Wind-Tunnel Investigation of an NACA 23012 Airfoil with Various Arrangements of Slotted Flaps

NATIONAL ADVISORY COMMITTEE

FOR AERONAUTICS

N A C 11 · IK --' ~ "f

REPORT No. 664

WIND-TUNNEL INVESTIGATION OF

AN N. A. c. A. 23012 AIRFOIL WITH VARIOUS

ARRANGEMENTS OF SLOTTED FLAPS

By CARL J. WENZINGER and THOMAS A. HARRIS REPRODUCED BY NATIONAL TECHNICAL INFORMATION SERVICE u. S. DEPARTMENT OF COMMERC E SPRINQFlELD , VA . 22161 AERONAUTIC SYMBOLS L FUNDAMENTAL AND DERIVED UNITS M etr ic Engli sh Symbol Abbr evia - Abbr e via - nit Un it tion ti o Jl m e te r __________________ foot (or mil e) _ __ ____ __ L c ngth _ _____ l m ft . (or mi.)

se cond _ __ ______________ Time _______ se cond (or hour ) __ __ _ __ se c.

t s (or hr.)

FOTce ________ we ight of 1 ki l ogram _____ we ight of 1 pound __ ___ F kg lb .

Power _______ hor e pow er _ _______ _ __ P hors e power (metTic) _____ hp.

-- - --- ---- {kilomet e rs p C I' ho ur. _____ miles per houL _ ____ __ k.p.h. m.p.h.

Sp e ed __ _____ V met ers p er second ___ ____ fe et p er s econd ____ __ __ m.p. s. f.p. s.

2. GENERAL SYMBOLS

w, Weigbt=my

P, Kinematic viscosity y, Stands . rd acceleration of gravity=9.80665 p, Density (mass per unit volume) 2 4 2 m/s or 32 .17 40 ft.fsec. Standard density of dry air, 0.12497 kg_m- _s at lIV 15° C. and 760 rom; or 0.002378Ib.-ft.-4 sec.

m, Mass=-g 3 Specific weight of "standard" au', 1.2255 kg/m or 0.07651lb. /cu. ft .

Moment of inertia=mk • (Indicate axis of I, radius of gyration k by proper subscript.)

Coefficient of viscos it y !J. , 3. AERODYNAMIC SYMBOLS Angle of setting of wings (relative to thrust Area S, line) Area of wing Sw, Angle of stabilizer setting (relative to thrust G, Gap line) b, Span Resultant moment Q, Chord C, n, Resultant angular velocity b Aspect ratio S' Vl Reynolds Number, where l is a linear diInension p - ' True air speed V, !J.

(e . g. , for a model airfoil 3 in. chord, 100 m.p.h. normal pressure at 15° C., the cor- q, Dynamic pressure= 4 p 112 responding number is 234,000; or for a model of 10 em chord, 40 m.p.s., the corresponding L, Lift, absolute coefficient OL = :S number is 274,000) Center -of-pressure coefficient (ratio of distance D, Drag, abso lut e coefficient OD = :; of c.p. from l ea ding edge to chord length)

Profile drag, abso lut e coefficient ODO= ~S Angle of attack

Angle of downwash D

Induced drag, absolute coefficient ODt = qS Angle of attack, infinite aspect ratio

Angle of attack, induced Parasite drag, absolute coefficient OD'P=~S Angle of attack, abso lut e (measured from zero- lift position)

0, Cross-wind force, absolu te coefficient Oa = q~

Flight-path angle R, Resultant force

/

REPORT No. 664

WIND-TUNNEL INVESTIGATION OF

AN N. A. C. A. 23012 AIRFOIL WITH VARIOUS

ARRANGEMENTS OF SLOTTED FLAPS

By CARL 1. WENZINGER and THOMAS A. HARRIS Lanller Memorial Aeronautical Laboratory I 47167-3f --1 , I NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS HEADQUABTEBS. NAVY BUILDING. WASHINGTON. D. C.

LABORATORIES. LANGLEY FIELD. VA.

Created by act of Congress approved March 3, 1915, for the supervision and direction of the scientific study of the problems of flight (U. S. Code, Title 50, Sec. 151). Its membership was increased to 15 by act apprO\'ed :\-larch 2, 1929. The members are appointed by the President, and serve as such without compensation.

ROBERT H. HINCKLEY, A. B., JOSEPH S. AMES, Ph. D., Chairman, Chairman, Civil Aeronautics Authority.

Baltimore, Md.

JEROME C. HUNSAKER, Sc. D., V.\~~EVAR BUSH, Se. D., Yice Chairman, Cambridge, Mass.

Washington, D. C.

SYDNEY M. KRAUS, Captain, United States Navy, CH.4.RLES G. ABBOT, Sc. D., Bureau of Aeronautics, ::-I'avy Department.

Secretary, Smithsonian Institution.

CHARLES A. LINDBERGH, LL. D., HENRY H. ARNOLD, Major General, United States Army, New York City.

Chief of Air Corps, War Department.

FRANCIS W. REICHELDERFER, A. B., GEORGE H. BRETT, Brigadier General, United States Army, Chief, United States Weather Bureau.

Chief Mat~riel Division, Air Corps, Wright Field, Dayton, JOHN H. TOWIIBS, Rear Admiral, United States Navy, Ohio.

Chief, Bureau of Aeronautics, Navy Department.

LYM.4.N J. BRIGGS, Ph. D., EDWARD WARNER, Sc. D., Greenwich, Conn.

Director, National Bureau of Standards.

ORVILLE WRIGHT, Sc. D., CI.1N·roN M. HESTER, A. B., LL. B., Dayton, Ohio.

Administrator, Civil Aeronautics Authority, GEORGE W. LEWIS, Director oj Aeronautical Research JOHN F. VICTORY, Secretary HENRY J. E. REID, Engineer-in-Charge, Langley Memorial Aeronautical Laboratory, Langley Field, Va.

JOHN J. IDE, Technical Assistant in Europe, Paris, France TECHNICAL COMMITTEES AERODYNAMICS AIRCRAFT STRUCTURES AIRCRAFT ACCIDENTS POWD PLANTS POR AIRCRAFT AIRCRAFT MATEBlALS I!'IVENTlONS AND DESIGNS Coordination oj Re8earch Needs oj Military and Civil Aviation Preparation oj Research Programs Allocation oj Problems Prevention oj Duplication Consideration oj Invention.

LANGLEY MEMORIAL AERONAUTlCAL LABORATORY OFFICE OF AERONAUTICAL INTELLIGENCE LANGLEY FIELD. VA. WASHINGTON. D. C.

Unified conduct, for all agencies, of scientific research on the Collection, classification, compilation, and dissemination of fundamental problems of flight. scientific and technical information on aeronautics .

• • I I \ ,

REPORT NO. 664

WIND-TUNNEL INVESTIGATION OF AN N. A. C. A. 23012 AIRFOIL WITH VARIOUS ARRANGEMENTS OF SLOTTED FLAPS By CARL J. WENZINOER and THOMAS A. HARRIS SUMMARY The foregoing considerations indicate that the most desirable form of high-lift device is one capable of An investigation was made in the 7- by 10100t wind providing high lift with relatively low drag, and also tunnel and in the variable-density wind tunnel of the probably high lift with high drag. Some other desirable N. A. O. A. 23012 airfoil with various slotted-flap ar- aerodynamic features are: no increase in drag with the rangements. The purpose oj the investigation in the 7- flap neutral; small changes in wing pitching moment by 10100t wind tunnel was to d~termine the airjoil section with flap deflection; low forces required to operate the aerodynamic characteristics aa affected by flap shape, slot flap; and freedom from possible hazard due to icing.

shape, and flap location. The flap position for maximum Some form of slotted flap was believed to be the most lift; polarsjor arrangements consickredjaoorabkjor take- promising for the conditions noted. Various forms of off and climb; and complete lift, drag, and pitching- slotted flap include the external-airfoil (references I moment characteristics jor selected optimum arrange- and 2), the Fowler (references 3 and 4), and the Handley ment8 were cktermi'TU'd. The be8t arrangement was Page types (references 5, 6, 7, 8, and 9).

tested in the variable-density tunnel at an effective Rey- The present investigation was made in two main nolds Number oj 8,000,000. In addition, datafrom both parts. The ~ts reported in part I were made in the 7- wind tunnels are incluckd for plain, SPJit, external-air- by IO-foot tunnel of slotted flaps somewhat similar to foil, and Fowler flapsjor purp08e8 oj comparisim.

the Handley Page type. Flaps of three different sec- TM optimum arrangement oj the 810Ued flap was tions and with several different slot shapes were tested.

