NASA Technical Memorandum86352

NASA-TM-86352 19850010645

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SOMEFIGHTERAIRCRAFTTRENDS

M. LeroySpearman

January1985 ,_l_ld _ _y

LANGLEYRESEARCH_?,£NTERLIBRARY,•NASA

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&I/ANationalAeronauticsandSpaceAdministration

LangleyResearch Cento¢Hampton,Virginia23665

https://ntrs.nasa.gov/search.jsp?R=19850010645 2018-04-26T00:46:49+00:00Z

3 1176 00191 6072

• SUMMARY

The computer sizing technique has been applied to a number of military missionprofiles. Performance data can bedetermined for all segments of the selectedprofile, which typicallyincludetakeoff, climb, cruise, loiter, reserveand landingsegments. Options are available for detailed calculationof combat performanceandenergy-maneuverabilitycharacteristics. Configurationchanges,such as externalfueltank drop and weapon expenditure,can be included in the mission. In the sizingmode, aircraft gross weight, wing loading, and thrust-to-weightratio are variedautomaticallyto determinewhich combinationsmeet the design mission radius. Theresultingperformancedata can be used to create a "thumbprintplot." This plot is•useful in determiningthe configurationsize that best satisfies the mission andperformancerequirements. The sizing mode can also be used to perform parametricstudiessuch as sensitivityof gross weightto alternatedesign conditions.

INTRODUCTION

In the preliminary design of a fighter aircraft, many possibilitiesmust beexamined in order to identify optimal configurations. Computersprovide a fast andinexpensivemethod of performingthese tasks. Certainaspects of the design process,such as performanceanalysis,can be assembled in a computer program. The computerthen can perform very rapid repetitivecalculations,varyingcertainparametersuntilan optimumcombinationof these parametershas been identified.

Reference 1 describesthe developmentof a computertechniquefor determiningthemission radius and maneuverabilitycharacteristicsof fighter aircraft. This tech-nique was applicableprimarilyto point designs. The computer program describedinthe reference1 has been modified to includea number of new capabilities. One ofthese is an automatedpreliminarysizing option. In this mode, startingwith a welldefinedbaseline configuration,the programwill automaticallydeterminethe combina-tions of aircraftgross weight, wing loading (W/S), and thrust-to-weightratio (T/W)that meet a required mission radius, For each of these combinations,additionalperformance items, such as takeoff and landing field length and maneuverabilitycharacteristicsare determined. This data is used to createa •"thumbprint"plot.This plot is used, in turn, to determinethe configurationsize in terms of TakeoffGross Weight (TOGW), W/S, and T/W that best meets all the mission performanceconstraints. This method permits rapid identificationof an optimum configurationsize.

- The purpose of this paper is to describe the performance program and thedevelopmentof the new sizing capability. Included are descriptionsof the militarymission profiles the program can represent and the methods used to calculate theperformancedata. The use of the sizingtechniqueto define an optimumconfigurationsize and the determinationof additionalperformancedata for the sized configurationis also described. The discussion is illustratedthrough examples taken from aconceptualdesign study performedat the NASA LangleyResearchCenter.

DISGUSSION

HistoricalBackground

U.S.A.F. Fighters.-A chronologicaldepictionof Air Force fightertypes (fiG. 2)begins with the first U.S. jet fighter, the Bell XP-59A Airacomet, in the early1940's. The "P" designationfor "pursuit"was in use through the era of the UnitedStates Army Air Force (USAAF). When the United States Air Force (USAF)was createdin 1947, the pursuit designationwas changed to "F" for "fighter." Hence, for aperiod of time, some service aircraft carried both designations,such as the P-86(F-86)and P-84 (F-84). Shown in figure 2 are the Air Force fightersthat have beenbuilt and flown overthe past 40 years, althoughnot all reachedoperationalstatus.All were jet-propelledwith the exceptionof the propeller-drivenP-82 twin Mustangand the P-81 with a combinationof turbopropand turbojet propulsion. The advent ofjet propulsion produced quite a flurry of fighter prototypes from the mid-1949'sthrough the mid-1950's. Beginningin the late 1950's,however, USAF fighter proto-types have been relativelyfew and far between.

U.S.N. Fighters.- A similar depictionof Navy fighters (fig. 3) shows the samerapid developmentof prototypes in the mid-1940 to mid-1950 time period. Followingthe F4H in 1958, however,new Navy fightershave been extremelyrare.

Composite U.S. Military Aircraft Trend.- A composite view of all U.S. militaryaircraft types since 1942 is shown in figure 4 together with some developmenthigh-lights. The P-59, of course, representedthe beginningof U.S. jet propulsion. Theuse of wing sweep was a highlight of the P-86. The F-92 introducedthe use of thetailless delta conceptthat was extendedto supersonicspeed with the F-102 and F-106interceptorsand the B-58 bomber. The F-IO0 introducedthe supersonic swept-wingconcept. Other supersonicswept-wing concepts with the added use of the area rulefor dra_ reductionwere the F-105 and F-11F. The F-104 introducedthe use of a thin,low-aspect-ratio,trapezoidalwing. The F4H introduceda slightly compromisedwingplanform having a relatively large leading-edgesweep angle but with a large rootchord that resulted in a low trailing-edge sweep angle. The F4H design alsoincorporated twin jet engines--a departure from many preceding classic fighterdesigns. Some other twin jet designshad previouslybeen developed,however, includ-ing the first jet (P-59),the XF-83, the XF-88,the F-89, the XF-90,the F-101, theF-5, the F3D, of which the principleoperationaltypes were the subsonic F-89 and thesupersonicF-10i.

Mach number 3 flight was achieved in the mid-1960'swith the SR-71 (YF-12)air-craft and with the XB-70 bomber. The XB-70 also representeda differentU.S. designtype with itsaft delta wing and canard controlsurface.

