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AD/A-002 569

AIRCRAFT GUN SYSTEMS EFFECTIVENESS ANALYSIS

Harry P. Jones

Rock Island Arsenal Roc k I sland, 11 linois

September 1973

DISTRIBUTED BY:

\M\ National Technical Information Service U. S. DEPARTMENT OF COMMERCE

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UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PA« (Whrr, n«f» Fnlrfil)

REPORT DOCUMENTATION PAGE I REPORT NUMBER

R^RR.T-4-45-73

2. COVT ACCESSION NO

4 TITLE fand Subl/Md)

AIRCRAFT GUN SYSTEMS EFFECTIVENESS ANALYSIS (U)

7 *UTHOR(«J

Harry P. Jones

9 PERFORMING ORGANIJATION NAM^ AND ADDRESS

Research Directorate GEN Thomas J. Rodman Laboratory Rock Island Arsenal Rock Island IL 61201

II CONTROLLING OFFICE NAME AND ADDRESS

Research Directorate GEN Thomas J. Rodman Laboratory Rock Island Arsenal Rock Island, IL 61201

M MONITORING AGENCY NAME » ADDRESSfi/ tllllerent trnm ConlroMIn« Olluel

KKAR INSTRUCTIONS BEFORE COMl'l.I.TlN'i FORM

3. RECIPIENT'S CA f ALOG NUMBER

QOrfi '//+ Si» 9 5 TYPE OF REPORT » PfRnn ro/ERFD

Final Report July 1972 - September 1973

6 PERFORMING ORG. REPORT NUMHEH

R.RR.T-4-45-73 CONTRACT OR GRANT NUMBf R»,

10 PROGRAM FLEMFNT PROJECT TA', AREA » WORK UNIT NyMBER'j

DA1F62201D02E

12 REPORT DATE

September 1973 11 NUMBER OF PAGE'j

15 SECL 1ITY CLASS "( f/n» irt'""

UNCLASSIFIED ISn DFCL ASSIFICATION DOWN OR * Dl N .

SCHEDULE

16 DISTRIBUTION STATEMENT (ol thin Htpatl)

Approved for public release, distribution unlimited.

18 SUPPLEMEN TARY NOTES

IMC i' I ■' i;

19 KEY AOSDS -ifMiue rjn reverse si Jo (/ necesiflrv and tdentlly bv h/n.fr r

1. Lethality 2. Effectiveness 3. Aircraft 4. Gun 5. Model 6. Computer

20. ABSTRACT fContlniim on revers« aid» If necBanary and Idenltfy hv block numbar.

The effectiveness of conceptual helicopter gun systems ranging fron 30 milli- meters to 105 millimeters is compared for both armored and personnel taraets. Projectiles considered are shaped charge and high explosive fraamentation. The scenario considered was a helicopter hover at low altitude with the tarnet fron 500 to 4000 meters away. At the longer range, the effectiveness of gun systems is shown to be low even when used with very accurate systems. The relative lethality is such that approximately eight rounds of 30nni are equivalent to one IGSmm round. This relative comparison is dependent on

OD l JAN 73 1473 EDITION OF I MOV 6S IS OBSOLETE

1 UNCLASSIFIED

SECURITY CLASSIFICATION OF THIS PA&r fWhen Hun, I ,

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UMiasSIEIED SECURITY CLASSIFICATION OF THIS PAa£(Whm Dmlm Bnlind)

specific gun system parameters and is shown to be very sensitive to projectile impact zone dimensions for personnel targets. (U) Jones, Harry P.

ii UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGEfHTian Da» Fnlemd)

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DISCLAIMER

The findings In this report are not to be construed as an official Department of the Army position, unless so designated by other authorized documents.

DISPOSITION INSTRUCTIONS

Destroy this report when it Is no longer needed,

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TABLE OF CONTENTS

PAGE

INTRODUCTION 1

PKEVAL 2

ARMORED TARGET ANALYSIS 2

PERSONNEL TARGET ANALYSIS A

CONCLUSIONS 8

APPENDIX A 10

APPENDIX B 11

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FORWARD

The guidance given by Mr. Thomas J. Redling of Rock Island Arsenal is gratefully acknowledged.

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INTRÜDUCTION

An analysis of conceptual gun systems for u^ ->n Army heli- copters was conducted. The objective of this «n*Lysis was to compare the relative effectiveness of gun systems in tha jOram to 105mm range, and to obtain an estimate of the actual lethality of these systems.

