WCA I'M s> ACER Wo. L5C2l^a NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WARTIME REPORT ORIGINALLY ISSUED April 19^5 as Advance Confidential Report L5C2l<-a COMPARISON OF PITCHING MOMENTS PORDUCED BY PLAIN FLAPS AND BY SPOILERS AND SOME AERODYNAMIC CHARACTERISTICS OF AN NACA 23012 AIRFOIL WITH VARIOUS TYPES OF AILERON By Paul E. Purser and Elizabeth G. McKinney Langley Memorial Aeronautical Laboratory Langley Field, Va. NACA WASHINGTON NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were pre- viously held under a security status but are now unclassified. Some of these reports were not tech- nically edited. All have been reproduced without change in order to expedite general distribution. 12k DOCUMENTS DEPARTMENT Digitized by the Internet Archive in 2011 with funding from University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation http://www.archive.org/details/comparisonofpitcOOIang 1(2, oS 30 1 3 NACA ACR No. L5C2l|.a NATK XL ADVISORY COMMITTEE FOR AERONAUTICS ADVANCE CONFIDENTIAL REPORT COMPARISON OF PITCHING MOMENTS PRODUCED L.Y PLAIN PLAPS AND BY SPOILERS WD SOME AERODYNAMIC CHARACTERISTICS OF AN NACA 23012 AIRFOIL WITH VARIOUS TYPES OF .HI 31 :. Paul E. Purser and Slizabeth 3. Mc Kinney SUMMARY An analysis and comparison has been made of the pitching-moment characteristics of airfoils with plain flans and spoilers. Aerodynamic section characteristics of an NACA 2 7 -;i2 airfoil having a retracted slotted flap with a plain, a slot- lip, and a retractable aileron are also presented for a large range of aileron deflections. The analysis indicated that the pitching moments produced by spoilers were less positive than those pro- duced by plain flaps of equal effectiveness. The data from two isolated cases indicated that the pitching moments created by the spoiler increased less with Mach number than the Ditching moments produced by the plain flap. The positive values of the pitching moments produced by both the plain flaps and the spoilers decreased as the devices were located nearer the airfoil leading edge. ROD ""ION The NACA has undertaken a brief investigation of the pitching-moment characteristics caused by various lateral- control devices far application to wing-twist problems in high-speed flight. Pitching-moment data for plain-flap controls have been published previously (see references 1 to 5 j f or example) and some data for spoiler-tyre controls have been published in references p tc 7« The effects of trailing-edge modifications on the pitching-moment characteristics of airfoils with plain flaps have been discussed in reference 3. CONFIDENTIAL NACA ACR No. L;G2ka Tests in two-dimensional flow of an NACA 23012 airfoil with a plain aileron and with two spoiler- type ailerons (a slot-lip and a retractable aileron) were reported in reference 9> but the pitching -moment data were not presented. The present report gives the section pitching-moment characteristics and other section data for these three arrangements. A brief analysis is also included of various data on the pitching-morient characteristics of airfoils with elain flaps and with spoilers. COEFFICIENTS AND SYMBOLS The coefficients and the symbols used herein are defined as follows: Cj, airfoil section lift coefficient (i/qc) C£ airfoil section profile-drag coefficient ( d /qc ) c airfoil section pitching-moment coefficient about quarter-chord point of airfoil (m/qc^) ch a aileron section hinge -moment coefficient (h a /qc a ) where I airfoil section lift d airfoil section profile drag m airfoil section pitching moment about quarter- chord point h a aileron section hinge moment q dynamic pressure ? -=rpy j \ 2 / c chord of basic airfoil with flap neutral c a chori of aileron CO [PIDENTIAL 7, NAOA AGO No. L5C2)ia CONFIDENTIAL V velocity of free stream p mass density of air and a angle of attack for airfoil of infinite asoect ratio, degrees 6 a aileron deflection, degrees; positive when trailing edge moves down 6-f slotted-flap deflection, degrees; positive when trailing edge moves down c 3 chord of. spoiler or retractable aileron p s projection from airfoil surface of spoiler or retractable aileron x distance from airfoil leading edge to flap hinge line or to outer edge of spoiler ■r-"-) rate of change of pitching -moment coefficient with •' 6 'cj control deflection at constant lift OaA ~] rate of change of angle of attack with control 5 / c 7 deflection at constant lift u [-_E| rate of change V^o/ct with effect! of cite hin a -mome it coefficient ve ansie of attack at constant lift M Mach number (v/a) a velocity of sound in free stream CONFIDENTIAL k CONFIDENTIAL '.MAC A ACR No. L'y:^h.