In the mid-1960's,the operational use of variable wing sweep appeared on theF-111 design. Previousdevelopmentof variablewing sweep had been done with the X-5and the XFIOF. Variablewing-sweepconceptsto follow later in the 1960'sand early197_'s were the F-14 and the B-I. Other than the Air Force F-111 and the Navy F-14, .no other U.S. fighter-typeaircraft that employs variable sweep has been produced.Subsequentfighter designs such as the F-15, F-16, and F-18 employ fixed wings withessentially trapezoidal planforms and aft tails. The X-29 experimental aircraftcurrently being developed employs a fixed forward-sweptwing and a canard controlsurface.

The many concepts developedduring the period from about 1942 to the mid-1960'srelied heavily on experimentaldata--bothwind tunnel and flight. Beginning in themid-1960's,computer-aideddesigntechniqueswere developedthat could greatlyreducethe design time and permit rapid turnaroundtime in examiningdesign changes and inmaking trade studies. Althoughthese techniquesare availablefor increaseddesigncapabilityand have been used in numerousdesign studies,the capabilityhas not beenreflectedin many new flight articlesover the past 20 years.

U.S. and U.S.S.R. MilitaryAircraft Trends.-The U.S. military aircrafttrend isrepeated in figure 5 and the U.S.S.R. military aircrafttrend has been added. TheU.S.S.R.trend does not show the early rapid growth of types followed by a tapering-off as occurred in the U.S. Rather,the U.S.S.R.trend has been steady and persis-tent with an influx of new types appearing at fairly regular intervalsup to thepresenttime. It should be pointedout that the U.S.S.R.trend does not reflecttheextensive modificationsthat are made to some designs. For example, the MiG-21Fishbedand the MiG 23 Floggerare each shown as single points,whereas, in reality,modificationsto such designshave resultedin a larger family of sometimesdramati-cally differentaircrafttypes.

Some other observationsrelativeto the U.S.S.R.trend are:

o Exploitation of jet propulsion (such as MiG-9) followed closely to U.S.developments.

o Swept-wing jet, MiG-15, in same time period as P-86, subsequentlyimprovedwith MiG-17.

o First supersonicjet, MiG-19,in same time frame as F-IO0.

o M = 3 flight,E-166 and E-266, achievedin same time frame as SR-71.

o Configurationtypes have included early straight wings; swept wings; deltawings with aft tails; trapezoidalwings; variable-sweepwings.

o Variablesweep development(FitterB, Flogger)in sametimeframeas F-111.

o Extensive use of variable sweep, being used on the Fitter B and Floggerfighter families, the Fencer fighter-bomber,and the Backfire and Blackjackbombers.

o Exploitation of V/STOL with direct-lift engines and vectored nozzles anddeploymentof Forger VTOL in same timeframeas AV-8.

PerformanceCharacteristics

Thrust-to-Weightand Speed Trends.- The maximum thrust-weight ratios and the. approximatemaximum Mach number for several U.S. and U.S.S.R. fighter aircraft are

shown in figure 6. It would be unwiseto expect a compilationof data of this typeto lead to definative conclusions since the considerationof many other factorsprecludesany necessarilydirect correlationbetweenT/W and M. However,in general,it would be expectedthat an increase in T/W would provide for increasedspeed, orconversely,that an increasein M would requiresome increasein T/W. Such a generaltrend is displayed for the various fighters shown. There is no question that some

aircraft have been underpoweredand thus restrictedin speed. Others may be over-poweredfor the maximum speed with the excesspower being dictatedby such considera-tions as improvedtake-off performance,improvedaccelerationor climb rate, improvedmaneuverability,and so on. However, there is still the possibilitythat somerelationexists between the speed and power factors and the aerodynamicdrag of theairframe. In addition,the type of inlet becomesa factor--normalshock inlets,forexample,may impose speed limitationssoonerthan a variablegeometry inlet.

The U.S. fighters follow a fairly linear trend from the early subsonic jetsthrough the more recent supersonicjets. Major departuresare the AV-8, which fallsabove the general trend, with the higher T/W being used for the V/STOL capability,and the F-111 and F-14 aircraft,which fall below the trend, with the higher speedspresumablyresultingfrom lower drag due to the high wing sweep and the larger sizeairframewhich should permit a more favorablearea distribution.

The F-15 has an indicated speed capabilitythat is about the same as the F-111and F-14 althoughthe maximumT/W isabout twice as large. This may be due, in part,to excessiveT/W in the F-15 for other purposesand, in part, to lower drag for theF-111 and F-14 due to wing sweep and better area distribution.

A tentativeassessmentof the U.S.S.R.aircraft indicatesa generaltrend of T/Wversus M that is slightlybetter than the U.S. trend. That is to say that generallyhigher speeds are indicatedat lower levels of T/W. For example,the MiG-21,MiG-23,MiG-25, MiG-31, SU-15, SU-27, and MiG-29 family all indicate speeds equal to, orgreater than the F-18, F-16, and F-15 family with the same, or less, T/W values.This difference reflects the probability of lower drag due to more slender areadistributionsand, in the case of the MiG-23,some added benefitsof wing sweep. TheYak-36 operateswith a lower T/W than the AV-8 presumablybecauseof the utilizationof direct lift engines to aid the V/STOL capability. The TU-28 which operates atabout the same speed as the F-16 and F-18 but with half the T/W, is an extremelylarge, long-rangeinterceptor,which should have a better area distributionthan thesmall fighters, llleSU-24 which, in many ways, is physicallysimilar to the F-111and F-14 has T/W and M characteristicsthat are also similar.

