1、REPORT No.THE DRAG OF AIRPLANE WHEELS, WHEEL518FAIRINGS.11-NONIWTRACTABLE AND PARTLY RETRACTABLEBy DAVIDBIERAtANNandWILLIAMH. HURRNSTEIN,JR.SUMMARYfih h thesecondpaper giving whereas in the second partan engine nacelle w-asmounted in the leading edge ofthe wing (fug. 1). Propeller teats -weremade in
2、 con-junction with several types of landing gears. Thewing and nacelle are described in detail in reference 3.The nacelle, which was of the N. A. C. A. cowled type,was looated in the position B described in the samereference.The wing was assumed to be a section of a wing of a16,000-pound low-wing mo
3、noplane scaled down to1/2.8 size. The model wing thus represented a full-scale wing having a chord of 14 feet and a thiolmess of2.8 feet. The model radial engine, which was 20 221Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-222 REPORT NATIONAL ADV
4、ISORYinches in diameter, therefore represented a fukcaleengine of 56 inches diameter.Only half of each landing gear was tested. Eachunit -WCSmounted at the center of the span of the wingPIQUEEl.bmlfng gearA monntwfonwfngwith xracdksection near the leading edge. The chordwise locationof the wheels wh
5、en in the landing position was deter-mined from an assumed center+fvity location ofthe complete airplane.+ modelofthe41bylS.fC-16low-presmm whwl.+ model of the 45-inchstmmlfne wbml.QU13Bolld tiewsof k3wDresTI19and skmdfne Wbd.%A l/2.8-scsJe -woodenmodel of a 42 by 15.00-16 Iow-pIWWM wheel was used f
6、or most of the teats. Someof the tests were also made with a model of a 45-inohCOMMITTEE FOR AERONAUTICSstreamline wheel. These wheels (fig. 2) how a load-oarrying capacity of 8,000 pounds each, according toreference 4.The principal dimensions of the nonretractable lund-ing gears (A, B, and C) are g
7、iven in figures 3,4, and 6.+.28”d M-5”FIGUEEZ-hmlfng hence the lift readings were neglected for a partof these tests. The aerodynamic characteristics of71046-3_16the wing andAND LANDING GEARS 223nacelle may be found in reference 3.It should be noted that zero lift of the wing occursat an angle of at
8、tack of about 7.5 and that thelift coefficient of the wing at 0 angle of attack is0.366;The measured lift was reduced to the usual coeffi-cient, CL. The drag due to the landing gears in thepresence of the wing, or the wing and nacelle, wasassumed to be equal to the drag of the complete set-up with t
9、he landing gear in place minus the drag ofthe wing alone, or the wing plus nacelle as the casemight be. The drag di.iference, in pounds, at 100des per hour was taken at constant values of liftcoefficient of the wing. The iinal drag results dueto the model landing gears are plotted against liftcoeffi
10、cient.Since the model was 1/2.8 full size, the drag of bothhalves of the Ml-scale landing gears, neglecting scaleeffect, would be:V9()2.81X2X )(D, or 15.68 () retractable typesin iigures 11 to 14, inclusive; of wheels in variouslocations in figure 15; and wheelswith difEerentdegreesof yaw in figure
11、16.The results obtained from tests of landing gears andwheels made in the presence of the wing and nacelleare presented in iigures 17 to 25, inclusive: Nonre-tractable landing gears in iigures 17, 18, and 19;retractable landing gears in figures 19 to 22, inclusive;Provided by IHSNot for ResaleNo rep
12、roduction or networking permitted without license from IHS-,-,-.-.224 REPOIW NATIONAL ADVISORY COMMI!rPDE FOR ABRONAUTK%2o1- 7FIGURE9.Dreg of kmdfm KE=W A h IR=Im of -.I I I INO te I12 Identical resulis were obiaitwd when10w-pres.su_e md sireomline wheelswei-e used affernafely.8 i 1- -H=.50P“, no f
13、ille ist,- -H=2jf”, - .11,:; - H = 30 “, filleis(shown)4 -%-+ - 1n -1 .2 .3 .4 .5 .6,Eif+ coefficiwi, C=$iqEoQ%ii83!4 “ B-,. 8 t. -Wheel touch-% ing wingi ! _ j% 70 20 40 80 80 100L omfion of wheel in percenfqe of -dFmm I wheel 20t-l Wheel touchi wingS I I. - IQ 16Eoa; 12Li=8+$34t8 / !- -:-.$ A A- “
14、g = - :- - “ Low-pres-=-+- “- - - - - - - -b J -? 3 - - - - _-Q -&- .3 - - - - - - _ _ _0 ./ .2 .3 .4 .5 .6L if+ coefficient+, CLFIQIIUE21.-Drag: landinggem D relrackd viwfoosamonnb Into wfng Jnwc$wuaormmlfaH20 qf.mm$.-ILLow-pressure wheel. ”.= B Lo- .8-.h % . ?7N/3.m - .6Qk v.4.02 20 2 0.4 .6 .8 1.
