603 Wind Tunnel Investigation Of Ailerons V Airfoil ... - Scale Soaring UK

combination, nmn.ely, th.ai &ernuLairfoil jkp8 applied to theN. A. C?.A. %0 airfoil ...... Flepangle+W. The ofrfoll fs the mme m m?d for kt 3240(llg. 10), eM the trap ...
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REPORT No. 603 WIND-TUNNEL

INVESTIGATION FULL-SPAN By

OF WINGS WITH ORDINARY EXTERNAL-AIRFOIL FLAPS

AILERONS

AND

ROBBET C. PLATTand JOSEPH A. SHOETAL

SUMMARY An invedigaiion was carried & in the N. A. C. A. 7-by 10-foot m“ndtunnel of an N. A. C. A. WOlfi airfoil equipped, jirst, wifh a jul+hpan N. A. C. A. %012 external-aiifm”l$ap havinga chord0.20 of the main airfoil chord and m“th a jull+nan aileron m“th a chord 0.12 of the main airfoil chord on the trailing edge of the main airfoil and equipped, second, with a 0.30-chordjull-span N. A. 0. A. 33019 externai%irfd$ap and a O.l%chord fu-hpan ai?eron. The results are arranged in three groups, th$rsi two of which &al with the airfoil chaTaeterWm oj the two aiq%il--p combinatti and with the lateral-conirol churacteridia oj the airji.i+%pd%ron combinations. The third group oj tests deals with several meansjor balm-wingai.krons mounted on a speciu.1lurgechord N. A. (?. A. 9301.2 ahfoil model with and wit?und a 0..2O-chordN. A. C. A. 23019 tzrternal-airfd $ap. The test8 included an ordinury aileron, a mmtaine&no8e balm-we,a .l%%ebaLanee,and a tab. The reds obtainzd for the 0.30 CUJ’ap uerijy the conclti made jrom previou8 te8t8 oj the 0..20 c. &p combination, nmn.ely, th.ai &ernuLairfoil jkp8 applied to the N. A. C?.A. %0 airfoil sec.tioiwgive chuTa&rM.cs morejavorabla to 8peed range, to low power requirem&8 a%[email protected] al high lift coq$L&nt8,and to [email protected] monwn18than do other types ojfip in general me. % ai?+ww can prodwe large rolling monwnt8uiih relatively 8maL?adverseyawing momerukinjlight conditimwranging from htih speed to minimum speed. The no8e balunee and Ftie Munce were in.q$edwe in reducing the stick jorctx regwiredfor a given conirol [email protected], but the wse oj tabs in eombindon wiih a di$erential aileron motion provided a maw of obtaining dkrable sttik forces throughout the j%ght range. The aerodynamic advatiages oj this aileron--ap combinaihn appear to ouiweighprobabk d%ign dijficultiei INTRODUCTION knproveinent of airplane speed range and performance by the use of trailing-edge high-lift devices has been hampered by the necessary compromise between obtaining the highest possible maximum lift coefficient and the necessity of providing at least a minimum of lateral control. The usual compromise has involved the use of flaps over the central portion of the span with

ailerons attached to the tip portion. This procedwe results not only in the direct loss of possible masimum lift over the unflapped mea but may lead to an additional hazard resulting from the tendency of partialspan flaps of the cmventional type to reduce, in some cases, the degree of stability and control n~ar the stall. It is therefore generally recognized that the development of a latemkontrol arrangement that can be used in combination with a full-span flap offers definite possibilities for improvements in speed range and wfety. In most of the numerous attempts that have been made to devise such an arrangement (for example, references 1, 2, and 3) unforeseen difficulties have practically canceled the anticipated improvement. In some casea reductions of maximum lift or increasw in minimum drag have had to be accepted in order to obtain the minimum acceptable lateral control; the mechanical complications or operational diiliculties of other arrangements have prevented their satisfactory ~pplication. At present no combination that makes Fulluse of the capabilities of high-lift devicw and protides satisfactory lated control has found general application to airplane design. The imwtigation reported herein dealt with an arrangement that, on preliminary study, indicated possibilities of meeting the foregoing requirements. The arrangement consisted of a main airfoil on the trailing edge of which were an external-airfoil flap and ailerons forming the lip of the slot between the main airfoil and the flap. This combination logically results from an attempt to combine the desirable oharacteristica of the slotAip ailerons described in referenee 3 with those of the external-airfoil flaps desoribed in reference 4. These ailerons being structurally similar to ordinary ailerons, relatively complicated mechankd and structural arrangements are avoided and the main airfoil oontour is left unbroken when the ailerons are unreflected, thus making available the full capabilities of extend-airfoil flaps for speed-range improvement and reduction of power requirements in low--speedfight. This wind-tunnel investigation was divided into three general phases 1. Measurement of the lift, drag, and pitohingmoment characteristics and the flap hinge moments of an N. A. C. A. 23012 &lilfOil with N. A. C. A. 23012 563