It cannot be overemphasizedthat conclusionsdrawn from this type of comparisonmust be kept in context with other considerationsthat enter into speed and thrustvalues. Some of these additionalconsiderationswill be discussedsubsequently.

PerformanceCapability.-Another measure of performancecan be presented in theform of maximum takeoff thrust-weight ratio and combat wing loading (about halffuel). This kind of measure (fig. 7) indicatesthat, in general, as T/W increasesand W/S decreases,a tendencytoward increasedagilityshould result--morepower withwhich to move and less weight to be moved. As the wing loadingincreases,a tendencytoward increased endurance generally occurs since the increased weight usuallyresultsfrom an increase in fuel. A large number of U.S. aircraftand U.S.S.R. air-craft can be placed within bounds that largely overlap. If anything,the U.S.S.R.boundary indicates a slightly greater tendency toward agility whereas the U.S.boundary shows a slight tendency toward increased endurance. Falling outside theregion of reasonably similar boundarieswere the U.S. F-15, F-16, F-18. These air-craft indicate increased agility due to high-thrust loadingswhile maintaininglowwing loading. Although parameters for the U.S.S.R. MiG-29 and SU-27 are notsufficientlydefined, it is reasonableto speculatethat they would be well outsidethe U.S.S.R. boundary shown and would probably be in the direction of increasedagility similarto the F-16 and F-18. The U.S. F-111 and the U.S.S.R.SU-24 are well

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outside the boundariesin the generaldirection of greater endurance. The U.S.S.R.TU-26 bomber is also shown as an example of an aircraft that would be expected tomaximize on endurancewith less concernfor agility.

Agility Potential.-Using data such as that on figure 7, another way of lookingo

at the implicationsis simplyto dividethe maximumthrust-weightratio by the combatwing loading for specific aircraft and arrive at a factor defined as the agility

; potential. The higher the ratio of T/W to W/S, the greater the potential foragility. This kind of measure is shown in figure 8 for a number of aircraftover theyears from the mid-1940's. Again it is recognizedthat a number of other factorsenter into agility, but taken in contextthis kind of measurecan providesome usefulinsights.

It is apparent that over the years a number of U.S. fighters having variousmeasures of thrust, weight, and size, resulted in agility potentials not vastlydifferent. Notable exceptions are the F-102 and F-106 in the late lg50's that,primarily because of low values of W/S (large wing area), displayed substantialhigher values of agility potentialthan what might be considereda nominal average.In fact, by this form of measurement,the F-102 agilitywas not exceeded until theF-15 was producedsome 20 years later and subsequentlywas about equaledby the F-16.In the same timeframe as the F-102 and F-106, the F-104 is an interestingexample.Originally intendedas an air superiorityfighter, based on the experienceof Korea,the F-104 was expected to reach combat altitude quickly and to be able to fight athigh altitudes. Accordingly,the airplane had a high T/W for its time but also ahigh W/S (smallwing area) and the result was again only an averagevalue of agilitypotential. A comment made by Kelly Johnson in 1954 concerning the F-104 is ofinterest--withairplanes such as the F-I01, F-I02, F-105, and F-I06 in mind he said".... what we have done is bring an end to the trend toward constantlybigger,constantlymore comPlicated,constantlymore expensiveairplanes."

The F-5 airplanes,while moderate in size ahd cost, indicatean agilitypotentialabout the same as that for the F-104 or the F-86. The mainstay for many years, theF-4 is about the nominalaveragein agility. The F-16 and F-15 representsubstantialimprovementsin this measure over the F-4. The U.S.S.R. MiG-21, Mig-23, and SU-15are about equal to, or slightlybetterthan, the F-4 but substantiallybelow the F-15and F-16. Again, it might be expectedthat the MiG-29 and SU-27 will be about thesame as the F-16--animprovementover previousU.S.S.R.fighters.

Sea Level Climb Rate.- Another performance gauge is the rate of climb at sealevel, which is shown for various aircraft in Figure 9 as a function of Machnumber. These data, within the accuracythat is available,show a reasonablylinearprogression of increasing sea-level climb rate with increasing maximum speedcapahility. In general, U.S. fighters appear to be somewhat better performers inthis measure than U.S.S.R. fighters. In early jet fighters, some advantage wasevident for the MiG-17 compared to the F-86A and for the MiG-19 compared to theF-IO0. The F-86D, however, performedbetter than the MiG-17. Some other observa-tions are:w

o The F-106 indicatesa marked improvementover the F-102.

o The F-I04, with advantages of lightweightand attendantpossible lower cost,exhibits a Climb rate that is about the same as the F-101 and F-106.

o The F-4D representedan improvementover previous U.S. tactical fighters andmost U.S.S.R.fighters--exceptionsbeing the MiG-23 and MiG-21N.

o The MiG-21N,with increasedthrust,has a substantiallyhigher climb rate thanthe MiG-21Fand, in fact, is about comparableto the F-16.

o The F-16 and F-15, both with high T/W, indicatethe highestclimb rates.

Insufficientdata precludesthe inclusionof the MiG-29 and SU-27 but it might be -expectedthat these aircraftwould be comparableto the F-16 and, perhaps,the F-15.

Maneuverin9 Parameter.-A maneuveringparameterhas been developedin the LangleyDifferentialManeuveringSimulator. This parameterincludes,not only T/W and W/S,but also takes into accountthe lift-dragratio and the maximum attainablelift. Themaneuvering parameter correspondsdirectly to the time-on-advantagefor one-on-onefighter combat. The maneuveringparameteris directlyproportionalto thrust-weight,lift-drag, and maximum lift, and is inverselyproportionalto wing loading. Theparameter is shown in bar-graphform in figure 10 for various U.S. fighters. TheF-104 and F-4C appear at the lower end of the spectrumpartly because of high wingloadings. The F-4E is measurably better than the F-4C because of better liftcharacteristics. The F-15 and F-16 indicatedramatic maneuver performanceimprove-ments because of the high thrust-to-weightand the low wing loading. Insufficientdata again precludesU.S.S.R.fightersbut intuitivelyit might be expectedthat someversions of the MiG-21 and MiG-23 would have respectfullyhigh maneuver parameters,and that the MiG-29 and SU-27 may be in a class with the F-15 and F-16.

