REG NACA-TR-534-1936 Aerodynamic characteristics of a wing with Fowler flaps including flap loads downwash and calculated effect on take-off.pdf

1、.+ , .J I -_ ; “+. _ FOR AERONAUTICS . _ - i 1 ., .;AERODYNAMIC CHARACTERISTICS OF A WING_,w llllFOWLER FLAPS INCLUDING FLAP LOADS-Do_AsIt, AND-. CALC_II_TED EFFECT- r.+_Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo

2、reproduction or networking permitted without license from IHS-,-,-NOTICETHIS DOCUMENT HAS BEEN REPRODUCEDFROM THE BEST COPY FURNISHED US BYTHE SPONSORING AGENCY. ALTHOUGH ITIS RECOGNIZED THAT CERTAIN PORTIONSARE ILLEGIBLE, IT IS BEING RELEASEDIN THE INTEREST OF MAKING AVAILABLEAS MUCH INFORMATION AS

3、 POSSIBLE.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-REPORT No. 534AERODYNAMIC CHARACTERISTICS OF A WINGWITH FOWLER FLAPS INCLUDING FLAP LOADSDOWNW

4、ASH, AND CALCULATED EFFECTON TAKE-OFFBy ROBERT C. PLATTLangley Memorial Aeronautical LaboratoryI145013-35-1Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICSHEADQUARTERS. NAVY BUILDING. WASHINGTON, D. C.LABORA

5、TORIES. LANGLEY FIELD. VA.Created by act of Congress approved March 3, 1915, for the supervision and direction of the scientific study ofthe problems of flight. Its membership was increased to 15 by act approved March 2, 1929. The members areappointed by the President, and serve as such without comp

6、ensation.JOSEPH S. AMES, Ph.D., Chairman,President, Johns Hopkins University, Baltimore, Md.DAVID W. TAYLOR, D. Eng., Vice Chairman.Washington, D. C.CHARLES G. ABBOT, Sc. D.,Secretary, Smithsonian Institution.LYMAN J. BRIGGS, Ph.D.,Director, National Bureau of Standards.BENJAMIN D. FOULOIS, Major Ge

7、nera, United States Army,Chief of Air Corps, War Department.WILLIS RAY GREGG, B. A.,Chief, United States Weather Bureau.HARRY F. GUGGENHEIM, M. A.,Port Washington, Long Island, N. Y.ERNEST J. KING, Rear Admiral, United States Navy,Chief, Bureau of Aeronautics, Navy Department.CHARLES A. LINDBERGH, L

8、L. D.,New York City.WILLIAM P. MAcCRAcEEN, Jr., Ph. B.,Washington, D. C.AUGUSTINE W. ROSINS, Brig. Gen., United States Army,Chief, Materiel Division, Air Corps, Wright Field, Dayton,Ohio.EUG_NE L. VIDAL, C. E.,Director of Air Commerce, Department of Commerce.EDWARD P. WARNER, M. S.,Editor of Aviatio

9、n, New York City.R. D. WEYERBACHER, Commander, United Statvs Navy,Bureau of Aeronautics, Navy Departmeat.ORVILLE WRIGHT, Sc. D.,Dayton, Ohio.GEORGE W. LEWIS, Director of Aeronautical ResearchJOHN F. VICTORY, SecretaryHENRY J. E. REIn, Engineer in Charge, Langley Memorial Aeronautical Laboratory, Lan

10、gley Field, Va.JOHN J. IDE, Technical Assistant in Europe, Paris, FranceTECHNICAL COMMITTEESAEaODYNA_CS XtECEAFT ACCID_TSPOWER PLANTS FOR AIRCRAFT INVENTIONS AND DESIGNSAIRCRAFT STRUC_rI_RES AND MATERIALSCoordination of Research Needs of Military and Civil AviationPreparation of Research ProgramsAll

11、ocation of ProblerasPrevention of DuplicationConsideration of InventionsLANGLEY MEMORIAL AERONAUTICAL LABORATORY OFFICE OF AERONAUTICAL INTELLIGENCELANGLEY FIELD, VA. WASHINGTON, D. C.Unified conduct, for all agencies, of Collection, classification, compilation,scientific research on the fundamental

12、 and dissemination of scientific and tech-problems of flight, nical information on aeronautics.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-REPORT No. 534AERODYNAMIC CHARACTERISTICS OF A WING WITH FOWLER FLAPSINCLUDING FLAP LOADS, DOWNWASH, AND CA

13、LCULATED EFFECT ON TAKE-OFFBy ROBERT C. PLXTTSUMMARYThis report presents the results of an investigation inthe N. A. C. A. 7- by lO-oot wind tunnel on a wing incombination with each of three sizes of Fowler flap. Thepurpose of the investigation was to determine the aero-dynamic characteristics as af

