in a divisional or nondivisional battalion. The cannon battery is organized as follows:
|
||
(1) Battery-based unit--consists of a battery headquarters and a firing battery.
|
||
(a) The battery HQ has the personnel and equipment to perform command and control; food service; supply; communications; nuclear, biological, chemical (NBC), and maintenance functions. (In some units, food service, communications, and maintenance may be consolidated at battalion level.)
|
||
(b) The firing battery has the personnel and equipment to determine firing data, fire the howitzers, and resupply ammunition. (In some units, ammunition assets may be consolidated at battalion level.)
|
||
(2) Platoon-based unit--consists of a battery HQ and two firing platoons.
|
||
(a) The battery HQ has the personnel and equipment to perform command and control, food service, supply, communications, NBC, and maintenance functions. (In some units, food service, communications, and maintenance may be consolidated at battalion level.)
|
||
(b) Each firing platoon has the personnel and equipment to determine firing data, fire the howitzers, and resupply ammunition. (In some units, ammunition assets maybe consolidated at battalion level.)
|
||
2-2. Battery or Platoon FDC
|
||
a. The battery or platoon FDC is the control center, or brains, of the gunnery team. The FDC personnel receive fire orders from the battalion FDC or calls for fire from observers and process that information by using tactical and technical fire direction procedures (Chapter 1). The battery FDC performs the technical fire direction, while the battalion FDC performs tactical fire direction. If the FDC is operating without a battalion FDC, the battery FDC conducts both tactical and technical fire direction. The battery FDC receives the call for fire and converts the request into firing data. The firing data are then sent to the howitzer sections as fire commands. In addition to an FDC, USMC batteries have a battery operations center (BOC), which is organized and equipped to perform technical fire direction. BOCs enhance unit survivability, simplify displacements, and enable split-battery operations. In battery positions, BOC personnel may augment the FDC to facilitate 24-hour operations.
|
||
2-1
|
||
|
||
FM 6-40
|
||
b. The FDC is organized to facilitate 24-hour operations (Appendix A). Duties of manual FDC personnel are described below
|
||
(1) Fire direction officer. The FDO is responsible for all FDC operations. He is responsible for the training of all FDC personnel, supervises the operation of the FDC, establishes standing operating procedure (SOP), checks target location, announces fire order, and ensures accuracy of firing data sent to the guns. USMC batteries also include an assistant fire direction officer-assistant executive officer (AFDO-AXO). The AFDO-AXO leads the BOC, assists the battery commander during displacement and stands duty in the FDC to enable 24-hour operations.
|
||
(2) Chief fire direction computer. The chief fire direction computer is the technical expert and trainer in the FDC. He ensures that all equipment is on hand and operational, supervises computation of all data, ensures that all appropriate records are maintained, and helps the FDO as needed. He ensures smooth peformance of the FDC in 24-hour operations and functions as the FDO in the FDO’s absence. The equivalent USMC billet description is operations chief.
|
||
(3) Fire direction computer. The fire direction computer operates the primary means of computing firing data. He determines and announces fire commands. He also records mission-related data and other information as directed. The equivalent USMC billet description is operations assistant. There is an operations assistant in both the FDC and the BOC.
|
||
(4) Fire direction specialist. There are two fire direction specialists per FDC to facilitate 24-hour operations. In a manual FDC, they serve alternately as horizontal control operator (HCO) and vertical control operator (VCO). The equivalent USMC billet description is fire control man. There are five fire control men in a USMC FDC and three more in a BOC to facilitate 24-hour operations. These fire control men may perform the duties of the HCO, VCO, radio operator, or driver as needed in either the FDC or BOC.
|
||
(a) The HCO constructs and maintains the primary firing chart and determines and announces chart data.
|
||
(b) The VCO constructs the secondary firing chart checks chart data, plots initial target location on the situation map, and determines and announces site.
|
||
(c) The radiotelephone operator (RATELO) or driver is normally the operator of the FDC vehicle. He maintains the vehicle and the FDC-associated generators. In a manual FDC, he may also act as the recorder.
|
||
2-3. Definitions a. Fire direction is the employment of firepower. The objectives of fire direction are to
|
||
provide continuous, accurate, and responsive fire support under all conditions. Flexibility must be maintained to engage all types of targets over wide frontages, to mass the fires of all available units quickly, and to engage a number and variety of targets simultaneously.
|
||
2-2
|
||
|
||
FM 6-40
|
||
b. The fire direction center is the element of the gunnery team with which the commander directs artillery firepower. The accuracy, flexibility, and speed in the execution of fire missions depend on the following:
|
||
Rapid and clear transmission of calls for free.
|
||
Rapid and accurate computations.
|
||
Rapid and clear transmission of fire commands.
|
||
Integration of automated and manual equipment into an efficient mutually supporting system.
|
||
Efficient use of communications equipment.
|
||
2-4. Relationship Between Battery or Platoon and Battalion FDC There are two modes of operation under which fire direction can be conducted: battalion
|
||
directed and autonomous.
|
||
a. Battalion Directed. In battalion-directed operations, calls for fire are transmitted from the observer to the battalion FDC. The battalion FDO is responsible for tactical fire direction and selects the unit(s) to fire. A fire order is transmitted to the firing units that are responsible for technical fire direction. The battalion FDC is responsible for transmitting all fire mission related messages (that is, message to observer, ready [if applicable], shot, splash, and rounds complete) to the observer. The firing units are responsible for transmitting all fire mission related messages to the battalion FDC.
|
||
b. Autonomous. In autonomous operations, calls for fire are transmitted from the observer to the firing unit FDC. The firing unit FDC is responsible for tactical and technical fire direction. The firing unit is responsible for transmitting the message to observer, ready (if applicable), shot, splash, and rounds complete to the observer. The battalion FDC and the battalion fire support officer (FSO) monitor the calls for fire. The equivalent USMC billet description for FSO is artillery liaison officer. The battalion FDC may take over control of the mission if the target warrants the massing of two or more batteries. The battalion FDC monitors the battery’s message to observer (MTO) to ensure that the battery has selected the appropriate ammunition and method of fire. The battalion FDC may change the battery’s plan of attack. If the target requires battalion fire, the firing unit FDO can request reinforcing fires from the battalion FDC.
|
||
2-5. Battalion FDC Personnel A battalion FDC is composed of a fire direction officer, a chief computer, an assistant
|
||
chief computer, three computers, a horizontal control operator, a vertical control operator, and a radiotelephone operator. USMC battalion FDCs are composed of a fire direction officer, operations chief, two operations assistants, and 10 fire control men to facilitate 24-hour operations. The operations chief is the equivalent of the chief computer, and the operations assistants are the equivalent of the assistant chief computer. The fire control men may perform the duties of computer, HCO, VCO, radio operator, or driver as needed.
