REG NASA-TN-D-1057-1961 Analysis of X-15 landing approach and flare characteristics determined from the first 30 flights.pdf

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1、hP!.rIloZZ/ ,J_ jNASA TN D-I057i I |TECHNICALD-1057NOTEANALYSIS OF X-19 LANDING APPROACH AND FLARECHARACTERISTICS DETERMINED FROMTHE FIRST 30 FLIGHTSBy Gene J. MatrangaFlight Research CenterEdwards, Calif.NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONWASHINGTON July 1961Provided by IHSNot for ResaleN

2、o reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IJNATIONAL AERONAUTICS AND SPACE ADMINISTRATIONTECHNICAL NOTE D-I057H22iANALYSIS OF X-15 LANDING APPROACH AND FLARECHARACTERISTICS DET

3、ERMINED FROMTHE FIRST 30 FLIGHTSBy Gene J. MatrangaSUMMARYThe approach and flare maneuvers for the first 30 flights of theX-15 airplane and the various control problems encountered are discussed.The results afford a relatively good cross section of landing conditionsthat might be experienced with fu

4、ture glide vehicles having low lift-drag ratios.Flight-derived drag data show that preflight predictions based onwind-tunnel tests were_ in general_ somewhat higher than the valuesmeasured in flight. Depending on configuration_ the peak lift-dragratios from flight varied from 3-5 to 4.5 as compared

5、with a predictedrange of from 3.0 to 4.2.By employing overhead_ spiral-type patterns beginning at altitudesas high as 40_000 feet_ the pilots were consistently able to touch downwithin about i_000 feet of a designated point.A typical flare was initiated at a “comfortable“ altitude of about$00 feet a

6、nd an indicated airspeed of approximately 300 knots_ whichallowed a margin of excess speed. The flap and gear were extendedwhen the flare was essentially comp!eted_ and an average touchdown wasaccomplished at a speed of about 159 knots indicated airspeed_ an angleof attack of about 7_ and a rate of

7、descent of about 4 feet per second.In general_ the approach and landing characteristics were predictedwith good accuracy in extensive preflight simulations. F-104 airplaneswhich simulated the X-I_ landing characteristics were particularlyvaluable for pilot training.Provided by IHSNot for ResaleNo re

8、production or networking permitted without license from IHS-,-,-INTRODUCTIONPrior to the first flight of the X-15, _t was apparent from wind-tunnel tests that the landing approach and flare maneuverswould beperformed in a range of lift-drag ratios low_r than previously flownwith rocket-propelled air

9、craft (ref. i). Sirce piloting problems wereanticipated, analytical and flight-test studies were undertaken by theNASAFlight Research Center, the manufacturer (North American Aviation,Inc.), and the Air Force Flight Test Center Io determine howwell thepilot could execute approach and flare maneuvers

10、at reduced lift-dragratios. References i to 3 are illustrative (f these investigations.This paper expandsupon the limited analyses of early X-15 landingspresented in references I, 4, and 5. The la_ding approach and flaredata acquired during the first 30 X-15 flights are considered in detailand are c

11、omparedwith the preflight predictions. Included are data forthe initial landings of each of the seven X-15 pilots. These results_it is believed_ are generally indicative of flight characteristics andpiloting problems which might be encountered in executing a normalflared landing with future low-lift

12、-drag-rat_o gliders.A detailed analysis of the X-!5 landing-gear behavior duringtouchdown and runout is presented in reference 6.H22iSYMBOLSa nCDCLghL/DMPqnormal acceleration_ g unitsairplane drag coefficientairplane lift coefficientacceleration due to gravity, ft/sec 2geometric altitude (referenced

13、 to touchdown point), ftlift-drag ratio_ CL/C DMach numberrolling velocity, deg/secpitching velocity_ deg/sect time before touchdown, secProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AtViVvWXZxxYga8fghincremental time before touchdown_ secindicated

14、 airspeed_ knotsvertical velocity_ ft/seclanding weight 3 iblongitudinal distance from touchdown_ fttouchdown dispersion from intended touchdown point_ ftlateral distance from touchdown_ ftangle of attack_ degangle of sideslip_ degaileron deflection (left horizontal-tail deflection minus righthorizo

15、ntal-tail deflection)_ degflap deflection_ deghorizontal-tail deflection_Left horizontal-tail deflection + Right horizontal-tail deflection2degSubscripts:The following subscripts apply to conditions during the particularportion of the landing approach and flare maneuver indicated.fgeTD9o18ofemaxflar