14、fected by flap chord andposition, the air loads on the flaps, and the effect of the.flaps on the downwash. The flap position for maximumlift: polars for arrangements considered favorable fl_rtake-off; and complete lift, drag, and pitching-mo_nentcharacteristics for selected optimum arrangements were

15、determined. A Clark Y wing model was tested with 20percent c, 30 percent c, and $0 percent c Fowler flaps ofClark Y section. Certain additional data from earliertests on a similar model equipped with the _0 percent cClark Y flap are included .for comparison. Results ofcalculations made to find the e

16、ffect of the Fowler flap ontake-off, based on data from these tests, are included inan appendix.The maximum lift coe_cient obtainable, based onorigiT_al wing area, had a nearly linear increase withflap chord up to 40 percent, but the maximum lift forceper unit of total area increased very little bey

17、ond thevalue obtained with the 30 percent cflap. The maximumload on the flap occurred very nearly at the maximumlift of the wing-flap combination and was nearly I/times the load that would result Jrom uniform distributionof the total load over the total area. In general, the flapappeared to carry a

18、large proportion oJ the additionallift caused by its presence and to have its center of pressuremuch nearer the leading edge than it would normally bein free air. The addition _ the Fowler flap to a wingappeared to have no appreciable effect on the relationbetween lift coey_cient and a_gle of downwa

19、sh. Thecalculations in the appendix show that, by proper use ojthe Fowler flap, the take-off _ an airplane having wingand power loadings in the range normally encountered intransport airplanes should be considerably improved.INTRODUCTIONDuring the past few years the use of flaps on high-performance

20、airplanes as a device for reducing spacerequired in landing has become common. Thus farsplit flaps have been most generally used, probablybecause of their simplicity of application and theirsuperiority in giving steep gliding approaches and shortlanding runs: the features of flaps with which designe

21、rshave been most concerned. In order to retain satis-factory operation from normal flying fields with fastairplanes, however, the use of high-lift devices thatimprove take-off as well as landing is desirable. Sincedrag is unfavorable to take-off, the comparatively largedrag of split flaps places the

22、m among the least promis-ing of high-lift devices in this respect. The Fowlerflap appears to offer a better compromise between theseconflicting requirements. For equal sizes it will givehigher maximum lift with no higher profile drag thanmost other flap arrangements and its comparativelylow drag at

23、high lifts is favorable to take-off and steepclimb. This effect would normally entail some sacri-fice of steep gliding ability.Although sufficient data to form some estimate ofthe performance to be expected from an airplaneequipped with Fowler flaps are available (references1 and 2), they are inadeq

24、uate for normal design pur-poses. The purpose of the tests reported herein is toprovide data to form a rational basis for the design ofairplanes equipped with Fowler flaps. It appears thatfor the present the purpose will be attained by makingavailable the following information: effect of flap sizeon

25、 aerodynamic characteristics attainable, aerodynamicloads applied to the flap in various conditions, andeffect of the flap on downwash. In addition, a con-venient method of estimating the effect of high-liftdevices on airplane take-off should prove of assistancein cases where this performance featur

26、e merits specialattention.The tests were made in the 7- by 10-foot wind tunnelof the N. A. C. A. (reference 3) at Langley Field, Vs.,during th, ummer and fall of 1934.MODELThe basic wing was built of laminated mahogany tothe Clark Y profile (table I) and had a span of 60inches and a chord of 10 inch

27、es. The trailing edgewas cut away and the upper surface replaced by a thincurved metal plate. The lower surface was left openat the rear to serve as a retracting well for the flaps.1Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-2 NATIONAL ADVISORY

28、COMMITTEE FOR AERONAUTICSBlocks were inserted to maintain the correct size ofwell for each size of flap tested. Figure 1 shows theprofile of the wing with the various flaps in place.The two smaller flaps were made of duralumin tothe Clark Y profile and had spans of 60 inches andchords of 2 and 3 inc

29、hes. The largest flap, which isthe one described in reference 2, was made of mahoganyand had a 4-inch chord. The flaps were supported onthe wing by fittings attached to ribs located in theretracting well. Several sets of attachment holes inthe ribs, combined with several sets of fittings, gavethe ra

30、nge of flap positions shown in figure 1. The flapswere supported on the fittings by hinges located at thecenter of the leading-edge arc of the flaps, angularadjustment being obtained by set screws attached to,_o /-z.s _Dofs locale center oF -_-+-_f-_-5.0_.L. E. arc of flap _ -7.585 90 35 I00 uPercem

31、f chord _FIGUR= L-Wing with various Fowler flaps. Flaps shown in maximum-lifteondRlons.the flap moving in quadrantal slots in the fittings. Ingeneral, where the term “flap position“ is used, theposition of the flap hinge axis is indicated, irrespectiveof angle, and flap angle is measured between the

32、 chordlines of the wing and the flap.TESTSFive groups of tests were made in obtaining thedata presented in this report. These five groups dealtwith maximum lift, optimum flap arrangement fortake-off, standard force tests of optimum arrange-ments, flap loads, and downwash behind the wing withvarious

