-.

.

Copy No. ? ‘ :.,

.RMNo. L8A12

.

FORCE, STATIC LONGITUDINALSTABILITY,ANDCONTROL

CtiCTERISTICS OF A i: $CALE MODELOF THE

BELL XS-1 TRANSONICRESEARCHAIRPLANE

AT HIG13MACHNUMBERS

Axel T. MattsonandDonaldL. Loving-.

LangleyAeronautical La’bo’ratory-L=@w ‘ieldJ‘% ASSIFICATIdtJCHANGEDTQ

c— D3xnmrY

DATE8.18.:

W.H.L

NATIONALADVISORYCOMMITTEEFOR AERONAUTICS

WASHINGTON

.

c L“.-

●

.

NACAW No.L8A12 coNFIDmrAL

NATIONALADVISORYCOMMTTIEE

TECHLIBRARYKAFB,NM

Illllll[ll!llllllllll[l!““cJ1439h4

FORAERONAUTICS

RESEARCHMEMORANDUM

FORCE,91’ATICLONGTFODINALSTABILITY,ANDCONTROL

CHARAOIWRISJ!ICSOFA ~ –SCALE

BEGLXS-1TRANSONICRESEARCH

MODELOFTHE

AT

By AxelT.

HIGHMACHNUMBERS

MattsonandDonaldL.Loving

SUMMARY

Thisreportcontainacompleteresultsobtainedtodeterminethe

effectsofcompressibilityathighMachnumbersona -J--scaiemodel16

oftheBellXE+ltransonicresearchairplanesndthereforesupersedesNACARM No.L7A03whichwaspreviouslypreparedat theLangley&foothig&speedtunnel.

Theseresultsarepresentedforseveralmodelconfigurationsthrougha Wch numberrangefrom0.4toapproximately0.95.Allthedatahavebeencorrectedfa tareforces.

At a Wch numberof 0.78a dragforcebreakoccursforthehigh-speedlevel-flightliftcoefficient(CL= 0.1). Thisforcebreakisaccompaniedby a rapid increase in drag coefficientwithincreaseinspeed.At a ~ch numberof0.925thedragcoefficientisaboutfiveendone-halftimesthesubcriticalvalue.A liftforcebreakoccursat a Machnumberpf0.80foran angleofattackof @. At aWch numberof0.875theliftcoefficientdecreasesrapidlytoapproxi–matelyzero.At a Machnumberof 0.92’5,theliftcoefficientincreasesagaintoa valueof 0.2.

Thisconfigurationhasa highdegreeofconstant-speedstaticlongitudinalstabilityexceptfora narrowrsngeofMachnumbers(approximately0.875 to 0.c30) at lowliftcoefficients.

Stabilizersndelevatoreffectivenesstendtodecreaseat thehighMachnumbers,butno seriouscontrolpro%lerasareexpectedup tothehighestWch nunberinvestigatedbecausethelowestde~ee ofeffectivenessisstilJof suchmagnitudeas tobe ableto producechangesintrimforlevelflightat thedesiredaltitudes.

Tuftsurveysoftheaftportionofthefuselageshowedno sepa-rationorunusualflowpatterns Upto a Mch nunherof 0,925 foramaxhum”angleofattackof 3° anda msxhumyawsngleof2.2°.

conrmmw\

2 commmm NACARM No.Z8A12

Theresultsshowthatthespeed-retardingbrakesarebarelycapableofreducingtheterminalvelocityoftheairplanetothecriticalhchnumberrange.

●

INTRODUCTION.

Thisreportsupersedestheresultspresentedinreference1 andpertainstodatarelativetotheforceandlongitudinalstabilityand

1controlcharacteristicsofa —-scalemodeloftheBellX&l transonic

16researchairplaneathighMachnumbers.TIMtestsweraconductedintheLsmgley&foothig&speedtunnelattherequestoftheAirMaterielCommand,_ AirForces.

