NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS WARTIME REPORT ORIGINALLY ISSUED October 19M4- as Advance Restricted Eeport IAJ05 Wnro-TUMEL HJVESTIGATION OF AN HACA 23021 AIRFOIL WITH A 0.32-AieFOIL-CHORD IDOHBLE SLOTTED FLAP By Jack Fischel and John M. Eiete Langley Memorial Aeronautical Latoratary 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. L-7 DOCUMENTS DEPARTMENT Digitized by the Internet Arcliive in 2011 witli funding from University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation http://www.archive.org/details/windtunnelinvest NACA ARR No. L4J05 RESTRICTED FATIOML ADVISORY COMMITTEE FOR AEROMUTICS 7/3 (elO ^ / -3 ^ . .. U ADVANCE RESTRICTED REPORT :7I1:D-TUNNEL IIvIVSSTIGATION of an NACA 23021 AIRFOIL VflTH A O.32-AIRPOIL-CHORD DO-QELE SLOTTED FLAP By Jack F'ischel and John M. Rlebe SUMMRY An Investigation was made in the LM/vL 7- by lO-foot vilnd tunnel of an NACA 25021 airfoil with a double slotted flap having a chord y?. percent of the airfoil chord (0.32c) to determine the aerodynamic section charac- teristics with the flajos deflected at various positions. The effects of moving the fore flap and rear flap as a unit and of deflecting or removing the lower lip of the slot were also determined. Three positions were selected for the fore- flap and at each position the maximu^'ri lift of the airfoil was obtained with the rear flap at the maximum deflection used at that fore-flap position. The section lift of the airfoil increased as the fore flap was extended and maximum lift was obtained with the fore flap deflected '^0^ in the most extended position. This arrangement provided a maximum, section lift coefficient of 5«51j virhich was higher than the value obtained with either a 0.2566c or a O.I,lOc single-slotted-f lap arrangement and O.25 less than the value obtained v/ith a O.^Oc double-slotted-f lap arrangem_ent on the same airfoil. The values of the profile-drag coefficient obtained Yi/ith the 0.32c double slotted flap were larger than those for the 0.2566c or O.Lj-Oc single slotted flaps for section lift coefficients bstvv-een 1.0 and approximately 2.7. At all values of the section lift coefficient above 1.0, the 0.1+Oc double slotted flap had a lov^rer profile drag than the 0.32c double slotted flap. At various values of the maximuja section lift coefficient produced by various flap deflections, the 0.32c double slotted flap gave negative section pitching-mom.ent coefficients that were higher than those of other slotted flaps on the same airfoil. The 0.52c double slotted flap gave approximately the same maximum section lift coefficient as, but higher profile- RESTRICTED 2 NACA ARR No. li4.J05 drag coefficients over the entj^re lift range than, a similar arrangement of a 0.30c double slotted flap on an NACA 25012 airfoil. INTRODUCTION The National Advisory Committee for Aeronautics has undertaken an extensive investigation of various high- lift devices in order to furnish information applicable to the aerodynamic design of wing-flap conihlnatlons that will improve the safety and performance of airplanes. For use in take-off and initial climb, a high-lift device capable of producing high lift with low drag is desirable. For use in landings, however, high lift with variable drag is believed desirable. Other desirable character- istics are: no increase in drag with the flap neutral, small change in pitching moment with flap deflection, low forces required to operate the flap, and freedom from possible hazard due to icing. The results of various investigations on the NACA 23021 airfoil are presented in references 1, 2, and 3. Results for the NACA 23021 airfoil with a single slotted flap having a chord 25.66 percent of the airfoil chord (0.2566c) are given In reference 1; results for the same airfoil with a 0.40c single slotted flap and with a 0,40c double slotted flap are given In references 2 and 3, respectively. The present investigation, in which tests were made of a 0,32c double slotted flap on the NACA 23021 airfoil (fig. 1), is a continuation of the investigation reported in reference 4 of a 0.30c double slotted flap on an NACA 23012 airfoil. APPARATUS AND TESTS Models An NACA 23021 airfoil with a 3-foot chord and a 7-foot span was the basic model used in these tests. The ordlnates for the NACA 23021 airfoil section are given in table I. The airfoil was constructed of lami- nated mahogany and tempered wall board and is the same MCA APR No. 1)4. JO5 airfoil previously used for the investigations reported in references 1, 2, and 3. The trailing-edge section of the model ahead of the flaps was equipped with lips of steel plate rolled to the airfoil contour and extending hack to the rear flap in order to provide the hasic air- foil contoiir when the flaps were retracted (fig. 1). The double slotted flap consisted of a fore flap and a rear flap. The fore flap ( 0. lk67c ). tested was the same one designated fore flap 3 in the investigation reported in reference l^. and had an upper surface and trailing-edge of diu?al and a lovifer surface of laminated wood. The fore-flap profile is shown in figure 1 and its ordinate s are given in table I. The rear flap (0,2366c) tested was the one used in the investigations