8Uperior to the plain, the split, and the ezternal-airjoil Surveys were made of flap location to obtain the best type8 oj flap on the basis oj 17UJ.2'imum lift coefficient, aerodynamic characteristics for each arrangement. In low drag at mockrate and high lift Coefficient8, and high addition, a plain flap, a split flap, an external-airfoil drag at high lift coefficient8. The increment oj 17UJ.2'imum flap, and a Fowler flap were included for purposes of lift due to the 810Ued flap was Jound to be practically comparison.

independent oj the Reynolds Number over the range Part II reports tests made in the variable-density inve8tigated. The 810Ued flap, however, gave slightly tunnel of the best slotted flap arrangement (2-h) de- lower maximum lift coefficient8 than the Fowler flap. It veloped in part I, to determine the effects at high Rey- was jound that 810t opening8 in the airjoil 8Urjace at the nolds Numbers. In addition, slotted flap 2-h was flap caused a mea8Urable increaae in drag oj the airjoil tested in combination with a 60-percent-chord plain for the condition oj high-speed flight even if the 810t was flap to see whether, as in previous unpublished tests of smoothly 8ealed on the upper 8Urjace and there was 11,0 the plain flap alone, rounded lift-curve peaks could be flow through the 81ot. It was also jound that, in order obtained.

to obtain the highest lift coefficient8, the M8e oj the flap The tests reported in part II were made by the var- should be located slightly ahead oj and below a slot lip iable-density-tunnel staff and the material presented as that direct8 the air downward over the flap. The M8e part II was prepared for publication by Harry Green- oj the flap should have a good aerodynamic jorm and the berg and Neal Tetervin.

slot entMJ shO'l.dd have an easy shape to obtain low drags at mOckrate lift coefficients.

INTRODUCTION I. TESTS IN 7- BY to-FOOT WIND TUNNEL Most present-day airpllUles, because of their high APPARATUS AND TESTS wing loadings and cleanness of aerodynamir deRign, employ some form of lift-increasing and drag-increasing THE MODInED 7. BY to-rOOT WIND TUNNEL device to assist in landing them in a field of restricted size. Also, increases in lift without increases in drag Before the present investigation was started, the 7- appear desirable in the take-uff and in the climbing by IO-foot open-jet wind tunnel (reference 10) had been conditions of flight. modified, mainly by the addition of a closed test 2 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS section and a new entrance cone! (See fig. 1.) With tween the model and the tunnel walls is indicated by these changes, the static pressure is practically constant the flashing of neon lamps connected in an electrical along the axis of the test section and the noise during circuit including the walls of the test section and thin tunnel operation is fairly low. In addition, by making metal plates fastened to each end of the model.

the top and the bottom of the test section parallel, an The standard force-test tripod used with the pre- arrangement is obtained whereby two-dimensional-flow vious open-jet wind tunnel (reference 10) to support tests can conveniently be made of large-chord models horizontally the smaller finite-aspect-ratio models has completely spanning the jet in a vertical plane. The use been replaced by a single cantilever streamline strut.

of such an installation permits a large ratio of chord of The opening in the floor of the closed test section model to height of jet together with small wind-tunnel through which the strut passes is made airtight by a corrections (references 11 and 12) so that the range of mercury seal. The existing scales are used with both Reynolds Numbers of the tests for obtaining airfoil types of test; however, in the case of the two-dimen- Horizontal sec lion ------------------------63'2·-------------·------------~ c Vertical secfion E, hoaeyoomb. H, propeller. A,eatranoeccme.

B,esltcou. F, balance IIId model· I, motor, 200 hp.

C, retum pun ... IUpportlDI strut. J, statIc platlll.

0, plde yane •• G,model. K, 8Dtlawlrl YIIIIII.

F10UKJ: 1.-DIairam 01 the 7· by 11).100t wind tUDDel with eloeed teat _tloD.

section data in a given wind tunnel can be considerably sional-flow tests, lift is measured on the cross-wind increased. scale and pitching moment on the yawing-moment The wind-tunnel balance has been slightly modified scale. (See reference 10 for arrangement of scales.)

by installing tubular supports on the top and the bottom Sphere tests have been made to obtain an indication of the turbulence present in the air stream of the closed of the balance frame surrounding the test section se "lilt test section. The turbulence was found to have the model can be held vertical. The tubular supports extend through circular holes in the closed test section changed slightly from that of the open-jet wind tunnel, to sockets with clamps in the ends of the model; they so that the turbulence factor (reference 13) has been can be rotated with II. motor drive by gears and shafting increased from a value of 1.4 to 1.6. The dynamic to change the angle of attack from outside the wind pressure of the air stream at the working section in tunnel. A clearance of about ~2 inch is allowed either horizontal or vertical planes is constant within between the ends of the model and the top and the ± 0.5 percent, and the air stream is parallel to the bottom of the test section (fig. 2). Any contact be- axes of the test section within ±0.5°.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS 3 MODELS Plain fiap.-The plain flap (fig. 3) also has a chord Plain airfoil.-The basic model, or plain airfoil, 20 percent of the airfoil chord and is mounted on a (fig. 3) was built of laminated pine to the N. A. C. A.

removable section, which replaces that of the plain 23012 section (table I) and has a chord of 3 feet and a airfoil. Fittings supporting the wooden flap are of span of 7 feet. The trailing-edge portion of this airfoil thin steel and are equipped with ball-bearing hinges so was made easily removable so that the model can be that the hinge moments of the flap can be measured.

quickly altered for testing different flap arrangements.

The flap angles (38° up to 75° down) are set by a push rod and bell cranks, so arranged that the settings can be changed from outside the wind tunnel. The gap between the flap and the airfoil is sealed top Ilnd bottom by thin metal plates.

Removab/e ~-------- __ --..,-..<. porllon , !

f::::=--- -.--;f~

f-I2.0"--· 10-, -------c· 36 0 "----=:..=---- I Wind Plain airfOil dir~ction ,

3,-J

I C :

~-.-.-.-.-.-.~

Splil flop, '~~ o , <:".

ZOe Plain flap, t C.' 36.0' [.02Be., Solonce frome·· ~_._._._ ~L0725;: , I , I

, , Exfernol-oirfoll flop, .Ic"m t'J.. - i

, , Z4C , I , Hinge aXIs .• ~ , , , , c~· .2667e", , .,

I

, " ;..., , ' .------- c. ·360"---- ---j , , , , --+-+-- . -t-.

~ _____ , __ . 7??m I ,OZ5c", , , . , , , , ,

~,.....! -----. 7436C.-------Il· .... ··· ...... ,:~

I

: ,:: , , Fow/~r flop, Cj • .2667e", ~./ : , . , FIG171I& 3.-Sections or the plaln N, A. C. A. 23012 aldoU and or the alrroil·wttll ditTerent types 01 !lap. - VerI/col s~ction ..!xternal-airfoll fiap.-The external-airfoil flap, avail- FI0171U: 2.-Model IDlltailatiOD ror two-dlmeDSionlll·!!,-'" teets In the 7. by l~root ;.ble il'om another mvestigat.ion, was used without wtnd tunnel.

alteration although it was somewha.t larger than de- Split dap.-A simple split fla.p with a chord 20 p" sired, having a chord 26.67 percent of the airfoil chord cent of the airfoil chord (fig. 3) was used in conjunctim (fig. 3). The flap has the N. A. t;J. A. 2301~ section and was.loca.ted with respect to the main.,airfoil in with the plain airfoil. This flap is of plywood, ~4 mcl!

accordance With the results of reference 2. The flap thick, and is fastened to the model by scre'~ s. The flap angles (0° to 75°) are set by wooden blocks cut to is supported on the main airfoil by thin metal fittings the desired angles and placed between the flap and arranged so tha~ the flap angle can be set 3° up to 50° down.

the airfoil.

. -----

4 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Fowler flap.-The external-airfoil flap was also used when the flap is neutral. Shape e was further modi- as a Fowler flap (26.67 percent of the main airfoil fied by different roundings of the slot entry. The slot chord) after modification of the main airfoil (fig. 3).

entry with the 0.02c radius' is designated as e2 and the No actual data were available showing the best location one with the 0.04c radius, as e •.

of a Fowler flap of N. A. C. A. 23012 profile with a Two methods of hinging flap 1 were employed. The main airfoil of the same profllt!';' however, the flap was first method was to hinge it about a single predeter- located on the basis of tests of external-airfoil flaps . mined axis location obtained from reference 8 for com- of N. A. C. A. 23012 profile (reference 2) and of tests .8270c I 2-h of Fowler flaps of Clark Y profile (reference 4). The

I~ ',~:, .07890 I .. R' . OB//<

flap is supported on the main airfoil by thin metal

I

F=-.:=-~- -.-.-.~

fittings so that the flap can be set from 0° to 60° down I 37' I, 0475 c when completely extended. The main airfoil is ar- '----------.808Ic I .