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564

REPORT

-—

ADVISORY

NO. 603-NATIONAL

external-airfoil flaps having chords (cJ) that are 0.20 and 0.30 of the main airfoil chord (cU). 2. k addition to the characteristics measured in the tit phase, the measurement of the rolling- and yawingmoment characteristics of the foregoing combinations provided with ailerons having chords (c=) of 0.12 and 0.13 of the main airfoil chord and deflected various amounts. (The aileron chord was made 10 percent of the over-all airfoil chord in each case to permit the results to be directly compared with the data of ref~rence 3.) 3. Measurement of aileron hinge moments and lift and drag increments of a wide+hord N. A. C. A. 23012 rirfoil with and without a 0.20 % external-airfoil flap. Various types of aileron balance were tested.

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out and some investigation of methods of overcoming these diliiculties is discussed. APPARATUS

AND METHODS

The investigation was carried out in the N. A. C. A. 7’- by 10-foot open-tboat wind tunnel (reference 6). The models used in the first phase of the investigation consistad of the following: (1) A rectangular N. A. C. A. 23012 airfoil of 10inch chord and 60-i.nch span, constructed of laminated mahogany. (2) One X.nch-chord and one 3-inch-chord durnlumin N. A. C. A. 23012 airfoil, mch having a span of 60 inches. These small airfoils served as flaps. The tests of the combination using the 2-inch+bord flap are described in reference 4; the data have been included in this report for completeness. Exactly similar methods were adopted for the tests of the combination using the 3-inch+hord flap; surveys were — 0.054cup H.%ge ~ made to determine the effect of flap position and angle, (a) a desirable flap-hinge-axis location was selected from contours similar to those in reference 4, and force tests were made to determine the [email protected] of the fimdly selected arrangement at various flap angles. In order to avoid section inaccuracies during the iinrd force teats, these tests were completed before ailerons lx’ \ were built into the trailing edge of the main airfoil. P For the second phase of the investigation the trailing edge of the main airfoil was cut off and ailerons extending across the full 60-inch span of the airfoil were installed. I?or the tests with the 2-inch flap the chord of the ailerons (back of the hinge) was 1.2 inches; for the tests with the 3-inch flap it was 1.3 inches. The 1.2-inch-chord ailerons were made of the wooden sec(a) N. A. O. A.m12till wJth 0~ C-N.A.O.A.=12~oil fip and tion” taken from the trailing edge of the main airfoil o.12 c. Ordltiaryaaerom. but difEcnlty in maintaining accurate settings of these (b) N. A. C. A.23012 Ok+Ou with0.?4e. N.A.O.A.2301Z [email protected] fiIIand ailerons indicated the desirability of using dumlumin 0.13 c. ordImry Oaeiwz% for the wider+hord ailerons. The settings of the 1.3FIGVEEL—Afkom and Saps W. inch ailerons were probably somewhat more accumte The results obtained have been studied with the than those of the 1.2-inch ailerons for this reason. purpose of clarifying the fundamental phenomena in- Figure 1 shows pertinent details of the models used. volved in the operation of the general’ type of device Figure 2 is a photograph of the model with the 2-inclI tested. They further provide the information neces- flap and 1.2-inch ailerons. If the details relating to the ailerons are disregarded, the figures show the condition sary for comparison of the particular arrang~ent tested with other devices intended to accomplish the of the models in the first phase of the investigation. A series of tests in which angle of attack, aileron same purpose. Certain diflicnltiea that may be encountered in flight applications of the device are pointed deflection, and flap angle were varied over the useful

.—.



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.

FIGURE z—~odol N.A.C.A.m12alrfofl with

02J3c. N. A. O A.

22012 extemakhfofl flap~d 0.12 c-

ordin8rY aileron.