|
||
2-3
|
||
|
||
FM 6-40
|
||
a. Fire Direction Officer’s Duties. The FDO’s duties areas follows:
|
||
(1) Is responsible for the overall organization and functioning of the battalion FDC.
|
||
(2) Coordinates with the battalion S3 to ensure that all information regarding the tactical situation, unit mission, ammunition status, and commander’s guidance on the method of engagement of targets and control of ammunition expenditures is known and ensures that all information is passed to battery FDOs.
|
||
(3) Ensures that all communications are properly established.
|
||
(4) Coordinates with the chief computer concerning data input, chart verification, transfer of registration corrections, average site or altitude, terrain gun position corrections (TGPCs) sectors, and any other special instructions.
|
||
(5) Inspects target locations and monitors messages to observer when a mission is received by a battery FDC and intercedes when necessary.
|
||
(6) Controls all battalion missions.
|
||
b. Chief Computer’s Duties. The chief computer’s duties areas follows: (1) Serves as the battalion FDO’s technical expert (the actual supervisor and/or
|
||
trainer of battalion FDC personnel) and assumes the duties of the battalion FDO in his absence.
|
||
(2) Ensures that all battalion FDC equipment is operational and emplaced correctly.
|
||
(3) Ensures coordination of all data throughout the battalion, to include current registration settings.
|
||
(4) Ensures that the HCO’s and VCO’s charts include all pertinent known data.
|
||
(5) Ensures that the situation map is properly posted, to include fire support coordinating measures and the current tactical situation.
|
||
c. Assistant Chief Computer’s Duties. The assistant chief computer’s duties are as follows:
|
||
(1) Monitors all operations performed by the HCO.
|
||
(2) Supervises maintenance and care of the generators.
|
||
(3) Assumes the duties of the chief computer when he is absent. d. Battery Computers’ Duties. The battery computers’ duties areas follows:
|
||
(1) Provide communications link with the battery FDCs.
|
||
(2) Monitor the appropriate fire direction net for their battery.
|
||
(3) Exchange information with the battery FDCs and pass battalion fire orders to the battery.
|
||
2-4
|
||
|
||
FM 6-40 (4) Record all data pertinent to fire missions that are sent to their battery. (5) Compute data for their battery when directed by the chief computer. (6) Use their fire direction net to communicate with the observer when battalion missions are conducted. (7) Assume the duties of the assistant chief computer when he is absent. e. Horizontal Control Operator’s Duties. The HCO’s duties areas follows: (1) Plots known data as directed by the assistant chief computer. (2) Determines chart data as appropriate. (3) Maintains equipment and associated generators. (4) Plots the initial target location when a mission is received. f. Vertical Control Operator’s Duties. The VCO’s duties areas follows: (1) Plots known data as directed by the assistant chief computer. (2) Plots the initial target location when a mission is received. (3) Checks chart data with the HCO. (4) Plots the initial target location on the situation map and determines and announces site for the appropriate battery. g. Radiotelephone Operator’s Duties. The RTO’s duties areas follows: (1) Establishes and maintains communications on the battalion command/fue direction (CF) net. (2) Determines and transmits the messages to observer when battalion missions are conducted on the battalion CF net. (3) Encodes and decodes messages, target lists, and fire plans. (4) Ensures proper authentication of appropriate messages and all fire missions.
|
||
2-5
|
||
|
||
FM 6-40
|
||
|
||
Chapter 3
|
||
BALLISTICS
|
||
|
||
Ballistics is the study of the firing, flight, and effect of ammunition. A fundamental understanding of ballistics is necessary to comprehend the factors that influence precision and accuracy and how to account for them in the determination of firing data. Gunnery is the practical application of ballistics so that the desired ejects are obtained by fire. To ensure
|
||
accurate predicted fire, we must strive to account for and minimize those factors that cause
|
||
round-to-round variations, particularly muzzle velocity. Ballistics can be broken down into four areas: interior, transitional, exterior, and terminal. Interior, transitional, and exterior ballistics
|
||
directly affect the accuracy of artillery fire and are discussed in this chapter. Terminal ballistics are discussed in Appendix B.
|
||
|
||
3-1. Interior Ballistics
|
||
Interior ballistics is the science that deals with the factors that affect the motion of the projectile within the tube. The total effect of all interior ballistic factors determines the velocity at which the projectile leaves the muzzle of the tube, which directly influences the range achieved by the projectile. This velocity, called muzzle velocity (MV), is expressed in meters per second (m/s). Actual measurements of the muzzle velocities of a sample of rounds corrected for the effects of nonstandard projectile weight and propellant temperature show the performance of a specific weapon for that projectile family-propellant type-charge combination. The resulting measurement(s) are compared to the standard muzzle velocity shown in the firing table(s). This comparison gives the variation from standard, called muzzle velocity variation (MVV), for that weapon and projectile family-propellant type-charge combination. Application of corrections to compensate for the effects of nonstandard muzzle velocity is an important element in computing accurate firing data. (For futher discussion of muzzle velocity, see Chapter 4.) The following equation for muzzle velocity is valid for our purposes:
|
||
MVV (m/s) = SHOOTING STRENGTH OF WPN + AMMUNITION EFFICIENCY
|
||
Tube wear, propellant efficiency, and projectile weight are the items normally accounted for in determination of a muzzle velocity. Other elements in the equation above generally have an effect not exceeding 1.5 m/s. As a matter of convenience, the other elements listed below are not individually measured, but their effects are realized to exist under the broader headings of shooting strength and ammunition efficiency.
|
||
|
||
SHOOTINGSTRENGTHOFWEAPONS 1. Tube wear 2. Manufacturer tolerances 3. Reaction to recoil
|
||
|
||
AMMUNITIONEFFICIENCY 1. Propellant efficiency 2. Projectile efficiency a. Projectile weight (fuzed) b. Construction of (1) Rotating band (2) Bourrelet (3) Obturating band
|
||
|
||
3-1
|
||
|
||
FM 6-40 a. Nature of Propellant and Projectile Movement. (1) A propellant is a low-order explosive that burns rather than detonates. In
|
||
artillery weapons using separate-loading ammunition, the propellant burns within a chamber formed by the obturator spindle assembly, powder chamber, rotating band, and base of the projectile. For cannons using semifixed ammunition, the chamber is formed by the shell casing and the base of the projectile. When the propellant is ignited by the primer, the burning propellant generates gases. When these gases develop enough pressure to overcome initial bore resistance, the projectile begins its forward motion.
