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i No. 659
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N _TIND-TUNNEL TESTS OF THREE LATERAL-CONTROL DEVICES IN C0]_I_II_ATION WITH A FULL-SPAN SLOTTED FLAP ON AN N.A.C.A. 23012 AIRFOIL By Carl J. Wenzinger and Millard J. Bamber
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T _anoley Memorial Aeronautical Laboratory _J / 7,
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L i =_ Washington August 1938 & T z NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS TECHNICAL NOTE I_0. 859 v WI_._D-TU!_NEL TESTS OF THREE LATERAL-CONTROL DEVICES IN COMBINATION WITH A FULL-SPAN SLOTTED FLAP ON AN N.A.C.A. 23012 AIRFOIL By Carl J. Wenzinger and _illard J. Bamber SUM_ARY A large-chord N.A.C.A. 23012 airfoil was tested in the closed-throat V- by 10-foot wind tunnel. The airfoil extended completely across the test section, and two- dimensional flow was approximated. The model was fitted with a full-span slotted flap having a chord 25.66 percent of the airfoil chord. The ailerons investigated extended over the entire span and each had a chord lO percent of the airfoil chord. The types of ailerons tested were: retractable ailerons, slot-lip ailerons using the lip of the slot for ailerons, and plain ailerons on the trailing edge of the slotted flap.
The data are presented in the form of curves of sec- tion lift, drag, and pitchlng-moment coefficients for the airfoil with flap deflected but with ailerons neutral, and of rolling-moment, yawing-moment, and hinge-moment coeffi- cients calculated for a rectangular wing of aspect ratio 6 with a semispan aileron and a full-span flap.
For the ailerons investigated the data indicate that, from considerations of rolling an_ y_wing moments produced and of stick forces desired, the retractable aileron is the most satisfactory means of lateral control for use with a full-span slotted flap.
INTRODUCTION Many types of trailing-edge flap have been developed for producing high lift coefficients. These flaps usually v extend over only the inboard section of the wing because the outer portion is required for lateral-control devices.
± N.A.C,A. Technical Note No. 659 _4 With such an arrangement, the average lift for the entire wing is less and the drag is more for a given lift than it would be if the flap extended over the entire span. The increase in the lift-drag ratio obtained with full-span flaps over that with partial-span flaps is especially im- portant for the condition of take-off with flaps deflected.
The purpose of the present investioa_ion w_s to de- termine the effectiveness of various lateral-control devices when used with a full-_-pan flap. An arrangement of the full-span slotted flap reported in references I and 2 was used because that flap appears to be one of the most promising high-lift devices developed up to the present time.
Three types of aileron were investigated: 1. Slot-liR_Ireference_ 3 and 4).- The lip of the flap slot was hinged to move up so as to change the slot shape and also to act as a "spoiler" on the upper surface of the airfoil.
_A___!_!_.- The trailing edge of the slotted flap was hinged to move as a plain aileron.
3m Retractable (reference 5).- A curved plate was installed that moved out of the upper surface of the air- foil ahead of the flap to act as a "spoiler."
APPARATUS AND TESTS _o de i The airfoil was built to the N.A.C.A. 23012 profile with a mahogany nosepiece, a pine flap and slot form, and the intermediate section of ribs was covered with tempered waterproofed wallboard. The mode] has a S-foot chord and a V-foot span. The chord of the flap, which extended along the entire length of the span, was 0.2566c. The airfoil profile, the slot a_d the flap dimensions, and the locations of the flap when deflected ,_ro $ivon in figure l(a) and in table I. Fi&_.res l(b) to l(d) show the ar- m_ rangements of the ailerons with their locations and dimen- o sions.
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N.A.C,A. Technical Note _o. 659 3 General Test Conditions v The model completely spanned the closed test section of the wind tunnel so that two-dimensional flow was prac- tically attained. The two-dimensional-flow installation in the 7- by 10-foot closed-throat wind tunnel is described in reference 1. The aileron hinge moments were measured with a torque-rod balance.
A dynamic pressure of I_$.37 pounds per square foot was maintained for all tests This o_y:,.... c pressure cor- responds to an air _peed of about 80 miles per hour and to an average test Reynolds _ Number of 2,190,000_ Measurements of lift, drag, and pitching moment were made for each aileron setting through a complete range of angles of attack up to the stall, with flap deflections (Sf) of 0 °, l0 °, 20 °, 300, 40 °, and 50 °. The aileron settings (Sa) were (minus, up; plus, down): 0 o .5 ° _i0 ° .20 ° .SO ° For the slot-lip aileron, -45 ° , and -60 ° .
For the plain aileron, -40 °, -30 ° -20 ° , -I0 °, 0 ° t I0 °, 200 , 30 ° 40 ° 50 ° and 60 ° For the retractable aileron, 0, up 0.033Zc, 0.0667c, and O.10c.