reported in references 1 and 5« Its profile is also shown in figure 1 and the ordinates are given in table I. Both the fore flap and the rear flap were attached to the main part of the airfoil by special fittings that permitted them to be moved and deflected independently. Each flap also pivoted about its own nose point at any position; increments of 5° deflection were provided for the fore flap and increments of 10° deflection for the rear flap. The nose point of either flap is defined as the point of tangency of the leading-edge arc and a line drawn perpendicular to the flap chord. The deflection of either flap was measiored betv."een its respective chord and the chord of the main airfoil. The model v;as made to a tolerance of ±0.015 inch. Tests The model was mounted vertically in the closed test section of the LMAL 7- ^7 10-foot tunnel and com.pletely spanned the jet except for small clearances at each end. (See re-ferences 5 ^-^d 6.) The main airfoil was rigidly attached to the balance frame by torque tubes that extended through the upper and lower boundaries of the tunnel. The angle of attack of the model v/as set from outside the tunnel by rotating the torque tubes with a calibrated electric drive. This type of installation closely approximates two-dimensional flow and the section characteristics of the model being tested can therefore be determined. k MCA ARR No.Ll|J05 A dynamic pressure of l6.57 pounds per square foot was maintained for most of the tests but, as the flaps were extended and the rear-flap deflection was increased to 60° and 70°» it was' necessary to reduce the dynamic pressure because of the linited power of the tunnel motor '\'ith the configuration for maximum lift, a dynamic pres- sure of 114.. SIj. pounds per square foot was maintained. These dynamic pressures correspond to velocities of 80 and "j6,2 miles per hour under standard sea-level con- ditions and to average test Reynolds numbers of approxi- mately 2.2i^5 X 10^ and 2.l[(-0 x 10^, respectively. Because of the turbulence in the wind tunnel, the effective Reynolds numbers Rq (reference 7) were approximately '^.6 x 10 and J.lj-? x 10 , respectively. In each case, Rg is based on the chord of the airfoil with the flaps retracted and on a turbulence factor of 1.6 for the LML 7- by iO-foot wind tunnel. ITo tests were made of the plain airfoil nor of the model with the flaps completely retracted because the characteristics of the plain airfoil had previously been investigated and reoorted in reference 1. -o^ The optimurc flap positions for the various flap deflections were considered, for p\a''poses of making the best selection, to be the positions at which either maximum lift, minimum drag, or miinimum. pitching moment was obtained, although, as previously indicated, a variable drag is desired for landing conditions. Three positions of the fore flap were selected in determining various extended positions of the flaps or a possible path for the extension of the flaps. The least extended fore-flap position, having a 5° deflection (position 1), and the chordwise location of the inter- mediate position (position 2) were chosen arbitrarily. The location perpendicular to the chord and the 20° deflection for position 2 were optimujn as determined from a maximum-lift survey with the rear flap deflected 50° and 60°. Because of the large niomber of tests involved in determining the optimum-lift position of the double slotted flap, a preliminary survey was made to determiine the optimum position and deflection of the most extended position (position 3) of the fore flap with the rear flap deflected 6o° and 70° at various positions. Tests were thereafter made with the fore flap at each of the three selected positions in order to determine the maximum lift ^■lACA APR No. l4J05 5 and the optimum position of the rear flap at several deflections. Data -vvei-e ohtained for rear-flap deflections of 10°, 20°, 50°, and l!.0° at position 1; 30°, 1+0°, 50°, and 60° at position 2; and l+O^ , 50°, 60°, and 70° at position 3- Inasmuch as it appeared likely that only small rear-flap deflections would he used with the least extended fore-flap position and that only large rear-flap deflections v;ould be used with the most extended fore- flap position, the tests were confined to these configu- rations. In order to determine the effect on the aero- dynamic characteristics, tests were also made with the lower lip of the slot in its normal position on the contoiir, deflected 19° within the airfoil contour (at fore-flap position 2), and completely removed (at fore- flap position 5) • No scale-effect tests were made Lecause the results of earlier tests of the MCA 23021 airfoil v:ith a slotted flap (reference 1) are considered ar)plicahle to the results of the present investigation. An angle -of -attack range from -6° to the angle of attack for maximum lift was covered In 2° increments over most of the range for each test; however, when the stall condition was approached the increment was red.uced to 1°. Very little data were obtained for angles of attack above the stall because of the unsteady condition of the model. Lift, drag, and pitching moment were measui-ed at each angle of attack. RESULTS AMD DISCUSSION