|
||
(2) Several parts of the cannon tube affect interior ballistics. (See Figure 3-l.) (a) The caliber of a tube is the inside diameter of the tube as measured
|
||
between opposite lands. (b) The breech recess receives the breechblock. The breech permits loading
|
||
the howitzer from the rear. (c) The powder chamber receives the complete round of ammunition. It is the
|
||
portion of the tube between the gas check seat and the centering slope. The gas check seat is the tapered surface in the rear interior of the tube on weapons firing separate-loading ammunition. It seats the split rings of the obturating mechanism when they expand under pressure in firing. This expansion creates a metal-to-metal seal and prevents the escape of gases through the rear or the breech. Weapons firing semifixed ammunition do not have gas check seats since the expansion of the ease against the walls of the chamber provides a gas seal for-the breech.
|
||
3-2
|
||
|
||
FM 6-40 The centering slope is the tapered portion at or near the forward end of the chamber that causes the projectile to center itself in the bore during loading. (d) The forcing cone is the tapered portion near the rear of the bore that allows the rotating band to be gradually engaged by the rifling, thereby centering the projectile in the bore. (e) The bore is the rifled portion of the tube (lands and grooves). It extends from the forcing cone to the muzzle. The rifled portion of the tube imparts spin to the projectile increasing stability in flight. The grooves are the depressions in the rifling. The lands are the raised portions. These parts engrave the rotating band. All United States (US) howitzers have a right-hand twist in rifling. (f) The bore evacuator is located on enclosed, self-propelled howitzers with semiautomatic breech mechanisms. It prevents contamination of the crew compartment by removing propellant gases from the bore after firing. The bore evacuator forces the gases to flow outward through the bore from a series of valves enclosed on the tube. (g) The counterbore is the portion at the front of the bore from which the lands have been removed to relieve stress and prevents the tube from cracking. (h) The muzzle brake is located at the end of the tube on some howitzers. As the projectile leaves the muzzle, the high-velocity gases strike the baffles of the muzzle brake and are deflected rearward and sideways. When striking the baffles, the gases exert a forward force on the baffles that partially counteracts and reduces the force of recoil. (3) The projectile body has several components that affect ballistics. (See Figure 3-2.) Three of these affect interior ballistics--the bourrelet the rotating band and the obturating band.
|
||
3-3
|
||
|
||
FM 6-40
|
||
(a) The bourrelet is the widest part of the projectile and is located immediately to the rear of the ogive. The bourrelet centers the forward part of the projectile in the tube and bears on the lands of the tube. When the projectile is fired, only the bourrelet and rotating band bear on the lands of the tube.
|
||
(b) The rotating band is a band of soft metal (copper alloy) that is securely seated around the body of the projectile. It provides forward obturation (the forward gas-tight seal required to develop pressure inside the tube). The rotating band prevents the escape of gas pressure from around the projectile. When the weapon is fired, the rotating band contacts the lands and grooves and is pressed between them. As the projectile travels the length of the cannon tube, over the lands and grooves, spin is imparted. The rifling for the entire length of the tube must be smooth and free of burrs and scars. This permits uniform seating of the projectile and gives a more uniform muzzle velocity.
|
||
(c) The obturating band is a plastic band on certain projectiles. It provides forward obturation by preventing the escape of gas pressure from around the projectile.
|
||
(4) The sequence that occurs within the cannon tube is described below.
|
||
(a) The projectile is rammed into the cannon tube and rests on the bourrelet. The rotating band contacts the lands and grooves at the forcing cone.
|
||
(b) The propellant is inserted into the chamber.
|
||
(c) The propellant explosive train is initiated by the ignition of the primer. This causes the primer, consisting of hot gases and incandescent particles, to be injected into the igniter. The igniter burns and creates hot gases that flow between the propellant granules and ignite the granule surfaces; the igniter and propellant combustion products then act together, perpetuating the flame spread until all the propellant granules are ignited.
|
||
(d) The chamber is sealed, in the rear by the breech and obturator spindle group and forward by the projectile, so the gases and energy created by the primer, igniter, and propellant cannot escape. This results in a dramatic increase in the pressure and temperature within the chamber. The burning rate of the propellant is roughly proportional to the pressure, so the increase in pressure is accompanied by an increase in the rate at which further gas is produced.
|
||
(e) The rising pressure is moderated by the motion of the projectile along the barrel. The pressure at which this motion begins is the shot-start pressure. The projectile will then almost immediately encounter the rifling, and the projectile will slow or stop again until the pressure has increased enough to overcome the resistance in the bore. The rotating band and obturating band (if present) or the surface of the projectile itself, depending on design, will be engraved to the shape of the rifling. The resistance decreases, thereby allowing the rapidly increasing pressure to accelerate the projectile.
|
||
(f) As the projectile moves forward, it leaves behind an increasing volume to be filled by the high-pressure propellant gases. the propellant is still burning, producing highpressure gases so rapidly that the motion of the projectile cannot fully compensate. As a result, the pressure continues to rise until the peak pressure is reached. The peak pressure is attained when the projectile has traveled about one-tenth of the total length of a full length howitzer tube.
|
||
3-4
|
||
|
||
FM 6-40
|
||
(g) The rate at which extra space is being created behind the rapidly accelerating projectile then exceeds the rate at which high-pressure gas is being produced; thus the pressure begins to fall. The next stage is the all-burnt position at which the burning of the propellant is completed. However, there is still considerable pressure in the tube; therefore, for the remaining motion along the bore, the projectile continues to accelerate. As it approaches the muzzle, the propellant gases expand, the pressure falls, and so the acceleration lessens. At the moment the projectile leaves the howitzer, the pressure will have been reduced to about one sixth of the peak pressure. Only about one-third of the energy developed pushes the projectile. The other two-thirds is absorbed by the recoiling parts or it is lost because of heat and metal expansion.
|
||
(h) The flow of gases following the projectile out of the muzzle provides additional acceleration for a short distance (transitional ballistics), so that the full muzzle velocity is not reached until the projectile is some distance beyond the muzzle. The noise and shock of firing are caused by the jet action of the projectile as it escapes the flow of gases and encounters the atmosphere. After this, the projectile breaks away from the influence of the gun and begins independent flight.
|
||
(i) This entire sequence, from primer firing to muzzle exit, typically occurs within 15 milliseconds but perhaps as much as 25 milliseconds for a large artillery howitzer.
|
||
(5) Pressure travel curves are discussed below.
|
||
(a) Once the propellant ignites, gases are generated that develop enough pressure to overcome initial bore resistance, thereby moving the projectile. Two opposing forces act on a projectile within the howitzer. The first is a propelling force caused by the high-pressure propellant gases pushing on the base of the projectile. The second is a frictional force between the projectile and bore, which includes the high resistance during the engraving process, that opposes the motion of the projectile. The peak pressure, together with the travel of the projectile in the bore (pressure travel curve), determines the velocity at which the projectile leaves the tube.
|
||
(b) To analyze the desired development of pressure within the tube, we identify three types of pressure travel curves:
|
||
An elastic strength pressure travel curve represents the greatest interior pressure that the construction of the tube (thickness of the wall of the powder chamber, thickness of the tube, composition of the tube or chamber, and so on) will allow. It decreases as the projectile travels toward the muzzle because the thickness of the tube decreases.