33、flap arrangements.Maximum lift.-The maximum lift coefficientsobtainable with the 0.20 c and 0.30 c flaps at variouspositions shown in figure I were found by tests inwhich the flap angle was increased from 20 in 10 steps until the peak of the variation of Or._=_ with flapangle was defined for each po

34、sition. The range ofpositions in both cases was sufficient to surround thepoint at which the highest lift coefficient was found,thus isolating an optimum position iu each case.Similar surveys had previously been made with the0.40 c flap (reference 2) and were not repeated at thistime.Optimum take-of

35、f arrangement.-Lift and dragdata were taken at a range of flap angles between 0 and that giving maximum lift for a series of flap posi-tions somewhat more restricted than the range usedin the maxinlum-lift tests. Care was exercised in thesetests also to surround what was judged to be theoptimum sett

36、ing, both as regards position and angle.Standard force tests of optimum arrangements.-A series of final force tests, consisting of lift, drag, andpitching-moment measurements, was made at the flappositions considered to be of special interest. Theseincluded tests of the maximmn-lift arrangement ofea

37、ch flap, of the optimum take-off arrangement ofeach flap, and of an arbitrarily selected arrangementrepresenting partial retraction of each flap.All tests in these first three groups were conductedin accordance with standard force-test procedure asdescribed in reference 3.Eap loads.-Air loads acting

38、 on the flaps werefound by supporting the flaps independently of thewing, at the same position and angle as used in thefinal force tests of the wing-flap combinations, and bymeasuring the forces ou the wing alone in the presenceof the flap. The flap loads could then be readily com-puted. In order to

39、 find the center of pressure of theload on the flap, the flap hinge moment was measuredby observing the an_o_ular deflection of a long slendertorque rod required to balance the flap at the angle inquestion. Similar measurements of loads and center-of-pressure locations on split flaps are more comple

40、telydescribed in reference 4.Downwash.-Measurements were made with “pitot-yaw“ tubes attached to the wing by a rigid support.The reference position thus moved in the air stream.as the angle of attack was changed but remained thesame with respect to the wing, as does the tail of anairplane. The angle

41、s of downwash, however, werereferred to the initial direction of the free air stream.The apparatus could be adjusted to various horizontaldistances behind the wing. The pitot-yaw tubes wereordinary round-nosed pitot tubes with two additionalnose holes at 45 above and below the tube axis.Alcohol mano

42、meters were used to read the pressures,and the tubes were calibrated in test position in theclear-tunnel air stream.The wind tunnel is of the open jet, closed returntype, with a rectangular jet 7 by 10 feet in size. AProvided by IHSNot for ResaleNo reproduction or networking permitted without licens

43、e from IHS-,-,-AERODYNAMIC CHARACTERISTICS OF A WING WITH FOWLER FLAPS 3complete description of tile tunnel, balance, andstandard force-test procedure appears in reference 3.Tests were run at a dynamic pressure of 16.37 poundsper squltre foot, corresponding to an air speed of 80miles per hour at sta

44、ndard sea-level conditions. TheReynolds Number of the tests, based on the 10-inchchord of tile wing without flaps, was approximately609,000. PRECISIONThe“ accidental errors in the results presented in thisreport are believed to lie within the limits indicatedin tile following table:Wing data Flap lo

45、ad datatx :_0 1)_ C.v! . :t:O. 10CL ., :h. 05 Cx t. -4-. 06-004C. :_ -. 00_ Ch I.C D (eL=Ill _. 0_)t Flap anie . =l=. 25C q :CL = 1. _ V_4 Flap position . 4-. _,CD (CL= 2) .OnsFlap angle . . 2._Flap position _. _115 cDownwash data4-0. 5Consistent differences between results obtained inthe 7- by 10-f

46、oot wind tunnel and in free air nmy beascribed to effects of the following factors: Jet boun-daries, static-pressure gradient, turbulence, and scale.In order that the present results be consistent withpublished results of tests of other high-lift devices inthe 7- by 10-foot tunnel, no corrections fo

47、r these effectshave been made. Corrections of several sets of airfoilresults have indicated that the values of the jet-boundary correction factors, _=-0.165, and _,=-0.165, used in the standard equations (cf. reference5) are satisfactory for a 10-inch by 60-inch wing.The static pressure in the jet d

48、ecreases downstream,producing an increment in C,_ of 0.0015 on normal12 percent c thick rectangular airfoils. Evidence atpresent available indicates that the effect of the tur-t,ulence in tiffs tunnel is small as compared with theother consistent errors.RESULTS AND DISCUSSIONAll test results are giv

49、en in standard nondimensionalcoefficient form. In the case of a wing with a retrac-table surface, the convention of basing coefficients onthe area that would be exposed in normal flight, thatis, the minimum area, llas been adopted. Thecoefficients used are then defined as follows:subscript w refers to the bqsic win