~---------c----------

L_________ -90Dc I I-a

. 8270c~ 2 ! I -1

~i~ ---~~~~~~~-~~-~~-:--CO-8-le~~'-'!'!..---.:~-.!: ~

~----~~

I 7;420 I 256k--: r--------.8000e I-b _------ __ :{:'~~-:..:.'O~7~89c ,'.R • . DBlle Frous 1I.-Sect1oDI of airfoil with arranltmeou of slotted tlap 2.

I

--.

parison with recent Handley Page practice. The second method was to mount the flap on the main air- >---------.80Ble------..!

_________ c---------~ foil by special fittings that allowed the flap to be

located at any point over a considerable area with

BOOOe . I I-c

respect to the main airfoil.

i '_~~~C ,:R-.08/1e

Slotted flap 2.:'-It was believed that a good airfoil

§ section would probably make the best flap shape, espe-

c i __________ -_ ~08-IC . ==esc j

cially from considerations of drag at low flap deflections.

r.~ -

The front portion of slotted flap 2 was therefore made

I .aaaoe I l-e

to the N. A. C. A. 6318 airfoil section back to the maxi- I' .8170c---j 3-f :R •. 03S0C

1-=--- --.----.~ ~

~

~

• ~~4JIC ~ 1'-.20c---: FIOUlls 4.-SectiODI of airfoil with arraDCtmeDU of slotted tlap 1.

ranged 80 that the N. A. C. A. 23012 Fowler flap may 'i'817DC1 3-g be almost completely retracted for the flap-neutral

k ___ . __ . __ ~c

condition. (See fig. 3.)

I ~ I <- ./858c-

Slotted flap 1.-The three slotted flaps tested are

I: .7~56C 'r-2148c~

designated by numbers and the slot shapes by appended letters. Slotted flap 1 (fig. 4), which is representative FloUIi 6.-Sec:tloDll of airfoil with arrangtmeots of slotted !lap 3.

of recent Handley Page practice, was built according to dimensions taken from reference 8. The ordinates mum thickness and was faired into the contour of the main airfoil over the rest of its length. The arrange- for this flap are given in table II. The slot variationFl ments of slotted flap 2 and the slot variations used in used with flap 1 are shown in figure 4 and in tablp; I ..

conjunction with it are shown in ~.:..'Ure 5 and in tables Shape a is also representative of recent Handl~,: Pagif T and II. Slot shape h is the same as shape a except practice and was built according to dimensions taken t "t the lip is made long enough to seal the slot on the from reference 8. Shape b is the same as shape a U?i>~r surface of the airfoil with the flap neutral. Slot except for an increase in the length of the slot lip to shape ~ (table I) is sea.led all the way through the wing close the slot on the upper surface of the airfoil with with the flap neutral except for the radius at the slot the flap neutral. Shape c is an intennediate step toward closing the slot on the lower surfa.ce, and shape entry. Flap 2 was hinged in a manner similar to the e has the slot sealed all the way thruugh the airfoil second method for flap 1.

AJ."I" N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS 5 Slotted flap 3.-Slotted flap 3 has an arbitrary shape angle-of-attack range tested. Hinge moments of the with a very blunt nose (fig. 6). Slot shape f is the same plain flap and of one slotted-flap arrangement were also as slot shape e except for the longer lip to seal the slot measured.

RESULTS AND DISCUSSION on the upper surfaces of the airfoil when the flap is neutral. The ordinates for this slot shape are given in COBPFICIENTS table I. Slot shape g (fig. 6) is designed to give a good All test results are given in standard section nondi- expanding slot shape for flap deflections up to 50° with mensional coefficient form as follows: the flap hinged at a point on the lower surface of the e" section lift coefficient (l/qe).

flap 20 percent of the airfoil chord from the trailing elo, section profile-drag coefficient Cdolqe).

edge. The same main fittings were used on the airfoil c"'c •••• >o' section pitching-moment coefficient about to support this flap as for flaps 1 and 2; they allow the aerodynamic center of section with flap in flap to be located at any point over a considerable area neutral position (m(a.e.lo/qc ).

with respect to the main airfoil.

Clip section hinge-moment coefficient of flap GENERAL TEST CONDITIONS (h/qcl)· where The two-dimensional-flow installation in the 7- by l is section lift.

10-foot closed-throat wind tunnel was used for the do, section profile drag.

tests. (See fig. 2.) The regular six-component balance m( .... )o, section pitching moment.

(reference 10) was used to measure the lift, the drag, and h, section hinge moment of flap about a speci- the pitching moment of the model. The hinge mo- fied axis.

ments were measured with a special torque-rod balance.

q, dynamic pressure (~p V').

A dynamic pressure of 16.37 pounds per square foot e, airfoil chord including flap; for models with was maintained for all of the tests except those of the external-airfoil and Fowler flaps, e is the external-airfoil and the Fowler flaps. This dynamic sum of the chords of the main airfoil and pressure corresponds to a velocity of about 80 miles per the flap (c .. +c,).

hour under standard atmospheric conditions and to an c" flap chord.

average test Reynolds Number of 2,190,000. Because and of the turbulence in the tunnel, the effective Reynolds ~ is the angle of attack for infinite aspect ratio.

Number R, of the tests was approximately 3,500,000.

8" flap deflection.

The models with the external-airfoil and the Fowler flaps were tested at a dynamic pressure correspon~ PBBCISlON to a velocity of 63.2 miles per hour under standard Accuracy of tests.-From repeat tests the accidental atmospheric conditions. With this velocity, the test experimental errors in the results presented in this Reynolds Numbers were also 2,190,000 for the teste report are believed to lie within the limits indic~t.ed in with the external-airfoil flap and with the Fowler flap the following table: fully extended, based on the sum of the chords of the ±0.5° ao- - ---------- ±0.0006 main wing and the flap. In addition, tests were made ±0.03 C'mas- --------- of the wing with the Fowler flap fully retracted at both C"o(CI_2.5) - - - - - - - ±O. 002 ±0.003

80 and 63.2 miles per hour. 0,_____________ ±0.2°

C"'(u.C·)o - - - - - - - - Tests were first made of the plain airfoil and of the C"o(CI_O)- ------- ±0.0003 Flap position ___ ±0.001e airfoil with split, plain, external-airfoil, and Fowler The profile-drag coefficient Clio of the airfoil-flap flaps through a complete range of flap deflections and angles of attack for comparison with other test.s and combinations has not been corrected for the effect of also for comparison with the slotted flaps of the pre~nt the flap-hinge fittings. From tests of the airfoil with investigation. As an examplo of one of the recently various flaps neutral and hinge fittings in place, but used Handley Page slotted flaps (reference 8), a few with all openings in the airfoil surface sealed, it was tests were made of one slotted flap hinged about a pre- found that the drag increment was consistently about determined axis location. The greater part of the 0.001. No tests were made to determine the hinge- investigation, however, consisted of surveys to deter- fitting drag with the flaps deflected because of the large mine the optimum flap positions and deflections for number of additional tests required. The relative maximum lift and climb. Sufficient angles of attack merits of the various flap arrangements should not be at each flap deflection were taken to determine envelope appreciably affected by hinge-fitting drag since the polars over the complete lift range from zero to maxi- same hinge fittings were used for all mum lift. Data were obtained at 2° increments of angle With a few of the slotted-flap arrangements, two sets of attack and at 10° increments of flap dE-flection for of data could be obtained, an indication of two types each flap location. Lift, drag, and pitching moments of air flow. For these cases, the data for the more were measured for all positions of the flaps over the stable of the two flow conditions were used.

REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONA.UTICS Wind-tunnel corrections.-Certain theoretical cor- the present time, however, indicate that the drag results are about 10 percent higher than expected.

rections have been derived for the effect of tunnel walls There are no theoretical corrections for the, drag on the lift of a flat plate completely spanning the jet (reference 11) except for a symmetrical body at zero at an angle of attack (references 11 and 12). An lift. No corrections for the apparent tunnel effect attempt was made to check these corrections experi- were applied to the drag data. Since any correction mentally for an airfoil in the two-dimensional-flow would presumably be about the same for any of the installation and, at the same time, to examine the effect airfoil-flap arrangements at given lift coefficients, the of tunnel walls on the drag and the pitching moment.

relative merits of the various combinations should not This experimental investigation showed the correction be markedly affected by a drag correction. All the for lift to be about 1 percent greater than the theoreti- drag data have been corrected in accordance with cally derived correction for ratios of model chord to jet reference 14 by a constant .6.Cdo of -0.0008 so as to height up to 0.4. The experimentally determined cor- rection has been used to correct all the lift data pre- apply at an effective Reynolds Number of 3,500,000.

sented in this report. The maximum lift coefficients Tests to determine tunnel corrections showed that the pitching-moment coefficients required no correc- tion within the experimental accuracy of the tests.

I ~ .048 PLAIN N. A. C. A. _12 AIRFOIL The section aerodynamic characteristics of the plain N. A. C. A. 23012 airfoil, as determined in the two- J.040 dimensional-flow installation, are shown in figure 7.

The polar is in good agreement with a generalized polar I J for the N. A. C. A. airfoils given in reference 14. The f rnirnirnum profile drag is, however, about 10 percent c~.

!

higher than the minimum profile drag of the same air- --.!.

/

- -

~~LL. foil section for the same effective Reynolds Number.

II :~.c.J.1 This difference is not considered serious, and some con-

'IIW

~ ,Olcc I V templated additional tunnel-effeet tests will probably ~ furnish infonnation as to the indicated differences.

/ The pitching-moment coefficient about the aerody- namic center checks the pitching-moment coefficient ~ I I ~ ti. given in reference 14 for the same effective Reynolds ~ /' A Number. The slope of the lift curve dc,lda is 0.107 I O""'i ./' I ./ I ~o from the present tests, as compared with 0.098 from ..0 I

V L

-

.008 Btj' the results for infinite aspect ratio of tests of models of a.

!

i.-P ~ finite aspect ratio given in reference 14. This difference ......

i ~ i C) I in lift-curve slope, although not yet adequately ex- ......

V- o V plained, should not affect the relative merits of the test !

o~ ! results of the flap combinations presented in this report.

".- A

t

The angle of zero lift, within the experimental accuracy -4 o ,4 ,B 1.2 1.6 of the tests, agrees with the angle of zero lift as deter- Section lift coefficient, c, min'ed by other tests (reference 14).

FIouu 7.-Sectlon ~ynamlc characteristiC! or N. A. C. A. 23012 plaln aIrfoU.

FLAPS FOR COMPARISON WITH SLOTTED ARRANGEMENT given are about 10 percent higher than those given by a rectangular airfoil of aspect ratio 7 but are probably Split fiap.-The- section aerodynamic characteristics the same as would be obtained with an airfoil designed of the N. A. C. A. 23012 airfoil with a 0.20c split flap to give elliptical lift distribution. This excess of lift are shown in figure 8. The lift curves have auout the was checked by testing the same model (12 inches same slope as that of the plain airfoil. The angle of chord by 84 inches span) in the two-dimensional-flow attack for maximum lift decreases from about 15° with installation and on the regular three-dimensionru-flow the flap neutral to 14° with the flap down 45°. With the set-up. The results agree very closely with the results flap down 60° or 75°, however, the angle of maximum of pressure-distribution tests and with theoretical con- lift is only about 12°, a change of 3° from the plain siderations of the span loading on rectangular wings.

airfoil. A change of this magnitude in the angle of (See reference 14.)

attack for maximum lift may have considerable effect The investigation to determine a correction for drag on the manner in which a wing stalls for combinations has not been conclusive. The tests completed up to with partial-span split flaps.

AN N. A. C. A. 28012 AIRFOIL WITH SLOTTED FL.ll'S a ~ .., E '4 ,.....

'- 0.....

.-P n

-

...

if P It vII" ~.

6, ,~ . : deg.

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a

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a.f- J,~ I""

o .4 .B 1.2 1.6 eo 2.4 208

-.4 Secfion liff coefficient, c.

F1GUU 8.-eectlon aerodynamlo characterlstIos of N. A. C. A. 23012 ahfon with I O.2Oc IPUt flap.

REPORT NO. 8M-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS I- ~

-

k - -.4 "

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,/ V /.' ./ ~ -8 /' ;/ ,- ,- V / "7 ,- / ,/ .,.- ,- ,- ;v ;- .......: -15 " "'" .8 /.Z. 1.5 2.0 2.4 -.4 D .4 Secfion It'lf coefflclenf, c, Frolln g.-Section aerodl'namlo characteristics or N. A. O. A. 23012 alrton with. O.2Oc plain Dap.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS 9 I I - , ,

::: ~-(67C ~OI4~ I--,--,---,-,-L'- I

~

-

-

-[ldc.lei""' TcrJ ~r- 2 0

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1\ 1\ \ \ i\ \ \ ~ \ \ A \ .\ 1\ 7 \ \ .

1\ 7"- .......

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rI

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V V ./ ./ V ./ ~a V /' V V- ./ ~' ~"'" ./ ...... 1--'" V- .1 l/: P" V ~ 0 !

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-16 -.4 o .4 .8 1.2 1.5 20 24 2.8 Section liff cQ,efficienf, c, FIOURE lO.-Section aerodynamic characteristics of N. A. C. A. 23012 airfoil with So 0.2667c. N. A. C. A. 23012 uternal-alrfoil flap.

Preceding page:;blank

10 REPORT NO. 664'-NATIONAL ADVISORY COMMl'ITEE FOR AERONAUTICS I , I I I TTl I I : !

i I I

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.- 0- : -16 .8 1.2 1.6 -,4 .4 20 24 28 o Secfk;n lift coefficient, c, FIGURII: n.-Sectlon aerodynamic characteriltica of N. A. C. A. 23012 alrloU with a 0.2667(. N. A. C. A. 23012 Fowler ilap.

AN N. A. C. A. 23012 AIRFOIL WITH BLOTTED FLAPS 11 The increment of maximum lift coefficient for a about 0.05 in maximum lift coefficient. The angle of given flap deflection is from 4 to 10 percent larger than attack for maximum lift with the flap set at 30° is only the increment obtained in previous tests of a model of 10°, which is a decrease of 5° when compared with that finite span at a much lower Reynolds Number (reference for the plain wing. This decrease is greater than that 15). The increases may be almost entirely accounted for any of the other flap arrangements.

for by the difference in span loadings because the PRBLDUNARY TESTS OF SLOTTED FLAPS reference tests were made with a rectangular airfoil A preliminary investigation was conducted of the in three-dimensional flow. Increments of maximum Handley Page slotted flap, designated flap 1, and of lift coefficient of an airfoil with a split flap may be four slot shapes, the combinations being designated considered to be practically independent of Reynolds Number. The increment of minimum profile-drag 2.8 f-H--+-+-+-+-+--+-+-+....,-+_--1. ~H>----+.-+-+--+-I: coefficient for a given flap deflection for these tests is about 10 percent greater than for the tests of reference f-j-+--+-+--+-+---I'---+~bq, hr- ~-+-+-'t-f----i-! _-.,1 15. The pitching-moment coefficients from the two- 1/ \ ! :

V /.....--~

dimensional-flow tests are in good agreement with the 2.41-+-+--+-+--11-+, J:-h4/---,-!£4-+-l-'-<\""'r\-+-+-+---t-i pitching-moment coefficients given in reference 15 for //1/ 1\ the same flap deflections.

Plain llap.-The section aerodynamic characteristics of the N. A. C. A. 23012 airfoil with a 0.20c plain flap are shown in figure 9. Comparison of these results with the plain-flap results of reference 15 shows about the same differences that were observed for the split flap.

The section hinge-moment coefficients given in figure 9 are of about the same magnitude as hinge-moment § coefficients of a 0.20c plain flap on a Clark Y airfoil

.~ .. ~ f-------~-~";, ~

(reference 15). It should be noted that the charac-

~ 1.21-+--+-r- /1-- '--t-

teristics for the plain flap with both up and down

t:: '------ - -;OS3Sc -r-r-

deflections are useful for the estimation of aileron as

j H--4- .BOc ffii.7C}eOXi5j'

well as flap effects.