Tnis analysis was limited to the following projectiles:

(a) 30 millimeter (similar to Army AMC 30mra),

(b) 75 millimeter,

(c) 105 millimeter (similar to Ml 105).

The projectiles considered were shaped charge and high explosive (HE) fragmentation. For the larger gun sizes a closed breech weapon with a recoil cancellation (impulse generator) or a Davis type gun were envisioned. A hit probability (P^/kill probability (P^) model (PKEVAL) was used to simulate the firing of the projectiles on a target by an aircraft.

The scenarios considered were liitited to a 50 foot hover altitude at ranges of 500, 1,000, 2,000, anc 4,000 meters.

.

Hypothetical launch angle errors of 2, 5, 10, and 15 milli- radians bias and dispersion (one standard deviation) in elevation and azimuth were used. The geometry of the delivery error situations used is presented in Figure 1.

WHERE:

(0.0) - AIM POINT

E - FIXED BIAS,

e.g., aiming error

o ■ STANDARD DEVIATION

OF RANDOM ERROR,

e.g., dispersion

(DEFLECTION)

Figure 1 Geometry of Delivery Error Situations (For Figures 2,3, and 4, E Is equated to a; this condition maximizes P.). n

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Both armored and personnel targets were considered. Data (Ph and Pk) pertaining to armored target vulnerability was obtained from the Joint Munitions Effectiveness Manual (JMEM)1. Three models were used in addition to PKEVAL for personnel target analysis.

It is interesting to note that the 30inm round produces more personnel casualties than the 75nim or 105mm round per pound of ammunition. This weight advantage of the 30mm HE rounds cannot be expected to hold for materiel targets such as trucks.

PKEVAL

This Ph^ model was used to simulate the firing of projectiles on a target by an aircraft. The input parameters to this model are:

(a) Weapon aiming and dispersion errors,

(b) Aircraft flight path (2 - dimensional),

(c) Weapon firing rate, burst length, time between bursts,

(d) Projectile ballistic data,

(e) Target vulnerability parameters (for point targets).

Output parameters from this model are:

(a) Probability of killing the target during an engagement,

(b) Projectile terminal velocity and impact angle,

(c) Projectile impact zone on the ground.

The last two sets of output parameters are used for subsequent analysis of area targets. See Appendix A for projectile data.

ARMORED TARGET ANALYSIS

The data for air-to-surface armored target vulnerability was obtained from the JMEM. The kill mechanism considered was that due to a shaped charge projectile. Data for kill categories M, P, or K were used in this analysis. If the target dimensions are small relative to the impact zone (so that the P^ can be considered uniform over the target area), then one can multiply the results of this analysis by relative vulnerable areas to estimate the vulnerability

'"Joint Munitions Effectiveness Manual. Air-to-Surface. Target Vulnerability". SECRET. (USAF) TH 61A1-1-1-1. (ARMY) FM 101-50-1. (USMC) FMFM 5-2, (NAVY) NAVAIR 00-130-AS-l, Fig 3C-^5, pg 3C-26

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of other armored targets. The target was represented by an effective vulnerable area that is a function of projectile diameter and impact angle. Data is also available for presentation of P. given a hit, but this method requires a calculation of actual target presented area. The agreement of these two methods was satisfactory for the trial cases.

Figure 2 shows the number of rounds required to achieve a 50 percent probability of killing the armored target. Since the scale for the number of rounds is logarithmic, the number of rounds (fig '^3) i: printed by the points for convenience in viewing. The ratios of the number of rounds, of the different projectiles, required to achieve a 50 percent P^ at all ranges are fairly constant. For example, the number of 30rara rounds to equal one 105mm round is approximately eight. The number of 30mm rounds to equal one 75mm round is approxi- mately five. The number of rounds required increases expone itially with increasing range to target.

<

10000

1000

8

-100

!0

1000 2000 3000 4000

RANGE (METERS)

Figure 2. Number of rounds to defeat armored target with 2 mR aiming and dispersion error in range and deflection

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Figure 3 shows the effect of changing launch error from 2 to 5 milliradians bias and dispersion in each axis. The number of rounds required in each case is increased by a factor of approximately six.

10000

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1000-

100

1Ü

1000 2000

RANGE (METERS)

3000 4000

Figure 3. number of rounds to defeat armored target with 5 mR aiming and dispersion error in raryte and deflection.