|
||
A permissible pressure travel curve mirrors the elastic strength pressure travel curve and accounts for a certain factor of safety. It also decreases as the projectile travels through the tube because tube thickness decreases.
|
||
3-5
|
||
|
||
FM 6-40 An actual pressure travel curve represents the actual pressure developed during firing within the tube. Initially, pressure increases dramatically as the repelling charge explosive train initiated and the initial resistance of the rammed projectile is overcome. After that resistance is overcome, the actual pressure gradually decreases because of the concepts explained by Boyle’s Law. (Generally, as volume increases, pressure decreases.) The actual pressure should never exceed the permissible pressure.
|
||
Figure 3-3 depicts different actual pressure travel curves that are discussed below. Initial Excessive Pressure. This is undesirable pressure travel curve. It exceeds the elastic strength pressure and permissible pressure. Causes of this travel curve would be an obstruction in the tube, a dirty tube, an “extra” propellant placed in the chamber, an unfuzed projectile, or a cracked projectile. Delayed Excessive Pressure. This is an undesirable pressure travel curve. It exceeds the elastic strength pressure and remissible pressure. Causes that would result in this travel curve would be using wet powder or powder reversed. Desirable Pressure Travel Curve. This curve does not exceed permissible pressure. It develops peak pressure at about one-tenth the length of the tube.
|
||
3-6
|
||
|
||
FM 6-40
|
||
(6) The following general rules show how various factors tiect the velocity performance of a weapon projectile family-propellant type-charge combination
|
||
(a) An increase in the rate of propellant burning increases the resulting gas pressure developed within the chamber. An example of this is the performance of the multiperforated propellant grains used in white bag (WB) propellants. The result is that more gases are produced, gas pressure is increased, and the projectile develops a greater muzzle velocity. Damage to propellant grains, such as cracking and splitting from improper handling, also affect the rate of burn and thus the muzzle velocity.
|
||
(b) An increase in the size of the chamber without a corresponding increase in the amount of propellant decreases gas pressure; as a result, muzzle velocity will be less (Boyles Law).
|
||
(c) Gas escaping around the projectile decreases chamber pressure.
|
||
(d) An increase in bore resistance to projectile movement before peak pressure increases the pressure developed within the tube. Generally, this results in a dragging effect on the projectile, with a corresponding decrease in the developed muzzle velocity. Temporary variations in bore resistance can be caused by excessive deposits of residue within the cannon tube and on projectiles and by temperature differences between the inner and outer surfaces of the cannon tube.
|
||
b. Standard Muzzle Velocity.
|
||
(1) Applicable firing tables list the standard value of muzzle velocity for each charge. These standard values are based on an assumed set of standard conditions. These values are points of departure and not absolute standards. Essentially, we cannot assume that a given weapon projectile family-propellant type-charge combination when fired will produce the standard muzzle velocity.
|
||
(2) Velocities for each charge are indirectly established by the characteristics of the weapons. Cannons capable of high-angle fire (howitzers) require a greater choice in the number of charges than cannons capable of only low-angle fire (guns). This choice is necessary to achieve range overlap between charges in high-angle fire and the desired range-trajectory combination in low-angle fire. Other factors considered are the maximum range specified for the weapon, the maximum elevation and charge, and the maximum permissible pressure that the weapon can accommodate.
|
||
(3) Manufacturing specifications for ammunition include a requirement for velocity performance to meet certain tolerances. Ammunition lots are subjected to test firings, which include measuring the performance of a tested lot and comparing it to the performance of a control (reference) lot that is tested concurrently with the same weapon. An assumption built into the testing procedure is that both lots of ammunition will be influenced in the same manner by the performance of the tube. This assumption, although accurate in most instances, allows some error to be introduced in the assessment of the performance of the tested lot of propellant. In field conditions, variations in the performance of different projectile or propellant lots can be expected even though quality control has been exercised during manufacturing and testing of lots. In other words, although a howitzer develops a muzzle velocity that is 3 meters per second greater (or less) than standard with propellant lot G, it will not necessarily be the same with any other propellant lot. The optimum method for determining ammunition performance is to measure the
|
||
3-7
|
||
|
||
FM 6-40
|
||
performance of a particular projectile family-propellant lot-charge combination (calibration). However, predictions of the performance of a projectile family-propellant lot-charge group combination may be inferred with the understanding that they will not be as accurate as actual performance measurements.
|
||
c. Factors Causing Nonstandard Velocities. Nonstandard muzzle velocity is expressed as a variation (plus or minus so many meters per second) from the accepted standard. Round-to-round corrections for dispersion cannot be made. Each of the following factors that cause nonstandard conditions is treated as a single entity assuming no influence from related factors.
|
||
(1) Velocity trends. Not all rounds of a series fired from the same weapon and using the same ammunition lot will develop the same muzzle velocity. Under most conditions, the first few rounds follow a somewhat regular pattern rather than the random pattern associated with normal dispersion. This phenomenon is called velocity trends (or velocity dispersion), and the magnitude varies with the cannon, charge, and tube condition at the time each round is fired. Velocity trends cannot be accurately predicted; thus, any attempt to correct for the effects of velocity trends is impractical. Generally, the magnitude and duration of velocity trends can be minimized when firing is started with a tube that is clean and completely free of oil. (See Figure 3-4.)
|
||
(2) Ammunition lots. Each ammunition, projectile, and propellant lot has its own mean performance level in relation to a common weapon. Although the round-to-round variations within a given lot of the same ammunition (ammo) types are similar, the mean velocity developed by one lot may differ significantly in comparison to that of another lot. With separate-loading ammunition, both the projectile and propellant lots must be identified. Projectile lots allow for rapid identification of weight differences. Although other projectile factors affect achieved muzzle velocity (such as, diameter and hardness of rotating band), the cumulative effect of these elements generally does not exceed 1.5 rids. As a matter of convenience and speed, they are ignored in the computation of firing data.
|
||
(3) Tolerances in new weapons. All new cannons of a given caliber and model will not necessarily develop the same muzzle velocity. In a new tube, the mean factors affecting muzzle velocity are variations in the size of the powder chamber and the interior dimensions of the bore. If a battalion equipped with new cannons fired all of them with a common lot of ammunition a variation of 4 meters per second between the cannon developing the greatest muzzle velocity and the cannon developing the lowest muzzle velocity would not be unusual. Calibration of all cannons allows the firing unit to compensate for small variations in the manufacture of cannon tubes and the resulting variation in developed muzzle velocity. The MVV caused by inconsistencies in tube manufacture remains constant and is valid for the life of the tube.
