I IASA - core.ac.uk

,,,¢,,_x_,,'-m-,?',¢#-_7

NASA-TM-84597 19830009239

NASA Technical Memorandum 84597

[

k

THEMINIMIZATIONOFPYLON-MOUNTEDSTOREEFFECTSONAIR COMBATCAPABILITY

M. LeroySpearman

January1983

Fi:f!15 1983IJ',I_,'GLEY RESKARCH CENTER

H.,_:.:._'ro_,,wRG,r.JzA

t,

I IASANalional Aeronautics and

Space Administration

Langley Research Centert4amplon, Virginia 23665

.{-/

https://ntrs.nasa.gov/search.jsp?R=19830009239 2020-03-21T05:33:06+00:00Z

SUMMARY

Some effectsof pylon-mountedmissiles on aft-taildelta wing supersonicfighterconcepts have been investigated. Whereasminimum drag penaltiesdo occur with theaddition of missiles,the effectsat higher lifts,correspondingto maneuveringflight, are less severe and often favorable. Lower speedsand altitudesenhancethemaneuveringcapabilityand one-on-oneair combat would probablytend to degeneratetosubsonic speedseven though the combatantsmay be _ying supersonicfighters. Higherspeed (supersonic)_ight might best be reservedfor interceptorswith long-rangemissiles where the weapon carriageeffectsat low angles of attack are of primeimportance.

INTRODUCTION

Since the advent of air-to-airmissiles for air combat fighters,the integrationof the weapon carriagewith the airplanehas been a problemthat must be considered.With the obviousexceptionof airplanesdesignedwith an internalweapons bay (suchas the F-101 and the F-106),missileshave typicallybeen carriedexternally,oftenon pylons. The aerodynamiceffectsthat may be associatedwith this type of externalcarriage includethe effectson lift and drag, controleffectiveness,longitudinaland lateralstability,and mutual interference.

Many fighters originally designed with gun systems were adapted to accept pylon-mounted missiles. With the proliferation of pylons and missiles, many newer fightershave also been required to accommodate a wide variety of existing standard pylon andstore arrangements. In some cases, such adaptation can be reasonably acceptable,whereas, in other cases, some performance limitation may result. It seems probablethat through judicious location of the pylon, the effects of a pylon/store combinationmight be minimized.

The objectiveof the paper will be to make some observationson the case forsimplifyingthe fighter/missileconfigurationso that adverse effectsare minimizedand the air combat capabilitymaximizedin the Mach number range from 0.60 to about2.0. Delta wing configurationswith two pylon mountedmissilesand aft tail controlswere considered. The arrangementswere similarto severalSovietconcepts such asFishbed, Fishpot,and Flagon,and are illustrativeof an approachto point-designaircombat fighters. Some examplesof the potentialmaneuveringcapabilityin terms ofnormal accelerationand turn radius for various speedsand/or altitudewill be shown.Previous NASA-Langleyfighter/storessummarypapers are containedin references1and 2. Resultsfor the delta wing fighterconfigurationused in the presentpaperare publishedin reference3. Resultsfor the delta wing interceptorconfigurationused are publishedin reference4.

SYMBOLS

The longitudinalresultsare referrredto the stabilityaxis system and thelateralresultsare referredto the body axis system. The coefficientsand symbolsare definedas follows:

an normal accelerationin g units

b wing span

wing mean aerodynamicchord

CD drag coefficient,dra_____gqS

CD,o drag coefficientat zero lift

C% rolling-momentcoefficient, .rollingmomentqSb

CIB effectivedihedralparameter,per degree

CL lift coefficient,liftqS

Cm pitching-momentcoefficient, pitching momentqS_

@Cm horizontaltail effectiveness@6h

@Cm longitudinalstabilityparameter

Cn_ directionalstabilityparameter,per degree

CyB side-forceparameter,per degree

h altitude

L/D lift-dragratio

M freestreamMach number

q freestreamdynamicpressure

R turn radius

S referencewing area includingfuselageintercept

W weight

W/S wing loading

angle of attack,degrees

2

angle of sideslip,degrees

6h horizontaltail deflection(positivetrailingedge down), degrees

DISCUSSION

Fighter

A lightweightfighterconcept, similarto a MiG-21 Fishbed,with two underwingpylon-mountedmissilesis shown in figure 1. Longitudinalcharacteristicsfor thisconcept (fig. 2) for M = 0.60 and 1.20 indicatea progressivereductionin thestabilitylevel as the pylon and missileare added with no change in the total lift.This characteristicof decreasingvalues of Cm with no change in CL was observedover the Mach number range from 0.60 to 2.00 and is apparentlycaused by a redistri-bution of liftingpressureon the undersideof the wing that occurs primarilyfromthe presenceof the pylon. The effectwas more noticeablein the speed range up toM = 1.20 and was somewhat reducedin magnitudeat higher supersonicMach numbers.

