REG NACA-WR-L-380-1941 Wind-tunnel investigation of control-surface characteristics II - a large aerodynamic balance of various nose shapes with a 30-percent-chord flap on an NACA .pdf

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1、i1iii,I1!, ARRAu.f3.1941.22-/NATIONAL ADVISORY cOMMlE FOR AERONAUTICSWARTIME Rlmm!rORIGINALLYISSUED -August1941aeAdvanoeRestirh)tedReportWmD4mmL INvlsmmmoN or coNTRo! CHARACTERISTICSII - A URGE AERODYNAMICRAIANCE OF VAIUOUSI?OSESHM?ESWITHA 30PENENWCHORDJWLI? ON AN NACAOO09AIRI?WL.ByIUahardI.Seam and

2、 H. Page Hoggard, Jr.Langley Memorial AeronauticalIaboratoqQU-eylteld9TEL. .,i lane, ,. , .1,! “-.NACA WARTIME REPORTS me reprintsofpapersoriginallyissuedtaproviderapitf-distributionofadvanceresearchresultstoanauthorizedgrouprequiringthemforthewareffort.Theywerepre-viouslyheldunderasecuritystatusbut

3、arenowunclassified.Someofthesereportswerenottech-nicallyedited.AU havebeenreproducedwithoutchangeinordertoexpeditegeneraldistribution.L -380Q,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-WIW-!2(T?NEL IIWESTIGAT ION OF CONTROL- SIUU3ACZ CHARACTERIS

4、TICS3ALAZ?CE 027VARIOUS NOSE SHAPESFLAP OilAX NACA 0009 AIE5OIL .and E.,Page Zoggard, Jr.SUiihlARYTests have ken n“ade of an NACA 0009 airfoil with aso-percent-chord flap having a 49.5-percent flap-chordtwlance with various nose shapes and *TO gaps. The re-sults have been presented in the form of ae

5、rodynamic sec-tion characteristics.Tesa :esults imlicated the flap to be overbalancedwLen deflected, regardless of nose shape. There was onlya slight change in hine moment with angle of attaclk. Ablunt-nose shape gave the greatest reductions in hingemoment andzthe smallest increment of drag over tha

6、t of aplain airfoil. ghe small Fap investigated affected theaerodynamic characteristics only slig-utly.A method has been proposed for reducing the controlforces to any desired value while, at tka sane time, mark-edly increasing the lift effectiveness of the airfoil-flapcombination ovr that of a plai

7、n flap of the same chord.ln addition, the flap can be made to float against therelative wind thereby causing the stability with contolsfree +0 exceed that with controls fixed. These resultsare accomplished _byusing a differentially operaied bal-ancing tab on an overklanced, flap to increase both the

8、lift and the hinge monent of ths. flap. . .airfoil section profile dragm airfoil section pitching moment about quarter-chord point of airfoilhf flap section hinge momentc chord of basic airfoil with flap and tab neutral -Cf flap chord .q dyriamic pressure,a. angle of attack for an airfoil of infinit

9、e spanProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-58f flap-deflection with respect to airfoilt tab deflection with respect to flapPrecisionThe accuracy of the data is indicated by the devia-tion from zero of lift and moment. The maximum error ine

10、ffective angle of attack at zero lift appears to be about*0.20. 3lap deflections were set to within 3=0.2, Tunnelcorrections, experimentally determined in the 4 by 6-footvertical tunnel, were applied to lift only. The hinge mom-ents, therefore, are probably slightly higher than wouldbe obtained in f

11、ree flight, but the values presented areconsidered to be conservative. The incements of dragshould be reasonably independent of tunnel effect, althoughthe absolute drag is subject to an nnknown correction. In-accuracies in the section data presented are thought to benegligible relative to inaccuraci

12、es that will be incurredin the application of t-hedata to finite airfoils. DiscussionThe desirability of reducing the hinge moments of con-trol surfaces is obvious, but the method of doing so mustbe carefully selected in order that the lift and the free-floating characteristics of the flap will not

13、be renderedunsatisfactory. It is considered desirable to make thefree-floating angle of the flap equal to zero or even tohave a slightly positive value at positive angle of attackso that the flap will float against the relative wind.This means that the parameter dCh(%)3- f (reference 5) mustbe made

14、zero or slightly positive. At the same time,aCh()3; must be made as small a negative value as possiblein ord;r to reduce the hinge moments without producingoverbalance. While the hinge moments are being reducedin this manner, the effectiveness of the flap in producinglift should be made as great as,

15、 or greater than, that ofa plain flap of the same chord. No appreciable incrementof drag over that of a plain flap can be tolerated at lowflap deflections used for trim. With these standardsProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-6 . .estahli

16、sbed, the analysis of the characteristics of a flaphaving a .495cf overhang caa more easily be made. ,Lift The tests indicate th=t with a sealed gap the slopeacof the lift cnrve$-zG was 0.099 with the sharp noseflap, 0.101 with the medium nose flap, and 0.102 with theblunt nose flap (figs. 2, 3, and