|
||
(4) Tube wear. Continued firing of a cannon wears away portions of the bore by the actions of hot gases and chemicals and movement of the projectile within the tube. These erosive actions are more pronounced when higher charges are fired. The greater the tube wear, the more the muzzle velocity decreases. Normal wear can be minimized by careful selection of the charge and by proper cleaning of both the tube and the ammunition.
|
||
3-8
|
||
|
||
FM 6-40
|
||
(5) Nonuniform ramming. Weak ramming decreases the volume of the chamber and thereby theoretically increases the pressure imparted to the projectile. This occurs because the pressure of a gas varies inversely with volume. Therefore, only a partial gain in muzzle velocity might be achieved. Of greater note is the improper seating of the projectile within the tube. Improper seating can allow some of the expanding gases to escape around the rotating band of the projectile and thus result in decreased muzzle velocity. The combined effects of a smaller chamber and escaping gases are difficult to predict. Weak, nonuniform ramming results in an unnecessary and preventable increase in the size of the dispersion pattern. Hard, uniform ramming is desired for all rounds. When semifixed ammunition is fired, the principles of varying the size of the chamber and escape of gases still apply, particularly when ammunition is fired through worn tubes. When firing semifixed ammunition, rearward obturation is obtained by the expansion of the cartridge case against the walls of the powder chamber. Proper seating of the cartridge case is important in reducing the escape of gases.
|
||
(6) Rotating bands. The ideal rotating band permits proper seating of the projectile within the cannon tube. Proper seating of the projectile allows forward obturation, uniform pressure buildup, and initial resistance to projectile movement within the tube. The rotating band is also designed to provide a minimum drag effect on the projectile once the projectile overcomes the resistance to movement and starts to move. Dirt or burrs on the rotating band may cause improper seating. This increases tube wear and contributes to velocity dispersion. If excessively worn, the lands may not engage the rotating band well enough to impart the proper spin to the projectile. Insufficient spin reduces projectile stability in flight and can result in dangerously erratic round performance. When erratic rounds occur or excessive tube wear is noted, ordnance teams should be requested to determine the serviceability of the tube.
|
||
3-9
|
||
|
||
FM 6-40
|
||
(7) Propellant and projectile temperatures. Any combustible material burns more rapidly when heated before ignition. When a propellant burns more rapidly than would be expected under standard conditions, gases are produced more rapidly and the pressure imparted to the projectile is greater. As a result, the muzzle velocity will be greater than standard and the projectile will travel farther. Table E in the tabular firing tables lists the magnitude of change in muzzle velocity resulting from a propellant temperature that is greater or less than standard. Appropriate corrections can be extracted from that table; however, such corrections are valid only if they are determined relative to the true propellant temperature. The temperature of propellant in sealed containers remains fairly uniform though not necessarily at the standard propellant temperature (70 degrees Fahrenheit [F}). Once propellant has been unpacked, its temperature more rapidly approaches the air temperature. The time and type of exposure to the weather result in temperature variations from round to round and within the firing unit. It is currently impractical to measure propellant temperature and apply corrections for each round fired by each cannon. Positive action must be taken to maintain uniform projectile and propellant temperatures. Failure to do this results in erratic firing. The effect of an extreme change in projectile or propellant temperature can invalidate even the most recent corrections determined from a registration.
|
||
(a) Ready ammunition should be kept off the ground and protected from dirt, moisture, and direct rays of the sun. At least 6 inches of airspace should be between the ammunition and protective covering on the sides, 6 inches of dunnage should be on the bottom, and the roof should be 18 inches from the top of the stack. These precautions will allow propellant and projectile temperatures to approach the air temperature at a uniform rate throughout the firing unit.
|
||
(b) Propellant should be prepared in advance so that it is never necessary to fire freshly unpacked ammunition with ammunition that has been exposed to weather during a fire mission.
|
||
(c) Ammunition should be fired in the order in which it was unpacked.
|
||
(d) Propellant temperature should be determined from ready ammunition on a periodic basis, particularly if there has been a change in the air temperature.
|
||
(8) Moisture content of propellant. Changes in the moisture content of propellant are caused by improper protection from the elements or improper handling of the propellant. These changes can affect muzzle velocity. Since the moisture content cannot be measured or corrected for, the propellant must be provided maximum protection from the elements and improper handling.
|
||
(9) Position of propellant in the chamber. In fixed and semifixed ammunition the propellant has a relatively fixed position with respect to the chamber, which is formed by the cartridge case. In separate-loading ammunition, however, the rate at which the propellant burns and the developed muzzle velocity depends on how the cannoneer inserts the charge. To ensure proper ignition of the propellant he must insert the charge so that the base of the propellant bag is flush against the obturator spindle when the breech is closed. The cannoneer ensures this by placing the propellant flush against the Swiss groove (the cutaway portion in the powder chamber). The farther forward the charge is inserted, the slower the burning rate and the lower the subsequent muzzle velocity. An increase in the diameter of the propellant charge can also cause an increase in muzzle velocity. Loose tie straps or wrappings have the effect of increasing the diameter of the propellant charge. Propellant charge wrappings should always be checked for tightness, even when the full propellant charge is used.
|
||
3-10
|
||
|
||
FM 6-40
|
||
(10) Weight of projectile. The weights of like projectiles vary within certain zones (normally termed square weight). The appropriate weight zone is stenciled on the projectile (in terms of so many squares). Some projectiles are marked with the weight in pounds. In general terms, a heavier-than-standard projectile normally experiences a decrease in muzzle velocity. This is because more of the force generated by the gases is used to overcome the initial resistance to movement. A lighter-than-standard projectile generally experiences an increase in velocity.
|
||
NOTE: Copperhead projectiles are not marked with weight in pounds. The precision manufacturing process used guarantees a weight of 137.6 pounds.
|
||
(11) Coppering. When the projectile velocity within the bore is great, sufficient friction and heat are developed to remove the outer surface of the rotating band. Material left is a thin film of copper within the bore and is known as coppering. This phenomenon occurs in weapons that develop a high muzzle velocity and when high charges are fired. The amount of copper deposited varies with velocity. Firing higher charges increases the amount of copper deposited on the bore surfaces, whereas firing lower charges reduces the effects of coppering. Slight coppering resulting from firing a small sample of rounds at higher charges tends to increase muzzle velocity. Erratic velocity performance is a result of excessive coppering whereby the resistance of the bore to projectile movement is affected. Excessive coppering must be removed by ordnance personnel.
|
||
(12) Propellant residue. Residue from burned propellant and certain chemical agents mixed with the expanding gases are deposited on the bore surface in a manner similar to coppering. Unless the tube is properly cleaned and cared for, this residue will accelerate tube wear by causing pitting and augmenting the abrasive action of the projectile.
|
||
(13) Tube conditioning. The temperature of the tube has a direct bearing on the developed muzzle velocity. A cold tube offers a different resistance to projectile movement and is less susceptible to coppering, even at high velocities. In general, a cold tube yields more range dispersion; a hot tube, less range dispersion.