Coefficients and Symbols All the test results are given in standard section nondinensional coefficient form corrected for tunnel-wall effect and turbulence as explained in reference 6. c^, • section lift coefficient (l/qc) C(=[ section profile-drag coefficient (do/qc) c-^. , section pitching -moment coefficient about (a.c.JQ aerodynamic center of plain airfoil (fig. 2) "^(a.c.)oA^ 6 MCA ARR No. i4J05 [cjn/ ^ j section pltching-Koment coefficient L ^^*^*'o|c7 at maximum section lift coefficient ''max C7 maximum section lift coefficient ''max c^ minimum section profile-drag coefficient %ln where I section lift (Iq section profile drag m/„ \ section pitching moment about aerodynamic o center of plain airfoil (fig. 2) q dynamic pressur e (|PV^) c chord of basic airfoil with flap fully retracted V ■ velocity, feet per second p mass density of air and Rq effective Reynolds number l^ distance from aerodynamic center of airfoil to center of pressure of tall, expressed in airfoil chords a,-5 angle of attack for infinite aspect ratio 5^ fore-flap deflection, measured between fore- 1 flap chord and airfoil chord 5-f. rear-flap deflection, measured betv/een rear- flap chord and airfoil chord X]_ distance from airfoil upper-surface lip to fore-flap-nose point, measured parallel to airfoil chord and positive when fore-flap- nose point is ahead of lip MCA ARR No. l1]-J05 7 y-i distance from airfoil upper -surface lip to fore-flap-nose point, measured perpen- dicular to airfoil chord and positive when fore-flap-nose point is below lip X2 distance from fore-flap trailing edge to rear-flap-nose point, measured parallel to airfoil chord and positive when rear- flap-nose point is ahead of fore -flap trailing edge Yp. distance from fore-flap trailing edge to rear-flap-nose point, measured perpen- dicular to airfoil chord and positive when rear-flap-nose point is below fore- flap trailing edge Precision The accuracy of the various measurements In the tests is believed to be within the following limits: a^, degrees *0.1 °^max ^°-°5 °^Ca.c.), -°-0°5 C(i ±0.0003 °miu C(i^. ±0.0006 '^°(c^ = 1.0) ca ±0.002 °(c^ = 2.5) 6^ and Of , degrees ±0.2 Flap position ±0.001c No corrections were determined (or applied) for the effect of the airfoil or flap fittings on the section aerod3n.iam_lc characteristics because of the large number of tests required. It is believed, however, that their effect is small and that the relative values of the results would not be appreciably affected. 8 MCA No. lL^J05 Plain Alirfoil The complete aerodynamic section characteristics of the plain NACA 23021 airfoil (froic reference 1) are presented in figure 2. Since these data have already "been discussed in reference 1, no fiirther coinraent is believed necessary. Determination of Optimum Flap Configurations Maxiraum lift .- The results of the maximum-lift inves- tigation with the fore flap at each of the three selected positions and with the rear flap deflected and located at points over a considerable area with respect to the fore flap are presented in figtu:'es 5 to 5. I'he results are presented as contoixrs of lift coefficient for various positions of the rear-flap-nose point at various rear- flap deflections. Ihe results shovi that at each fore- flap position, the conto-irr-s did not close at the smaller rear-flap deflections investigated. At positions 1 and 2, it is indicated that the open contours would close at positions of the rear-flap nose that would be impracticable because of the large gap betv/een the two flaps. At each of the three fore-flap positions, as the flap deflection increased, the position of the rear flap for maximum section lift coefficient c-j ^^ generally 'm.ax became more critical - that is, a given m.ovement of the rear-flap-nose point caused a greater change in the value of c-j . Since the nosition of the rear-flap nose max for Cy tends to move forward and upward as its ''max deflection Increases, the gap betv/een the two flaps is reduced. The values of C7 obtained at each fore- "m-ax flap position and the approximate position of the rear- flap nose with respect to the fore-flap trailing edge are given in the follov>ring table; Position of rear-flap nose Pore-flap position Ahead of lip (percent airfoil chord) Below lip (percent airfoil chord) C7 max 1 2 3 1 6 2 3 2.71 3.06 3.31 MCA ARR Wo. UI-JO5 Prom the contours of rear-flap-nose position for C7 , the best path to be followed by the rear flap at ''max all deflections within the range Investigated, from a consideration of Cy alone, can be determined. The ''max range of flap positions covered v;as considered sufficient to allow for any deviations or compromises from the best path. Complete aerodynamic section characteristics for the optimum-lift and optimum-drag rear-flap-nose positions at each selected fore-flap position are presented subse- quently herein. Minimum profile drag .