FERSÜMEL TARGET ANALYSIS

Three models were used for the personnel target analysis in addition to the PKEVAL Model. These models are:

(a) A Computational Method for Predicting from Design Para- meters the Efftctive Lethal Area of Naturally Fragmenting Weapons2. This model furnishes projectile fragmentation data (size, number, velocity, angular zone) given the basic HE projectile dimensions, material, and filler.

Z"A Computational Method for Predicting from Design Parameters the Effective Lethal Area of Naturally Fragmenting Weapons," Unclassified, Research & Development Department, Naval Ordnance Station, Indian Head^

MD, AD 857 530, Nos - IHTR-295.

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(b) Computer Program for General Full Spray Personnel Mean Area of Effectiveness Computations3. This model gives a matrix of Pk or incapacitation on the ground plane. The required inputs are fragmentation data, target vulnerability data, pro- jectile impact angle, and projectile terminal velocity.

(c) General Purpose Matrix Program1*. This program uses impact zone and kill matrix data from other models to summarize the effect of firing several rounds.

The personnel casualty criterion data used in this analysis was obtained froto the JMEM for air-to-surface target vulnerability. Data1 contained in the third row of the clothed soldier column (a, b, n) was used.

Figure 4 shows the number of cajiualties inflicted per 10,000 personnel in a 300 by 300 foot target area when using high explosive ammunition at various ranges. The gun launch errors for this case are 5 milliradians of bias and dispersion in both range and deflection. Note that the 105mm air burst produces approximately three times as many casualties as the ground burst. The curves are fairly flat over ranges of 1000 meters to U000 meters, and actually curve upward at the longer ranges. This is due to the fact that, a better impact zone dis- tribution is obtained at longer ranges. With this 5 milli- radian bias and dispersion system, the number of rounds required to achieve a 50 percent casualty level at 3000 meters range -for personnel in a 300 by 300 foot target area are:

105mm Air Burst 110 Rounds 105mm Ground Burst 350 Rounds

30mm Ground Burst 9900 Rounds

ä'MMEM Computer Program for General Full Spray Personnel Mean Area of Effectiveness Computations, Volume 1. Users Manual. Confidential," 25 May 71 61JTCG/KE-70-6-1, AMXSY-S, Aberdeen Proving Ground, MD.

"♦Einbinder, S.K. "General Purpose Matrix Program". TR 4600, AD 917313, Picatinny Arsenal, Dover, NJ.

lTbld; ^Igure 2A-19, Page 2A-13, "Paramete-s for P.. Curves - 100^ Incapacitation" Row 3 - Tumbling Flechettes, Clothes Soldier Columns a, b, n.

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5 MIL AIMING ERROR 5 MIL DISPERSION

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10 ROUNDS) .

1

^ 105MM

~* V^N^^ ^ 105HM

1 1 1 1000 2000

RANGE (METERS)

3000 4000

Figure U. Fractional personnel casualty level.

See Appendix B for grapns of fractional casualty level versus target size for various aiming errors.

Figure 5 shows the number of 30mm rounds that are re- quired to equal one 105nim round's casualty level. This ratio was obtained by averaging over a wide range of aiming errors and target areas. Unlike the armored target case, where the ratio was approximately constant at 8 to 1, it varies widely here with range. The reason for this variation is that the 30inm round has a flatter trajectory than the 105mm round at medium ranges, hence, a more elongated dispersion pattern results. At short ranges both rounds have fairly flat tra- jectories so the lethality ratio approaches an approximate 9 to 1 ratio. As the range is extended to 3000 meters and beyond, the 30mm is slowed down relatively more than the 105mra, and its impact angle approaches that of the 105nim round.

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NO. ROUNDS OF JO« AVERAGED OVER IKE FOaONIlK TO INFLia CASUALTY 0. 5. 10. IS. NIL AIN ERRORi LEVEL DUE TO ONE Mm 1. 15. NIL DISPERSION.

50. MO, 600 FOOT TAR6ETS (S0UARE TARGETS)

15 —

30 — ^ -—^ j

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15 — /

10 —

5 —

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RAME (NETENS)

Figure 5. Comparing the 30nim and lOSmra round lethality ratios.

Figure 6 shows the ratios of the impact zone sizes for various launch altitudes and ranges. At higher altitudes the variation in impact zone size with range decreases.

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Figure 6. Comparison of a BOmm round Impact zone size to that of a 105mm round ltnp«ct zone size.