|
||
(14) Additional effects in interior ballistics. The additional effects include tube memory and tube jump.
|
||
(a) Tube memory is a physical phenomenon of the cannon tube tending to react to the firing stress in the same manner for each round, even after changing charges. It seems to “remember” the muzzle velocity of the last charge fired. For example, if a fire mission with charge 6 M4A2 is followed by a fire mission with charge 4 M4A2, the muzzle velocity of the first round of charge 4 may be unpredictably higher. The inverse is also true.
|
||
(b) Tube jump occurs as the projectile tries to maintain a straight line when exiting the muzzle. This phenomenon causes the tube to jump up when fired and may cause tube displacement.
|
||
3-11
|
||
|
||
FM 6-40
|
||
|
||
3-2. Transitional Ballistics
|
||
Sometimes referred to as intermediate ballistics, this is the study of the transition from interior to exterior ballistics. Transitional ballistics is a complex science that involves a number of variables that are not fully understood; therefore, it is not an exact science. What is understood is that when the projectile leaves the muzzle, it receives a slight increase in MV from the escaping gases. Immediately after that, its MV begins to decrease because of drag.
|
||
|
||
3-3. Exterior Ballistics
|
||
|
||
Exterior ballistics is the science that deals with the factors affecting the motion of a projectile after it leaves the muzzle of a piece. At that instant, the total effects of interior ballistics in terms of developed muzzle velocity and spin have been imparted to the projectile. Were it not for gravity and the effects of the atmosphere, the projectile would continue indefinitely at a constant velocity along the infinite extension of the cannon tube. The discussion
|
||
of exterior ballistics in the following paragraphs addresses elements of the trajectory, the trajectory in a vacuum, the trajectory within a standard atmosphere, and the factors that affect the
|
||
flight of the projectile.
|
||
|
||
a. Trajectory Elements. The trajectory is the path traced by the center of gravity of the projectile from the origin to the level point. The elements of a trajectory are classified into three groups--intrinsic, initial, and terminal elements.
|
||
|
||
(1) Intrinsic elements. Elements that are characteristic of any trajectory, by definition, are intrinsic elements. (See Figure 3-5.)
|
||
|
||
(a) The origin is the location of the center of gravity of the projectile when it leaves the muzzle. It also denotes the center of the muzzle when the piece has been laid.
|
||
|
||
(b) The ascending branch is the part of the trajectory that is traced as the projectile rises from the origin.
|
||
|
||
(c) The summit is the highest point of the trajectory.
|
||
|
||
(d) The maximum ordinate is the difference in altitude (alt) between the origin and the summit.
|
||
|
||
(e) The descending branch is the part of the trajectory that is traced as the projectile is falling.
|
||
|
||
(f) The level point is the point on the descending branch that is the same altitude as the origin.
|
||
|
||
point.
|
||
|
||
(g) The base of the trajectory is the straight line from the origin to the level
|
||
|
||
3-12
|
||
|
||
FM 6-40
|
||
|
||
(2) Initial elements. Elements that are characteristic at the origin of the trajectory are initial elements. (See Figure 3-6.)
|
||
|
||
extended.
|
||
|
||
(a) When the piece is laid, the line of elevation is the axis of the tube
|
||
|
||
(b) The line of departure is a line tangent to the trajectory at the instant the projectile leaves the tube.
|
||
|
||
(c) Jump is the displacement of the line of departure from the line of elevation that exists at the instant the projectile leaves the tube.
|
||
|
||
(d) The angle of site is the smaller angle in a vertical plane from the base of the trajectory to a straight line joining the origin and the target. Vertical interval is the difference in altitude between the target and the origin.
|
||
|
||
(e) The complementary angle of site is an angle that is algebraically added to the angle of site to compensate for the nonrigidity of the trajectory.
|
||
|
||
(f) Site is the algebraic sum of the angle of site and the complementary angle of site. Site is computed to compensate for situations in which the target is not at the same
|
||
altitude as the battery.
|
||
|
||
(g) Complementary range is the number of meters (range correction) equivalent to the number of mils of complementary angle of site.
|
||
|
||
(h) The angle of elevation is the vertical angle between the base of the trajectory and the axis of the bore required for a projectile to achieve a prescribed range under standard conditions.
|
||
|
||
(i) The quadrant elevation is the angle at the origin measured from the base of the trajectory to the line of elevation. It is the algebraic sum of site and the angle of elevation.
|
||
|
||
3-13
|
||
|
||
FM 6-40
|
||
(3) Terminal elements. Elements that are characteristic at the point of impact are terminal elements. (See Figure 3-7.)
|
||
(a) The point of impact is the point at which the projectile strikes the target area. (The point of burst is the point at which the projectile bursts in the air.)
|
||
(b) The line of fall is the line tangent to the trajectory at the level point. (c) The angle of fall is the vertical angle at the level point between the line of fall and the base of the trajectory. (d) The line of impact is a line tangent to the trajectory at the point of impact. (e) The angle of impact is the acute angle at the point of impact between the line of impact and a plane tangent to the surface at the point of impact. This term should not be confused with angle of fall.
|
||
3-14
|
||
|
||
FM 6-40
|
||
b. Trajectory in a Vacuum.
|
||
(1) If a round were fired in a vacuum, gravity would cause the projectile to return to the surface of the earth. The path or trajectory of the projectile would be simple to trace. All projectiles, regardless of size, shape, or weight, would follow paths of the same shape and would achieve the same range for a given muzzle velocity and quadrant elevation.
|
||
(2) The factors used to determine the data needed to construct a firing table for firing in a vacuum are the angle of departure, muzzle velocity, and acceleration caused by the force of gravity. The initial velocity imparted to a round has two components--horizontal velocity and vertical velocity. The relative magnitudes of horizontal and vertical components vary with the angle of elevation. For example, if the elevation were zero, the initial velocity imparted to the round would be horizontal in nature and there would be no vertical component. If, on the other hand, the elevation were 1,600 mils (disregarding the effects of rotation of the earth), the initial velocity would be vertical and there would be no horizontal component.
|
||
(3) Gravity causes a projectile in flight to fall to the earth. Because of gravity, the height of the projectile at any instant is less than it would be if no such force were acting on it. In a vacuum, the vertical velocity would decrease from the initial velocity to zero on the ascending branch of the trajectory and increase from zero to the initial velocity on the descending branch, Zero vertical velocity would occur at the summit of the trajectory. For every vertical velocity value on the upward leg of the ascending branch there is an equal vertical velocity value downward on the descending branch. Since there would be no resistance to the forward motion of the projectile in a vacuum, the horizontal velocity component would be a constant. The acceleration caused by the force of gravity (9.81 m/s) affects only the vertical velocity.
|
||
c. Trajectory in a Standard Atmosphere.