16、e initiationgear extensiontouchdownpattern base legpattern downwind legflap extensionmaximum condition during flareProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AIRPLANEThe X-15 is a single-place research airplane designed to performat speeds up to

17、 6_600 ft/sec and altitudes _p to 250_000feet. Thepeak performance is attained during short-d_ration_ rocket-poweredflight following which the airplane perform_ an unpoweredglide to thelanding. A three-view drawing of the airplane is shownin figure i.Figure 2(a) is a photograph of the airplane in th

18、e normal groundattitude_ and figure 2(b) showsthe airplan_ in flight just prior tomain-gear touchdown. Table I contains pertinent X-15 physicalcharacteristics.The airplane has a 5-percent-thick win_ with an aspect ratio of 2.5.Plain flaps are located at the trailing edg_ of the wing.All aerodynamic

19、control surfaces are actuated by irreversiblehydraulic systems. Movable horizontal-tail surfaces are deflectedessentially symmetrically for longitudinal control and differentiallyfor lateral control by meansof either a cor_ventional center stick ora side-located controller. The controllers are linke

20、d mechanically andhydraulically to provide simultaneous movementof both control sticks;however_ to obtain a given stabilizer motio_ only about one-third asmuchmovementof the side stick is required as of the center stick.The movable portions of the upper and lower wedge-sectioned verticaltails_ actua

21、ted by conventional rudder pedals_ provide directionalcontrol. Just prior to flare initiation, t_e lower movable portion ofthe vertical tail (also referred to as the _Lovablerudder) is jettisonedto allow sufficient ground clearance for lalding. Speedbrakes arelocated on the rear fixed portion of the

22、 up,er and lower vertical tails.Augmentedaerodynamic damping of the a_rplane is provided aboutall three axes in a conventional manner. An additional interconnectdamper_termed “yar“_ furnishes a crossfeed of the yaw-rate signal intothe roll damper. The characteristics of th_ stability augmentationsys

23、tem are given in table II.A nominal flap deflection of 40 was u_ed for the first five flightsof the numberi X-15 airplane and the first three flights of the number2airplane. However_in order that a reduced drag could be obtained withoutappreciably affecting the lift_ the nominal deflection was reduc

24、ed to 30for all subsequent flights. The actual fla, deflection recorded duringeach flight and the flap-actuation time are included in the tabulationof flight-measured characteristics in table III.The landing gear consists of a comparalively conventional dual-wheel nose gear located far forward of th

25、e airplane center of gravityand steel skids located to the rear under tle horizontal tail (fig. i).Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Extensive detail of this gear system and its operation is presented inreference 6. Table III lists the

26、gear-actuation time for each flight.INSTRUMENTATIONThe following quantities pertinent to this investigation wererecorded on NASAinternal-recording instruments_ synchronized by acommontimer:Airspeed and altitudeNormal and longitudinal accelerationAngle of attack and angle of sideslipRolling_ yawing_

27、and pitching velocityAileron_ vertical-tail_ horizontal-tail; and flap deflectionThe airspeed and pressure altitude were measuredwith a conven-tional NASApitot-static tube mounted on a nose boom. A descriptionof the nose boomand its accuracies is given in reference 7. Also onthe nose boomwere free-f

28、loating vanes used to measure angles of attackand sideslip. The angles presented in this paper were not corrected fortransient position errors_ since these errors were considered negligible.The angular velocities were measuredabout the airplane body axes.Geometric altitude and ground coordinates fcr

29、 the approach-patternanalysis were obtained from multistation solutions of position datafurnished by Air Force Flight Test Center Askania cinetheodolite cameras.These cameras; operating at 4 frames per second; tracked the airplanethroughout the pattern; flare; touchdown; and ground runout. Akeleypho

30、totheodolite cameras_ running at 19 frames per second; tracked theairplane through the final phases of the flare_ the touchdown; andground runout. A combination of the Askania and Akeley camera dataprovided altitude and rate-of-descent information during the flare andtouchdown.During someof the more

31、 recent landings reported in this paper,an analysis of the skid imprint on the lakebed (see ref. 6) and measure-ments using the skid itself as a trailing arm (somewhat similar inprincipal to the method of ref. 8) afforded additional cross checks fordetermining the value of rate of sink at touchdown.