WIND-TUNNEL

INVESTIGATION

OF WINGS

WITH

ranges was made for each wing-flap-aileron combination, The deflection of one half-span aileron w% varied from the selected maximum up to the maximum down deflection. The effect of moving both ailerons simultaneously may be obtained by the addition of the effects produced by one aileron deflected to each of the assumed settings, due account being taken of the signs of moments and deflections. This method of obtaining rolling, yawing, and hinge momenta of ailerons deflected in various ways from the data for one aileron is explained in detail in reference 2. All tests involved in the fit two phases were coqducted according to standard force-test procedure in the 7- by 10-foot tunnel (reference 5). The dynamic pressure in the jet was maintained at 16.37 pounds per square foot corresponding to a speed of 80 miles per hour in standard air. The *t Reynolds Number was 730,000 for the model with the 0.20 CWflap and 790,000 for the model with the 0.30 cmflap. The flow conditions correspond approximately to those that would e.xkt in free air at Reynolds Numbem of 1,000,000 and 1,100,000 respectively (reference 6). Hinge moments of the flaps and ailerons were measured in the usual manner. A calibrated torque rod, attached to the surface under test and shielded from the air stream, was turned by a pointer mounted next to CLgraduated diek outside the jet. The difference of the pointer deflections required to bring the surface to the required deflection with the wind off and on was read from the disk. This diflerenca is proportional ta the mrodynamic moment about the hinge; the magnitude of the hinge moment follows directly from the known calibration of the rod. The third phase of the investigation arose as the result of analysis of the data already obtained, which indicated that the ailerons would require excessive operating moments under certain conditions. It was therefore considered desirable to investigate the eilectivenes-s of several methods of obtaining aileron balance. In order to reproduce ailerons of practical sizes with satisfactory accuracy, a special wide-chord model was constructed to be mounted between end planes. Although such an expedient does not reproduce fnllscale conditions, practical aileron details, such as clearances and hinges, can be reproduced. As will subsequently be noted, leaks ahead of the aileron hinge resulting from clearance between the wing and the aileron have an appreciable effect on aileron characteristics and the clearance should therefore be accurately controlled. The wide-chord model consisted of a rectangular N. A. C. A. 23012 airfoil having a chord of 4 feet and a span of 8 feet, equipped with an aileron of 3l-inch span and 5.76-inch chord back of the hinge, located centrally along the span. The testsincluded the typw of ailerons shown in figure 3: An ordinary aileron, an aileron with a nose balance shielded by curtains, an aileron with a I?rise nose, and an aileron with a tab. An

AILERONS

AND

EXTERNALAIRFOIL

FLAPS

565

N. A. C. A. 23012 [email protected] flap of 9.6-inch chord and 8-foot span was provided. The section of this model as tested waa an accurate enlargement of that used for the standard-size model tested with the 0.20 CUexternal-airfoil flap and 0.12 cmailerons. The model, complete with aileron and flap, was mounted between large end planes in the jet of the 7- by 10-foot tunnel. (See fig. 4.) The regular force-test support, with two special struts for augl~f-attack adjustment, was used to permit measurement of the forces on the model. The aileron hinge moments were measured by rLtorque-rod and graduated-disk arrangement similar to that used for the standmd-size model. Values of lift and drrqg increments due to aileron deflection and the variation of aileron hinge moment with deflection were measured

Ordiiwy

oikron

k

FIGURE

3.—v8ii0ud hahncfd dlemns testd cm the wfda-chord N. A. O. A. a!rfoil with and without a O.Zlc. N. Ai O. A. 23012mterIGEMoIl tip.

!ZW12

at several angles of attack and flap angles. The tests were repeated with the flap removed to determine the effectiveness of the balancing means for narrow+hord ordinary ailerons mounted on a plain wing. ~ The tests of the wide-chord model were made, in general, at a dynamic pressure of 4.o93 pounds per square foot, corresponding to an air speed of 40 miles per hour in standard air. The reduced speed was used to avoid placing excessive loads on the balance parts used as the model support. The effective Reynolds Number in this case was of the order of 5,000,000 but it should not be considered so accurate an index of flow similarity as is usually the case in wind-tunnel testing.

566

REPORT

NO. 603-NATIONAL

ADVISORY

COMMITTEE

FOR AERONAUTICS —— .,-~,.

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>.‘ .-!=. . ,: >’ q%- ~ f ,., ,’!

. ‘-lly

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4 by Moot mmkl of the N. A. C. A. 23312afrfoIl with an extemel+drfofl IMP and an cudhmry atlemn, monnkl 10-foot windtnnnel.