|
||
(1) The resistance of the air to projectile movement depends on the air movement, density, and temperature. As a point of departure for computing firing tables, assumed conditions of air density and air temperature with no wind are used. The air structure is called the standard atmosphere.
|
||
(2) The most apparent difference between the trajectory in a vacuum and the trajectory in the standard atmosphere is a net reduction in the range achieved by the projectile. A comparison of the flight of the projectile in a vacuum and in the standard atmosphere is shown in Figure 3-8.
|
||
3-15
|
||
|
||
FM 6-40
|
||
(3) The difference in range is due to the horizontal velocity component in the standard atmosphere no longer being a constant value. The horizontal velocity component is continually decreased by the retarding effect of the air. The vertical velocity component is also afected by air resistance. The trajectory in the standard atmosphere has the following characteristic differences from the trajectory in a vacuum:
|
||
(a) The velocity at the level point is less than the velocity at the origin.
|
||
(b) The mean horizontal velocity of the projectile beyond the summit is less than the mean velocity before the projectile reaches the summit; therefore, the projectile travels a shorter horizontal distance. Hence, the descending branch is shorter than the ascending branch. The angle of fall is greater than the angle of elevation.
|
||
(c) The spin (rotational motion) initially imparted to the projectile causes it to respond differently in the standard atmosphere because of air resistance. A trajectory in the standard atmosphere, compared to a trajectory in a vacuum, will be shorter and lower at any specific point along the trajectory for the following reasons:
|
||
Horizontal velocity is not a constant value; it decreases with each succeeding time interval.
|
||
Vertical velocity is affected by both gravity and the effects of the atmosphere on the projectile.
|
||
The summit in a vacuum is midway between the origin and the level point; in the standard atmosphere, it is actually nearer the level point.
|
||
The angle of fall in a vacuum is equal to the angle of elevation; in the standard atmosphere, it is greater.
|
||
d. Relation of Air Resistance and Projectile Efficiency to Standard Range.
|
||
(1) This paragraph concerns only those factors that establish the relationship between the standard range, elevation, and achieved range.
|
||
(a) The standard (chart) range is the range opposite a given elevation in the firing tables. It is assumed to have been measured along the surface of a sphere concentric with the earth and passing through the muzzle of a weapon. For all practical purposes, standard range is the horizontal distance from the origin of the trajectory to the level point.
|
||
(b) The achieved range is the range attained as a result of firing the cannon at a particular elevation. If actual firing conditions duplicate the ballistic properties and met conditions on which the firing tables are based, then the achieved range and the standard range will be equal.
|
||
(c) The corrected range is the range corresponding to the elevation that must be fired to reach the target.
|
||
(2) Air resistance affects the flight of the projectile both in range and in direction. The component of air resistance in the direction opposite that of the forward motion of the projectile is called drag. Because of drag, both the horizontal and vertical components of velocity are less at any given time along the trajectory than they would be if drag was zero (as it would be
|
||
3-16
|
||
|
||
FM 6-40
|
||
in a vacuum). This decrease in velocity varies directly in magnitude with drag and inversely with the mass of the projectile. Several factors considered in the computation of drag areas follows:
|
||
(a) Air density. The drag of a given projectile is proportional to the density of the air through which it passes. For example, an increase in air density by a given percentage increases drag by the same percentage. Since the air density at a specific place, time, and altitude varies widely, the standard trajectories reflected in the firing tables were computed with a fixed relationship between air density and altitude.
|
||
(b) Velocity. The faster a projectile moves, the more the air resists its motion. Examination of a set of firing tables reveals that given a constant elevation, the effect of a 1 percent change in air density (and corresponding 1 percent increase in drag) increases with an increase in charge (with the greater muzzle velocity). The drag is approximately proportional to the square of the velocity except when velocity approaches the speed of sound. At the speed of sound, drag increases more rapidly because of the increase in pressure behind the sound wave.
|
||
(c) Projectile diameter. Two projectiles of identical shape but of different size will not experience the same drag. For example, a large projectile will offer a larger area for the air to act upon; thus, its drag will be increased by this factor. The drag of projectiles of the same shape is assumed to be proportional to the square of the projectile diameter.
|
||
(d) Ballistic coefficient. The ballistic coefficient of a projectile is a measure of its relative efficiency in overcoming air resistance. An increase in the ballistic coefficient reduces the effect of drag and consequently increases range. The reverse is true for a decrease in the ballistic coefficient. The ballistic coefficient can be increased by increasing the ratio of the weight of the projectile to the square of its diameter. It can also be increased by improving the shape of the projectile.
|
||
(e) Drag coefficient. The drag coefficient combines several ballistic properties of typical projectiles. These properties include yaw (the angle between the direction of motion and the axis of the projectile) and the ratio of the velocity of the projectile to the speed of sound. Drag coefficients, which have been computed for many projectile types, simplify the work of ballisticians. When a projectile varies slightly in shape from one of the typical projectile types, the drag coefficient can be determined by computing a form factor for the projectile and multiplying the drag coefficient of a typical projectile type by the form factor.
|
||
e. Deviations From Standard Conditions. Firing tables are based on actual firings of a piece and its ammunition correlated to a set of standard conditions. Actual firing conditions, however, will never equate to standard conditions. These deviations from standard conditions, if not corrected for when computing firing data will cause the projectile to impact at a point other than the desired location. Corrections for nonstandard conditions are made to improve accuracy.
|
||
(1) Range effects. Some of the deviations from standard conditions affecting range are:
|
||
Muzzle velocity.
|
||
Projectile weight.
|
||
3-17
|
||
|
||
FM 6-40
|
||
Range wind.
|
||
Air temperature.
|
||
Air density.
|
||
Rotation of the earth.
|
||
(2) Deflection effects. Some of the deviations from the standard conditions affecting deflection are:
|
||
Drift.
|
||
Crosswind.
|
||
Rotation of the earth.
|
||
3-4. Dispersion and Probability If a number of rounds of ammunition of the same caliber, lot, and charge are fired from
|
||
the same position with identical settings used for deflection and quadrant elevation, the rounds will not all impact on a single point but will fall in a scattered pattern. In discussions of artillery fire, this phenomenon is called dispersion, and the array of bursts on the ground is called the dispersion pattern.
|
||
3-5. Causes of Dispersion a. The points of impact of the projectiles will be scattered both in deflection and in
|
||
range. Dispersion is caused by inherent (systemic) errors. It should never be confused with round-to-round variations caused by either human or constant errors. Human errors can be minimized through training and supervision. Corrections to compensate for the effects of constant errors can be determined from the TFT. Inherent errors are beyond control or are impractical to measure. Examples of inherent errors are as follows:
|
||
(1) Conditions in the bore. The muzzle velocity achieved by a given projectile is affected by the following:
|
||
Minor variations in the weight of the projectile, form of the rotating band, and moisture content and temperature of the propellant grains. Differences in the rate of ignition of the propellant.