- Drag data obtained with the fore flap in the three selected positions and the rear flap deflected at various positions over a wide region are presented in figures 6 to 8. The data are presented as drag contours for the rear-flap-nose position at certain selected section lift coefficients and rear-flap deflections. A comparison of the section profile-drag characteristics of the plain airfoil (fig. 2) with the prcfile-drag characteristics given in the contours of figure 6(a) and 6(b) shov;s that the plain airfoil gives the lower drag value at c^ = 1.0. Inasmuch as only a very few of the contours v;ere closed about Indicated optimiim-drag positions of the rear- flap nose (figs. 6 to 3), it is obvious that a sufficient range of rear-flap position was not covered and that the true optimum values may exist at some other positions. At each of the fore-flap positions, hovirever, it is indi- cated that the contour-s would close at positions of the rear-flap nose which v/ould be somewhat closer to the lip of the fore flap than the positions tested. As the fore flap was extended and as the rear flap v/as deflected, the optimuja-drag rear-flap-nose position generally moved forward and up, closer to the fore-flap trailing edge. More than one region of mininiujn di^ag exists at various values of section lift coefficient cj and various rear- flap deflections and the minimum drag is seen to be prin- cipally a function of section lift coefficient and rear- flap deflection and relatively independent of the fore-flap position. In each position of the fore flap, as the section lift coefficient or the rear-flap deflection increased, the contours generally became more critical or cloF.ely spaced; tiiat is, a given movement of the rear- flap-nose point generally caused a greater change in the value of the section profile-drag coefficient c^^ . (See figs. 6 to 8 ° 10 MCA ARR IIo. lUJ05 Inasmuch as the rear-flap-nose positions for maximtmi lift and minim-um drag generally do not coincide, a com- proraise Is necessary. The carves for the complete aero- dynamic section characteristics are therefore presented for both conditions. Pi tching moment . - Contoiors of section pitching- moment coefficient for the rear-flap-nose positions at selected section lift coefficients and rear-flap deflec- tions are given for each of the three fore-flap positions in figures 9 to 11. These contours indicate that an increase in the negative value of c™ , , at a ^(a.c.)^ given Cj was obtained r/ith increased rear-flap deflection and that "the maxim-urn negative values of c^, , were ^(a.c.)^ usually obtained at or near the position of the rear-flap- nose point for maximum lift at each rear-flap deflection (co-mpare with figs. 3 to 5). At 5^. = 50°," 60°, and 70° at position J), however, a decrease in the value of c™, vv'as indicated vmen c, increased, (a.c.)^ ^ At a given lift coefficient and rear-flap deflection, the negative values of pitching moment also increased as the fore flap was extended from position 1 to position 3' It appears desirable therefore to use the minimum flap deflection or extension necessary to obtain any given lift coefficient. In addition, the contoTjjrs indicate that the position of the rear-flap nose becomes more critical with increased rear-flap deflection and lift coefficient. With these contours of flap location for Cjj^, . (a, c . ; Q in figures 9 to 11, the designer can determine or antici- pate the values of c^ , to be encountered at a ^(a.c. )q given value of c? within the range of position and deflection indicated. Aerodynamic Section Characteristics of Selected Optimum Configurations The complete aerodynamic section characteristics of the airfoil with the rear flap at the optimiom-lift and MCA ARR No. l).|.J05 11 optimum-drag positions at each, flap deflection and at each of the three fore-flap positions are presented in fig-ores 12 to ll\.. The consecutive flap-nose positions as 5^ increases are indicated in the figures by those key symbols that are connected by dashed lines. The lift-c\arve slopes decreased with Increased rear-flap deflection, although at rear-flap deflections below 5^°, the lift-curve slope was sometimes as much as 0.03 greater than that of the plain airfoil. At each fore -flap position, the angle of attack for maximum lift usually decreased v/ith increased rear-flap deflection but in some instances remained fairly constant. At position 5 (fig. 1^) and 5fp = 50°, the position of the rear flap for maximum lift and minimum drag coincide. Irregularities in the curves at the larger flap deflec- tions (figs. 12 to ll\.) indicate changing flow conditions. At the small rear-flap deflections and lift coeffi- cients, the slopes of the pitching-moment curves were negative and, at high flap deflections and lift coeffi- cients, were usually positive; smaller negative values of Cm/ X were therefore sometimes obtained with a ^(a.c. )q large flap deflection than with a small one at high lift coefficients. (See figs. IJ and ll|. ) I ncrement of maximum section lift coefficient . - The Increment of the maximum section lift coefficient Aci^^^, based on the value of c? of the plain airfoil, ''max ' increases as the rear flap is deflected and as the fore flap is extended (fig. 15). At each fore-flap position, the values of Ac7 are higher for the opt imi.-un- lift ''max ° position than for the optimum-drag rear-flap position, as was anticipated. The maximum increment of lift coefficient obtained was at position 5 with 5f - "JO^, where a value of I.96 is indicated. The scale effect on the values of Acy ''max was not investigated but it is expected that the values would increase slightly v;lth Reynolds number with the 0.3.2c double slotted flap as did the values for the single -slotted-f lap arrangem.ents of references 1 and 6. 