17、 4). When the gap at theflap nose was 0.0015c, the slope of the lift curve forall three nose shapes was 0.098. Co?rectioas for aspectratio are preseuted in refersnce 5.With a sea-led gap, the effectiveness of the flap inproducing lift, for all tnree flap nose shaes, was prac-tically identical with t

18、hat of a plain flap of the samechord (reference 6). The flap with the medium nose was,however, slightly better than aither the blunt or sharpnose flaps, which two shapes hail about the same effective-ness.Zhe curve-s .of figures 2, 3, and 4 indicate that witha 0.00-15c -gap, -the flap with a olunt n

19、ose was sY.ightlymore effective in prodmcimg. lift than the flap with amedium nose, but with the medium-nose the flap maintainedits .effect%enas. to higher flap.deflections and conse-quently higher lift cc-efficients. The sharg nose flaphad akout the same-lift effectiveness as the medium noseflap an

20、fL.aJMcti the same”ange of effect-iveness as theblunt noseflap. Cons-e-quatiy, as far a.s lift cheracter-.istics were. .conee-m.e-. , .-. s.-.:-,;.,. .: . “.- .,- - * “.:.:.;,.;., ,.*. , .: , “.,.,.:“ ,;.,.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-

21、,-,-7.gaps. Cross plots, similar to figure 59 giving hinge-moment coefficient as a function of angle, of attack andalso of flap deflection are more convenient for analysis,but these curvesp of courseO will be affected by aspectratio. Reference 5 discusses fully the manner in whichaspect ratio affect

22、s hinge-moment charactoristicsO Thi Sdiscussion indicates that()bch will always decreasez; fwith decrease in aspect ratio except when its value iszero. For this case, because theory shows there can be()bchno change in the value of K 6* , there can be no()%h.change in the value ofa with aspect ratio.

23、 If. .for infinite aspect ratiot%f n +)aflre Ofaspect ratio is decreased. If, howevsr, thess parameters0bchhave the same sign,“ will always decrease as thooaspect ratio is decreased. In some cases tho valuo of()achwf . may even pass through zero and change sign as the()acumagnitude of is changed by

24、aspect ratio. It iSg fImportant that these facts be established bocauso$ with a0.495cf overhang, tho slopes of theso parameters ara verysmall and the signs are critical.A 0,495cf overhang on a 0.30c flap produced overbal-ance through some range of flap deflection regardless ofthe nose shape and gap

25、(figs. 2, 3, and 4). Ovcrbalancooccurred first at high flap deflections and high negativeangles of attack for all nose shapes and was slightly morepronounced with a 0.0015c gap than with a sealed gap. ASthe bluntness of tho flap nose increased, the flap deflec-tion at which overbalance first occurre

26、d became less, andthe magnitude of the overbalancing moment was greater.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-8When flow separation occurred overwas a sudden change in the hinge momentthe flap, thereto large-negativevaluqs indicating a rear

27、ward movement of the center ofpressure”: “ . -DragAt zero angle of attack with flap neutral, the flap.wth a sharp nose gave aa increase in profile-drag coef-ficient”, bcdo, of 0.0042 over that of a plain airfoil.iiththe medium nose the increment was 0.0015, wheraas with the blunt nose the increment

28、was not measurable. Be-cause. ths drag of control surfaces at high flap deflec-tions is of relatively miaor importance and the abolutevalue of the drag coefficient for these data is in errorby an unknown tunnel correction, no drag curves have beengiven. I?or the blunt nose.,-however, the Increments

29、ofdrag caused by lC”W flap deflections such as may be neces-sary for trim changes at high speed are given in figure 6 for several angles of attack. The hunt nose seems to betka only one which was -satisfactory as far as drag is “concerned.Pitching Momentth the lunt- and the medium-flap nose shapes,

30、theLrate of change of airfoil sec ion pitching-noment coeffi-cient with lift coefficient at zero flap deflection,acm()q,- : ,;. . . ,., ,. .-”,. , .-, -, - - . . : ., -.-, ,Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-)9It is possible, however, to

31、 use in conjunction with thisflap arrangement a trailing-edge ta-i, defectad in thesame direction as the flap, in order to overcome the over-balance of the flap.Accordingly, tests were made to determine the effectof a tab deflectad with the flap. 3igura 7 gives the.in-crements of lift coefficients a

32、nd flap hinge-moment coef-ficients caused by deflection of a 0.20!5cfplaiatab atseveral angles of ,attack and flap deflections. The incre-ments were determined for the flap with a blunt nose andsealed gap. The curves indicate that on a flap with a0.49cf overhang, a tab is just about as effective in

33、pro-ducing lift but ouly approxima.t.ely 75 percent as effectivein increasing hinge moments asit is when on a plain flap.These results ara logical because of the manner in whicha flap or tab affects the pressure distribution over anairfoil.The tab characteristics having been determined, cal-culation