RESULTS

Application of results.-The precision of standard force tests in the 7- by 10-foot tunnel is discussed in references 2 and 5. The results as corrected are considered applicable to ~~ht conditions with normal engineering accuracy at the previously stated values of the effective Reynolds Number. These values are too smaII to be directIy usabIe in most cases but, with the aid of referenm 7, a number of the characteristics of the present airfoils may be inferred for larger value-sof the Reynolds Number. The conditions under which the aiIerons on the widechord airfoil were tested were far removed bm those for which theoretical wind-tunnel corrections may be applied; they therefore do not appear susceptible of accurate interpretation in terms of fundamental parameters. The ideal conditions in this respect were disregarded in favor of obtaining a reasonably accurate reproduction of the full-size ailerons themselves, including the end effeots, to facilitate accurate comparison of the various ailerons tested. Consequently, any application to &cht characteristics must be considered qualitative in nature. For compwison of the aiIerons among themselves, however, the accuracy is probably much better than that usually obtained in standard small-scale tests, owing to the relatively large maggtude of the forces acting on the large model. The tiectivenew of the data subsequently presented in showing consistent differences between tbo ailerons serves as an indication of the accuracy with which the valuea were measured. Presentation and analysis of results.-The data obtained in the tests have been reduced to nondimensional coefficient form and are presented in a series of standard plots. The usual N. A. C. A. absolute coefficients are used throughout, except for a few

between end plmes In the 7- by

symbols that have not been standardized. In the computaticm of the standard airfoil coefficients, the nominal area has been taken as the sum of the individual areas of the nonretracting surfaces (see references 2 and 4); the chord lengths have been similarly treated. The nonstandard coefficients are: C.,, induced yawing-moment coellicient. CW profile yawing-moment coefficient. O*,hinge-moment coefficient based on the dimensions of the surface whose hinge moment is being measured.

(

Thus, (?,,=%)

ACL, the increment of lift coefficient produced by a specified deflection of the aileron on the widechord model. AC~, the increment of &yg corresponding to AcL. ~,angular deflection of the chord line of an ausilimy surface from the chord line of the surface to which it is attached, having the same sign convention as angle of attack. The following subscripts serve to identify the various parts of the compIete wing model: w, of the main airfoil. j, of the flap. a, of the aileron. t, of the tab. The resuhs of the first phase of the investigation :onsist entirely of lift, drag, pitching-moment, and flap inge-moment data relating to the two high-lift arrangonents -ted. Data for the plain N. A. C. A. 23012 Lirfoilused as the basic airfoil are shown in figure 6 ogether with data from another airfoil of the same section. The data for the basic airfoil equipped with a ).20 c. N. A. C. A. 23012 external-airfoil flap deflected hrough various angles appear in figures 6 to 9.

INVESTIGATION

WIND-TUNNEL

OF WINGS

WITH

AILERONS

AND

EXTERNAL-AIRFOILI?LAPS 567

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FIGUEE5.—The N. A. O. A. 231M2 afrbfl.

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of offack.m (degrees)

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FbpwUon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- N. L 0. A.23J112 [email protected], cm--------------------------------------------atme mDtid. cJ. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 0.26c- .1M7C Dntnm [email protected]+CJ. Pivot aft of tmlflng edge of c----------------------------------.m c. .02a5 c

Plwt wow t=---------------------------------------------Pivot aft of flap kadfng ~-------------------------------PfvotMow cf------------------------------------------------

Flapdisplacement AL-------------------------------------(L C.~ fcom leatig -L--------------------------------------(a. c.), above mafn [email protected] ~fi---------------------------------

FIOUBE6.—Tim N. A.C. A.2?412alrfoll with O.XIC.N. A. O. A. extanmldrfoIl

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568

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REPORT

NO. 603-NATIONAL

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ADVT.SORY COMMITTEE

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FOR AERONAUTICS

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N. A: 0. A. m12 bialn W@ mUOn---------------------------------------------FfnP @m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- N. A. O. A. 23312 over-all wing chord, C.c+cf. Mofn JYIngOhord, c“-------------------------------------------i17@ac Flap Ohord, c/. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 0.20 c. .231 c Datmm ChO@ C=CW+CJ. FIGUEE10.-The N. A. C. A. 22612airfofl with O.M”C.N.

Liffcoeffjciw~ C.

Ffvotaft of taflingadgeof c.—--------------------------------FfvOt Imlow c-------------------------------------------------Fivot aft of ftap loading die------------------------------------Flap dfsplacwnent @&---------------------------------------u. fmm kdfng *-------------------------------------------a.c. aixwe mafn wfrrg tiofi-.. -.---—---------------------------A. O. A. 23012axtanml+,frfefl I18P. Flap an@O,–~.

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570

REPORT

NO. 603—NATIONAL

ADVISORY

COMMITTEE

FOR AERONAUTICS

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5p. Flap angl% 10°. The akfoil k the same es UM for tcot 3240 (Ilg. 10), F1OURElL—The N. A. O. A. 2M2 airfefl wfth O-33c. N. A C. A.2W12ortemd+frfeil ~Pt ~ ~P mm. The v81ueof C- (...J ~fs mmputd almut the aarodynamio center used for kt 22J0.

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