COMPARISON OF FLIGHT AND WIND-TUNNEL MEASUREMENTS OF HIGH-SPEED-AIRPLANE STABILITY AND

oDlab77i?TECHNICALNUTE 3859COMPARISONOF FLIGHT AND WIND-TUNNEL~OF HIGH-SPEED-AIRPLANESTABILITYANDCONTROLCHARAC’IEUSTICS1By Walter C.“Willisms,HubertM. Drake, and Jack FischelComparisonsofwind-tunneland controlcharacteristicsaresince thewind-tumnelmethd ofSUNMARYand flight-measuredvalues of stabili~of,considerableinterestto the designe.r,testing is one of theprime sourcesuponwhich estimatesof the characteristicsof a new configurationarebased.IiLthispaper comparisonsme made of some of themore @ortant stabilityand controlcharacteristicsof three swept-wingairplsmesasmeasured inflight and inwind tunnels. Wind-tunneldata from high-speed closed-throat.tunnek, a slotted-throattransonictunnel, and a supersonictun-nel sre used.The campsrisonsshow that, generallyspeaking,thewind tunnelspredict all trends of characteristicsreasonablywell. Th.eraare, how-ever,differencesin exactvalues of parameters,which couldbe attrib-uted samewhatto differencesin themodel causedby themethod of support.The small size of themode~ mqy have some effect onmeasurements of flapeffectiveness. When nonline=ities in derivativesoccurduringwind-tunnel tests, additionaldata shouldbe obtained in the region of thenonlinesritiesin order to predictmore accuratelythe f12ght character-istics. Also, nonl.inesritiesin staticderivativesmust be analyzedonthebasis of dynamicmotions of the airplane. Aeroelastic correctionsmust be msiieto thewind-tunneldata for mode~ of airplaneswhich havethin surface~and sre to be flown at high dynsmicpressures. Inleteffectscsm exert an influenceon the characteristics,dependingupon airrequiraents of the engine and locationof the inlets.%?he informationin this reportwas also containedin a p~er bythe same authorsentitled: “SomeCorrelationsof Flight-MeasuredandWind-Tunne+Measured Stabilityand Control Characteristicsof High-SpeedAirplsnes. The latterwas presented to the Wind Tunnel smdModel TestingPanel of theNATO Advisory Group forAeronauticalResearch and Developmentat themeeting in Brussels,Belgium,A-t 27-31, 1956.