34、s were Dade to determine the tab deflections required to give desirable hinge-moment characteristics to .a flap with a 0.495cf blunt-nose overhang ad with sealedgap. The curve of tab deflection as a function of flap Chdeflection given in figure 8 was selected to make() a.equal to zero at 0 angle of

35、attack, The differential tablinkage will change the flap hige-moment characteristicsfrom those of figura 5 to those of figure-8, which is across plot of actual test data. The curves of $igure 8show that except for high positive angles of attack withlarge flap deflections the hinge moments of the fla

36、p canba trimmed out with a small deflection of the trim ta%.At a large flap deflection and a high positive angle ofattack, which is comparable to a critical condition forrudters, separation caused the flap overhang to lose itsbelancing effectivenes which resultad ia an increase inhinge-moment coeffi

37、cient. This difficulty can be avoided,however, by using a flap of sufficiently larga flap-chordc-pratio, -=, to secure adequate control without reachingccritical deflections.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-10.Thus by means of a large

38、aerodynamic balance used in “ “conjunction with a differentially operated balancing tab,the hinge-moment parameters may be independently varied,By making aCh()aCh-5zj positive and ()%-)ao slightly negative,the flap can bemade to float against the relative windw“aen free and yet not be over?.)alanced

39、 wen deflected.This floating tendency of the flap will cause the airplanestability with controls free to exceed that with controlsfixeci.Yigur9 9 compares the lift effectiveness of the flaphaving both a 0.495cf blunt-nose overhang and a differen-tial balancing tab with that of a plain flap of the sa

40、mechord (reference 6). As expected, the tab deflected withthe balanced flap gave considerably greater lift effec-tiveness than did the plain flap.Thus it appears that a differential balancing tabused in conjunction with an overbalanced flap can be madeto give very desirable lift and hinge-moment cha

41、racteris-tics. iTithstick force and free-control stability regu-lated in the manner already indicated, flaps having verylarge ratios of flap chord to airfoil chord and operatingat low deflections can be used to great advantage for con-trol surfaces.“CONCLUDING REMARKSThe results of the tests showed

42、that a flap with49.5-percent overhang was aerodynamically overbalancedwhen deflected regardless of uose shape. The large amountuof overhang reduced the slcpe of the curve of hinge momentagainst angle of attack to practically zero. The flap ef-fectiveness in producing lift was shout the same as for t

43、heunbalanced flap of the same chord. The small gap testedhad little effect on any of the characteristics. The small-est increment in drag was obtained with the blunt-nose shape.A tab deflected in the same direction as the flap inorder to. increase both the lift ahd the hinge moment of anoverbalanced

44、 flap chows promise of being a very satisfactoryarrangement for reducing stick forces and iroving free-control stability.Langley Memorial Aeronautical Laboratory,National Advisory Committee for Aeronautics,Langley Iield, Pa. .Provided by IHSNot for ResaleNo reproduction or networking permitted witho

45、ut license from IHS-,-,-u1- Goett, Harry J, and Reeder, J. P : Effects of Elevator Noseg Shaye, Gap, Balance, sad Tabs on the Aerodynamic CXacteristicsof a Horizontal Tail Surface. Rep No. 675,NACA, 1939.l-i 2. Ames, Milton B., Jr., and Sears, Richsrd I.: 2ressure-Dis-, Jr., andars, Richard”I.: Pres

46、sure-Distii-bution Investigation of snN.A.C.A. OOOg Mfoil with an853.854.”856.856.8“5“ “7.858.869.8510 a71 8511.8512.8513.85“ 14.-85 “15,85 . 16.85 :19.30Ordinate(percent c)o.88. “1.261.681.962.15 12.30 , 2.42 -.2.522.582.642.66 “.2.70”.2.71 ;2.72. . 2.73 2;.72 2.63.“:2.55 2.40Fair to l.iAcA0009 pro

47、file “totrailing edge c .Nose radius =.1.23 percent c,. .,.;. .,. . .Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NACAI IFig,1R =0.00PA is srmuhl lineA B is arc ocircleRATWMU AM-C-ouw-mfuHmmm Sharp nc=fiGu 1, “Nose dqpes A. ., :.,. ,.:. , -.” ,.Pr

48、ovided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-/ s-“/ / / I I I I I-12 / ./ / / t ,(a)-16“” I-.8 .6 -.4 .2 .2 .4 .6 .81 1 1 1 1A;dm7 sediiw IIW cv, cl(a) Sealed gap.Figure 3a,b.- Section aerodynamic characteristics of an NACA 0009 airfoilwith a 0.30c flap having a 0.495cf overhang with medium nose. . . - -. y-.- .,- .- ” .+., k.-. , . :,., ,. ., “ . ,7.;. . .:.-:”.“i - ,.