At thetimeoftheX&l modelinvestigation,forwhichresultswerepu%lishedinreference1,difficultywasexperiencedinobtainingtaredata. Itwasno lessdifficultto obtaintarecorrectionsfcmthepresentresults,butpriorto thetestsa moresensitivebalancesystemwasinstalledandduringthetestprogramsufficienttareconfigurationswereincludedto correctallconfigurationsoftheregularmodelinvesti-gated.Themoresensitivebalancesystemwasusedfortheregularmodeltestingalso. Therefore,thisreportwillsupersedetheresultsquali-tativelypresentedinreference1,

Theresultspresentedhereinwereobtainedforthemodelwithoutthesimulationofrocketpower.Anglesofattackof+o, 0°,30,~d Gowereinvestigated,aswellas stabilizersettingsof-3°,0°,emd3°andelevatordeflectionsof-30,0°,30,and60. Theaerodynamiccharacter-isticsofa fuselagespeed-rsductlonbrakewerealsoinvestigated.Visualobservationsweremadeofwoolentuftslocatedonthefuselagesideaftofthewingtrailingedgeas an indicationofanyflowdisturbanceinthisregion.

—

SYMEm8s

ThesymbolsusedInthisreportand‘theirdefinitionsareasfollows:

v free-streamvelocity,feetpersecond

P free+streamdensity,slugspercubicfoot m—

q -c Presswe,poundspersquarefoot()$$

a velocityof sound,feetpersecond(49.O@, T in % absolute) +

CONFIDENTIAL

u

NACARM No.L%l12

M (}TWch nunber -

L lift,pounds

D drag,pounds

Mcg pitthingmoment,foot-pounds

% wingarea, 0.508.-C mea aerodpamic

LCL=—~h

%=~~%

c! =mcg

a

dCL

a%outcenterofgravity(25percent‘E),

squarefoot

chord,3.6o7inches

3

angleofattackmeasuredwithrespectto fuselagecenterline,degrees

angleof incidenceofthehorizontaltallwithrespecttofuselagecenterline,degrees

elevatoranglewithrespecttohorizontal-tailchordline,degrees

effectivedownwashemgle,degrees

distancefromcenterofgravitytoaerodynamiccenterofwigfuselagecombination(positivewhencenterofgravityisrearwerd)

yawanglemeasuredwithrespectto fuselagecenter(positivewithrightwingreterded),degrees

staticlongitudinalsta%ilityofthewi~fuselage

lift-curveslopeofthew-fuselage combination

line

combination

~ateof chmge ofdownwashatthetailwithliftofthewing

lift-curveslopeofthehorizontaltail

CONFIDENTIAL

commmm4

Su-bsoripts:

t horizontaltail

w wln#’usel.agecombination

m-, APPARATUSANDMETEclDs

NACAW No.I&l12

—

i-

AlrplaneandMdel

TheBellXS-1isa single-plaoe,straightdesignedfor extremevariationsinspeed,wing

mldwingresearchairplaneloading,andaltitude.

Theairplaneemploysa rocketmotorand1sequippedwithan ad$uitablepowe-iven stabilizer.

A’—-scale,all-metal,solid-oonstructhnmodel,whiohoonsisted~6ofa wing,fuselage,andempennage,wassuppliedby theEellAlroraftCorporatIonforthisinvestigation.TheprincipaldimensionsoftheBell-1 researohairplaneas testedIntheLangley8-foothigh-speedtunnelareshownInthethree+ibwdrawinginfIgure1. Thephysicalcharacteristicsoftheairpl+nearegivenintgbleI. Thespeed+reductionbrakessuppliedby theNACAweremadeofsolidcluraluminandlocatedonthesidecenterlineofthefuselageaftofthewingtrailingedgeas showninfigure1. Themodelstabilizercouldbe setforincidenoeanglesof&6°,*3°, andOO. Hcmizontaltailswithbuilt- Vinelevatorsettings,leavingno gapsbetweenthestabilizerandelevator,weresuppliedfortheelevatadeflections.

