1、.REPORTTHE DRAG OF AIRPLANE WHEELS,No. 522WHEELFAIIUNGS, AND LANDINGGEARS-IIIBy WILLIAM H. HmmNsmn?, JIL, and DAVID BIEIUAMSUMMARYThe te8t8reported in this paper conclude the iwtxtigtion of lunding-geardrag tti has been carried out in hN. A. (7. A. 90oot wind tunnel. They supplementearlier tests (re
2、portedin TechnicalReport No. 5) landing gears 15a, 15b, 15c, and 16 were types notin the rear. Tail skid 2 consisted of two struts intandem, one of which was an oleo unit. TrLilskid 3was of the cantilever spring-leaf type; tail skid 4was of cantilever construction with the shock-absorberunit inside
3、the fuselage.TESTSDrag and air speed were measured for all teats rmdadditional lift measurementswere taken in conjunctionpreviously tested. Dimensions for the wheel fairingsused on landing gears ha, llb, and 13 maybe obtainedfrom reference 1.Tail skids and tail-wheel unit.-The tail-wheel unitused in
4、 the tests was taken from service and consistedof an Air Corps tail-wheel fork and a 10 by 34 wheel.The principal dimensions of the unit maybe obtainedfrom reference 4. Figge 14 shows the location ofthis unit with reference to the test fuselage and alsoshows the dptails of tail skids 1, 2, 3, and 4.
5、 Tailskid 1 was of tripod construction with an oleo unitwith the tests of landing gems 13 and 16. Lrmdinggear 13 was the only landing gear whose drag wasmeasured in the presence of the wing. Landing gearslla and 13 were tested in conjunction with a radialair-cooled engine located in the nose of the
6、fuselagebut in the absence of propeller slipstream.landing gears equipped with four different wheels,Landing gears la, ha, llb, 15n, Mb, and 160 weretested when equipped with 8.50-10 low-pressurewheels,and with 21-inch,r6ti,x- ,%” z.-I l/45“39” IFIouEE7.- anddimensfonsofb?JIdfJM the additional drag
7、representsthat duo to the struts. (Cf. figs. 6 and 9.)Expanding finet,- - -, / f36 “I Q.?zu14”t v139 “4 42 “ a.so-lo low -pressure wheelFIGURE10.DImemfoIuoflanti mar 10.lever types. It is apparent horn ures 7, 8, and 9that landing gear 15a with the oleo-sxle intersectionnext to the wheel is not the
8、equal of landing gears 15b30e “ III , IWJWifhouf exphnd; fillefsw, With u , 20f/0I*OF Liff, wifh and wifIOUfexpandfngf;l.efsg ,1, /.$40 /I /+0t / G-40 / -4 -2 0 2 4 GAngle of pifch, degreesFIQUEE11.Lfftand dragOfIaIIdfng 10.or 15c on which the interference has been reduced byhavimg the intersection
9、placed a considerable distanceup the axle. Landing gears 15b and 15c lmdpracticallythe same drag when tested under similar conditions.Both had very low drags for tripod landing gears.With streamline wheels the drag of land gear 15cLanding gears with various fairings and modifloa-tions,-Figure 4 show
10、s the effects of two di.fbrent fair-ings at the wheel-strut intersection of landing gear la.One faking had a long tail and the other was blunt atthe rear. The long-tailed fairing was appreciablymore effective in reducing the drag, as may be seen byan examination of the drag values. This fairing when
11、used in conjunction with the 24-inch streamline wheelreduced the lamhg-gem drag from 44.0 pounds to31.0 pounds thereby effecting a saving in drag of 30percent. Fairing all strut intersections at the fuselageand also the axle cross accounted for a further decreaseof 4.0 pounckThe negligible effect of
12、 an engine on the drag oflanding gear lla with 8.50-10 low-pressure wheels andwheel fairing C is shown in figure 6.The effecti of vmiou.s modi.ktions to landing gear13 are shown by figure 13(b). At a lift coefficient of0.2 the drag of the original lading gear is shown to be12.6 pounds at 100 miles p
13、er hour. The addition ofexpanding fillets (moWcation 1) reduced the dragto 11.0 pounds. When the engine was placed in thonose of the fuselage (modification 6), the drag of thelanding gear dropped to 10.5 pounds. These dragvalues are the lowest recorded for any nonretractablelanding gem tested during
14、 the investigation. Whenmodification 2 (wheel fairing extended to wing) wasmade to the original landing gear, the drag was in-creased from 12.5 to 21.0 pounds. The addition ofmodifications 3 and 4 (expcdiug fillets of difhrente) to the landing gear in this condition reduced thedrag horn 21.0 pounds
15、to 17.0 and 15.0 pounds for themmll and large iillets, respectively. When streamlineProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-DRAG OF AIBPIXNE WHlmlH3, W13mErl FGS AND L4NDING CEFIARS 329side brace struts were added (modification 5) to modi-fic
16、ations 2 and 3 and to modifications 2 and 4, the dragwas increased to 26.0 and 23.0 pounds, respectively.Mutual effect of wing and landing gear on landing-gear drag.-l?igure 13 shows how the mutual effect ofa wing and landing gear may affect the drag creditedu Modificafhn 1,expondinq fillef. W, Mod.