Turn Rate.- Turn rates, instantaneousand sustained, are shown for severalfighters at M = 0.9 and an altitude of 15,000feet in figure 11. The F-16 and F-15represent improvements over the predecessor F-4E, particularly in sustained turnrate, and also indicate better turn characteristicsthan two operational U.S.S.R.fighters--the MiG-21 and MiG-23. However, some reported values for the newerU.S.S.R. MiG-29 and SU-27 turn-rate performanceare considerablybetter than pre-ceding U.S.S.R.fightersand superiorto the U.S. F-16 and the F-15.

The F-5E is included to indicate the comparabilitywith the MiG-21 and MiG-23.This is one of the reasonsthat the F-5 has been utilizedby aggressorsquadrons.

Some Other MissionConsiderations

Again, it would be presumptuousto think that all factorsthat enter into missioncapability could be addressed in this paper. However, a few observationswill beofferedfor considerationon some mission characteristics.

Supersonic Flyout. Some resultsbased on a type of analysisthat has been doneby Riccioni (fig. 12)show the mission radiusas a functionof average outboundspeed(from 0 to Mmax) for severalU.S. fightersperforminga supersonicflyout from take-off with an optimum cruise back. Internalfuel only is used except where noted.Obviously, other values of radius would result for other conditions, particularlywhere subsonic segments are includedin the flyout. The purpose of these data, how-ever, is to attempta comparisonof supersonicefficiencyby indicatingabout how farout you might fly (radius)as a function of the time (speed)utilized in reachingthat distance. The desired results would be those in the upward and outwarddirections,of course. There is a generaltendency toward reducedefficiency (less

radius)with increasingaverageoutboardspeed as the fighter-typesprogressfrom theF-IOOD,to the F-5E, the F-104, the F-4E, and the F-15A. Exceptionsare the F-104with tip tanks (additionalfuel) which goes considerablyfartherthan the basic F-104but at a lower average speed; the F-106, which has the greatest radius on internalfuel only and flys out at the same average speed as the F-4E, thus reflecting acleaner design;and the F-16A,which reflectsbetter efficiencyin thatthe radius isabout equal to, or greaterthan, the F-5E, F-104, and F-4E, but at a higher averagespeed. The F-15A indicatesa decrease in efficiencysince the radius drops rapidly

__ with increasedaverage speed.

One familiar message from this type of comparison is that the efficiency ofsupersonic-capablefighters needs to be improved. Or, put more simply, if a super-sonic flyout radius greater than 100 nautical miles is required,then the maximumaverage outbound speed capabilityof the F-15A cannot be utilized. In comparison,anF-106 using an averageM of 1.5 would fly out 150 nauticalmiles. The main consider-ations here are simply: "How far do you need to go?" and "Howquicklydo you need toget there?"

Supersonic Air-to-Air Potential. Another mission consideration is shown infigure 13 for the same fighters illustratedin figure 12. This considerationhas todo with the air-to,air potentialcapability--orwhat you potentially can do afterreachingthe supersoniccombat radius. The supersonicflyout radius is shown in bar-graph form and the air-to-air ordnance carried is tabulated for each airplane.Observationsthat can be made from this figure are:

o The F-IO0 at about 150 nauticalmiles would operatewith guns only.

o The F-104 with a range from 140 to 180 nautical miles could use a gun andcould fire two missiles.

o The F-106, also at a range of about 150 nautical miles, could fire fivemissiles,one of which was a Genie, and carriedno gun.

o The F-4 at a lesser range of about 120 nauticalmiles could fire four missilesand also use a gun.

o Both the F-5 and the F-16, with nearly comparableranges of about 130 nauticalmiles could fire only two missilesand use a gun.

o The F-15, with the shortest range of about 100 nautical miles, could fireeight missilesand also use a gun.

This kind of informationposes some questions,such as: "is a shorter radiusofaction with more firing opportunitiesa fair trade for a larger radius of action withless firing opportunities?" The extremes, of course, are to have tremendous fire-power capability but not to be able to take it anyplace, or to have a tremendousrange capability but no firepower. The answer lies somewhere between and must begiven seriousconsiderationwith the ultimate goal of having tremendousfirepowerata tremendousradius.

Internal Fuel and Maximum Ordnance Trends.- The data presented in figure 14 isintended to suggest another consideration in the assessment of fighter missioncapabilitytrends. These data show the internal fuel capacity and the maximumordnance load (includingair-to-ground)for various fighter aircraft over the past

40 years. These data interrelatethe vehicle size and volume with the potentiallethality. Early jet fighters were quite small and hence had relatively smallquantities of internal fuel and relativelylow maximum ordnance load capability. Ageneraltrend toward increasedsize over the years has resultedin increasedinternalfuel capacityand increasedload-carryingcapability.