ApparatusandWthods —

TheIangley8-foothigh-peedtunnel,inwhiohthisinvestigationwasconduoted,isa singl-return,closed-throatt~e capableofobtafning- tunnelempty- a Maohnumberofunityinthetestsection.Thetunnelalrvelocityiscontinuouslycontrollable.Forthisinvestigation,hch nunibersup toapproximately0.95 wereobtainedbytheuseofa sti~upport system.

Tunnelsti~upport system.-Jhordertodispensewiththeinterferenceeffectsof conventionalsupportstrutsathighMachnumbersandtopermitmodeltestingata Mch nuniberapproachingunity,themodelwasmountedona sti~upport systemas showninfigure2. Thestingsupportextendedfromtherearofthefuselagetoa shieldedstrut rmountedverticallyandconnectedtothetunnellalancesystem.Thestingshieldextended2.60 inchesinfrontofthevertioalsuppcm+strutfairing.A smoothfairi~waslocatedonthestingdirectlyin #

coNFIDmIAL

.,

NACARM No.L8A12 coNFIDENTm 5

frontofthegapbetweenthestingendstingshieldin orderto preventdirectflowintothesupportshield.I?igure2 showsthesti~upportsystemandalsothetaresetupintheIangley&foot hig&speedtunneltestsection.

Tme setupandevaluation.-Auxiliaryarmsto supportthemodelasshownInfigure2 wereusedtodeterminethetarevaluesofthesupportsystemandinterferenceeffects.Thesupportsintheregionofthemodelwere&percent+thickairfoilssweptback30°tominimizeinterferenceeffectsanddelayeffectsdueto compressibilityforthetestWch numberrange.Thereminingpsrtsofthetaresupportswerethinplatesextendingbackandconnectedto thesupportstrut.

Thetaresetupsandthemethodby whichallthedatapresentedinthisreporthavebeencorrectedareillustratedinfigure3. Guywiresfromthewingtipswereusedonalltsrerunssothatthesystemwouldbe rigidwhenno stingwasused. Threemodeltareconfigurationswererequiredto evaluatethetsxeforces.Forthetareconfigurationwithoutthesting,thestingwasreplacedby a smallfuselagefairing.Thisfairingwasrelativelybluntbecauseofthegeometryofthefuselagecontours,smdalso,itwasbelievedthata longerfuselagefairingwouldchangethebasicpitchin~omentcharacteristicsofthefuselage.Theassumptionsincludedinthetsreevaluationsrethattheinterferenceeffectsofsrmson stingandstingonarmsarenegligible.

k orderto indicatethemagnitudeoftheeffectsofthetaresonthepltchi~nt coefficientofthe=1 model.figure4 hasbeenprep&edf= anglesofattackof 0°and3°. “ -

TESTSAND~S

TestConditions

Thesetestswererunthrougha Machnumberrangeapproximately0.95. ThemcdelReynoldsnuniberranged

from 0.4 toforthesetests

fromapproximately1.03x 106to1.8 x 106 andwasbasedona modelmeenaerodynamicchordof 3.607inches.

Measurements

Theforcemeasurementserepresentedaa standardNACAnondimensionalcoefficients.Thesecoefficientsarebasedona modelwingsreaof 0.508squarefoot. Thepitchingmomentsw’eretakenabouta cente~of-gravityposition(0.253)indicatedinfigure1,whichalsogives

6 CONI?IDENTIIUI NACAW No.L8A12

theprincipaldimensionsofthemodelas testedintheLangley&foothig&speedtunnel.Thefollowingmodelconfigurationsweretested:

(a)

(b)

(c)

(d)

(e)

(f)

(i3)