17、3,expand;ngfillefmax.rod.6-) Y Mod 5,afrcumlme fube,/( 97 2(850 IO!OW-,t Mod. 2, wheel foir(ng ex+endedh whg. X, =W4, - “ R - . -Nofe:-Modificof;on6,rodfalengine inmse of fuselage6 x 18 Clyk Y wing*t8=41;1I1;II11tit %It v %11If:-i1 N ./2 “- Wheel fuiring A-*.53”,FIeUEEla.-IXm0nsf0IU otffmdfnggear13w
18、ith varfommcdficatfonModification 6 (engine in fuselage) in combination withmodifications 2 and 4 resulted in a drag of 13.0 pounds,just 2.6 pounds greater than for the landing gear in itsbest condition (modifications 1 and 6). In all testswhere the engine was used it was in the uncowled con-dition.
19、 Results reported in reference 1 showed, how-ever, that there was little difference in the effect of theengine on landing-gear drag when the engine wcsuncowled and when it was equipped with N. A. C. A.cowling.The effect of adding a wheel-strut fairing to ladinggear 16a is shown in iigure 7. “The fak
20、ing decreasedthe drag but not nearly as much aa did a similarfakingon landing gear la (iig. 4). The reason for thi9 differ-ence is not clear for the fairings were very much alikeand so were the intersections at the wheel and struts.Figure 9 shows how a fillet at the wheel-strut inter-section Mected
21、the drag of landing gear 15c. Thefillet reduced the drag 1.5 and 1.0 pounds when usedwith the 8.50-10 low-pressure and 24-inch streamlinewheels, respectively. Although the reduction was notgreat, it is probably sufficient to warrant the use ofsuch Mets.The results of drag and lift tests made with la
22、ndinggear 16 (fig. 10) are presented in iigure 11. Inasmuchm this landing gear had a large lifting surface, it wasthought advisable to take lift data in conjunction withthe drag measurements. The landing gear wastested with and without an expanding iillet at thefuselage junction. The flet had practi
23、cally no effecton the lift and little effect on the drag. The drag waahigher than expected, being about 28.0 pounds at 100milks per hour.to the landing gear, depending upon the manner ofpresenting the results. Landing gear 13 (fig. 12) wasused for this illustration. The curves in figure 13(a)UI , ,
24、, , , I-4 -2 0 2 4 6Angle of pitch degreesm _ ,.6 -1 -235- $ A .-.,*-:13%” -40 by 3-4 toil wheel ,-.: .J,5X-:*2 Mom,A?-Tail-wheel unit and several tail skids,-Figuro 14givas the drag of a tail-wheel unit and several tail skidswhen measured TV-MIno landing gear on the fuselage.The addition of a wheel
25、 fairing to the tail wheel didnot decrease the drag of the unit. Adding o stream-line fairing to the fork did decrease the drag a smallamount (0.6 pound). Tail skid 1, which was built ofround tubing, had slightly less drag than the tnil-wheel unit in its best condition, 3.0 pounds as com-pared with
26、3.5 pounds at 100milesper hour. Tail skid3 had me highest drag, being equal to Qmt of the tail-wheel unit in the unhired condition (4.0 pounds).Tail skid 2 had but 1.5 pounds drag and tail skid 4.Tail skfd lDregat lW m. p. h-. -. -. - .- wnn 3.0Tail sHd 2-Dreg at lCBIm. p. h.-pmnds- L5 Tail skid S-D
27、rag at lIXIm. p. h-nnck. 4.0 rail Md 4Dragat lwIm. p. h_pmmd.- LOFmtmE M.Dragand dlmemkm Of-whd IUdtand varioustailgklds.0.2, which is a reasonable assumption for the high-speedcondition, the angle of pitch for the set-up withoutIandhg gear was 0.75. If no induced-drag changeduo to the presence of the landing gear be assumed,the&- l%s 8.CO-10wh*- 2&S. . . . . . .- - 17.6n-hmhwh- %5n-hmhwhwQ MS of rafaranca1- 2L5MO-1owh* . . . . . . . . . . . . -8OW1Owheel%tam of *m L . . . . . . 2:Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