|
||
Variations in the arrangement of the propellant grains. Differences in the rate of ignition of the propellant. Variations in the ramming of the projectile.
|
||
Variations in the temperature of the bore from round to round.
|
||
For example, variations in the bourrelet and rotating band may cause inaccurate centering of the projectile, which can result in a loss in achieved range because of instability in flight.
|
||
3-18
|
||
|
||
FM 6-40 (2) Conditions in the carriage. Deflection and elevation are affected by the following:
|
||
Play (looseness) in the mechanisms of the carriage. Physical limitations of precision in setting values of deflection and quadrant elevation on the respective scales. Nonuniform reactions to firing stress. (3) Conditions during flight. The flight of the projectile may be affected by the difference in air resistance created by variations in the weight, achieved muzzle velocity, and projectile. Also, the projectile may be affected by minor variations in wind, air density or air pressure, and air temperature from round to round. b. The distribution of bursts (dispersion pattern) in a given sample of rounds is roughly elliptical (Figure 3-9) in relation to the line of fire. c. A rectangle constructed around the dispersion area (excluding any erratic rounds) is called the dispersion rectangle, or 100 percent rectangle. (See Figure 3-10.) 3-6. Mean Point of Impact For any large number of rounds fired, the average (or mean) location of impact can be determined by drawing a diagram of the pattern of bursts as they appear on the ground. A line drawn perpendicular to the line of fire can be used to divide the sample rounds into two equal groups. Therefore, half of the rounds will be over this line when considered in relation to the weapon. The other half of the rounds will be short of this line in relation to the weapon. This dividing line represents the mean range of the sample and is called the mean range line. A second line can be drawn parallel to the line of fire, again dividing the sample into two equal groups. Half of the rounds will be to the right of this line, and half will be to the left. This line represents the mean deflection of the sample and is called the mean deflection line. (See Figure 3-9.) The intersection of the two lines is the mean point of impact (MPI). (See Figure 3-10.) -
|
||
3-19
|
||
|
||
FM 6-40
|
||
3-7. Probable Error Probable error is nothing more than an error that is exceeded as often as it is not exceeded. For
|
||
example, in Figure 3-11, consider only those rounds that have impacted over the mean range line (line AB). These rounds all manifest errors in range, since they all impacted over the mean range line. Some of the rounds are more in error than others. At a point beyond the MPI, a second line can be drawn perpendicular to the line of fire to divide the "ovens" into two equal groups (line CD, Figure 3-11). When the distance from the MPI to line CD is used as a measure of probable error, it is obvious that half of the overs show greater magnitude of error than the other half. This distance is one probable error in range. The range probability curve expresses the following:
|
||
a. In a large number of samples, errors in excess and errors in deficiency are equally frequent (probable) as shown by the symmetry of the curve.
|
||
b. The errors are not uniformly distributed. Small errors occur more frequently than large errors as shown by the greater number of occurrences near the mean point of impact. 3-8. Dispersion Zones
|
||
If the dispersion rectangle is divided evenly into eight zones in range with the value for 1 probable error in range (PER) used as the unit of measure, the percentage of rounds impacting within each zone is as indicated in Figure 3-12. The percentage of rounds impacting within each zone has been determined through experimentation. By definition of probable error, 50 percent of all rounds will impact within 1 probable error in range or deflection of the mean point of impact (25 percent over and 25 percent short or 25 percent left and 25 percent right).
|
||
3-20
|
||
|
||
FM 6-40 3-9. Range Probable Error
|
||
The values for range probable error at various ranges are given in Table G of the tabular firing tables (TFT). These values may be used as an index of the precision of the piece at a particular charge and range. The values for range probable error are listed in meters. Firing Table (FT) values have been determined on the basis of actual firing of ammunition under controlled conditions. For example, FT 155-AM-2 shows that the value of range probable error for charge 5 green bag (GB) at a range of 6,000 meters is 15 meters. On the basis of the 100 percent rectangle, 50 percent of the rounds will impact within 15 meters (over and short) of the mean range line, 82 percent will impact within 30 meters (over and short), 96 percent will impact within 45-meters (over and short), and 100 percent will impact within 60 meters.
|
||
3-21
|
||
|
||
FM 6-40
|
||
3-10. Fork
|
||
The term fork is used to express the change in elevation (in mils) needed to move the mean point of impact 4 probable errors in range. The values of fork are listed in Table F of the firing tables. For example, FT 155-AM-2 shows that the value of fork for a howitzer firing charge 5GB at a range of 6,000 meters is 4 mils. On the basis of the value for probable error in range (paragraph 3-9), adding 4 mils to the quadrant elevation would cause the MPI to move 60 meters. Fork is used in the computation of safety data (executive officer’s minimum QE).
|
||
3-11. Deflection Probable Error
|
||
The values for probable error in deflection (PED) are listed in Table G of the firing tables. For artillery cannons, the deflection probable error is considerably smaller than the range probable error. Values for PED are listed in meters. With the same parameters as those used in paragraph 3-9, the deflection probable error is 4 meters. Therefore, 50 percent of the rounds will impact within 4 meters of the mean deflection line (left and right); 82 percent, within 8 meters (left and right); 96 percent, within 12 meters (left and right); and 100 percent, within 16 meters.
|
||
3-12. Time-To-Burst Probable Error
|
||
The values of time-to-burst probable error (PETB) (Figure 3-13) are listed in Table G of the firing tables. Each of these values is the weighted average of the precision of a time fuze timing mechanism in relation to the actual time of flight of the projectile. For example, if a 155-mm howitzer fires charge 5GB at a range of 6,000 meters, the value for probable error in time to burst is 0.11 second. As in any other dispersion pattern, 50 percent of the rounds will function within 0.11 second; 82 percent, within 0.22 second; 96 percent, within 0.33 second; and 100 percent within 0.44 second of the mean fuze setting.
|
||
3-13. Height-Of-Burst Probable Error
|
||
With the projectile fuzed to burst in the air, the height-of-burst probable error (PEHB) (Figure 3-13) is the vertical component of 1 time-to-burst probable error. The height-of-burst probable error reflects the combined effects of dispersion caused by variations in the functioning of the time fuze and dispersion caused by the conditions described in paragraph 3-5(a). The values listed (in meters) follow the same pattern of distribution as for those discussed for range dispersion. These values are listed in Table G of the firing tables.
|
||
3-14. Range-To-Burst Probable Error
|
||
Range-to-burst probable error (PERB) (Figure 3-13) is the horizontal component of 1 time-to-burst probable error. When this value is added to or subtracted from the expected range to burst, it will produce an interval along the line of fire that should contain 50 percent of the rounds fired. These values are listed in Table G of the firing tables.
|
||
3-22
|
||
|