Mciiellesswingwithendwithouthorizontaltail

Mcdellesshorizontal

Completemodelwith

it

it

it

Completemodelwith

tt

it

it

Completemodelwith

it

it

Modellesshorizontal

tall

= 00, ae = -30

= 00, be = 00

= 00, Ee = 30

.—

‘-30, ae = 00

= 30, be = 00

= 30, 5= =-30

= 30, t5e= 30

= 3°, be = ~“

tailwithspeed-reductionbrake

Completemodelwithspeed-reductionbr~e

CORRECTIONS●

Becauseoftherelativelysmallmodel&ch numbers,wind-tunnelcorrectionssuch

requiredfortestingathighasmodelconstrictionand

-.

?.

—

wakeconstrictionaresmallup tothehighesttestMachnumberattained.An estimationofthetunnelcorrection,obtained%yusingmethalsdescribedInreferences2, 3,4,and5, indicatesthatthecorrectionsto theMachnuniberwill%e approximately1.5percentata tunnelMch..numlerof 0.9forthehighestliftcoefficientqattained.Correctionsindynamicpressurewillbe ofthesameorder.ofmagnitude.Thelift

.- .

vortex-interferencecorrectionissmall,beinga changeinangleofattackoflessthanO.1°atthehighestliftcoefficient.obtained.

#

Becauseof.thesmallmagnitudeofthecorrections,theyhavenot%eenappliedtothedatapresentedherein. -7

corimmra

NACA~No. ti2 CONFIDENTIAL 7

.

*

.

Tmnel-wallpressuremeasurementsshowedthattheflowinthetestsectionwasfreeof Interferencefromtunnelchokingeffectsandfromtheflowfieldofthesupportstrutat thehighestMachnwrherforwhichdatasxepresented.

Themodelwasaccuratelyconstructedand,%eingofall-metalconstruction,remainedthesamethroughouttheinvestigation.Displacementofthemodelcenterofgravityrelativetothetrunnionexlsofthetunnelduetoairloadswascontinuouslyobservedby theuseofa cathetometer.Correctionsformodeldisplacementshavebeenappliedto thepitchingmoments.Theangleofattackofthemodelwasalsocheckedhy theuseofthecathetometer:fm themsximumloadsoltainedthecherweinsndeof’attackduetodeflectionofthemodelwasoftheorderof-0.20.&edeflectionswereinvestigated.

considerednegligiblefortheengl-f-attackrange

RXSUZTSANDDISCUSSION

AerodynamicCharacteristics

Dragchexacteristics.-F@re 5 presentsthevariationofangleofattackanddragcoefficientwithliftcoefficientforthecompletemodelthrougha Machnumberremgefrom0.4to 0.925.ThevariationofdragcoefficientwithMachnumberforliftcoefficientsof 0.1end0.4isshowninfigure6. Figure6 alsoindicatesa completemodeldrag-coefficientvalueof 0.0155fora liftcoefficientof 0.1at a Machnumberof 0.6. WhentheMachnumberincreasestoapproximately0.78,a dragforcebreakoccursforthehigl+speedlevel-flightliftcoeffi-cient (CL= 0.1). Thisforcebreskisfollowedby a rapidincreaseindragcoefficientwithincreaseinMachnumber.At a Machnumberof 0.925thewag coefficientreacheqa valueofapproximately0.083whichisaboutfiveendone-half’timesthesubcriticalvalue.Tigure6alsoindicatesa liftforcebreakat a Machnumberof 0.765 fora liftcoefficientof 0.4. Therapiddra~oefficientrisethatfollowsresultsina valueofapproxhately0.1055at a &ch numberof 0.925.