15、0OU!&E ?4.-Effed Oflanding A andBOnluOuchamci.wi!thRmr* diameter4fwbsetlr at 0.76radkw angfe of attack of Wfng. w.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-.228 REFO13T NAITONAL ADVISORYnumber of tests were made on land gears with onlyslight ch
16、ange+ it was possible to improve the accuracyby fairing at one time a series of curves for one typeof landing gear. The rcmdts are considered sticientlyaccurate for comparative purposes and should givefairly close approximations when applied to full-scaleairplanes. The faired lift curves are conside
17、red correctwithin +1 percent at 0 angle of attack.The thrust and power coefficients are thought to becmrect within +1 percent over the greater portion ofthe curves, while the propulsive eiiiciency is believedto be correct within +2 percent./2 I Wingam nocdle,no -. . .TF- withgeor D (H-. . . .R (H-2m
18、lo_ .-_: . . .1.0! +-l-i-lgear s- bock,# wheelreimcfed info wi%FIGURE ZS.-Wf Ofhdh gmr D on PIOLETc&IIuMddks. ROpdk Wdfamatar4 f- sd 1P at 0.76radius a.nglaof atk of wing, 0.DISCUSSIONLANDING GEARS AND WHEEL9 OUNTBD ON WING WITHOUTNANonretractable typeso-Figure 9 presents the resultsfrom teats of km
19、 gear A. At low VUCS of hftcoei%cientthe drag due to the landing gear was reducedconsiderably by the presence of an expanding Wet.The term “expanding” refers to the fillet radius andmeans that it increasesprogressively in the downstreamdirection. In this instance the fillet started with nearlyzero r
20、adius at the maximum section of the landing-gearfsiring and increased to about 4 inches at the trailingedge of the ftig. The drag of the landing gear wasnot critical to changes in lift coefficient when a filletw-aspresent.The results from tests of landing gear B are givenin figure 10. It should be n
21、oted that this landing gearhad the lowest drag of any nonretractable gear tested.Even though the oleo strut was small in comparisonto the faking used on landing gear A, the presence ofexpanding fillets materially reduced the drag of thelanding gear.The resultsfrom tests of landing gear C, which was
22、ahalf-fork type equipped with both low-pressure andstreamline wheels, are given in figure 11. For thistype of land& gear the drag was considerably lowerwhen streamline wheels were used. The presence ofthe airfoil section adjacent to the wheel was thought tobe an important factor in obtaining the low
23、 drag.Partly retractable types,-Figure 11 also shows theresults horn tests of landing gear D. As may be seen,the only di.fTerencebetween landing geara C and D wasthe lack of the streamlhe faking on the fork and oleostrut of landing gear D. At a lift coefficient of 0,2the drag was increased horn 6 to
24、 17 pounds for the30%-inch landing gear by remotig the strut and forkfairings. It is noteworthy that the slopes of thesecurves are much greater than for those of landinggear C. The probable reason for this increase is theincreasingly disturbing effect of the oleo strut onthe flow over the wing with
25、decreasing values of liftcoefficient. The same effect waa previously noted inthe case without fillet on landing gear A.Values of drag due to landing gear D when partlyretracted into the wing by various amounts are shownin iigure 12 for both streamline and low-pressurewheels. The drag of the landing
26、gear equipped withstmrunline wheels ranges from 15 to 20 percent lessthan for low-prwwre wheels, regardless of the amount Jthe lading gear is retracted into the wing: Althoughthe landing-gear drag (with low-pressure wheels) isreduced considerably by folding the wheel against thewing, the wheel must
27、be retracted at least one-fourthinto the wing before the drag bccomea less than thatfor lamjing gear C and one-half before the drag becomesless than for landing gear B.From structural considerations it maybe undesirableto retract the landing gear either fully or partly intothe wing. Figure 13 illust
28、rates the results from testson lanQu gear D partly retracted into a streamlinefairirqg mounted on the lower surface of the wing.The drag of the landing gear when folded against thewing was reduced about 50 percent by the presenceof a streamline fairing behind the tire (gap openbetween tire and fairi
29、ng, see fig. 8) and was reducedan addition 12 percent by closing the gap between thewheel and the fair. Removing the oleo strut andfork reduced the drag still further by about 20 percent.With the landing gear one-half retracted into thewing the presence of a fairing (gap open) behindthe portion of t
30、he wheel that remained in the airstream reduced the drag approximately 60 percent.(See figs. 12 and 13 for comparison.)Still greater reductions in drag may be gained bycompletely retracting the landing gear into a streamlinefairing (. 14). The landing-gear fairing, with thecap on, had less than half
31、 the drag of the landing genrProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-!l!HElDR4G OF Al13PIANElEIJ3, WHEEL FAEUNGS, AND LANDING GEARS 229partly retracted inta the fairing previously discussed.Removal of the fairii cap, how-ever, increased thedr
32、ag about 66 percent at a lift coefficient of 0.2.Wheels.-The results from tests of wheels at variouschordwise locations and with various degrew of retrac-tion into the wing are given in figure 15. At low valuesof the lift coefficient (0.2) the drag due to the wheelincreased rapidly as the wheel was