The drag characteristicsfor the delta wing fighterat M = 0.60 and 1.20(fig. 3) indicatean expected increasein CD at lower lifts but a reductionin thedrag-due-to-liftas the pylon and missileare added. The net result is only a smallreductionin maximum L/D and essentiallyno effect of stores on L/D at the higherlifts that are associatedwith maneuveringflight.

A summaryof some of the longitudinalcharacteristicsfor the delta wing fighter(fig. 4) indicatethe progressivedecreasein stabilitylevel and increasein

CD,o as the pylon and missile are added, and also show that no measurablechangeoccurred in the horizontaltail controleffectiveness. Hence, despitethe increasedCD.o due to the stores,the resultsindicatedno degradationin maneuveringcapa-bility becauseof the reducedstabilitylevel,the reduceddrag-due-to-lift,and theunchangedlift and controleffectiveness.

Lateral stabilitycharacteristicsfor the fighterat M = 0.60 and 1.20

(fig. 5) indicatean increasein the magnitudeof Cy_ that might be expecteddue to

the additionof the stores. This was translatedinto a decrementin Cn_ that wasfairly large in the transonicrange only (aboutM = 0.90 to 1.20) but still permitted

positive CnB to sufficientlyhigh angles of attack for good maneuveringcapability(about 16° to 18°)becauseof the inherentlyhigher valuesof Cn_ that exist in thetransonicrange for the basic configuration. At higher supersonicMach numbers,the

adverse effect of stores on Cn_ disappearsand may even become favorable.

Interceptor

Some of these higher Mach number effects can be better illustrated with someresults from an investigation of a delta wing interceptor configuration (ref. 3).The interceptor configuration (fig. 6) is similar to the fighter configuration ingeneral geometry but is representative of a slightly larger airplane and missile suchas the Su-ll Fishpot or the Su-15 Flagon. The longitudinal characteristics for theinterceptorat M = 1.60 (fig. 7) indicatelittle effect of the pylon and missile onthe controleffectivenessand show a slight increasein lift at higher m's and asmall decreasein stability. The increasein lift shown for this Mach number probably

3

results from the fairlylarge pylon inducingan increasein local dynamicpressureover a large portionof the undersideof the wing. The increasein CD and decreasein L/D at low to moderate lifts would have some detrimentaleffect on accelerationand cruise flightregimes. However,if maneuveringrequirementsshould occur, thedrag and L/D at angles of attack of about 16 degreesto 18 degreesare essentiallyunaffectedby the storesbecauseof the decreasein drag due to lift.

The lateralcharacteristicsfor the interceptorat M = 1.60 (fig. 8) indicate

a substantialincreasein Cn_ due to the storeswhich would be of specialbenefitif maneuveringrequirementsto high anglesof attack shouldoccur. The effectivedihedral is reducedby the additionof the stores resultingin a favorablereductionin the roll-to-yawratio. The reductionin -C£_ , as has been noted in otherinvestigationsin the supersonicspeed range, ismapparentlycaused by an interferenceflow field from the store installationthat, in sideslip,resultsin a reductionoflift on the inboardsectionof the windwardwing and an increasein lift on theinboard sectionof the downwindwing.