Liftcharacterlstics.-ThevariationofliftcoefficientwithMachnumberforanglesofattackof-2°,0°,3°,snd60 ispresentedinfigures7 and8 foralLmodelconfigurationsinvestigated.At snangleofattackof0°theliftforcebreakforthecompletemodeloccursat a Machnumberof 0.80.Forthisconditionthemmlelliftcoefficientisapproximately0.30.Withincreaseinkch numberto 0.875theliftcoefficientdecreasesrapidlyto approximatelyzero.WithafurtherincreaseinWch numberto 0.925,theliftcoefficientincreases “againto 0.2. ThisincreaseinliftcoefficientathighsupercrfticalMachnumbers,althoughsubjecttomorefundamentalinvestigation,isbelievedtobe mainlytheresultoftheresrwerd movementoftheshockdisturbanceontheuppersurfaceofthewing,

coNFmmTIAL

8 coNFIDmm NACARM No.123A12

Pitchlw omentcharacterlstlcso-Figures7 and8 alsopresentthepitchi~cxnentcoefficientsforconstantanglesofattackagainstMachnumber.Foralltheconfigurationspresented,”nolsxgechangesinthe ““pitch~ment vsriatfonwithhkchnumberoccuruntila Machnumler ●

of0.85isreached.Thereafter,froma Machntiberof 6.85toapproxi-mately0.95,largec~ges ~ Pitch@ momentOCCUrOWese change~inpitchingmomentoc”curwithrelativelysmallincreasesinMachnudber. .

Aerodynamiccharacteristicsofa speed-reductionbrake.-Figure9presentsthevariationofincrementaltiq?jliftjad p~tchi%+~ntcoefficientswithMachnumberduetotheadditionofa speed-reductionbrakeontheX+1 withandwithouthorizontaltail. ThevariationforallpracticalpurposesisessentiallythesamethroughouttheMachnuniberrangetested;thatis,up toa Machnumberof0.925,thelimitforthesetests.The?nodelconfigurationwastestedatan angleofattackof-2°whichrepresentsapproximatelythezer-liftcondition.

Ifa wingloadingof40 poundspersqusxefoot is assumed,theterminelMachnumberoftheX&l withspeed-reductionbrakesextended65°isfoundtobe approximately0.83oraround598milesperhourat15,000feet.‘Withoutthespeed-reductionbrakes,thete~~l velocitY-”wouldcorrespondtoa Machnumberof0.93or670milesperhour. Thisshowsa 10.7>percentreductioninterminalvelocitydueto thebrakesandindicatesthatthebrakesarebarelycapableofreducingthespeedof themodelto thecriticalMachnuniberrange.

Figure9 showsthattheliftincrementproducedby<he speed–●

reductionbrakesisnegligible.-. —

Theincrementalpitchi~mmnt coefficientdueto thespeed- ‘ creductionbrakes,figure9, shins that at a ~ch numberofapProx~-mately0.85a divingmcnnentisproducedandwitha furtherincreaseinMachnumberthisdivingmomenthasdecreasedsothatat~alhchnumberof 0.94a pull-outmomentisindicated.Theseinetrendisshownforthemodelwithouthorizontaltailexceptthatthepull-gutmomentata Machnumberof0.94 issomewhatlessthanthatwiththehorizontaltail.

Tuftmrve~.-Woolentuftswereplacedontheslde_ofthefuselageintheareabetweentheV@ trafli%Wge ~.the e~re~ tailendofthemodel.Neitherseparationnorunusualflowpatternswerenotedfor

—

theconfigurationstestedthroughoutthe~ch.pumberrseo me _configurationsobservedwereas follows:

..—

1 1 ‘-a ‘t be +

0’.10 00 o~ 0° *

3° 0° 6° 0°

3° 0° 6° ,2*ZO●

cow~m~

NACAM No.ti2 CONFIDENTIAL 9

StaticLongitudinalstabilityCharacteristics

.

.