Some observationsare:

o Some supersonicdesigns remainedsmall, such as the F-104 and F-5, with littlegrowth in internalfuel capacity,but with some increase in ordnance load forthe F-5E.

o The F-101 and F-106 were large airplaneswith large internal fuelcapacity.The ordnance load was low, however, since the primary weapon was air-to-airmissiles.

o The F-105, althoughhaving little growth in internalfuel capacitycomparedtopreceding aircraft, did show considerable growth in maximum ordnance loadbecauseof the number of air-to-groundweapons carriedexternally.

o The F-4 provided further growth in load carrying capability through theadditionof externallycarriedair-to-groundweapons.

o The F-111 is a large airplane with an exceptionally large internal fuelcapacity and a large ordnancecarryingcapability. The internalfuel capacityof the F-111A is a little over 5000 gallons comparedto about 400 gallonsforan F-80 or F-86 and about 1800 gallonsfor an F-15.

o The F-14 has a large internal fuel capacity (about 2500 gallons)and a largeordnance load comprisedmainly of large air-to-airmissiles.

o The F-15, F-16, and F-1R are all good load carrierswith a mix of air-to-airand air-to-groundweapons. The F-18 appearsto be an exceptionallygood loadcarrierfor its size.

SomeWeight Factors

Combat Weight.- The trend in combat weight as a function of Mach number is shownin figure 15 for several U.S. fighters. For these data, the airplanes are configuredfor air-to-air missions and the combat weight is composed of the empty weight, halffuel, full gun ammunition, and air-to-air missiles. The general trend is an increasein combat weight as the maximum Mach number increases. There is a lower bound ofwhat might be considered lightweight fighters including the F-5, F-I04, and F-16.

For some aircraft, such as the F-Ill, F-18, and A-7, the combat weight isdictated more by the large fuel capacity rather than by munition weight. For theF-14, both a larger fuel capacity and a large munition load are contributingfactors. At the highest Mach number, the large difference in combat weight for theF-15 and F-Ill reflects a design emphasis for air superiority with the F-15 and adesign emphasis for multipurpose ground attack and long range with the F-Ill. Henceany attempt to compare fighter capability in terms of combat weight should be donewith great care because of the many factors included.

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Operating Weight Empty.- The trend in operatingempty weight with Mach number isshown in figure 16 for U.S. and some U.S.S.R. fighters. The empty weight includesall fixed equipmentbut no fuel or munitions. The trend is again toward an increasein weight with increasing Mach nUmber. These data also reflect the influence ofaircraft size with the smalleraircrafton the lower bound and the larger aircraftonthe upper bound. In general,the U.S.S.R.fightersappearto be slightly betterthanthe U.S. fighters in terms of empty weightand speed. Exceptionsare the TU-28, anexceedinglylarge interceptorfor which there is no U.S. counterpart,and perhapsthe

. Yak-36with its direct-liftengines.

To some extent,the empty weight provides a measureof cost--thelarger,heavieraircraft being more expensivethan the smaller,lighteraircraft. The cost, however,must also be tempered by other factors such as the complexity.

Fighter Weight Distribution.-The distributionof the empty Weight for variousbasic U.S. fighters over the past 40 years (fig. 17) providesan interestingpattern.The percentof empty weight allottedto structure,propulsion,auxiliaries,avionics,and fixed weapon equipment is shown for each airplane. The followingobservationsare made:

o With little exception,the percent of empty weight allottedto each categoryhas remainedabout constantsince the days of the F-80.

o The largest single part of the empty weight is the structure. Thus, thepossibilityfor meaningful reductions in empty weight lies in the areas ofmanufacturingand structuraltechniquesand in the area of materials.

o Reductions in the weight of propulsion systems and various auxiliary•mechanismsoffer the possibilityof large payoffs in weight reduction.

o The percentof weight allottedto avionicshas remainedrelativelysmall.

o The percent of Weight allotted to the fixed equipment necessary for weaponscarriage is almost insignificant.

A general observation regardingthe distributionof fighter weight is that alarge amount of equipment (almost90% in structures,propulsion,and auxiliaries)isrequired in order to provide support for the primary purpose of the fighter--thecarriage and delivery of weapons. Hence, very careful attentionshould be given toimprovingthe cost effectivenessof fighters by reducingthe complexityand the costof systemsused simplyto get the weaponsairborne.

DCPR Weight.- The Defense Contractor Planning Report (DCPR)weight is, perhaps,more nearly related to the structural cost. This weight is comprised of thestructural airframe includingthe necessaryfixed wiring, tubing, and controls but

" does not includethe engine, wheels, or instrumentation. The trend in DCPR weightfor fighters over the last 40 years (fig. 18) again shows a progressiveincrease inairframe weight for most fighters primarilydue to size. Those airplanesthat haveremained relatively small (F-104, F-5, F-16) show little change in airframe weightover the years. The F-111 weight, which seems to be exceptionallyhigh, is partlydue to weight associatedwith the variablewing-sweepstructure. It is reasonabletoassume that the manufacturingcost will increasewith increasingDCPR weight. Hence,a clear message to detect--althoughchallengingto implement--isto reduce the sizeand weight of fighters while retaining, or improving,the mission capability. The

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challenges are in such areas as manufacturingtechnology,materialstechnology,andimprovedaerodynamicsto reduce volumeand thrust requirements.

Some Cost Factors

Quantityand Cost Trends.-The trends in U.S. fighter/attackaircraftprocurementand flyawaycost from 1968 to 1982 (fig. 19) shows a decrease in quantity and costimmediatelyfollowingVietnam,but, since the early 1970's,the quantityof fighter/attack aircraft accepted has been more or less constantwhile the flyaway cost hasrisen significantly. This is a pictureof a fundamentalproblemtoday--canwe affordwhat we believeto be needed, or can we expect to maintain an adequate defensewithwhat we believewe can afford? Indeed,this is an easy problemto state,but a quitedifficultone to answer.

Flyaway Unit Costs.- The flyaway unit cost for several fighter/attackaircraftprocured in 1981 is shown in figure 20. As might have been expectedfrom some of theprevious discussionon aircraftsize and capability,the F-14 and F-15 are relativelyexpensive, and the F-18 is, as yet, quite expensive. Other factors, such ascomplexity,also must be considered. Questionsthat may be asked--"Areyou gettingwhat you are paying for?" or "Do you need what you are getting?"are easily askedbut, again, difficultto answer.