Maneuverability

Some indicationof the resultantmaneuveringpotentialis indicatedby the nexttwo figures. The normal accelerationfor a wing loadingof 50 Ib/ft2 and with themaximum CL limitedto 0.8 (_ = 16 degreesto 18 degrees)is shown in figure 9 forM = 0.60, 1.20, and 1.60 at variousaltitudes. Sustained an'S shown at M = 0.60and 1.20 are for a hypotheticalengine of about 13,000pounds static sea-levelthrustwith no afterburning. These resultsare includedto show the greaterdetrimentaleffects on sustained an'S at supersonicspeeds due to the differencein drag levelfrom subsonic speeds. The effectsof sustainedmaneuvercan be improved,of course,through the use of higher thrust enginesor throughafterburning. The expected trendsare apparent--theincreasein an with decreasingaltitudeand with increasingspeed--both due to an increasein dynamicpressurethat resultsin lower lift required forlevel flight and greaterexcess lift availablefor maneuvering. It is more or lessobvious that the slower flying fighterwould want to descend to low altitudesin orderto achievehigher values of an. The fighterin supersonicflightwould obviouslysuffer while maneuveringat lower altitudesdue to structurallimitations,and one-on-one air-to-aircombatwould eventuallytend to degenerateto subsonicspeedseventhough the combatantsmay be flying supersonicfighters. These effectscan also betranslatedin terms of turn radius where the combat advantagewould generallygo tothe airplanecapableof sustaininga tighterturn. Figure 10 illustratesthe effectsof an and M on the turn radius. The obviousis readilyapparent in this nomograph--that is, turn radius can be reducedby increasing an for a constant M or bydecreasing M for a constant an. The illustrationshows that, for an = 4, theM = 0.6 airplanehas a turn radius about three-eighthsthat of the M = 1.2airplane. For the M = 1.2 airplaneto achievean equivalentradius,it would benecessaryto increase an to about 10. The turn radius for the M = 1.6 airplanewould be about 4 times that of the M = 0.6 airplaneand the equivalentan iscompletelyunrealistic. Also for an = 4, the M = 1.2 airplanecan turn wellwithin the capabilityof the M --1.6 airplaneand the M = 1.6 airplanewouldrequirean an of about 6 to become equivalent. It appearsthat air-to-aircombatsufferslittle penaltyfrom store installationat high lift. For high speed inter-ceptorswith long-rangemissiles,the weapon carriageeffectsat low angles of attackare of prime importance. Thus, the judiciouslocationof pylon/storearrangementsisan importantconsideration.

4

CONCLUDINGREMARKS

Some effectsof pylon-mountedmissileson aft-taildelta wing supersonicfighterconcepts have been investigated. Whereasminimumdrag penaltiesdo occur with theaddition of missiles,the effectsat higher lifts, correspondingto maneuveringflight, are less severeand often favorable. Lower speeds and altitudesenhancethemaneuveringcapabilityand one-on-oneair combat would probablytend to degeneratetosubsonicspeeds even though the combatantsmay be flying supersonicfighters. Higherspeed (supersonic)flightmight best be reservedfor interceptorswith long-rangemissileswhere the weapon carriageeffects at low angles of attack is of primeimportance.

REFERENCES

1. Spearman,M. Leroy: Some Effectsof ExternalStores on the Static StabilityofFighter Airplanes. NASA TN D-6775,April 1972.

2. Spearman,M. Leroy; and Sawyer,Wallace C.: ExternalStore Effectson theStabilityof Finhterand InterceptorAirplanes. NASA TM X-71935,March 1974.

3. Spearman,M. Leroy: Effect of ExternalStores on the Stabilityand ControlCharacteristicsof a Delta Wing FighterModel at Mach Numbers from 0.60 to 2.01.NASA TM 84596, January1983.

4. Spearman,M. Leroy; and Monta, WilliamJ.: Effectsof ExternalStores on theAerodynamicCharacteristicsof a 60° Delta-WingFighterModel at Mach 1.60 to2.87. NASA TM 74090, December1977.

i

Figure l.- Delta wing fighterconfiguration.

0

-.04 -

-.08 - PYLONMISSILECm OFF OFF

-.12 - ON OFF

-.16 - ON ON

-.20 , , I I l , I , I _" ,

20- , /16 -

a, deg12

8

4 - M =0.60

I ,,/ I I I I I I0 .2 .4 .6 .8 1.0 0 .2 .4 .6 .8 1.0 1.2

CL CL

Figure 2.- Longitudinal characteristics for delta wing fighter at M = 0.60 and 1.20.

8

D 4

2

0 I I I I I I I I I

.12 -

.10

Cn.08 - M 0.60 M =1.20.06- PYLON MISSILE

OFF OFF.04 ON OFF

.02 ON ON

I I I I I0 .2 .4 .6 .8 1.0 0 .2 .4 .6 .8 1.0 1.2

CL CL

Figure 3.- Drag characteristics for delta wing fighter at M = 0.60 and 1.20.

0PYLONMISSILE

c3C -.i- __o.°FFoFFOFF

OCL-.2- "_'_> ---__ ON ON

-.3 _ I f I ] J_

_Cm 0 f- .02 f I I I I I I I I I.0_ -

CDo.02 -- j ......... --'-:_'_

1 I I I I I I I I I

0 .4 .8 1.2 1.6 2.0M

Figure 4.- Longitudinal summary for delta wing fighter.

oo_=M=o_o PYL°NM'ss"__-_.M=12oChrOmo02 oNoNOFFoNoFFOFF

__ \\\\0 I I I I I\ I

o . __..=._C[_-.002

-.004 I I I t" I v0

-.o2 - ---_-_-=_----.04 I I I I I [- I I I I I

0 4 8 12 16 20 0 4 8 12 16 20a, deg a, deg

Figure 5,- Lateral characteristics for delta wing fighter at M = 0.60 and 1.20.

pc_

Figure 6.- Delta wing interceptor configuration.