Thestaticlongitudinalstabilitycharacteristicsforthecompletemodeltith It= 0°) be= 0° arepresentedas thevariationofpitching+nomentcoefficientwithliftcoefficientforMachnumbersfrom0.40to 0.925infigure10. TheusuallyexpectedstabilityincreasewithMachnuniberincreaseis indicatedforthepcsitivelift-coefficientrange.Theslopeofthepitch~momentcwe ~b%@L)M isapprOxi-mately-0.08at a hch numberof 0.40 and increases toabout-0.16 ata l%chnumberof0.925.Inthenegativelift-coefficientrangeinvesti-gated,howeverthetrendisquitedifferent.Forthestabilizersetting(of0°~themodelbecomesunsta%leinthisnegativeCL rangebetweenapproximatekch numbersof 0.85to 0.90. Infiguresu to13thissametrendmaybe notedforallstabilizerandelevatorsettingstested.Itshcmldbe notedthattheanalysistie hereinisforen .untrimmedconditionandtheairplanemayormaynotexperiencedifficultydependingontheflightplan. However,itshouldbe noted(infig.11)thatfora Machnuniberof 0.875, a liftcoefficientofaboutO.@, anda stabilizeranglefortrimofapproximately3.0, the airplane isstaticallyunstable.&causeofthelimitedrengeofliftcoefficientandhch nuniber,theseriousnessofthisinstabilitymaybe questionable.However,becauseoftheverylowliftcoefficientsattainedinsealevelflight(fig,20),itwouldprobablymakeflightintheMachnumberrangeveryneartotheground hazardous becauseofthedangerofovercontrolling.Heretoforethegenerallongitudinalstabilitycharacteristicsinthesupercriticalnumberatlowto thestall.regioninthecriticalMach

s~ed rengeindicatedan increasingstabilitywithMachliftcoefficients,aswellas highliftcoefficients,upThepresentinvestigationindicatesthatanunstablelowornegativelift-coefficientrangeathighersupe~nunibersdoesexistforthisconfiguration.c

Contributionofveriouscomponentsto constantipeedlongitudinalstabilit~.-Thefollowinganalysishasbeenmadeto detertie qu~ita_Eivelytheugnitudeofthecontributionofthevariouscomponentsintheapprox~testaticlongitudinalstabilityequationto theunstableconditionindicatedfortheX&l airplaneIntherangeoflowliftandhighspeed.Tnordertoascertainthecomponentcontributingmost,eachprincipalcomponentofthegeneralstabilityequationforthecompleteairplanehasbeeno%tainedandevaluated.Theapproximateconstan+speedstaticlongitudinalstabilityequationusedisas follows:

d%

(J

a%—=—dCL ac w

coNFIDmw

10 CONFIDENTIAL NACARM No.L8A12

Thisapproximateequationthenqualitativelyindicatesthattheprincipalcomponentsaffectingthelongitudinalstabili~y(d~dCL) oftheairplaneare:

.,(neglectingqt/q)

--

1.

2.

39

4.

(Wc@L)w,.

staticlongitudinalstabilityofthewing-fuselage ——combination

●

d.

?K@a, thelift-curveslopeofthewin@?uselagecombination

d~/dCL,therateof changeofdownwashatthetailwithliftofthewing

(acL/@t, thelift-an?veslopeofthehorizontaltail

Twoliftrangese.re,consideredincomparingthesefactors: ,,-...

(a)Thelowliftrangefroma liftcoefficientof-0.1to 0.1,(measuredatapproximately~ = O)

(%)Thehighliftrangefroma liftcoefficientof0.2to 0.3.(measuredatapproximatelyO.3) —

Tn orderto ilhstratetheconstsnt+peedstaticlongitudinal.stabilitycharacteristicsofthe233-1inthelowliftrange,as comparedwiththestaticlongitudinalstahilftycharacteristicsinthehighliftrange,figure14hasbeenprepared.Itmaybe notedtl&tthemcdelinthelowliftrangebeginstobecomeunstableatapprox}~telya Mach ?

numberof 0.80,andthedivergencebetweenthestabilityatthetwolift ‘“coefficientsreachesa maximumat a Machnumberofapproximately0.885.