& APPARATUS, MODEL, AND TESTS The apparatus, model, and tests are described in reference 9. I n brief, the J- by 7-f °t model was built to the NACA d'^Old airfoil profile and, when mounted in the Langley 7- by ]. 0-foot tunnel (described in reference J ) , completely spanned the test section. The tests were made at a dynamic pressure of 16.J7 pounds per square foot, which corresponds to a velocity of about 30 miles per hour and to e test Reynolds number of about 2.19 x 10 |J , based on the chord of the basic airfoil. The effective Reynolds number (for maximum lift coefficients) was about 3*5 x 10°, based on a turbulence factor of 1.6 for the Langley 7 _ by 10-foot tunnel. The airfoil profile, the slot and flap dimensions, and the arrangements of the plain-flap end spoiler-type ailerons are given in figure 1. The chords of the plain and slot-lip ailerons and the chord of the retractabls aileron in its most extended position were 10 percent of the basic airfoil chord. The slotted-flap installation was that designated 2-h in reference 3« All tests reported herein were made with the slotted flap retracted (5^ = 0°). METHODS OF ANALYSIS The primary aerodynamic factor contributing to wing- twist during rolling in high-speed flight is the pitching moment produced by the lateral-control aevice. For normal wings and ailerons, the pitching moment produced by aileron deflection twists the wing In such a way that the lift induced by the twist opposes the lift induced by the aileron deflection and thus effectively reduces the lateral control available. The pitching moment (or the wing twist) produced by a given aileron deflection increases approx- imately as bhe square of the speed and at some point the lift indue sd by the wing twist balances the lift induced by the aileron deflection and the airplane does not roll when the ailerons ere deflected. The speed at which the lateral control becomes zero is known as the reversal speed. In order to judge the relative merits of various lateral-control devices with respect to wing twist, the pitching-moment characteristics must be compared on the CCiM T < n ID3MT'IAL NACA AGP. No. L5C2i;a CONFIDENTIAL 5 basis of equal effectiveness. The pitching-moment parameter used should therefore be based on the change in rolling moment, lift, or effective angle of attack oroduced by the aileron rather than on the aileron /b c m \ deflection or sooiler projection. The slope \ r / \ 6a o/o l was therefore used to compare all the plain flaps and spoilers on an equal-effectiveness basis, since this parameter indicates the change in pitching -moment coef- ficient resulting from a unit change in the effective angle of attack of the portion of the wing covered by the aileron. The slooe of the oitching-moment-coef f icient curve was taken at constant lift (c-, = 0.1) because, when the airplane is rolled by the ailerons, the aileron section of the wing operates at nearly constant lift. Although spoiler-type ailerons, since they are used en only one wing at a time, operate farther from conditions of constant lift than the plain-flap ailerons, the parameter at constant lift is still believed to be more nearly repre- sentative of actual conditions than a parameter at constant anele of attack. A logical abcissa against which to plot /6 \da a I for plain flaps would be the flap chord but, when spoiler data must also be presented on a comparable basis, such an abcissa is no longer logical because spoiler chord (or projection) is analogous to flap deflection rather than to flap chord. The data were therefore plotted inst the chordwise location of the plain-flap hinge line Oi' of the outer edge of the spoiler. For devices such as the slot-lip ailerons, which were considered to be spoilers, the location used was the average location of the aileron trailing edge over the deflection range considered. All the finite-span data (references 5 sn< 3- 6) were converted to section characteristics by use of refer- ences 10 and 11. The values of aspect ratio used with the charts of reference 10 in computing section character- istics from the data of reference 6 were corrected for Mach number effects by the method of reference 12. At each value of Mach number, the geometric aspect ratio was multiplied by the factor ••. 