Because of possible structural advantages, narrow-chord retractable ailerons were tested with deflcctions greater than the aileron chords so that a gap was left between the upper surface of the airfoil and the bottom of the aileron.
O_ue aileron with a chord 0.066Vc was tested up 0.10c, and one aileron with a chord 0.0333c was tested up 0.0518c and 0°0686c. The chords of tho:retractable ailerons were measured along their SUZl_nded are.
RESULTS Airfoil Section Coefficients The airfoil section coefficients are given in stand- ard nondimen_ional coefficient form as follows: 4 N.A.C,A. Technical Note i_o. 669 section lift coefficient, _/qc.
section profile-drag coefficient, d/qc.
cd 0 , section pitching-moment coefficient about
Cm(a.c. ) '
aerodynamic center of airfoil with flap and aileron neutral, m/qc 2 whore I is section lift.
d, section profile drag.
section pitching moment m, dynamic pressure, ½ p V 2 q, airfoil chord including flap.
Ct section _ngle of attack.
C_ 0 , Aileron Coefficients aileron hinge-moment coefficient, ha/(q a_ Sa).
Ch a , where is ai].eron hinge moment about the aileron ha hinge.
ca, aileron chord.
Sa, aileron area.
CL', rolling-moment coefficient.
Cn', yawing-moment coefficient.
Rolling-moment and yawing-moment coefficients for a rectangular wing of aspect ratio 6 with one semispan ai- b leron were computed from the two-dlmen_ional-f!ow tests by the following method: c_, : -o.ooT1/(_c_/a_) _c_ .
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Cn ' = Cni On o r where Gni' = -0.180 C_' c12, and Cno' = 0.125 A Cdo.
T_ N.A.C.A. Technical Note No. 659 is the average of the slopes of the lift curves (gc_ per degree)for the airfoil with aileron neutral and for the aileron deflected.
the increment in the section lift coeffi- cient produced by the deflected aileron at any given value of angle of attack _.
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the induced ya_ing-momen% coefficient pro- Cn I , duced by the Increment of section lift the average c$ of the airfoil when the C%s , aileron is deflected on one side.
the yawing-moment coefficient due to the in- Cno !
crenent of profile drag (ACdo) produced by the deflected aileron.
(The constants 40.0071 and -0.180 are taken from" figure 13(a) of reference 6. These constants in- clude the effects of aspect ratio and lift dis- tribution produced by the deflection of the ai- leron on one side. The constant 0.125 assumes that the profile drag pro<uced by the aileron is concentrated at the center of the aileronLspan.)
Accuracy of Results Experimental errors in the results presented in this report are believed to be within the following limits: c% ±0.02 (near maximum lift) • 0.0003 (minimum drag with cd° 8f = 0 ° ) C$ ' ............ ±0.005 On ' ±0. 002 Cha .... ± O. 005 c_ ±0.5 ° 0 ° to-I.0 ° 8f
6 N.A G.A Technical Note }To 659
• • • | Flap petition .... ±0,002c +0.3 ° 8 a Aileron position - - -±0.0003c No tests were made to determine the effect of flap and aileron fittings on the results. The lift and the drag have beGn correctea for tunnel-wall effects, as explained in reforencc 1. The effects of the fittings and the tun- nel corrections probably would nob appreciably change the rolling or the yawing moments given in this report• Thc given limits of accuracy do not include any un- certainties in the assumptions used for computing C_ w and Cnt. The same relations, howcver, were used in this report for all coefficients• DISCUSSION Characteristic_ of Airfoil with Slotted Flap The section characteristics of the airfoil with ai- leron neutral and the _lotted flap deflected are given as plotted against the curves of c%, Cdo, and Cm(a.C.)o section angle of attack _o in figure 2. These data are given to show the general characteristics of the slotted flap. As previously mentioned, the data were no_ correct- ed for the effects of the aileron and the flap fittings.
Aileron Characteristics The rolling-moment, the yawing-moment, and the hinge- moment co0fficlcnts computed as previously described are given in the form of curves of the coefficients plotted against aileron deflection. The coefficients are all given for a rectangular wing of aspect ratio 6 with the full-span flap a_d for a single aileron extending ovcr the entire semispan. The data are given in this form so that all ailerons will be on a convenient basis for comparison.
An indication of aileron performafice may be obtained from the wind-tunnel data by consideration of the following factors: N.A.C.A, Technical Note No. 669 i, The value of C_ I should increase with lift coefficient, i.e,, it should increase with angle of at- tack and with flap deflection so that the airplane will have about the same response for a given control movement regardless of flying attitude, should increase with aileron 2. The value of C_ w should be large for small al- deflection, and dCst/d8 a leron deflections.