*Thefirstcomponenttobe analyzed,thestaticlongitudinalstability

ofthewi~fuselageccmibination,IsshownInfigume15andindicatesadivergenceforthetwoliftremgesconsideredbetweena Kch nuniberof 0.825and0.9.

— ——

Thelif%urve slopeforthewingisshowninfigure16forthetwoliftranges~onsidered.ThisfigureindicatesthatthevtifationandtrendwithMachnumberisessentiallythesame.~< low-speed;alues‘“arethesame,themaximumvalueofthelif%curveslopeoccursat aMachnumberofabout0.80forbothliftranges,andthelowestvalueof-thelift-curveslopeoccursata Machnuniberofapprox+tely0.875.It shouldbe notedthatthemagnitud.esforthe.rangesconsideredsrequitedifferent,thelowliftrangeproducingtheh~ghestandtheluwestvalues.,,

Tnconsideringthedownwashcamponent(dc/dCL) +tn~ be noted ..

infigure17thatthevariationandtrendwithWch numberaxenotthe‘-”sameforthetwoliftrangesconsidered,especiallyathighhbchnumbers.Thevalueofthe d~/dCLisidenticalforbothliftremgesat a I’&ch ?numberof0.70.However,inthelowliftrangethevu”iationofdownwashwithliftcoefficientincreasesrapidlywithMachnumberuntil”

CONFIDENTIAL

,

NACARM No.L8A12 CONFJDENTDL 11

.

.

a valueof8.2 isreachedata Machnuniberof 0.875.~is valueis142percentgreaterthanthevalueat a Wch numberof 0.70. Inthehighliftrange,ontheotherhand,thevalueof de/dinonlydecreaseswhena Jbchnunherof 0.875isreached.ThetrendisalsodivergentfrcunaMachnumberof”O.~5to 0.925.

Thelift+urveslopeofthehorizontaltailas showninfigure18isthesameforbothliftremgesconsideredandthereforeithasnoeffectonthedifferenceinstaticlongitudinalstabilityfortheliftrangescotiidered.

Thisanalysisillustratesqualitativelythattheprimarycontributorsto theinstabilityoftheX&l modelat lowliftcoefficientsandhighMachnumbersare: (1)Thelongitudinalinstabilityofthewing-fuselagecombinatio~snd(2)theincreaseintherateofeffectivedownwashwithliftcoefficient.

Figure19presentsthestick-fixedneutral-pointvariationwithMachnumberwhenthemodelis inlevelflightat sealevelandaltitudesof 30,000feetand40,000feet.An averagerearwardshiftoftheneutralpointfrom3&percentmeanaerodynamicchordat a &ch numberof 0.60to4&percentmeanaercxQnamlcchordat a Machnumiberof 0.925isshownforthealtitudeof40,000feet.

Ccmtrolcharact6ristics.-Thevariationof level-flightliftcoeffi-cientwithl.kchnumberforthemodelwitha wingloadingof40 pounds

Q, persquarefootat sealevelandaltitudesof 30,000feetand40,000feetispresentedinfigure20. Thestabilizersettingsendelevatwdeflectionsrequiredto trtmthemodelinlevel-flightat sealevelandaltitudesof 30,000feetand40,000feetshowninfiguresElend22 indicatea*changeof onlya fewdegreesforeitherthestabilizeror elevatorintheMachnumberrangebetween0.825end0.925.Itshouldbe noted,however,thatthesechanges,althoughnotexcessive,occurrapidlywithsmallincreaseinMachnumberandrapidmanipulationofthecontroltillbenecessary.

Thestabilizerandelevatoreffectivenessareshowninfigures23and24forangles-ofattackof-2°,0°,and3°. Theeffectivenessofbothstabilizerandelevatmispracticallythesamefortheangl~of+ttackramgetested.ThestabilizereffectivenessdecreasesWhincreaseinspeedfroma Machnuniberof O.~ to 0.925.