12 NACA ARR No. lLJO^ E nvelope polar c"upves .- The envelope polar s of section profile-drag coefficient 0^ at each fore-flap o position, obtained from figures 12 to li|- for the optimiim- lift and optimum-drag configurations, and the polar of the plain airfoil are presented in figure l6. These curves indicate the c^^ available at any c, when °min the rear flap is located to give c, (fig. l6(a)) and c^T (fig. l6(b)). max 'O mm For both the maxim,um-lif t and minimum-drag configu- rations (fig. l6), the plain airfoil gives the lowest c^ for values of Cy less than 1.3^ and for values of above 2.6 tl position 3» above 2.6 the lowest value of c^i is indicated at "■o Comparison of Flap Arrangements When the lift-drag characteristics of the 0.2566c and O.I1.OC single slotted flaps (references 1 and 2) and the 0.1j.0c double slotted flap (reference 3) 3.re compared with those of the optimum-lift and optimiom-drag configu- rations of the 0.32c double slotted flap (fig. I7), it is apparent that the O.Ii-Oc double-slotted-f lap arrange- m.ent produced the highest lift coefficient ( c, = 3»5^) on the NACA 23C21 airfoil. The c, obtained with max the 0.52c doLible slotted flap is considerably higher than that obtained with either single slotted flap but it is approximately O.25 less than that of the O.i^Oc double slotted flap. The 0.32c double slotted flan had a larger c^ than either single slotted flap for values of c, between 1.0 and approximately 2, "J and had a larger C(3_ than the O.Lj.Oc double-slotted-f lap arrangement at all values of c^ above 1.0. The 0.52c double-slotted-f lap arrangem.ent had values of c^ for the envelope polar s that differed by o MCA ARR No. LkJ05 15 about 0,02 for the optimum-drag and optimum- lift configu- rations at a value of c, of about 2,5. At values of c^^ less than I.5 and greater than 3«1> however, the two polar curves practically coincide. When the polar s of the 0.32c double -slotted-f lap arrangement on the NACA 23021 airfoil are compared with a similar arrangement of a O.JOc double slotted flap on the NACA 25012 airfoil (reference l\-) , it is apparent that the c, obtained with each is approximately the same ''max (fig. 18). The values of 0^5 , however, are hlgjier at o all values of c, for the arrangement on the 2 1-percent - thick airfoil than for that on the 12-percent-thick air- foil but the relation between optimum-lift and optimum- drag conf IgTirations is about the same for each arrangement, A further comparison of the various slotted-flap arrangements on the NACA 2$021 airfoil indicates that a fairly linear variation exists for each arrangement at a given flap configuration between the c, and the ''"^(a.c.)^ max (fig. 19) and this variation max appears dependent on the flap arrangement. The 0.32c double slotted flap gave higher values of fc^j^ t' Ha.c.) o at any value of C7 than any of the slotted flaps ''max Inasmuch as there will be a tail load required to trim the negative pitching moment of the wing of an air- plane, the loss in maximujn section lift coefficient in trimming the airfoil section pltching-moment coefficient has been calculated, for the case when the center of gravity is at the aerodynamic center of the plain airfoil, from the following expression and is indicated in figure I9: P^(a.c.)o] ' 'max Loss of C7 ''max C7 The loss in ci has been presented for tall lengths 1/ th Q -v "max of 2, 5 J and 5 airfoil-chord lengths and, by means of the curves of figure 19, the effective c-, can be max determined. iL^ NACA ARR No. LliJ05 Effect of Various Modifications on the Aerodynamic Section Characteristics Eff ec t of moving t he two flaps as a unit .- The effect on the aerodynamic section characteristics of moving the fore flap and rear flap as a unit perpendicular and parallel to the airfoil chord is shov/n in figures 20 and ?1, respectively. A OcOlc displacement downward of the flaps, perpendicular to the chord, was quite critical in that a large decrease in lift and an increase in drag resulted (fig. 20). Figure 21 Indicates that a movement of the flaps parallel to the airfoil chord had a consid- erable effect on the aerod^-TLamic characteristics; that is, at positions of the fore flap downs cream from x-, - O.7O (position 5)> large decreases in lift and increases in drag resulted and unsteady flow conditions existed. A comparison of figures 20 and 21 with the contours of figiires I4. and 7 and 5 ^rid 8, respectively, indicates that the position of the fore flap is more critical than the position of the rear flap. Moving the two flaps approximately as a unit from position 1 to position 2 and then to position 5 along two different paths, A and B, gave an increase in lift, drag, and pitching moment. (See figs. 22 and 23.) Since the model fittings only allowed Increments of 10° for the deflection of the rear flap, it was not possible to have a 5^^, of 35° for figure 22 and a df^ of I|.5° for fig-'ore 25 at position 1. Although motion of the tv/o flaps as a -unit is only approximately simulated, figures 22 and 25 are thought to be si;ff iciently illi.istrative . Effect of the airfoil lower lip .