3. Lag in rolling motion with control movement should be small, probably less than 1/10 second (reference 7).
4. The values of CnV should bo small in any case and preferably favorable (positive _Then C%t is positive).
5. The hinge moments of one aileron should be small or of such a nature that they can be counterbalanced against those of the other aileron through a differential linkage.
6. The control force required to deflect the ailerons should be small and should increase uniformly with aileron deflection _less a servocontrol mechanism, such as hy- draulic operation of the ailerons, is used.
Slot-li_ aileron.- The rolling-moment coefficients for the slot-llp aileron are unsatisfactory for the condi- tion from 8f = 0o to 8f = 20o with aileron angles less than 100 because about l0 ° movement of the ailerons from neutral is required before any appreciable amount of roll- ing moment is obtained (fig. 3). The lag in rolling mo- _ion with control movement is probably less than 1/10 sec- ond, (See references 3 and 4.)
The yawing-moment coefficients are generally adverse (negative) for small aileron deflections and favorable (positive) for large aileron deflections. Theme moments generally become algebraically less as the flap angle is increased (fig, 3).
The hinge moments required to hold the aileron neu- tral are large and increase with flap deflections (fig. 4).
As the aileron is moved up, the moments change sign and force must be applied to move the aileron higher. The slopes of the curves of Cha against 8a arc irregular and, for small flap deflections, they change sign. The
N.A.C.A. Technical Note No. 659
fact that the hinge moments are irregular, combined with
the condition that only one aileron is moved, necessitates
a complicated control linkage if satisfactory stick forcez
are to be obtained unless a servoco1_trol mechanism is used.
Plai_ aileron.- The rolling-moment coefficients for
the plain aileron on the flap decrease with increased flap
deflection. A value of C%v of 0.04 (indicated as a min-
imum satisfactory value in reference 6) or larger may be
obtained provided that the flap deflection does not exceed
40 ° and that both ailerons are deflected (fig. 5).
would generally be adverse and large, e_pocially _ith
The values of the yawing-moment coefficient (fig. 5)
l_rge flap deflections.
The hinge moments are comparatively small for small
flap deflections but they become large with increasing
flap deflections (fig 6) The curves o_ C, against
" " _ _a 8 a are fairly regular and, as one aileron i_ moved down, the other can be made to move up and the moments will bal- ance when 8a = 0 °. Because the hing? moments increase with flap deflection, a_)_ appreciable amount of difforon- tia_ would cause ove_balance with flaps deflected.
Retractable aileron,- The rolling-moment coefficients for the retractable aileron are satisfactory for flap an- gles of 40 ° or less (fig. 7). For the flap angle of 50 °, the rolling moments are less than those for the 30 ° flap angle. The yawing moments are favorable for 0 ° angle of attack, becoming less as the angle of attacl_ is increased, and at 12 ° they are adverse except for the condition of 8f = _, 8a = -0.10c. The hinge moments were not measured because this type of aileron has no aerodynamic hinge mo- ment when the hinge i_ located at the center of the ailer- on radius. It appears that a satisfactory "feel _: for the control could be obtained by placing the hinge axis slight- ly below the center of the aileron radius.
Figures 8 and 9 show the effects of using narrow- chord retractable ailerons and deflecting them through a range greater than the aileron chord, leaving a gap be- tween the wing and the lower edge of the aileron. In prac- tically all cases the rolling-moment and yawing-moment co- efficients wore reduced but the percentage reduction was loss than the reduction in aileron chord. When the gap between the aileron and the wing was too great, a sharp
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N.A.C.A. Technical Note No. 659 9 break occurred in the lift and drag. This break would J show as a sharp discontinuity in the curves of rolling- moment and yawing-moment coefficients if plotted against angle of attack. The break occurred only with the flap deflected and with the 0.0333c aileron deflected 0.0686c.
The maximum anglo of attack at which the break occurred was 3 ° with the flap deflected 20 e, The lag in rolling motion with control movement would probably be less than 1/10 second for a retractable ai- leron as far back on the wing as those tested. (See ref- erence 3. ) CONCLUDING RE_,_ARKS When all factors are considered with regard to the rolling and the yawing moments produced and of the stick forces desired, the retractable aileron is the only one of the three ailerons tested that would be satisfactory when used in combination with the full-span slotted flap.
The retractable aileron may be deflected through a some- what greater range than its chord with an increase in roll- ing and yawing moment.
The plain ailerons on the slotted flap were unsatis- factory because of the small rolling moments and large adverse yawing moments produced with large flap deflec- tions. The _lot-lip aileron as tested would be unsatis- factory for lateral control because of the ineffectiveness of the ailerons for deflections lo_z than lO ° with small flap deflections. The characteristics of the hinge moments of the plain and the slot-lip ailerons are such that they are likely $o cause difficulties in obtaining satisfactory stick forces.