Theelevatoreffectivenessincreaseswithspeeduntila &chnumberof 0.825isreached.Thena slightdecreaseisnotedforanglesofattackof 0°and3°. Thedecreaseisslightlymorerapidforamangleofattackof+!”up tothehighesttest&ch numberof0.925.

b thefiguresjustpresentedforstabilizerandelevatoreffectiveness,theeffectofduwnwashanddynamicpressureat thetail

CONFIIENTW

12 CONFIDENTIAL NACARM No.Ii3A12

is included.However,infigure25 theeffectivenessofthehorizontaltailwithoutdownwasheffectsisshownwithMachnumberandindicatestheeffectsofcompressibilityandfuselageinterferenceonthehorizontaltail● .

CONCLUSIONS .-.

1.A dragforcel)reakoccursat a Machnuniberof 0.78,followedby a rapidriseindragcoefficientwithMch nunberfora liftcoeffi-cientof0.1.

2.A liftforcebreakoccursata Machnumberof 0.80,followed%y a decreaseemdthenan increaseinliftcoefficientwithMachnumberforanangleofattackof OO. —

3. Thisconfigurationhasa highdegreeof constan~peedstaticlongitudinalstabilityexceptfora narrowrang?ofMachnumber(approximate=0.875to 0.90)atIowliftcoefficients.

.

h. Stabilizerandelevatoreffectivenesstendtodecreaseat thehighWch nunhers,butno seri.cn+controlproblemsareexpectedup tothehighestMachnumberinvestigatedbecausethe,lowestdegreeofeffectivenessIsstillofsucha magnitudeas to controlchangesintrimforlevelflightat thedesiredaltitudes.

5. Tuftsurveysoftheaftportionofthe@selageshowednoseparationorunusualflowpatternsup toa &ch.numbero~0.925foramaximumangleofattackof3°anda msxinmmyawangleof2.2°.

6. Theresultsshuwthatthespeed-retardingbrakeslocatedonthefuselage%ehindthewingarebarelycapable.ofreducingtheteti~l ““__velocityoftheairplanetothecriticalMachnumberrangq.

—

—

—

.-

r

LangleyI@mmrialAeronauticalLaboratory--

NationalAdvJsoryComaitteeforAeronautic-sLangleyField,Va.

*-

CONT’DENTIAL

NACARM No.L9A12 13

REFERENCES

.

.

1. &ttson,AxelT.: ForcesndLongitudinalControlC%a.racteri.sties

ofa >-scaleMcdeloftheBellXSl TmnsonicResearchAirplaneAU

atHighlkchNbmbers.NACARMNO.L7A03,1947.

2.~ne, RobertW.: ExperimentalConstrictionEffectsinWindTunnels.NACAACRNo.Lk~7a,1944.

3.Glauert,H.: WindTunnelInterferenceonWings,I!diesR. &M. No.1566,RritishA.R.C.,1933.

Hig~eed

andAirscrews.

4. Thorn,A.: BlockageCorrectionsandChokingintheR.A.E.HighSpeedTunnel.Rep.No.Aero1~1, BritishR.A.E.,Nov.1943.

5.Goldstein,S.,andYoung,A.D.: TheLinearPerturbationTheoryofCompressibleFlow,withApplicationstoWind-Tunnelinterference.R. &M. No.19@, lkitishA.R.C.,1943.

coIIKIlm’’IAL

commmw NACARMNO.L8A12

TABLEI.-PEYSICALCHARACTERISTICS~ THEHELL

RESEARCHlmPLAm1 —.

Power:Fourrocketunits,

groupedinrear

Wi~ loading:Take-off,1%/sqftLanding,lt/sqft

wing:Area,sqft . . .Span,ft....

eachcapable—●

r>

.

.

.

.

.●

✎

✎

✎

✎

✎

●

✎

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