32、 The values obtainedfrom these independent sources generally agreed to within i ft/sec.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TESTCONDITIONSTable III presents a listing of the pilo_ landing weight_ dampersetting_ and control stick used durin

33、g the fll_re_ together withconditions existing on the downwindand base i_egsof the pattern_ atflare initiation, during flap and gear extens2on_ and at touchdown foreach flight. This tabulation forms the nucleonsof this paper and willbe referred to frequently in the subsequent sections. In the flight

34、designation used in the first column of the t_le_ the first digitindicates the airplane by number (i or 2), th._ second indicates thefree-flight numberof the particular airplane, and the third indicatesthe total airborne X-15/B-52 flights for that airplane.At least one landing has been performed _y

35、each of the seven X-15pilots (A to G in the tabulation). Three were NASApilots_ two wereAir Force pilots_ one was a U.S. Navy pilot_ and one was a NorthAmerican Aviation pilot.Weights at touchdownhave ranged from a _.owof 13_234 pounds whichwas experienced on the initial glide flight (_.-i-5), as di

36、scussed inreference 4_ to a high of 15_153pounds recorced on flight 2-3-9. Theaverage touchdownweight was about 14,600 pou_Lds_which correspondsto a wing loading of 73 ib/sq ft.The numbers in the column labeled damper setting indicate thesettings for the pitch_ roll (plus yar)_ and _w dampers_respec

37、tively,for each flight. The relationship between da_er setting and gain ispresented in table II. Dampergains have varied from all dampers offfor flight 2-8-16 to all damperson at the se_ging of 4-4-8 used formost of the flights. The landing of flight 2-$-16 was madeintentionallywith all dampersoff.

38、In flights i-i-5_ 2-2-_, 2-3-9, i-2-7_ 1-3-8,and 1-6-11, the zero gain for one damping mod_was caused by amalfunction in that particular mode.The side stick was utilized to perform t_e flare on only theinitial flight (i-i-_) and two subsequent flights (2-9-18 and 2-10-21).On all other flights the co

39、nventional center _tick was used.Pattern geometry varied from S-shaped pa_terns to full 360 overheadpatterns_ depending on space-positioning requirements at the high keyor initial point.All landings reported herein were made or designated runways onthe hard surface of Rogers Dry Lake at Edwards Air

40、Force Base_ Calif._except for flight 2-3- 9. This flight terminated in an emergencylanding on nearby Rosamond Dry Lake following an in-flight explosionin the engine compartment. Figure 3 is an aezial photo map ofProvided by IHSNot for ResaleNo reproduction or networking permitted without license fro

41、m IHS-,-,-HD “4Rogers Dry Lake, showing the marked lakebed runways. The initiallanding and i0 subsequent landings were performed on the longest RogersDry Lake runway, designated as i in figure 3. Seventeen landings wereperformed on the runway designated as 2. Also, because of appreciablecross winds

42、on runway i, the pilot for flight 1-5-10 elected to land onthe runway labeled 3.For the first five flights of the number i airplane and the firstthree flights of the number 2 airplane, the nominal flap deflection fortouchdown was 40. Subsequent flights were performed with a nominal30-flap deflection

43、 at touchdown.RESULTS AND DISCUSSIONTo provide general information on the ranges of lift, drag, andangle of attack covered in this study, the following section presents,first, performance data for the X-15 in various landing configurations.This is followed by a discussion of the approach patterns fl

44、own and theflare maneuvers performed prior to landing. These maneuvers aregraphically illustrated by typical time histories and summary plots.Finally, an assessment is made of the extensive in-flight simulationsemployed in the flight program, with particular attention to the valueof such simulations

45、 and their applicability to future low-lift-drag-ratio gliders.PerformanceFigure _ presents angle of attack, lift-drag ratio, and dragcoefficient as a function of lift coefficient for the X-15 in variousapproach configurations. All data were measured during approach andflare maneuvers and are thus r

46、epresentative of the lift and angle-of-attack range covered during this portion of the landing. Because ofthe transient nature of the flare and the relatively short intervalsduring which the airplane remained in some fixed configurations(notably, those with the flaps extended only) data in severalco

47、nfigurations are limited. Also shown in this figure are themanufacturers estimates of these variables based on wind-tunnel data.Clean airplane.- Figure 4(a) presents the performance data for theclean airplane at approach speeds (M _ 0.5 to 0.7). The flight-measuredpeak lift-drag ratio is about 4.25,

48、 occurring at a lift coefficient ofabout 0.45 and an angle of attack of approximately 8 . With fewexceptions, the pilots have flown on the “front side“ (low CL) of theL/D curve throughout the approach pattern. The low-lift condition ismaintained by increasing bank angle as normal acceleration is inc

49、reasedProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8at constant speed or by increasing bank angle or decreasing normalacceleration, or both 3 as speed is reduced. This trend is normal, sincepilots usually like to allow some margin for reducing glide angle byincreasing lift