Lot Average Cost.- The lot averagecost of severalairplanesin 1981 dollarsoverthe years from about 1950 is shown in figure 21. These average costs reflect thetotal number of aircraft procured and the number of years during which they wereprocured. Although the numbers change slightly when averaged in this manner, thegeneraltrend in cost increaseis unchanged.

Lot Average Cost Distribution.-The distributionof lot average cost for severalcurrent fighters is shown in bar-graphform in figure 22. Althoughthe amountsvaryconsiderably,some generalobservationscan be made:

o The largest amount is applied to the airframe as might be expected frompreviousdiscussionof the weight distribution.

o Propulsionis the second largestexpense.

o The airframecost appearsto be, by far, the largestcost item for the F-18--exceedingthe total cost of the F-15, for example.

o The avionics cost for the F-18 seems surprisinglylow compared to the totalF-18 cost, as well as in comparisonto the avionics cost for the other air-planes.

Flyaway Cost Distribution.-The distributionof flyaway cost for various basicU.S. fighters over the past 40 years is presentedin figure 23. Again,the airframeis shown to be the largest cost factor, averagingabout 60 percentof the total fly-away cost over the years. The second largest cost contributor is generally thepropulsionsystem. The beginningof the era of avionics in the 1960's is evident bythe increase in percentcost devotedto avionics--becomingabout the same as that forpropulsion. The same results are shown in bar-graphform in figure 24 for the morerecentfighters (past 20 years). The cost fractionfor each item shown is dependent

lO

L •

upon a number of factors such as the number of units built, the complexityof theitem, variationsin manufacturingtechniques,and so on.

CONCLUDINGREMARKS

It has been the purposeof this paper to reviewsome fighteraircrafttrends overthe past four decades in order to illuminatesome of the factorsto be consideredin

. assessingthe relativemerit of fighter aircraft. Where possible,comparisonsweremade between U.S. aircraft and U.S.S.R. aircraft. While it is not presumed thatspecific conclusionscould be drawn from this trend study, some pertinent observa-tions are made.

o The assessmentof fighter capability is dependeDton many factorsand extremecaution should be used to assure that conclusionsare not based on the use ofany preconceivedobvious indicatorsto the exclusionof some less obvious andpossiblyconflictingindicators.

o Some fighter aircrafttend to excel in air-to-aircapabilityand some in air-to-ground capability--thetrue multipurpose fighter still appears to beelusive.

o For the most part, U.S.S.R. fighter trends have been quite similar to U.S.fightertrends.

o The latest U.S. operational fighters are apparently superior to U.S.S.R.fighters, however, this may be offset by U.S.S.R. fighters currently beingreadiedfor deployment.

o The empty weight distribution of U.S. fighters has remained relativelyconstant over the past 40 years, with the largest contributingfactor beingthe structure.

o Generally speaking, about 90 percent of the empty weight (structures,propulsion,auxiliaries)is required to supportthe mission of weapon carriageand delivery.

o Since the early 1970's,the quantity of fighter/attackaircraft accepted hasbeen essentiallyconstant,whereasthe total flyaway cost has tended to rise.

o The largestcost item is that due to the airframestructure.

o The challenge to fighter technology is to reduce the size and weight offighters while retaining, or improving, the mission capability--thesechallenges being in such areas as manufacturing, structural design andmaterialstechnology, and in improvedaerodynamicsthat reduce the volume andthrust requirements.

REFERENCES

1. Anderton,D. A.: The Historyof the U.S. Air Force. CrescentBooks, New York,1981.

II

2. Mondey, D.: The InternationalEncyclopediaof Aviation. Crown Publishers,Inc., New York, 1977.

3. Encyclopediaof U.S. Air Force Aircraft and Missile Systems,Volume I, Post-World War II Fighters 1945-1973. MarcelleSize Knaack, Office of Air ForceHistory,Washington,D.C., 1978.

4. Jones, L. S.: U.S. Fighters. Aero Publishers, Inc., Fallbrook,California,1975.

5. Spearman, M. L.: Some Historical Trends in the Research and Development ofAircraft. NASA TM 84665, 1983.. _

6. Spearman,M. L.: HistoricalDevelopmentof WorldwideSupersonicAircraft. NASATM 85637, 1983. '_

7. Arold, L. J., Jr.; and Hill, W. F.: Soviet Air/Land Military Power-. Airlandco,La Puente, California, 1976.

8. Krivinyi, N.: World Military Aviation. Arco PublishingCompany, Inc., NewYork, 1977.

9. Aviation Week and Space Technology. McGraw Hill, Inc., New .York, publishedweekly.

10. Couhat, J. L." "Combat •Fleets of the World 1984/1985. Naval Institute Press,Annapolis, Maryland, 1984.

11. _ Air Force Magazine. • Air Force Association, Washington, D.C., published monthly.

12. Jane's Defence Weekly. Jane's Publishing Company, Ltd., London, published

weekly.

13. Jane's All the World's Aircraft. Jane's Publishing Company, Ltd., London,publishedannually.

14. DuPuy, W. E.; Moyer, R.; Palmer,P. R.; McKinney,B. J.; Kreisel, G. R.; Balut,S. J.; MdNichols, G.R.: U.S. Military Aircraft Cost Handbook. ManagementConsul'tingand Research,Inc., Falls Church,Virginia,1983.

15. Stanley, W. L.; and Miller, M. D.: Measuring Technological Change in JetFighterAircraft. R-2249-AF,Rand Corporation,Santa Monica,California,1979.