.8~-+~4-+-~-+~4-+-~-+~~~ External.airfoilllap.-The section aerodynamic char- acteristics of the N. A. C. A. 23012 airfoil with an

Slotted flop 1-0 0J±~

N. A. C. A. 23012 external-airfoil flap are given in ~-+-+-4-' . I-b --------0 I

·I-~r- I-e -----------<J I

figure 10. The relative merits of this flap arrangement .4f--1f--+--+-+.. • I-e ____ +: ' are about the same as a. similar arrangement tested in I I !

three-dimensional flow (reference 2) at the same effec- : ! I tive Reynolds Number. Peculiarities in the curves of !

lift, profile drag, and pitching moment at the high O~~O~~~~20~~~~4~O-L~~6~O~~~80 Flop deflecfion, 0, , deq.

flap deflections seem to be characteristic of this type of FIGUaa 12.-Etrect ohio' shape OD (,_. Flap 1 at predetermiDed axis locaUon.

flap and probably indicate a marked change in flow pattern around the combination. As pointed out in I-a, I-b, l-c, and l-e (fig. 4). For this part of the reference 2, the pitching-moment coefficients with this investigation, the axis about which the flap was de- type of flap are higher than with the split or plain flaps.

flected was determined from the data of reference 8.

Fowler llap.-The section aerodynamic character- Effect of slot shape on maximum lift.-The maximum istics of the N. A. C. A. 23012 airfoil with an N. A. C. A.

lift coefficients c'",az are plotted against flap deflection 5, 23012 Fowler flap are given in figure 11. The data for in figure 12 for the several slot shapes. These data the model with the Fowler flap fully retracted included on this figure are taken from the tests at 80 miles per show that extending the lip of the slot so that the slot is sealed at the eXIt when the flap is neutral (shape I-b) hour. These results are in good agreement with pre- vious results of tests of Fowler flaps. (See references 4 gave an increase of 4 percent in maximum lift coefficient over shape I-a. Increasing the slot-entry angle (shape and 16.) The large pitching-moment coefficients ob- l-c) caused a very slight decrease in maximum lift tained with this flap may, in a large measure, affect its use for a particular design. It is of interest to note that, coefficient. A further change in slot shape to close the gap through the airfoil with the flap neutral (shape I-e) with the flap fully retracted, there is no measurable decreased the maximum lift coefficient 11 percent from increase in profile drag over that of the plain wing (fig. 7) the value obtained with slotted flap I-b.

for lift coefficients (c,) below 0.8 but there is a loss of REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Effect of slot shape on pro:fUe drag.-A comparison coefficient for take-ofl with a good slotted flap seems to of the envelope polars for slotted flaps I-a and I-b be around 2.5j therefore, it is important to have as low (fig. 13) shows that, for both mgh lift and low drag, a profile drag as possible at these high lift coefficients.

slotted flap I-b is superior. The higher drag of arrange- It is probable that the lower drag of slotted flap I-b at .24 i\ Slotted flop {-b -------- . .