- The effects of deflecting the lov;er lip of the airfoil from its normal position at fore-flap position 2 and of removing the lower airfoil lip at position 3 £^re shown in fig-ores 2l|. and 2S, respectively. Deflecting the lip upward 19° decreased c^^ and increased c^^^ over most of the angle-of -attack range, possibly because of the poorly shaped slot entry ahead of the fore flap when the lip is deflected. On the other hand, removing the lip at the extended fore-flap position (fig. 25) had a slightly favorable effect on the aerodynamic section character- istics at low values of C7, by causing a reduction in the profile drag, and a slightly adverse effect at high HACA ARR No. L)4-J05 15 values of c^ . Such a result Indicates that a smoother slot entry ahead of the flaps raay he desirable, provided it does not reduce the values of ct available. ''max Although no data \vere obtained at small flap deflections, it is probable that the smoother slot entry would be even more favorable under such conditions. CONCLUSIONS An investigation was made in the LMAL 7- by 10-foot tunnel of an NACA 2,5021 airfoil v;ith a double slotted flap having a chord p2 percent of the airfoil chord (O.JSc) to deteriains the aerodynamic section characteristics v/ith the flaps defl-?cted at various positions. The results of this investigation shov; -chat; 1. The 0.32c double slotted flap on the NACA 23021 airfoil gave a maxifflTiiJi section lift coefficient of 3ol> v;bich V7as larger than the value obtained with the 0.25660 or O.lj-Oc single slotted flaps and O.25 less than the value obtained with the O.L{.Oc double slotted flap on the same airfoil. 2. The values of the profile-drag coefficient obtained with the 0.32c double slotted flap were larger than those for the 0.2566c or O.iiOc single slotted flaps for section lift coefficients between 1.0 and approximately 2.7. At all values of the section lift coefficient above 1.0, the present arrangement had a higher profile drag than the 0.i|.Oc double slotted flap. 5. At a given value of the maximum section lift coefficient produced by various flap deflections, the 0.52c double slotted flap gave negative section pitching- m.oment coefficients that were higher than those of other slotted flaps on the same airfoil. i|.. The 0.52c double slotted flap gave approximately the same maximum lift coefficient as, but higher profile- drag coefficient over the entire lift range than, a similar arraneement of a O.3OC double slotted flap on an NACA 23012 ai?foil. 5. Moving the flaps slightly from their optimum positions sometimes proved critical and resulted In b. l6 MCA ARR No. LI^J05 large increase in drag and a reduction in lift. The position of the fore flap appears to be F.ore critical than that of the rear flap. 6. Deflecting the lower lip of the airfoil 19° upward generally decreased the section lift coefficient and increased the section profile-drag coefficient over most of the angle -of -attack range: removing the lip at the extended fore-flap position reduced the profile drag slightly in the lower-lift range but was slightly unfavorable at high section lift coefficients. Langley Memorial Aeronautical Laboratory National Advisory Committee for Aeronautics Langley Field, Va . MCA ARR ?To. LI+JO5 1? REFERENCES 1. Wenzinger, Carl J., and Harris, Thomas A.: ¥/ind-Tunnel Investigation of an F.A.C.A. 25021 Airfoil with Various Arrangements of Slotted Flaps. ITACA Rep. No. 677, 1939. 2. Duschik, Frank: VJind-Tunnel Investigation of an N.A.C.A. 25021 Airfoil with Two Arrangements of a i|0-Per cent -Chord Slotted Flap. NACA TN No. 728, 1959. 5. Harris, Thomas A., and Recant, Isidore Q. : Wind-Tunnel Investigation of NACA 2^012, 25021, and 2505O Airfoils Equipped with I|.0- per cent -Chord Double Slotted Flaps. NACA Rep. No. 723, I9I1I. I|-. P-urser, Paul E., ;^ischel. Jack, and Riebe, John M.: Wind-Tunnel Investigation of an NACA 23012 Airfoil with a 0.50-Airf oil-Chord Doiihle Slotted Flap. NACA ARR No. 5L10, 1943. 5. Harris, Thomas A.: The 7 by 10 Foot Wind Tunnel of the National Advisory Corimiittee for Aeronautics. NACA Rep. No. 1+12, I95I. 6. V/enzinger, Carl J., and Harris, Thomas A.: '/^'ind-Tunnel Investigation of an N.A.C.A. 23012 Airfoil with Various Arrangements of Slotted Flaps. NACA Rep. No. 66k, 1939. 7. Jacobs, Eastman N. , and Sherman, Albert: Airfoil Section Characteristics as Affected by Variations of the Reynolds Number. NACA Rep. No. 586, 1937. MCA ARR No. lI^-JO^ 18 PQ < Eh p< 03 rH 'H 0\_:d--cNDvO uf-NrH CM LOCO roico cv L^^aM^-^f^cx) roicx) naco ro 0^ CO . LO LO • 1 O iH c\j CM K^^f^K^^^^K^c\J c\j rH iH i i 1 1 1 1 1 1 1 1 1 1 1 1 1 CN 30 -^ ■ • • Cij Upper surface lpnoncx) o\JOCO_3<30 ONCM crvj:icM cm <-i 1 o •H ■P 03 -P CO CM-ChCO KM>-_d-0 0-NAOM3 KAOvO r-CM LfM>-co CM rvJ CM^^ CM ovo Lr\ t^-aM>-CM Lr\CM^£> ^-LTNtH o L.E. radius: I.58 Center of L.E. radius located on chord line O rH tH iH rH 1 1 1 1 1 1 Upper surface vovo CM iHOO O J-(\J (H LOO O ^— iH CM K> rH CTnMD cm CO KA OrHCMCMCMCMrHrHrH O o •H -P c3 -P 00 Cr\CO !