16. Jackson, S. K., Jr.: Quality, Quantity, and Technology - A Perspective onFighterDevelopment. SAE Paper 811097,1981.

17. AerospaceFacts and Figures. AerospaceIndustriesAssociation.of America, Inc.,Washington,D.C., publishedannually.

12

F-80,1945 F-4,1963

F-86,1948 F-15,1972

F-lOOi1954 F-16,1974

Figure 1,- Some U.S. fighters.

30- - o YF-I7YF-16o

_-- OyF_15.. F-IlIA o25 - F_4C_ o F-SA- O

o YF-12Ao F-106YF-107Ao

20.- XF-104o°YF-105Ao F-101AYF'I02Ao

Number YF-93o o YF-100Aof -15 - XF-91oo XF-90

prototypes XF-94o -XF-89o.°XF-92

10 - o XF-87XF-88o.

o XF-85XP-86o _:First-flight of NavyF-4:1958XP-82o o XP-84

5 - oXP-79B .XP-83o

XP-80o0XP-81

°Xrl-59AI_ I I I l I I I0

40 44 48 52 56 60 64 68 72 76 80Yearof first flight

Figure 2.- Chronology of U.S. Air Force fighters.

16-o F-18

14 - o F-14o F4H

12 - o F8Uo XFV-1

10- o F11FNumber o XF2Y

of 8- o XFIOFprototypes o F4D

6- o F3Ho F3D

4 - o FTUo F2H

2 -. o F9Fo FH-1

0 I I I I I I I I I !40 44 48 52 56 60 64 68 72 76 80

Yearof first flight

Figure 3.- Chronology of U.S. Navy fighters.

64 - • B-1 F-18<>• • • " • F-16_

• F_I58. ,-," " - F-Ill . F-14<>A

56 - " " B-7n-'-__Variable_..'l:1.sweepF4H "- M= 3 CanardDelta

F4H-_SR-_M"° _USAF Phantom48 - " " z_ = I-,:: Computer }"-B-15nS_,B <,,LNavyPhantom aided---_ o Area ruled Delta designF11F_ Arearuled swept .

40 - F-105_ Area ruled•swept ..F-104_ Supersonictrapezoid

Number F-](_--]_ SupersonicDeltaof 32 - • r- JA--DSupersonicswept

types B-52o8

24 - F-92" _ " " •

._ TaillessDelta

16- 47_Sw o USAFfighter/attack "eptwing .o USAFbombersO USNfighters

8 -5 A USN.attack

0 Jetpropulsion I I I I I I I I40 44 48 52 56 60 64 68 72 76 80

Year

Figure 4.- Chronologyof U.S. military aircraftdevelopments.

64 - r In F-18<>• F-15_-'_F-16

O USAFfighter/attack AV-Sz_8 A-1056 - F-140o USAFbombers F-111nz_

O USN fighters F-4_[3B-70z_USN attackz_ °SR-71

48- B_58_F_I0_6F4H Newfighters _Blackjack

40- _-II_ 0 FoOrg_erncer-zS'-F-101 _ Backfire

Number _ F-I02 erof 32 - on

types - Fitter Bo 8 VlSTOL

24- F-92 _} Foxbatr

Bear

16 - B-47_ ' _ BadgerYAK25_ OMIG-21 O U.S.S.R.fighters,

P-861_ ^ OMIG-19 bombers,interceptors0 0 "Bison ..FB-20 9MIG-17 "8

io ' 8 ,0 •MIG-9

' -800 I I I I I I I I I I40 44 48 52 56 60 64 68 72 76 80 84

Year

Figure 5.- Chronology of U.S. and U.S.S.R.military aircrafttrends.P

1.5

F-I04F-105B F-18 1-16F-I06F-I05F

1.0AV-8~ .

T/w, F-5A~YAK-36max MIG-17

.5 MIG-l~ ~-102F-86F84F • F-IOOF-80-"F-84-A

F-IIIA

0 I 2 3 4M

Figure 6.- Thrust-to-weight and maximum Mach number trends,U.S. and U.S.S.R. aircraft.

• i i a

1.4 --

_Agility o F-151.2-F-16

MIG'19,21,23,25°o F-181o0SU-7,9,15,17,20

YAK-28,26-_

•8 TU-28Tmax

WT.O. .6 -F-I05 o o F-111F-4 F-IO0_ '"/ . SU-24

•4 - F-5 F-106_ vA-7 F-I01 o TU-26

•2 - A-10 F-I04nduranceF-14F-102

I I I I I I I_ I0 20 40 60 80 100 120 140 160

•WcombatS

Figure. 7.- Thrust-to-weight versus combat wing loading forU.S. and U.S.S.R.aircraft.

SU-15qF-111A--7/ mF1:11FF-105- rF-4 / / / mF-14

7tl,t)}tlt71tlIF-8_-86F-IO0

p°tential " ?l I , .' 160 -

0 0

Wcombat, o

kt o o80 - o oq i• dlIb ,o o o o o

0

0 I I I I1.6-

- 0

Tmax .8 - ° o o o

00

WT-O- o °° °°° °°°O- O

0 I I I I1940 1950 1960 1970 1980

Year

Figure 8.- Agilitypotentialfor IJ.S.and U.S.S.R.aircraft.

Figure 9.- Sea-level rate of climb versus Mach numberfortI.S. and U.S.S.R. aircraft.

F-16AF-15A

F-IOSDF-IO0F-4E F-SE

Figure 10.- AerodYnamicmaneuveringparameters.

i h • •

Figure 11,- Turn rate for U.S. and U.S.S.R.aircraft,M = 0.9 at 15,000feet.

200- F-104(Tiptanks)• /F I06

F IOOD"F 5_7 %F16AF I04_e eRadius F4E

nm 100 •F-15A

I I I !0 0.5 1.0 1.5 2.0 "

M, averageoutbound

Figure 12.- Supersonic flyout mission.