{-c 60· .20 ; 1\ \ 50·' ~ \ J ,

I1lL

40· / .I

~~~~~'5ttti

.• Oc . -. :;"9' ax;.

/ ..

t

•

-¥"

, 0::: V ,~ ..... ~ ZO° .04 l--!'I'- f"'" j..-or Of -10· 1,..000 -H-r - I-- o o Z4 2.8 .4 .8 lZ l6 ZO 5t!Ction lift c~fficienf. c, FtoOJl lJ.-ComparlloD of alotteclllapll'" aDd l-b.

1\ .ZO'~-+~~4-+-~-+~~+-~-+-+~~+-~-+-r~~sot.~~~rr~ f-~--+-+Slo tted flop 1-0 ------ t--t--t--t--+-+--+--t--t--t-+l\-Irl-_'\--t • • I-b ----- \ IO <Sf- • ....-~-

--

0~~0~~~-.4~~~~.8~~~-I.~.2~~~~1.~6~~~~G~O~~~2~.4~~~2~.8 Section lift coefficient, c, FlotraJl 14.-Comparison or slotted ftaps 1-b and 1-e.

ment I-a in the low-lift (high-speed) range can be the higher lift coefficients may be accounted for by the accounted for by the open slot through the airfoil with better shape of this slot lip, which directs the air down- the flap neutral. With the wing and the power loadings ward over the flap and prevents it from stalling at the of present-day large transport airplanes, the best lift higher flap deflections. There is no appreciable dif- AN N. A. C. A. 23012 AIlU'OIL WITH SLOTrED FLAPS ;- ____ 1 __ ~_1 I of.deq. I I -:--

--f-._.,," ... I--

./ '.~~

0---<3 IO--J:l I-- 535c

If-TT-r", , Llf

20 I r- 30----0 ~ .80c:--;.--.-;..r -'-Hinge axis I-- 40-----Q 45---0 0 r- SO_ l-- 55 q 60--.:.

r- -. 2 a. ..q r-

-

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-

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4" -. 4 .

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...,.

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V / ..~ / ,/' ;....- ./ l? /' -""- ~ /11'" ~ ~ V ...... k::: ~

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~ f<" [...-<t V .......- ....-::: ~ ;;..-- .-K .......

~ ~ ~

---

fo"'" ,v:: ~ I----'" ~ ~ V

---

. ./ v.

~ l.,;; % .t" V ~ V p .......- ~ ~V .......- ~ ".., ~

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-.4 o .4 .. 8 1.2 1.6 20 24 28 Section lift coefficil!!nf, c; FIOVU 16.-Sectlon _odyuamio characteristics 01 N. A. C. A. 23012 airfoil with liotted !lap I-b.

14 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

ference in drag between slotted flaps I-b and l-c up to axis location was used. The profile drag was also among lift coefficients of about 2.5 (fig. 14). Because of the the lowest. An inspection of the curves of ao against lower maximum. lift of slotted flap l-e, the drag data c, in figure 15 shows that the slope of the lift curves is for it were not obtained. Other tests of slotted flap l-e practically unaffected by flap deflection except for the will be discussed later. very large values. As previously _mentioned, com pari- (d) .,-40".

(0) .,- ....

Chord (f)

\

\

\ .~ (0 ,,-60".

Flo".. i6.-Contoun of llap locatloD for c .... Slotted llap i-b.

son of the c.... with the flap neutral with the cdo of Complete data on slotted dap l-b.-The complete -~~ .~ section aerodynamic characteristics of the N. A. C. A.

the plain wing (fig. 7) shows that there is a difference of 23012 airfoil with slotted flap I-b deflected downward about 0.001. The greater part of this increase in drag is caused by the flap hinge fittings; the remaining ~Cdo is various amounts are given in figure 15. This flap ar- rangement gave the highest lift coefficient of any of the due to the break in the lower surface of the airfoil four arrangements for which the Handley Page fixed- caused by the slot and will be discussed later.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS The pitching-moment coefficients for this flap arrange- than for the same deflection about the predetermined ment are about the same as for the external-airfoil flap. axis location (fig. 15). The optimum position of the A small change between the pitching-moment coeffi- nose point of the flap for this deflection is about 1 per- cients for the flap undeflected (15,=0°) and for the plain cent below the slot lip.

airfoil (fig. 7) may be attributed to 0. slight downward The contours of figure 16 show that, for small flap deflection of the slotted flap. The hinge-moment co- deflections, the optimum position of the flap for maxi- efficients are about one-half as great as those for the mum lift coefficient is much less critical than it is for plain flap (fig. 9) because the hinge-axis location for the larger flap deflections. It is also evident that there the slotted flap was designed to give partial balance. is 0. considerable loss in lift coefficient if the nose of the flap is moved back of the slot lip. These results are in DETERMINATION OP OPTIMUM SLOTTED.PLAP ARRANGEMENT agreement with previous test.'! of external-airfoil and POR MAXIMUM LIPT Fowler flaps. The highest maximum lift coefficient The data presented in this section are the results of the maximum-lift investigation of the various flap-and- slot combinations in which the flap, at a given deflec- 2.8 I -_ I !

-- tion, was located at points over 0. considerable area , ' I ~- '1\.

with respect to the main airfoil. The data are presented

v

,b?: as contours of the position of the nose point of the flap

" r/

!\ 2.4 for a given lift coefficient. The nose point of the flap is V ,'l' ~ V defined as the point of tangency of a line drawn per- I 'b , .

pendicular to the airfoil chord and tangent to the lea.d- = ~ ,'./ ing-edge arc of the flap when neutral.

:/ Slotted flap l.-Contours of flap location for maxi- mum lift coefficient for 0. given fla.p angle are given in :/ figure 16 for flap I-b. At 10° flap deflection (fig. 16 fJ (0.», the area of flap positions covered was not suffi- cient to define the optimum. position. The highest ~.

e, .... is, however, 19 percent higher than it was for ,Path of flap nose flap I-b at 10° deflection about the predetermined axis It ....... q,:;drio·~.

- - -

-'!?:' \ d: ' location (fig. 15). It appears that a large gap between \ '-- -:- \ \ wing and flap is desirable for low flap deflections from \ ~ \ \ considerations of maximum lift. At 20° flap deflection \ \ \ (fig. 16 (b», the optimum position of the nose of the .8 \ \ flap is 4 percent below and 2 percent ahead of the slot \ \ I \ \ lip. In this position, the maximum lift is 10 percent ~ i ~ - higher than it WIl8 for the combination given in figure 510 fled flop Slot-entry radius, R - .4 o O.OOc .- 15. At 30° deflection (fig. 16 (c», the optimum posi- I-e I-e. r-

- .02· -

f- /1----------

tion of the flap for maximum lift is slightly above the f-e - 0-- - - .04' I-+-- position for the 20° deflection. The maximum lift is 3 I I i I I I I I I • percent higher with the flap in the optimum position at

a

o 20 40 60 80 this deflection than it was for the same deflection about Flap deflecfion, 0, , deq the predetermined axis location (fig. 15). The optimum FlOUR 17.-EtIect ohloHntry radius OD e _ •.

l position of the flap for deflections up to 30° probably should be chosen from a 'consideration of the drag coeffi- WIl8 obtained with the nose of the flap directly under cients rather than the maximum lift coefficient because the slot lip and with a gap between the flap nose and the take-off distance of an airplane may be decreased the slot lip of about 1~ percent of the wing chord.

by depressing the flap. It is therefore desirable that Because of a possible hazard from icing of large the drag coefficient be a minimum for a given lift coeffi- openings in the surface of a wing, flap 1 was also tested cient corresponding to the lift coefficient for best climb.

using slot shape e, with the flap in the best position With the flap deflected 40° and 50° (figs. 16 (d) and for maximum lift coefficient from the tests of shape b.

(e», the maximum lift coefficient is about the same as The results of these tests are given in figure 17 as plots for the same deflections about the predetermined axis of maximum lift coefficient against flap deflection.

location (fig. 15). The optimum positions of the nose The effect of rounding the slot entry on maximum lift point of the flap for these deflections are, respectively, coefficient is also shown in this figure. The maximum about 2.5 percent below and 0.5 percent ahead of the lift coefficient of slotted flap l-e from these tests is slot lip and 1.75 percent below and 0.5 percent ahead of about 8 percent higher than it was for this combina- the slot lip. For the GOO flap deflection (fig. 16 (f», tion with the flap deflected about the predetermined the maximum lift eoeffieient is about 4 percent higher 1171fi7-:l~-3 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS axis location (fig. 12). With the slot entry rounded to bination with flap I-b, which accounts for the increases a radius 2 percent of the wing chord (slotted flap l-e2), in lift. The best positions for the nose of flap 2-h rela- the maximum lift coefficient is about the same as it tive to the slot lip are practically the same as fo~ flap was for slotted flap I-b (fig. 16 (f)). A further rounding I-b.

of the slot entry to a 4-percent-chord radius had a The contours showing the maximum lift coefficients detrimental effect on the maximum lift. It appears for the various deflections of slotted flap 2-i are given in figure 19. This arrangement is inferior to both I-b from these results that the shape of the slot is not Percenf wing chord (al .,-10". (b) .,-20".

Chord (d) (d) &,-40".

(el 11,-30°.

(tl FIGURa 1S.-Contours of ftap locatlon for e, •• ; Slotted ftap 2-b.

critical for maximum lift provided that the flap is and 2-h throughout the complete range of flap deflec- located properly with respect to the slot lip. tions. The maximum lift coefficient was obtained with Slotted fiap 2.-The contours showing ma.ximum lift the flap deBected 60°, which is 10° greater than for coefficients for the various deflections of slotted flap either flap I-b or flap 2-h. The maximum lift coefficient 2-h are given in figure 18. This combination gives a with Bap 2-i is about the same as it was for flap 1-62 (fig.