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CONCLUSIONS

This analysis was limited to three projectiles and was not a complete relative effectiveness analysis. Several additional factors should be considered to obtain the optimum caliber for a helicopter gun system. These factors are:

1. Specific scenarios and relative frequencies of each,

2. The total number of rounds carried per mission,

3. The cost of flying a mission,

4. The cost of projectiles of various sizes,

5. Round-to-round dispersion and bias aiming errors as functions of caliber,

6. Aircraft vulnerability to antiaircraft fire as a function of aircraft altitude, range, and exposure time,

7» Firing rate as a function of caliber,

8, Production and maintenance costs of the weapon system amortized per round fired.

Several different effectiveness criteria may be considered in applying the lethality data calculated for this report. The lethality of all the gun weapon systems considered is generally low. Even the hypothetical 2 milliradian bias and dispersion system is not very lethal at longer ranges, when fired at point targets. The lethality of gun systems used against personnel targets is rather insensitive to range when fired from low alti- tudes. Several trade-offs are indicated among aircraft altitude, projectile muzzle velocity, and fire control accuracy. Firing high velocity projectiles from low altitudes causes a detrimental increase in the length of the impact zone on the ground. Firing from higher altitudes may decrease the aircrafts' probability of survival if air defense units are present. Firing lower velocity projectiles will improve the impact zone; however, it will have a detrimental effect on fire control accuracy.

The importance of fire control accuracy depends on the target size. For point targets accuracy is very important, however, for very large area targets accuracy may be relatively unimportant.

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Per pound of ammunition, the 30mra round produces more casualties than the 75mm or 105mm. This is due to the 30mm projectile breaking into more optimum fragment sizes (smaller) for personnel casualties. The xcight advantage of 30mm HE rounds can not be expected to hold for other materiel targets such as trucks.

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APPENDIX A

30mm and 105mm

PROJECTILE DATA

PKWECTILE oispmsioN RANdK UISPQISIUN (METEHS) IMPACT ANGLE TOUUNAL VKLOCITI (nil i) (meter») UP DOWN DUX. (degreea) (Mtart/tM.)

30» 10 4000 3t0 (.05 W 6.2 306 1C 2000 735 725 20 1.5 604 10 1000 625 3i5 10 1.2 826 10 MX) 210 115 5 1.8 960

5 UOOO 180 195 20 6.2 306 5 2000 3ao 385 10 1.5 604 5 1000 280 205 5 1.2 826 5 500 90 65 2.J 1.8 960

105» 10 i.ooo 150 150 40 14.3 263 10 2000 185 185 20 6.1 29« 10 1000 175 160 10 3.4 325 10 500 UO 85 5 2.9 343

5 4000 y5 70 20 14.3 263 5 2000 95 90 10 6.1 296 5 1000 85 80 J 3.4 32J 5 500 55 U> 2.J 2.9 34)

30aB Muxzl« Velocity - 366 netere/eecond

JOm ProJectUe K*a* - 0.326 kUogru*

105M Muttle Velocity - 1097 Mtara/i

105M Projeotlle Hw« - 13 kUofruw

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APPENDIX B

FRACTIONAL CASUALTY LEVEL

Vs

TARGET SIZE

TMMCT SIZE (fMl/Mat

Figure B-l. Fractional casualty level vs target size for one round of 105inm at 500m with a 5 mR dispersion.

11

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Figure B-2. Fractional casualty level vs target size for one round of 105inm at 500m with a 15 mR dispersion

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Figure B-3. Fractional casualty level vs target size for ten rounds of 30Tnm at 500m with a 5 mR dispersion.

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Figure B-5. Fractional casualty level vs target size for one airburst (20ft) round of 105mm at 1000m with a 15 mR dispersion.

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Figure B-6. Fractional casualty level vs target size for ten rounds of 30nim at lOOOra with a 5 mR dispersion.

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Figure B-7, Fractional casualty level va target size for ten rounds of 30Tnm at 1000m with a 15 mR dispersion.

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Figure B-8. Fractional casualty level vs target size for one round of 105mm at 2000m with a 5 mR dispersion.

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Figure B-9. Fractional casualty level vs target size for ten rounds of 30ram at 2000m with a 5 mR dispersion.

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Figure B-10. Fractional casualty l«vel vs target size for one round of lOSmm at 4000m with a 5 mR dispersion.

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Figure B-ll. Fractional casualty level vs target size for ten rounds of 30mm at 4000m with a 5 mR dispersion.

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