>-VD_chKA(rvl rH O OM>- KM>-fH LOCrNNAC— rH LOCQvO O rH CM -zt LOVO CO Cr> rH CM N^J" rH tH cH rH H •H O -CM rOvO O CM O rH LOLOK\LrNNM>-CrNCX) iH O C—rH KAKACM Xi LTN bOO li K\ . ,^ CO -P • •* -d- w th ^ Ph .H •• 'd ^ 0-3 o3 •H CH ■d i^-i o rvi K\^ Lovo r-co co oo co co o- Lr^_rt cm iH i 1 1 1 1 1 1 1 1 1 1 1 1 r 1 1 1 Upper svirface 1 i>-_::frOihr\K>0AO ltv-o ctnO O onlomd nocm 1 CO rH CTnH O hod O O_zt-d"0\0 O I^Lf^OJ 1 rH rH tH rH iH rH iH o •H 4J cC +^ CO LO CM LO LO . • * OrHcMLTM^-OLOOLOOOOO O O OlOO rH H aj r^ kv^ltnmd ixo o^o^o L.E. ra Slope c end CO M Pi < o ^; CO o > W P <: 1-1 o Eh Eh o o NACA ARR No. L4J05 Fig. 1 rorQ flap Rear f/ap .32c NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Chord line F/gurz /- Sections of the A/ A C A 250EI airfoil and the 0.52. c double slotted flap. Fig. 2 NACA ARR No. L4J05 if ' ■': -■-- ■■■- "'^ lil- n to ^iU ::: B'-' ^ US - 1 7- t - -:: -^ fc '4 I'-: '-' vi.-r r+ ■1 te •^. A . 1. _. " .r -:- •^ P J't 4- : '•1* P '• 'i - -.' ''■''. h^ A w. -; 7=7- --_-- '% pr r\ 1/1 -_- - -^f -f r- n P w -U ■-'1 -\5 1 ;-- - ^- Ee __ n^ lA -r. :-; .,;t -; - ■ - -:^ '>; i*' U- ^O ^-- ->- ';3 ^ -r _-- ^^ -:'' _, -r / - L--r ^t ;/ ^ 1^. el. --^ ~: ;— / - - ; :-- ■-^T ^ n 1^ ^ . L. """ ^ \ ^i_ A St ft h^ U. - :- S ,, -^ «^ .c, . ^ _ — — ' : ^ -- - yX ' ■— — „ *_ _. — - — J; - 1- --- +^,_ ■* 0-. Of Tr ' r^ j: ^ n^ TO 5 " i ■?_' '%\ Ti Uc -U --" = 1 - r sS ;,- -VT ,/ - - M Jlf ■'-~J 1 1 / ~ r) M " Z:_ ,/ :-; ^-' i4 ---- Ui t41 -- / At ?Y -.J __. — ,--: ' 1 / iptt tJTT Ef «/! ERO IftJI n t; -- /_ -^ : i • Ui .u /^ ,_ ^ 17 f - - i -: - / ^ i:- i-"-: ;* p -. / P - -^ ':^^ ^ n /^ y ^ -^ /A ,_'"': c * Ul u ^ / " 1 /O V -.- '-- ^; V ' - -- er- ^ p^ f 1" r^^ it '"I o -a- -et- ■ < >■ — 1 — -^ " CT- / /'> l^ J^ ^ ■ a — ► ^ 'C J. <> 1 % — - ff > 3" "" :_ / < T f) '^/ ^n sf^ y' • J\ lU -- --' L^ < ■^/' ^rl-.'. -o' '^ ,7 ^: ^.^ ^rii"'" ■ ' ■.-- ^ ^ - / "j / >.- 5^ V )4 — ^ ^ o ^ — — ^ ^ ,^ -y " '.«) 1 i ^ -' ■ ; L \- - :- ' u- , " (it) B J o » _ — T r «; — 6 ^ \, ^J 7 r ^ o [/' :_ . -^ 5 tJ _- <; Q ^ ,- -= u ^ ,!i^ rr" - Q) <0 f^- <; ■ / — ^ — p L. t ) c A !. ( > i ? h 1 /, ? /. ^ ,'»<= \h m // z'/ J '"( )e t ?( t/. ="/■ >/ c. ' I F '9 t/t 'e r - ■ / <^ ri (ly n 7/ 1/ ^ ,0 ? 1 pi afr ) a ''r ''O // if "n in 7 ri 't ^1*^ '(^1 '?(' 1^ 1 j M. i±± L£i ii^ ■ .^■'■ k^d ;^i r-vr NACA ARR No. L4J05 Fig, ? ZQO /..OS 270 \ ^> S.I5 >: 1 -- ' ZiO \ ^ 1/ ^ 1 t- -^ ^ /„ -4 ze4 12B- ■■\ I " ~^ K 1 AS 14 4 I 'i -4 -b -8 Percent o/r foil chord (a) S^ 'lo: Percent airfoil chord msf-za. 4 Z -Z -4- -6 Bzrcent airfoil chord ft; &f =30'. NAIIUNAL ADVISORY •* Z -Z -4- -6 -8 ftercent airfoil ciiord (d) Sf^ 40'. FigureSrConfours of rear-flop position for c^^^^. Position I ■6fi--^°-Xi'J.70-y^'3.-+S.Cvo/ues of7.,^yiOre gii^en in pf^rrzenf a/'rfo/7 chord.) Fig. NACA ARR No. L4J05 B 6 4 2 O -2 —i -6 Percent airfoil chord (a) Sf^ > 30°. « 6 ■* S Percent airfoil chord (b) Sft -40'. uiiumu. tovisoiir C0HHI11EE FOR AERONAUTICS e 6 ■* t 0-^-^-6 Percent airfoil chord &) Sf^ -- cot e 6 4 e o -e. -■* Percent otrfoilc/mrd (diSf^'60'. Figure ^-.-Contours of rear-flap position for Percent airfoil c/iord (e) c^'1.5- ■5^=-*W. 6 -ft a -z -4- -6 Percent airfoil c fiord Figure 6.- Cor/cluc/ed. Fig. 7a NACA ARR No. L4J05 6 4' 2 -Z -4 -t -8 Psrcent airfoil c/Tord (a) c^ -l-S. 5f^ = Jo: NHIUNAl ADVISOR* i;ilUMITIEE FOR AERONAUTICS 6 -^ e, -e^ -4 -6 -6 Percent airfoil cr?ord (b)Cg=£.0; Sf^ JO'. 6 -p B o -e,-4--6 -e Percent atrfoi I chord CO Cg - e.O; Sf = 4o'. Figure 7.- Contours of reor-fiopposff/or? for C^^. Posifion 2 :6f=20° :Xr2.70:y--a.4S. (Values of x,;i/^ore g'/yer? /n percent o/rfoi/ chora/.J ' ^ , ' NACA ARR No. L4J05 Fig. 7b 6 -f 2 -e. -^ -t Percent airfoilchord (d) ■Cg-&.S. 4.^ 40: NATIONAL ADVISOHr CUMMITUe FOR AEKONAUTICI 6 4- B> -Z.-'f'-e, Percent airfbil chord 6 4- & O -e. -4- -6' Percent airfoil chord (f) C;. -- £.3- bf. -- 60: Figure Z-Concladed. Fig. 8a NACA ARR No. L4J05 e 6 * e, O -Z -4- -6 Percent o/rfoH chord a ,6 -f & -s -4 Percent airfoil cliord NAIIUNAl ADVISORY CUMMintE FOR AEHONAUIICS .160 "/ ^ 'c" ^ 148 130 JSb t ^ \^ W/ / /5* -' ^ / > > ^ 160 ,y \ J \ tP. 3 e ■* 2 -z -4 -e Percent oirfoi/ chord CO C; . z.S; 5f -so: ■^ & o -z -4- -6 Percent airfoil criorO (mci'^-Oyiif 'JO'. /^igare8.-Confour:5 of mor-f/at> pos/tion for c^ . R>sitior>.3 ■ 6f'^0°:;<.'0.7Ojy,'2.^S/ya'/i/es of Xij-y, ore ff/i^en /f7 joerce/of o//-fo// c^^ord.J j t, i i NACA ARR No. L4J05 Fig. 8b a 6 ■4' z o -z, -■*■ -6~ Percent airfoil c/iord S 6 -* £ O -Z-4'- Percent airfoil ciyord (f)Cg-.3.0-6f^-60-. NAIIUNAL AOVISURY CUMMITIEt F0« AERONAUTICS a 6 4 Z O -Z -4- -6 Percent airfoil chord <5 6 -^ Z o -2 --* -6' F^rcent airfoil chord Figure 8 r Concluded. Fig. 9a NACA ARR No. L4J05 6 4 S, -2 -4^ -6 -a Percent airfoil chord (a) Ci ' iOj ^ • /o: NAIIUNAL ADVrSUftY COMMIHEE FOR AERONAUTICS 6 * 2 0-2.-4-6-8 Percent airfoii chord (b) Ci ' 10^ &f Z0°. 4- Z -8 -4- -6 -a Percent airfoil cliord (QCp - I.5'- s^ -.ao'. Figures.- Confours of rear- flop position for c^,^^. . Position J:6f'='5°jX^J-70jy'3^S.(Vo/ues ofx, ,v, ore giKen in percent oirfo// chord.) ' "^uVi ' ■ chord.J NACA ARR No. L4J05 Fig. 9b 6 -P Z -Z -4 -6 Percent airfoil chord id) c, -/.5. Sf -JO'. NAIIONAl AOVJSUHr COMMITIEE FOB URONAUTICS e 4' z -2 -4- -6 Percent airfoil chord (e) Cg - IS- a,^ • 40°. 