higher lift coefficient at each deflection than was ob- 17), a comparable arrangement. The position of the tained at the corresponding flap deflections with flap flap nose for maximum lift coefficient for this arrange- 1-b (fig. 16). The total projected area of flap 2-h ment is only about 0.5 percent of the choru below unu and the main airfoil is greater than the area of the COUl- about 0.25 percent back of the slot lip.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS (a) 4 -- __ _ Percenf ..,,,-:'~,..n"rn - __ _ (b) ,,_20°.

(a) ,,-10".

(el ',-31)0.

(e) "- SO".

FlOUBS IO.-Contours 01 ftap location for c '_. Slotted flap 2-1.

EFFECT ON PROFILE DRAG OF BREAK IN AIRFOIL SURFACE Slotted flap 3.-Contours of the fla.p-nose position DUE TO SLOT for the maximum lift coefficients of slotted flaps 3-f The increments of profile drag ~CdO caused by the and 3-g are given in figures 20 and 21, respectively.

Both of these flaps are inferior to all the other slotted- breaks in the airfoil surface at the flap Ilre plotted in flap combinations tested, and both have about the same figure 22. These data were obtained by making tests maximum lift coefficient. No tests were made at with the flap undeflected both with and without the the small flap deflections because of the inferiority of breaks in the surface. (The breaks in the surface were the flaps at the large flap deflections. The nose shape sealed with plasticine for the tests without the breaks.)

of this flap is probably too blunt to obtain a satisfactory The curves given in figure 22 are differew'cs between flow of the air over the upper surfuce of the flap. faired curves through the test points for the inuividuul 18 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS tests. Slotted flap 1-0., which has an open slot through gave 0. ~c"o of 0.0004, which increased to 0.0009 at the the airfoil with the flap undeflected, gave the largest higher lift coefficients. Slotted flaps 1-e2 and 2-i increment of profile-drag coefficient for all lift coefficients a:re the next in order giving, at zero lift, 0. ~c"o of 0.0003 up to 0.60. At the higher lift coefficients, the ~c"o de- increasing nearly to 0.0008 at the higher lift coefficients.

creases probably because of some boundary-layer con- Slotted flap 1-e gave a ~c"o of about 0.0001 for the low- • (d) ',-00".

FIGURS 2O.-Cootoun of nap location for ',_. Slotted nap 3-f.

(al ,,-rH'o

(h) "_~o.

FIGURS 21.-ConWurs of llap location for c,.... Slotted llall 3-C.

trol from the air ejected on the upper surface of the lift condition, which increased nearly to 0.0003 at a lift airfoil. The ~Ctfo for slotted flaps 1-b and 2-h in- coefficient of about 0.50 and then decreased to zero n t creased from about 0.0008 at zero lift to about 0.0013 higher lift coefficients. Slotted flap l-c showed no Itt a lift coefficient of 1.0. At zero lift, slotted flap)-e.

increase in profile drag. It should be pointed out AN N. A. C. A. 23012 AIRFOIL WITH SLOTl'ED FLAPS that a Ac"o less than 0.0003 is too small to measure drag at CI= 1.5, 2.0, and 2.5 are, respectively, about 15°,22°, and 30°.

definitely because such a small value is within the No detailed surveys were made with slotted flap l-e, experimental accuracy of the tests.

but the e1lect on ClIO of rounding the slot entry is shown DETERMINIt.TlON 01' THE OPTIMUM SLOTTED.I'LIt.P in figure 24 as envelope polars. Rounding the slot AaaIt.NGEMENTI'ORPRO~EDRIt.G entry with a radius 2 percent of the wing chord gives The results presented in this section are intended to aid in the determination of the optimum positions of the several slotted flaps for take-01l and climb from considerations of low drag. The best take-01l and climb to clear a specified height in the shortest hori- zontal distance will be the lowest drag coefficient at the lift coefficients corresponding to take-01l and climb.

The data are therefore given as contours of the nose position of the flap for constant drag coefficients at 4 Z certain selected lift coefficients that cover the range Percenf wing chord for which the drag coefficient is decreased by deflecting (a) c.-1.1I.

the flap. The data previously presented show that, for

T I I

".

"

.-

I I

I

-~ Slot arrangement ./ '-,

--

~.

·······-1-0 ~

,.-'

1.-'

'. - - --I=b and c-"

. ' ......

......

-"I-e

.. -

>.,

,/ '- (b)

'--I-e, and c·i ,/ -·--I-e.

/

-

i--'

T T

-- .,- I

6 4 Z .

I I

"- I

Percent wing chord

-

.4 .8 .8 1.0 I.e 1.4 1.6 Section lift coefficient, C, l"IGUU 22.- Effect of slot opealup In mrfaoe of alrfoU DO IDcnmtDta of proJlle dnI.

If, 0"; effective ReJDOidS Number, 3,800,000.

lift coefficients of 1.0 or less, the drag is lowest with the flap undeflected.

Slotted flap 1.-The ('on tours of the position of the nose point of slotted flap I-b for constant ClIO are given in figure 23. The best position for this flap at a lift coefficient of 1.5 (fig. 23 (a)) is with the nose point of the flap 5 percent of the chord below and 4 percent of the chord ahead of the slot lip. The minimum profile- drag coefficient is 0.027, and the position for drag coefficients up to 0.028 is not very critical. At a lift coefficient of 2.0 (fig. 23 (b)), the best position is about 1 percent above and much more critical than the best position for a lift coefficient of 1.5. The minimum FIGUBII 23.-Contours of flap location (or c... Slotted lIap I-b.

profile-drag coefficient is 0.046 with the flap in the best position at a lift coefficient of 2.0 .. The optimum a considerable decrease in Cd at ~U values of the l'rt o position of the nose of the flap, for minimum drag at a coefficient. When the entry radius is increased to 4 lift coefficient of 2.5 (fig. 23 (c)), is 2.5 percent below I percent of the wing chord, however, there is no further and 2.5 percent of the chord ahead of the slot lip.

decrease in Cdo but a considerable increase at the high The minimum profile-drag coefficient, when the flap lift coefficients. The best arrangement of slot shape is in this position, is 0.096 and the position for the low e, slotted flap 1-e2, is inferior to slotted flap 1-b through- drag is very much more critical than at the lower lift out the complete range of flap deflections.

coefficients. The flap angles for minimum profile REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS Slotted dap 2.-The contours of the position of the ceding comparison of slotted flap I-b and 2-h shows nose point of slotted flap 2-h for constant Cfto are given arrangement 2-h to be superior throughout, probably because of the better nose shape of the flap.

in figure 25. At c,=1.5 (fig. 25 (a)), the minimum profile-drag coefficient is about 4 percent less than it The contours of the position of the nose point of was for slotted flap I-b. The position of the flap slotted flap 2-i for given profile-drag coefficients are nose for the_minimum profile-drag coefficient is not very shown in figure 26. A comparison of these contours critical and ... the tests did not cover a sufficient area to with those for slotted flap I-b (fig. 23) and 2-h (fig. 25) close any of the contours. For cl=2.0 (fig. 25 (b)), shows flap 2-i to be inferior to both of the others through- the minimum profile-drag coefficient is about 8 percent out the lift range. It is therefore apparently necessary '\ .28 Slotted flop. Slot-entry rodiu5. R I-e O.OOc 70' \ I-- I-e.

----- .02- I-e. r---- .04- I--

'"

\ '\ .24 ,\ \

..... I'

c: \.

:~.20 60o~ !O:: '\;; I ..

a

'I

B' 500if

~.16 I IL' :!!

f,l .,;:

r ---,d,,':"h of flop nO$'

4( oJ!

~

R~

W c:.12 \ I \ \ 1.

~ \ \ \.l \ \ 30·

III , f

\ II') \ \ I~ \ \ \ \ / \ \ .08 \ \ \ , ~ \~

~

.......: ~ o,-/~ rP .04 ~ V

:-::::: r-

~ I

-

o o .4 .8 1.2 /.6 2.0 2.4 2.8 Section lift coefficient, c, FIOVU 24.-E1rect of sloWDtry radlwl on c 4.'

lower than for slotted flap I-b. The contours are not that the slot have an easy entry in order to ha ,-e low closed for this lift coefficient and the position for mini- drag together with high lift.

mum profile drag is again not very critical. The EJ'I'ECTS 01' SLOTTED FLAP WITH SPLIT I'LAP contours of profile-drag coefficient at c,=2.5 (fig. 25 Effect on maximum lift.-The effect on c, of the (c)) show the minimum to be 25 percent less than it was ""a for slotted flap I-b. The position of the flap nose for addition of a 0.05c .. split flap, deflected downwaro 1'11)0, minimum profile drag is critical at about 3.5 percent to slotted flap I-b is shown in figure 27. This compari- below and 3.0 percent of the wing chord ahead of the son was made with the slotted flap hinged in such a slot lip. There is, however, a second region of low way that it was in the optimum position for the maxi- drag farther ahead and closer to the slot upper bound- mum lift coefficient when deflected downward 60° ary for which the contours are not closed. The pre- without the split flap. The increase in maximum lift

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS 21

coefficient for small deflections of the combination is higher drag than the slotted flap alone for lift coefficients quite large. The maximum lift coefficient with the less than 2.2. It is possible, however, that lower drags combination down 25° is the same as it is with slotted could be obtained by using smaller deflections of the· flap I-b alone down 50°. The maximum lift coefficient split flap at the smaller deflections of the slotted flap.

with the combination down 50° is, however, only 2 per- The combination has a lower drag than the slotted flap cent higher than for the slotted flap alone in its opti- alone at lift coefficients above 2.2. These results indi-

-·-·-·-:~~~~I

Chord (a) -.

Chord (b) Chord (e) (c) cl-2.5.

FIOU" 28.-ContourJ of flap location ror c • Slotted flap 2-\' FIOUU 2&.-CODlO\lll or flap location ror c 4,' Slotted flap :r-b.

4e mum position. It is possible, however, that higher cate that multiple-slot flaps might be developed which maximum lift coefficients may be obtained by a more would be superior, from considerations of low drag for comprehensive investigation.

take-off and high lift for landing, to any of the slotted Effect on profile drag.-The effect on CliO of the flaps investigated. Further investigation is recom- mended of multiple-slot flaps and of slotted flaps in addition of the split flap to slotted flap I-b is shown in combination with plain and with split flaps.