Guns v' v' - v' ,/ ,/ ,/Missiles - 2 5 4 2 8 2

F-IO0 F-I04 F-I06 F-4 F-5 F-15 F-16200-

Tip, tank... ,

• I

Radius, 100 -rim

Figure 13.- Air-to-air combat potential for supersonic flyout mission.

Including F-11120- air-to-ground • F-18

F-I05 oF-4B F-14A ®Q.

F-104_° F 101 F-SE'-__ F-16AMaximum I0 - F-100C--x_\_//_F-106A _ _^_ _ •ordnance :-80

wt. . ,. F-86A", _I Im"_r-"l , F-15A1000Ibs 0 I

40-

• F-11130-

Internal

fuel 20 " F-102A _ F-101wt, F-100( F-106A F-14A

• • F-15C1000Ibs F-86D • F-4B F-15A • F-1810

8- F-105 mF-16A0 • • F-5A • F-5E1944194819521956196019641968197219761980

Year

Figure 14.- Internal fuel and maximumordnance trends.

EmDtyweight+ half fuel + full ammo,+ AAM's80-

F-111A F-111F• ®

O0- e. F-14A

CombatF-101 F-4weight, 40- F-105F •

1000Ib • • F-18 eeF-105• F-1.5A-7 F-102• • • F-100 >

20 F-86 • 104F-80• • oO F-SE

F-SAI I I I I I

0 0.5 1.0 1,5 2.0 -2.5 3,0

Mmax

Figure 15.- Combatweight versus Mach number.

60-

Figure 16.- Empty weighttrends versus _lachnumber fortl.S.and tI.S.S.R,aircraft.

60-F-80 F-86F-100F-104F-4 F-14F-15F-16

40 Structures (43%)Percent

of empty __.......e....__....e_ ....e Propulsion (26%)

weight _ "20- Auxiliaries (20%)

Avionics (7%)

Weapons (4%)0 t " - i--"r- t - j1940 1950 1960 1970 1980

Year

Figure 17.- Distribution of empty weight for various U.S. fightersover the past 40 years.

DCPR'M.= Airframe, wiring, tubing, controls(Noengine,wheels,instruments)

40[- _F-IIIF

F-111A_ "

30_- F-IOSD-_rF-I(SF i

I0__80 1 "_ oL F-IO6A m

_9441948 19521956 196019641968 19721976.1980Year

Figure 18.- The DCPR weight trends for U.S. fighters.

Numbers 1000 -

0 I I I I I

8000-

Flyaway

value, 4000-$ million

0 I 1 , _ •1964 1968 1972 1976 1980 1984

Year

Figure 19.- Trend in quantity procuredand total flyawaycost forU.S. fighter/attackaircraft,1968 to 1982.

Airframe,engines,avionics,armamentinstalledequipment,non-recurring costs,nospares

40 - (10)F-18

30-

Unit (30).F-14

flyaway 20cost, - (67)

•$ millions F-1..__.5•

(6)10 - (161)(44) A-7 (141)

" 0 _]

Figure 20.- Flyaway unit cost, U.S. fighter/attack aircraft, 1981.

Figure 21.- Lot averagecost for severalU.S. fighterssince1950 _ 1981 do]]ars.•

F-4 F-15 F-16 F-14 F-18

20 - :=_ ---- Other

Avionics

$Million 10 - Propulsion

•

0 _ "_ Airframe

Figure 22.- Distribution of lot average cost for. current fighters,1981 dollars.

F-80 F-86 F-100F-I04F-4 F-14F-15F-16F-18i00 - Other

,avionics

Propulsion

Percent Airframeflyawaycost

0 I I I I, 1940 1950 1960 1970 1980

Figure 23.- Distributionof flyaway cost for variousU.S. fightersover past 40 years.

F--4 F-15 F-16 F-14 F-18100 _ -----

• . Other-_- Avionics

Percent Propulsionflyaway50 -

costAirframe

0

Figure 24.- Percentage distribution of flyaway cost.

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

NASATM-863524. Title and Subtitle 5. Report Date

January 1985SOMEFIGHTERAIRCRAFTTRENDS e.Performing Organizath_nCode

505-43-43-017. Author(s) 8. Performing Organ;zation Report No.

M. Leroy Spearman10. Work Unit No.

9. Performing Organization Name and Address

Lanolev Research Center '11.ContractorGrantNo.NASAHampton, Virginia

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address TechnicalMemorandum,_ational Aeronautics & Space Administration 14. Sponr,oring Agency CodeWashington, DC 20546

15, Supplementary Notes

Collateral publication of AIAA Paper No. 84-2503 presented at the AIAA AircraftDesign, Systems, and Operations Meeting, October 31 - November 2, 1984,San Diego, CA ,,,

16. Abstract

Some basic trends in fighter aircraft are traced from the post WorldWar II era. Beginning with the first operationaljet fighter,the P-80, thecharacteristics of subsequent fighter aircraft are examined in terms ofperformance,mission capability, effectiveness,and cost. Characteristicspresented include such items as power loading, wing loading, maximumspeed,rate of climb, turn rate, weight and weight distribution,cost and costdistribution. In some cases, the characteristicsof U.S.S.R. aircraft areincluded for comparison. The trends indicate some of the rationale forcertain fighter designsand indicatesome likely characteristicsto be soughtin futurefighter aircraftdesigns.

"17. Key Words (Suggestedby Author(s)) 18. Distribution Statement

Fighteraircraft Unclassified- UnlimitedAircraftdesign

SubjectCategory 02

19. Security Classif. (of this report) _. Security Claudf. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 37 A03

.-30s ForsalebytheNationalTechnicalInfumati0nService,Springfield,Virp,inia22t61

3 1176 00191 6072