Langley Memorial Aeronautical Laboratory, National Advisory Committee for Aeronautics, Langley Field, Va., July 14, 1938.
I0 N.A.C.A. Technical Note _o, 859
REFERENCES I • Wenzinger, Carl J., and Harris, Thomas A." Tests of an N.A.C.A. 23012 Airfoil with Various Arrange- ments of Slotted Flaps in the Closed-Throat 7- by 10-Foot Wind Tunnel. T.R. No. (to be published), N.A.C.A., 1938.
2w Wenzinger. Carl J., and Delano, James B.: Pressure Distribution over an N.A,C.A. 23012 Airfoil with a Slotted and a Plain Flap. T.R. No. 633, N.A.C.A., 1938.
Weick, Fred E., and Shorta!, Joseph A.: Development of the N.A.C.A. Slot-Lip Aileron. T.N. No. 547, N.A.C.A,, 1935.
Shortal, Joseph A.: Wind-Tunnel and Flight Tests of Slot-Lip Ailerons. T.R. No. 602, N.A.C.A., 1937.
• Shortal, J. A.: Effect of Retractable-Spoiler Loca- tion on Rolling- and Yawing-Homent Coefficients.
T.N. No. 499, N.A.C.A., 19_4.
t s @ Weick, Fred E., and Jones, Robert T.: Resume and Analysis of N.A.C.A. Lateral Control Research.
T.R. No. 605, N.A.C.A., 19_7.
• Soul@, H. A., and _cAvoy, W. H.: Flight Investigation of Lateral Control Devices for Use with Full-Span Flaps• T.R. No. 517, N.A.C.A., 1935_ % ll N.A.C.A. Technical Note No. 659 TABLE I _4 Ordinates for Airfoil and Slot Shapes chord) (Stations and ordinates in percent of airfoil Slotted Flap N.A.C.A. 23012 Airfoil Upper Lower Lower Upper surface surface Station surface surface Station -i. 29 -1.29 -2.05 -.32 .40 -1.23 I. 25 2.67 -2.21 .04 .72 -I. 71 2.50 3.61 -2.36 .61 1.36 -2.26 5 4,91 -2.41 1.04 2.00 -2.61 7.5 5.80 -2.41 1.40 2.64 lO -2.92 6,43 1.94 3.92 7,19 -3,50 2.30 5,20 2O 7.50 -3.97 -2.16 5.66 25 7.60 -4. °-8 2.53 6.48 3O 7.56 -4.46 2.63 7.14 -4.49 7,76 4O "4 2.58 9.03 5O 6,41 -4.17 2.46 10.31 5.47 --3.67 6O -1.23 1.68 15,66 4.36 -3.00 -.70 .92 20.66 8O 3.08 -2.16 -.13 .!3 25.66 9O 1,68 -1.23 95 .92 -.70 Center of leading-edge arc: | -1.29 0.91
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Leadlng-edge radius:!.58.
Leading-edge radius: 0.91 Slope of radius through end of chord: 0.305.
Contour of Slot (Distances measured from trailing edge of slot llp) Station Ordinate 72.32 -I.02 ....... p fh__o$ 2 so 74.57 .67 Y af (dog.) x 76.32 1.76 77.82 2.30 3.91 8.36 79.32 2.65 3.63 5.41 I0 2.82 80.82 3.45 3.83 82.70 2.64 3.37 3O 2.63 40 1,35 2,43 Radius of arc: 7.97 .50 1.63 5O Center of arc: 1.48 .12 66.65 4.67 _ 7
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i.A.O.k. Technioal _ote No.659 Fig. 1 -- ,82"/0 o \ \ (a) 8lotted flap, no aileron.
\ \ \ \ \ \\ •. ?_70 c (b) Slot-llp aileron.
(o) Plain ailoron.
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Figure 2.- 5ect_ota lift,dr'a_,a_d pi_ch_r_5-moment coefficients of i N.A.C.A.2301£ airfoil with full-span slotted flap.
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° -64 -56 -48 -40 -3 -N :i6_-"_ Aileron deflection, 5 a,deq.
Fisure 3.- l_ollins-moment and yawins-mornent coefficients of slot-lip ail- erons on an N.A.C.A.23012 rectansular wJn_ of aspect ratio 6 with full-span slotted flap. (a)a_ = 0 , (b)o_ = 17.°.
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i Figure 6.- Hinge-moment coefficients of plain ailerons on the full-span slot- ted flap of an N.A.C.A. Z301Z rectangular wing of aspect ratio 6.
(a) a = 0", (b)c_ = IZ °.
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