33、moved towardthe leading edge. For higher values of the lift coeffi-cient (0.4) the wheel location was less critical, withthe exception of the wheel one-fourth retracted. Forany chordwise location the drag due to the wheelreduced rapidly with retraction.Figure 16 shows the results from tests of both
34、low-prossure and streamline wheels in yaw. At a liftcoefficient of 0.2 the drag due to tlmlow-pressure wheelwhen touching the wing at the 50 percent chord pointwas increased about 10 percent due to 10 yaw andabout 55 percent due to 20 yaw. Although thestreamline wheel had less drag, the increased dr
35、ag dueto yaw amounted to about 17 percent for 10 yaw andabout 75 percent for 200 yaw. With the low-pressurewheel one-half retracted into the wing the increaaeddrag due to yaw amounted to about 30 percent for 10ynw and over 100 percent for 20 yaw.LANDING GEARS AND WHEEIJ3 MOUNTED ON WING WITHNACELLET
36、hese tests were almost identical with the tests oflanding gems and wheels mounted on the wing with-out nacelle and, in general, the results are about thesame, There are, however, a few interesting points.Nonretraotable types,-Expanding fillets on landinggear A (fig. 17) were not so effective at low
37、valuea of thelift caefficiont as they were without the nacelle. Evi-dently the nacelle had the effect of preventing separa-tion of flow at the intersection of gear and wing forthese negative angles of attack.Increasing the sim of the expanding Mets used onlanding gear B (fig. 18) did not rdlect the
38、drag, eventhough the small fillets materially reduced the drag.The streamline wheel, as well as the low-pressureweel, ww used both on hind gears C and D (fig. 19).The drag due to landing gear C was materially lesswith the streamline wheel than with the low-pressurewheel. When the streamline fairings
39、 had been re-moved from the hti-fork and oleo strut (.lane gearD), there was no apparent advantage, however, in tlmstreamline wheel.Partly retraoted typas,-It appem from figure 20that partly retracting landing gear D vertically into thenacelle at its maximum cross section is undesirablewith respect
40、to drag. At a lift coefficient of O.!?thedrag due to the landing gear when half the wheel wasretracted into the wing (leaving only slightly morethan the tire protruding out of the nacelle) was greaterthan tho drag due ta landing gears A and B and almostm high as for landing gear C. The drag of landi
41、nggear D when partly retracted by this method was con-siderably higher than when retracted by swinging thewheel back into the wing (fig. 21).The drag due to landing gear D enclosed in a stream-hne f (. 22) was somewhat less with the namllein place than when tested on the wing without nacelle(. 14).W
42、heels.-The results from tests of wheels in yawmeasured in the presence of the wing and nacelle (&.23) are almost identical with the results from tests ofwheels in presence of the wing without the nacelle.Propeller characteristics.-The propeller character-istics meaaured in the presence of the W and
43、nacellealone and also in the presence of the nonretractablelanding gears A and B are given in figure 24. Thepeak propulsive efficiency was reduced about 2.5 per-cent by the presence of landing gear A, the reductionbeing manifested by an increased power coefficient.The propeller was less affected by
44、the presence of land-ing gear B, the propulsive efficiency being reducedonly about 1 percent.The propeller characteristics measured in the pres-ence of landing gear D in the land. position and alsoone-fourth retracted into the wing are given in iigure25. Both the thrust and power curves are somewhat
45、lower than those for the w- and nacelle alone through-out the range for both attitudes of the landing gear.The peak propulsive efficiency, however, was reducedonly about 1 percent for the landing gear in the partlyretracted position as well as for the landing gear of30%-inch height in the landing po
46、sition. For the land-ing gear of 24Yiinch height in the landing positionthe propulsive efficiency was reduced about 2 percentfor the climbing and high-speed range of V/nD.EFFEmOF LANDING GEARS ON HIGH SPEEDFigure 46 of reference 1 may be found convenientin computing the effects of the various types
47、of land-ing geara on the high speed of an airplane.CONCLUSIONSThe resuhk of this investigation indicate the fol-lowing:1. In general, the presence of the engine nacelle didnot appreciably affect the drag due to the landinggears.2. The retractable landing gears were at least one-half retracted into t
48、he wing or a fairing before thedrag became less than that due to the best nonre-tractable landing gears.3. Lane gears that were partly retracted into anacelle near the maximum section or partly retractedinto the wing near the leading edge had a much higherdrag than landing geara that were partly retractedfarther aft on the wing.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-230 REPORT NATIONAL ADVISORY COMMPITDD FOR AERONAUTICS4. Streamline wheels tied on retractable landin!ggears had less drag than low-pressure wheels
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