.I 8-

L 6-

Cm-.1 -D'6h,deg 4-10 2

-.2 0 0 I I ! I ! I

.12-

20 .10

- /.08a, 16 8h,deg CD

/41

PYLON MISSILE--- OFF OFF

8 .04_ -- ON OFF4 .02 ----- ON ON

I I I I I I I I I

0 .2 .4 .6 .8 1.0 0 .2 .4 .6 .8 1.0 1.2

CL CL

Figure7.- Longitudinalcharacteristicsfor delta wing interceptorat M = 1.60.

.006- PYLONMISSILE

__-_---_- _-.].. _.. OFF OFF- --- ....... ON.004- _---_._-_... OFF

Cn_ _. _ ---------ON ON.oo2-

0_ _ I _ i I I w t I"''_'-

0 "

C_ 002 ..................... "m o

-.004 I i I I I I I I I Ir

0

........ Cyl3 m.02---- ..... ------. -- _ -- _ :-----_=--_--_

-.04 _ I _ i i i i I i ]0 4 8 12 16 20

a,deg

Figure8.- Lateralcharacteristicsfor delta wing interceptorat M : 1.60.

• i

W---_-=2.3KN/m2 (50Ib/ft2)

INSTANTANEOUS..... SUSTAINED(NOA/B)

h -M =0.60 .... CL M a 8hkm ff M _2o=1.20 _M = 1.50 0.8 0.60 16°12- 40000- . k._.... 0.8 1.20 15° -12°

\\\\\_\,_\\\ _ 1.60 18° 12°6 20000 \\_\

_ \\\\

O- 0 I I ! I I I I I4 8 12 16

an, gIs ..

Figure 9.- Normal accelerationcharacteristics.

TURN RADIUSI I I / ,,

M=0.61.0 1.2 1.6 2.0

M 0.6 1.2R1.6 2.5

__ / 3.0

I I __.t I

20 16 12 8 4 0 2 4 6 8 I0 12

an,g's R,n.mi.

Figure lO.-Turn radiuscharacteristics.

i

I. Report No. 2. GovernmentAccessionNo. 3. Recipient'sCatalogNo.NASATM 84597

'4. Title and Subtitle 5. Report Date

THE MINIMIZATION OF PYLON-MOUNTEDSTOREEFFECTSON January 1983AIR COMBATCAPABILITY 6. PerformingOrganizationCode

505-43-43-017. Author(s) 8, Performing Organization Report No. -

M. Leroy Spearman10. Work Unit No.

9. Performing Organization Name and Address

NASALangley Research Center 11.Contractor Grant No.Hampton, VA 23665

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address Technical MemorandumNational Aeronautics and Space Administration 14.Sponsoring Agency CodeWashington, DC 20546

15. Supplementary Notes

16. Abstract

Delta-wing point-design fighters with two pylon mounted missiles and aft-tailcontrols (similar to several Soviet designs) have been investigated for a Mach numberrange from about 0.6 to 2,0. Whereas minimum drag penalties that are expected withthe addition of external stores do occur, the effects at higher lifts, correspondingto maneuvering flight, are less severe and often favorable. The drag-due-to-liftfactor is less with stores on although the lift-curve slope is unaffected. Thelongitudinal stability level is reduced by the addition of stores while the pitchcontrol effectiveness is unchanged. The directional stability was generally reducedat subsonic speeds and increased at supersonic speeds by the addition of stores butsufficiently high stability levels are obtainable that are compatible with the longi-tudinal maneuvering capability. Measures of the maneuvering potential in terms ofnormal acceleration and turn radius are included,

"17. Key Words (Suggested by _.uthor(s)) 18. Distribution Statemer_t '

External stores Unclassified - UnlimitedAerodynamic Characteri sti csManeuverabi I i ty

Subject Category 02

19. Security Classif.(of this report) 20. SecurityClar4if.(of this page) 21. No. of Pages 22. Price

Uncl assi fied Uncl assi fied 16 A02

,-30s ForsalebytheNationalTechnicalInformationService,Springfield.Virginia22161

i