1 - l'~. This procedure gives an effective reduction in aspect ratio as the Mach number is increased. CONFIDENTIAL CONFIDENTIAL NACA ACR No. L5'C2i|a RSKIITS AND DISCUSS IOK Test arts.- The aerodynamic section characteristics of an NACA 23Q12 airfoil having a retracted slotted flap with a plain, a slob-lip, and a retractable aileron are sented in figure 2. The lift and drag (or rolling- moment ana yawing-maiaent ) characteristics and the hinge- moment characteristics have bean amply discussed in refer- ence 9* The pitching -moment data presented in figure 2, together with other published ana unpublished data for Mach numbers up to about O.J, have been summarized ana are presented in figure J . Pitching moments produced b y pi"in fires .- The experimental data or; the pitching moments produced by plain flaps shown in figure 5 agree very well with values computed from Glauert's thin- airf oil theory (references 1 and 2) both in magnitude and in variation with x/c . These data indicate that, for equal changes in effective Le of attack (equal rolling moments), wide-chord flaps produced smaller pitching moments than nsrrcw-chord flaps s;d, consequently, that the use of wide-chord flaps would allow the attainment of higher values of the reversal speed. The use of wide-chord flans, however, will be limited by whether their hinge moments can be well enough balanced to produce reasonable values of stick force. It should be noted that the dsta of reference 3 indicate that the pitching moments produced by plain flaps may be reduced by increasing the angle between the unpen and lower surfaces of the flap at the trailing edge. Pitchin g moments pro duc ed by spoilers.- The experimental d*ata on fhe "pitching moments" produced by spoilers force a relatively smooth curve (fig. 3) sn d indicate that, for equal effectiveness, the spoiler located nearest the sir-foil leaping edge oroduces the smallest positive values of i ... ..S i . With a spoiler V a oJo z located ahead of about 0. 14.5c, the wing twist might augment rather than reduce the rolling effectiveness. The use of spoilers located so near the airfoil leading edge, however, is not recommended since many previous wind-tunnel and flight investigations have indicated that the tendencies toward lag and erratic action increase as the spoiler is olaced nearer the airfoil leading edge. C0NFIDEB3TIAL NACA JiGH No. L5C2l+a CONFIDENTIAL 7 The locations of the spoiler installations found acceptable have v?ried from about 0.60c to about O.G^c. G o". - ' pr ison of 'it cuing- moments produced by olain flaps a nd sp oi lers. - The (let a presented in figure 3 indicate that the pitching moments produced by plain flaps and spoilers have about equnl variations with flap or spoiler chordwise location and that the values of ( -— ; '- ) are \SOo/cj less positive for the spoilers than for the plain flaps. When a comparison is made at chordwise locations normally used - that is, 0.7Cc to 0.75c for spoilers and O.SOc to 0.85c for plain flans, the Ditching moments produced by spoilers are about one-half or less of the pitching moments produced by plain flaps of the same effectiveness. 7;ach number effects.- Data or the effects of Mach number or the pitching moments produced by cortroi surfaces are relatively scarce. A comparison is oresented in figure I4., however, of the effects of Mach number on the pitching moments produced by a spoiler aileron on the wing of reference 6 and en the pitching moments produced by a plain flap on an NACA 66,1-115 airfoil tested in the Langley 8-foot high-speed tunnel. Th^ pitching moments produced by the plain flap, in addition to being larger than those produced by the spoiler, also increase with Mach number at a rate greater than that indicated by the Glauert-Prandtl factor / ■ • ■ ^- . The Ditching moments VI - I. 2 produced by the snoiier, however, increase at a rate slightly less than that indicated by .. ■r . -rrr over VI - M 2 most of the Mach number range tested. Although the data shown in figure '14. are not strictly comparable and are for two isolated cases, there appears to be a possibility that Mach number effects may be smaller on pitching moments produced by spoilers than on pitching moments oroduced by plain flaps. CONCLUSIONS An analysis of data on the pitching-moment character- istics of airfoils with plain flaos and sooilers indicated the f o 1 1 owing c on c 1 u3 i on s : CONFIDENTIAL C0' T ?TD2 T 'TIAI kCA riCR No. L^C^a 1. The pitching moments produced by spoilers were less positive than those produced by plain flaps of equal effectiveness . 2. The positive values of the pitching moments produced by both the plain flaps and the spoilers decreased as the devices were located nearer the airfoil leading edge. 3* The data from two isolated cases indicated that an increase in Mach number caused less increase in the pitching moments produced by tne spoiler than in those produced by the plain flao. Langley Memorial Aeronautical Laboratory National .Advisory Committee for Aeronautics Langley Field, Va. CONFIDE] HAL NACA ACR No. L5C2!|a CONFIDENTIAL REFERENCES 1. Ames, Milton B. , Jr., and Sears, Richard I.: Dster- mination of Control -Surf ace Characteristics from NACA Plain-Flap and Tab Data. NACA Reo. No. 721, 2. Glauert, H. : Theoretical Relationships for an Aerofoil with Ringed Flap. R. & M. No. 1095, British A.R.C , 1927. 7 Wenzinger, Carl J., and Harris, Thomas A.: Wind- Tunnel Investigation of an N.A.C.A. 2*012 Airfoil with Various Arrangements of Slotted Flaps. NACA Rep. No. (#64/1959. L . Purser, Paul £., end Riebe, John Iv 1 . : Wind-Tunnel Investigation of Control-Surface Characteristics. XV - Various Contour Modifications of a 0.50- Airfoil-Chord Plain Flap on an NACA 66 (215) -Oil; Airfoil. NACA ACR No. 3L20, 19^3 ■ 5. Purser, Paul E. , and Turner, Thomas R. : Wind-Tunnel Investigation of Perforated Split Flaps for Use as Dive Brakes on a Rectangular NACA 2J012 Airfoil. NACA ACR, July I9U1. 6. Leitone, Edmund V.; An Investigation of the High- speed Lateral-Control Characteristics of a Sooiler. NACA ACR NO. 1^025, 191*4, 7. Sliortal, J. A.: Effect of Retractabie-Sooiler Location on Rolling- and Y a wine -Moment Coefficients MAC A TN No. 1+99, 1954- 8. Purser, Paul E., and Johnson, Harold S. : Effects of Trailing-Edge Modifications on Pi tching-Moment Characteristics of Airfoils. NACA CB No. LI4.13O, 191+4. o Wenzinger, Carl J., and Bamber, Millard J.: Wind- Tunnel Tests of Three Lateral-Control Devices in Combination with a Full-Span Slotted Flap on an N.A.C.A. 25012 nirfoil. NACA TN No. 659', 1933. CONFIDENTIAL 10 CONFIDENTIAL NACA ACS Ko . L'5C2l|.a 10. Weick, Fred E., and Jones, Robert T.: Resume and Analysis of N.A.C.A. Lateral Control Research. NACA Rep. No. 605, 1937 . 11. Pearson, Henry A., and Anderson, Raymond F.: Calculation of the Aerodynamic Characteristics of Tapered Wings with Partial-Span Flaps. NACA Rep. No. 665, 1939. 12. Goldstein, 5., and Young, A. D. ; 'The Linear Perturbation Theory of Compressible Flow, with Applications to Wind-Tunnel Interference. R, & M. No. 1909, British A.R.C., I9I4.3 . CONFIDENTIAL NACA ACR No. L5C24a CONFIDENTIAL Fig. 1 00 lc gap . X Plain aileron Slot-lip aileron ^-Locus of aileron X^IOc u PP er wd lower \ edges Retractable aileron CONFIDENTIAL NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Figure L- The NACA 230IB airfoil with various types of ai/eron and with a slotted flap. NACA ACR No. L5C24a Fig. 2a CONFIDENTIAL 2.0 ^v V 1.6 V tf v- 5: j.X o <^ «0 .8 \ X 1) .4 .<^ *0 I 1 s. .1i t I Angle of attack , a ,deg (a) Plain aileron-, c a =0./Oc. Figure Z .-Aerodynamic section characteristics of ft AC A Z30/2. airfoil with various types of aileron. 6 f =0? CONFIDENTIAL NACA ACR No. L5C24a Fig. 2b CONFIDENTIAL 1 $ s: <0 >s >^ V s . .^ Q. ^ ^ $ ^ k '^v. £ > V <: "N» <-1 V" ■S <» ~K v: v «0 .* ,^ Ss. »\ o> Is «s ^ <^ ■5? <0 5; s> .Vi V "+> 11 *>* V ^> ^ 6.67 > 6.67 9^^r. Y -.4 J&K J Y < I0.0i I W i Y -.8 < V C( NAT MMin DNAL ;e FOR UJVISO AEROt AUTICS I.Z -t \ -" \ t 7 i i i r~ / 2 / 6^ 2 I Ps 3.33 5.18 6.86 6.67 10.00 10.00 Angle of attack, a , deg (c) Retractabte aileron. Figure £.- ConcJudecl. 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