6 4- t -e -^ -6 Percent airfoil cfTord (f) Cg-£.o- a^^40°. f^igure9.- Conc/uded. Fig. 10a NACA ARR No. L4J05 a 6 4' £, o -& Percent airfoil chord (a) Cg= '.s ■ <^^ = -30'. NATIONAL »DVIS01IY COMMITTEE FOR AERONAUTICS 6 6 <- & o -&-4 -6 Percent airfoil c fiord (id) Cp^ £.0- Sf --^0\ Percent airfo/i c fiord (C)C^'SO ; Sf^^'fO'. Figure 10.- Contours of reor-f/ap position for c^^^^. . Position 2; 6f'S0°j/L.'£.70jP'2f^S. (\/aiues of x,,y, ore giren /n percent a/rfoil chord.) ' '" NACA ARR No. L4J05 Fig. 10b 6 * £. -C -4 -6 Percent oirfoi/ chord NATIONAL ADVISOKY noMMITIEE FOR AERONAUTICS 6 4' 2. -Z -4 -& Percent airfoil ciiord Parcent a/rfoiJ chord (f) Ci'Z.T S^^- 60°. Figure /Or Concluded . Fig. 11a NACA ARR No. L4J05 'B4 T«- V- V z 4 :b5- h,^ W ^ r :£S8 ■:6b- --X- f< ^Cf h n ^7- - ^'' ^^ g^ ;«5 ^^s^ 65' \ ; \y fp 6 < 3 -1 «■ ^ 3 0-1,-4 -(■ Percent oirfoi/ chord (a) c, -• 2.0- Sf 40'. a 6 ■* Z O -Z-4 -6" Percent o/rfoi I chord 5; Q) lAMUNAl ADVISUBY COMMIlIEt FOB AERONAUTICS e 6 4' Z -Z -4—6 Percent airfoil chord (c) c^ ■■ S..3-. 5^-- so'. Q 6 -* s o -e-4 -6 Percer>t airfoil c/Tord (d) Cg --JO; Sf^.SO'. Figiure a.- Contours of rear-flop position for c„,„^, .P^/fior?3j6fr30'jZ-a70yra.-^S.fy<7/aes of;i:,,v, or:? g/r'er? rn percent 5/rfoii chord.) '■■'° -^ '' ' ^' ' '•'^' NACA ARR No. L4J05 Fig. lib b 4' Z -£-• * -6"' Percent airfoil chord (e) Ci 'ZS^ 5^ • 60°. I s 10 '^ Percent airfoil chord (f) c,--30 Sf'60' . ««IION«l ADVISOHr MMMITIEf FOB »E«0II«UT1C» 6 6 f S O -Z -4- -6' Percent cr/rfo/f ciiord (a) c,'£S. S^r ' 70°. -IE -^ \ -n- . ^ V, ^ % :Z? -777 ■T6- -- -^ ^ ^, N ^ -.77- f'; / \ r^ ^ -14- '-72 L.r^ r^ \ \ 6 t -^ & - 3 C -) -c I --* !. -6 Percent oirfoi/ c/)ord Fig'ure a- Conc/oded. 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I-. i'v 5- ~-^iC. ? i 1 ^-i ^^- ; ! i ■ I " it -^. , ^ k y / i 1 ! - '■■■rq^-i i ^ - - ■ i t- . ■ ;"" 1 , ^h- ^ J S' ^ ^^ ^ ' ! ■ 1 i ' ::m -J^ a _ 1 -" ■" ..A_ N r^ -^ ;S-:-;^fe ; ."^ .^ j^,^\ ;:--i-!^-: ! ■ i ! i ^ vA ■^ ^ ^ K^ i 1 -f- — lA : j 1 i 1 1 1 .^ a ! 1 i ~A 1 ( ) A J- 1 ^ 1 i / f. ■ f f>\ <' (1 R 4 ;^f^ I'i ^, - - - 1 t 1 \' ,^< "T fj, •>& Uff rof ffir f^f . 4 n 1 1 - " ! --- 1 . flA 1 [ ■ 4k f^ 'j2 rz: ■JM: ''^ ir^-1/ f'O t±s- \ ~c^ Hi L ~ "- ^)\m EEfm lEffi W^H3 - - 1 -:ir: i -Jl •i - ] - .■ ' ~ .' r/o //r? > /,? -c CLfeC ■lUc lAd 1 \ I ■ -1 - ■ j : ; ( i i ~ i" ■ ! 1 -^:t4^:t^k-k .■i-:t i - ^ 1 i ; 1 \ - 1 1- - 1--, i.--. -- rt-k" rU : \- ^ri--., ^H-l^^i- i.Ui .-a:!.;. si'L ,.\-^ Fig. 14a NACA ARR No. L4J05 .^oMi) NACA ARR No. L4J05 Fig. 14b t - - ! 1 "('" .1 1 i ( -:. "^ "=1 ■^-C 1 ■■ 1 T - -;- 1 ■: i "'" ^sfsra s J j /^=^ £* "ni : . 1 ■ i*-r Ifrt ^i. i -•' -= = — _.' 1 1 \ - % ■ / s ^1 -:' G - -^ / ' " ^,T""r a a wa / - ""^ -■ V X ^'^ _■ ■ 1 1 I / ■ -- - \ ^■■v \ f ^ 1 - 1 ' / -7- = ^--^ \ i- "f ■Li ,-^ 1 A Y >n: 3 " / 1 ^->N ~TT Ti / / ^ 1 . u. ^^ <« k / .:; S" --_ i ^"" r^ r ^1 - 1 - — - 1 1 - v^KtiT ^ •P _j i 1 _«> U; \-y^ Si 1 1 " - ' '7 — ?3 -^- ■f— — ! 1 — Vh- ,^ tjl:^ >S;J : / ^"t _i — h ■ r M •^ -'n 1 / ' ~t -f"^ . i/ ^ 1 - J / ^ ' ^x '-^ — p /v ^ / / I .\ ' \' :?0' / / / / \ / ! A / / 1/ V i f / / / 1 ! . '1') / , ' f ' / rr~;^' : - 1 / / / / r- - i - 1 / / /' uJ. ' 1 - " \ \ 1 J 1 '>rt \o c 1 1 t ii^cieg 40 to. (k) n) / -^ 1 1 /i 1 ^v \ o./p -oay^ jJO L 170 1 - ^ i ; \ t ** 4 1 ',] ■ ~ J / j /j >.. 1 u ! M: I Z£6 "t56"- ^■SFy ' 6() /] J // 1 ti 1 1 1 1 1 ^ ]/■ f s3 ^ V \ / 4 [^ •d Od- \ ■ \ \ ■^^ / , / / ' \ ^ \ '^ ^ / / h ^ _ \ \ ^. /: ^r s t I ' s. \ ^ / y" 1 _ ■" ^ \ A ^- A >^ S|_ TO" V ^ !w i '^ J y :/ " - "w 1 ■ \ \ J /■ I - 1 ? \ \ y f- f ! 1 ; ^ \ y' / 'S k i^ / ■^ ^ \ /' - i 1 - • " --- _j i < ^< j -: T § <> : - 1 j t ^i i -" j >1 \ \ \ 1 H \ \ \ \ 1 A SI \ \ \ 'i \ h tl \ \ ^5 -^CVJCT) O Q \ i \ 9 \ \ \ — c ) ^ D tv i OC J s o 00 ^ ^ ^ o I O ^ • ^ > ^ ■ \ .1 ,^ ^ ^.c It ^ CO XPU/ 2 ov''4.u3pij^90o ij!i uoipps" uinuf/xvuj J.0 ^.uaai^jowx NACA ARR No. L4J05 Fig. I6a s: f t <0 .44- ' r? 'l .40 / .36 '^p Plain airfoil Fore - flap position I Fore - flao oasition 2 i jfj 1 1 .Z6 Fore -flap position 3 \.deg 10 ZO ° 30 40 > 50 60 70 Z4 ( o / .20 / / / / , 1 / / .16 1 1 / / / 1 / / / J l/ ./^ / / ^^' ■"/ .08 <^^ ■/ - '^J .^ nA ^ — ■ I- 7 .1/4 - — - " ' ^ COI NATION MITTEE IL AOVl! ^ORAER DRV irtAunci — — — -A I c ■) i • .6 J L z /. 6 Z 2 4 2. 6 3. 2 31 Section lift coeff/cientjC^ (a) Rear -flap positions for c^^g^. r/gure 16.- Profi/e-c/ragf e/^ve/ojoe po/or carves for the /VAC A 22021 o/rfo/7 with o 0.32c double s/otted f/ap. Fig. 16b NACA ARR No. L4J05 .u- "<3 c o I 1 o .40- .36- .32- .28 .24 .20 .16 .12 .08 .04 Plain airfoil Fore -flap position 1 Fore - flap position 2 Fore-flap position 3 -Section lift coefficient, c^ (b) Rear- flap positions for Cd,„i„. f/g'ure /&.- Concluded . NACA ARR No. L4J05 Fig. 17 Si «5 v; >. ^ ? >n 10 D)iM^ '^{jgpij_^gOD iUQbUOUU-GuiLIO^ld U0liD9^ Fig. 20 NACA ARR No. L4J05 NACA ARR No. L4J05 Fig. 21 Fig. 22 NACA ARR No. L4J05 NACA ARR No. L4J05 Fig. 23 Fig. 24 NACA ARR No. L4J05 . l-iri-l-i.- BSEj^fcl 3^^ ■■ ,~^.,.. y ■■■-l^ ^r>;/ / . / < ^ ■ ^ l otte d ^[ n n r ^npw^^^ -ff>. . 73~j-J-J- J!riUlv.-U:-;-^ I ^:. NACA ARR No. L4J05 Fig. 25 UNIVERSITY OF FljORIRft,, 3 1262 08104 971 9 UNIVERSITY OF FLORIDA DOCUMENTS DEPARTMENT 120 MARSTON SCIENCE LIBRARY RO. BOX 117011 GAINiSVILLE. FL 32611-7011 USA