-.
.
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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