figure 28 by envelope polars. The combination has REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS OPTIMUM ARRANGEMENT 011' SLOTTED FLAP The optimum. flap arrangement was chosen on the basis of minimum. profile-drag coefficient at a given lift coefficient for lift coefficients less than 2.5 and of maximum. lift coefficient for the larger flap deflections.

On this basis, slotted flap 2-h was superior to any of the other flap combinations tested. The data for slotted flap 2-h, when moved along the optimum path shown, are given in figure 29. Flap-load and moment data from pressure-distribution tests will be available for this combination at a later date.

COMPARISON 011' PlVE TYPES 011' FLAP § .~ Effect on maximum Iift.-Increments of maximum ~ 21-t-IH~/r-r---- __ -=--~ ,Path of flal2 nose: 1;:/. 39~-~ 1 lift coefficient Ac,_% are plotted in figure 30 against flap

.~ d. ~'Jo.\ \ -I" 6O.-fj

.... 'I-=- \. ' -i---J

deflection to show how the effect of flap deflection lJ , \ i

~ , \ '

upon maximum lift varies with the five types of flap , \ I .8 t-I-+-+-+-+-+-+-+-t--t--t-, \ tested; namely, split, plain, external-airfoil, Fowler, t-I-+-+-+-+-+-+-+-t--t--+-+' \ -+-+-+-' and slotted flap 2-h. All coefficients are, of course, \ \ ' t-I-+-+-+-+-+-+-+-t--t--+-+-+ f, \ +-+-+----1 based on area with the flap neutral and the increments, t-I-+-+-+-+-I--+-+--+--+--+-~ f..# +-+-t----c: except for the external-airfoil flap, are taken from the .4t-1-+-+-+-+-+-+-+--+--t--+-+-+-+-+-+-~,

_%

c, of the plain wing.

Slotted flap /-b -- -- --' - R

Siolled flap 1-6 and I I 1 I 1- It is evident that the two slotted types which give H-+-+0.05c split flap down 60· 0- I increased area in the deflected positions give the 0~~Q~~~-2~O~~~4-0~~~-6~O~~~~80 highest maximum-lift increments. The values for Flop deflection, 0, . deq.

slotted flap 2-h are somewhat lower than for the Fowler flap. The Fowler flap, however, may be con- Flov.. 27.-Elrect OD c,_ 01 oomblDlnl spllt Cap with slotted Cap. Slotted sidered as a special case of the slotted flap in which the Cap l-b.

t l

s)ot;eJ fI~P I/_b

I Slotted flap I-b and ~ ,I 1 1 0.05 c iP~it (lor ~oin ~O·II I I 50· I '~alh of flap nose I 40·1 ~~60"-<-~ d ' JO'\ _\ 60' /

f

'1:::::='-'-r-'. \J-+- ~ 1\ \ \ \ '. \ , \ \ \ I \ \ '30~'

I \ , \ \

II I i

If ~, \

, , I 1/ I I I~ .. ~: I • I /1 V ...... ! I I

.-

i f..-;' 20· /"

--

-

--

I I--

.- l- ./

l- I

-

1- ~ r- ...... / I IS, -10· I-

-

I

-

-

-

!

a Z.8 o 2.4 .8 1.2 1.6 2.0 .4 Section 11ft coefflc/~!nf, c, FIGUIIJ: 28.-EClect on c,, of comblDtDI split flap with slotted lIap. Slotted flap I-b.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS

o

!

I I ~ j .J -.4 ""'""' I : 0/, deg.

i .20 t>.

I~ 20 v

r

130~ I I 50----t> I 60 t- --.

"

I ,J.16 :7 Ii?

[

~

~ Pafh of flap no~ T

r

V /7 !

!

V 'I !

...-/ i I

....-

,......

_.-"" ..... ""'" ,......1-"'" ~ it'"' ~ I k:::

-

.... -

_r0-

-

c:;. 16 t {: I r ) .... i I I r:J' ..,- /" A ~

••

-g" /' -tv'

V ,....""

8 "

....

/ ...... ..AI ......

.... V tl 1/ ",,"" V .....

V ....... v ---- .....

~ Vj V /" ..,- 0- A"" c: VI-"'" ~ ..,- "{ l.Y fJ" 14"

o .4 .8 1.2 1.6 2.0 2.4 2.8

Section lift coefficient, c, Path of flap nOH lor various flap delIactlona. DistanCII meuured from 10_ edge of Up in percent akloU abord c , % (~) 3. 91 0 8.38 3.81 10 6.'1 3.~ 20 3.83 3.37 30 2.83 .0 1.34 2..a 50 • .50 1.63 60 .12 1 • .a FIGUItI!: 2II.-Sectlon aerodynamic charactarlstics 01 !'f. A. C. A. 23012 airfoil wltb slotted flap ~h.

24 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

lip of the slot is extended to the trailing edge of the ; ! I I j i I ;:,4 I 1 I I 1 ,~, basic airfoil. The flap is therefore moved through a

greater distance when extended and deflected and, r---S;;~!nr/~p ------ : I

~ [--,- External-airfoil flap ------ ~ consequently, gives more lift because of the greater

J [__I- Fowler flap-------------------- 1 i

lifting surface exposed to the air. Slotted flaps could

~Z.O[--r-5Iorter f(a12ih IT-ili-Ti--- T'

be developed with the slot lip terminated at any point ,§ /11111 1~ between the location for slotted flap 2-h, or farther

forward, and the trailing edge of the airfoil. These ~ ~60~!-+-+-1

~ L-/~4a' slotted flaps would be expected to give c, increases " _s

8 /. r-- 'r-'r- lS, ~h of flap ~o1e -1--,.:,.1 .,-l--4

corresponding to the increased airfoil area. ~ ,(slotted flap c-h) Etrect on pro1ile drag.-The effect on CliO of the five § types of flap is shown in figure 31 by envelope polars.

'~ ~c~~-+-+~~1-~~~~~_,_+~~ The five types of flap have about the same profile-drag ~ c: , coefficients for lift coefficients less than 0.90. The , , ,0 , V L .;::

-

airfoil with slotted flap 2-h has the lowest profile drag u , , I---r- V III .8 I/) for lift coefficients from about 1.0 to 1.7. The airfoil ,,IV 1 I ./ ~ '4.. , , 1/ with the Fowler flap is somewhat better than slotted 0 I , \ ,/ ....

j..- flap 2-h as regards low profile drag at lift coefficients

i !d

i

greater than 1. 7. Here again it is pro bable that a LI. L .4 ~ 'V \,j 1/ slotted flap with a greater lip extension could be oS L/

W

developed to give an even lower drag' at high lift .:/ coefficients.

JIj/ When the horizontal distance to land over a given 0 40 80 0 20 60 obstacle is restricted, if a high drag together with a high nap deflection, 6, . deq.

lift is desirable, slotted flap 2-h is superior to the four lI'IOVU ao.-Compar\loll of 1IlInm8ll&s of maximum Uft coelllclel)&s Cor live types oC other types of flap tested.

!lap.

i"Qo 7S· III .20 \ Split flap L\ Plain· ---- '.

\ I 6!-· external-airfoil flap ----- \ I~ J Fowler flap---- -------- I Slotted flap 2-h--------- \ JI6 \ \Ii / \ lL

Y 1\

4S , , , '/ l \ / , , L 30" J •

-~~LUJJ

I ! I 'L V /

r

J 4 'Path of flap nose 0' '/ J / (5lotted flap2-h) , J J I 20· ~ ~ L ~ ~ / ~ , // , , 1", , ,/ lab ~ .

~ .--:i;.: s· i""" ~ .....

I 0, ~ 10~_ ~ o ." ---'--- ,8 /.Z 1.6 2,0 c.d o .4 2.4 Section liff coefficient, c, FlonK 3L-Compar\loll oC prollJe.drlll coeJ!IoImw for live types or ftap.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS II. TESTS IN VARIABLE-DENSITY WIND lower surface. When the flap was deflected, the V- TUNNEL shape groove formed on the upper surface at the 40- percent point was filled with plaster of paris, forming APPARATUS AND TESTS a fair and rounded juncture.

The variable-density wind tunnel is described in The lift, the drag, and the pitching moment were reference 17, except that an automatic electric balance measured from below zero lift to beyond maximum lift has been insto.lled to measure. force coefficients. The at an effective Reynolds Number of about 8,000,000.

precision is discussed in references 14 and 18. The lift in the region of maximum lift was also measured The basic airfoil was made of duralumin to the at an effective Reynolds Number of about 3,800,000.

N. A. C. A. 23012 profile. The 25.66-percent-chord The measurements were made at flap settings of 0°, slotted flap was built of brass to the ordinates given for flap 2 in table II. The shape of the slot and the posi- ------B27oc-------1 _---- ___ -....::R~ •. ~0~78:9c~ 1 R-.OBlle

C S;~I

,...------- BOO/e ------ . 6,-0

---------c----------

c;; ___ -~

~~

----- ~9ge-----~~ 20' ; ---_.-/.~ 0" BI36c------1 30' P'lOUU aa.-SectioDI of airfoU with O.6Oe plaiD IIap dedected 12" and o.~ slotted IIap 2-h.

20°, 30°, 40°, and 50°. In addition, at flap settings of 30° and 40°, the Reynolds Number range from 900,000 C;;;;; ___ 72fti~, to 8,000,000 was covered .

. 0071c -----.8272c ------ The slotted flap was also tested at deflections of 40' 20°, 30°, and 40° in combination with the 60-percent.

chord plain flap deflected 12° .

C;; ___ -72S~,

. 0129c I RESULTS AND DISCUSSION

------.8366c ------ .

PRESENTATION 50' The results are presented as a series of lift curves for FlO11U 32.-Seetl0D8 of atrtoU with o.~ slotted IIap 2-h.

a rectangular wing of aspect ratio 6 in figure 34; the two groups of curves in the figure correspond to the two tions of the flap for the various flap deflections (8,) are Reynolds Numbers at which all the tests were run.

shown in figure 32. In the investigation made in the 7- The section characteristics, indicated by lower-case by lO-foot tunnel, these positions were selected as the letters and presented in figures 35 and 36, were worked optimum, the critprion being low drag in the lift range up as explained in reference 18.

below a value of 2.5 and high maximum lift above this range.

MAXIMUM LIJIT The flap was attached to the wing by five smoll steel brackets i 0. different set of brackets was made for The lift reaches a maximum at a flap deflection of each flap position because the position was determined 40° (fig. 34). The variation with Reynolds Number is by the size and the shape of the brackets. shown in figure 37. The maximum lift increases with The 60-percent-chord plain flap (fig. 33) was built by Reynolds Number but appears to be leveling off at the cutting the wing at the 40-percent station and connecting end of the Reynolds Number range tested (about the two parts by a narrow flexible plate flush with the 8,000,000). The results of tests in the 7- by IO-foot

26 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

wind tunnel are also shown on the figure and the had practically no effect on the drag. If the slot is agreement with the variable-density-tunnel results, for perfectly sealed when the flap is neutral, a decrease of the two points shown, is good. It will be noted that the minimum drag ot the order of 15 percent may the increment of maximum lift is nearly constant over accordingly be expected.

the range tested. A comparison of these results with The drag of the wing at high lifts, with slotted flap those of references 2 and 19 shows that, at a Reynolds 2-h deflected to its most favorable position at each Number of 8,000,000, the slotted flap can reach a maxi- lift coefficient, is included in figure 39. This curve, mum lift coefficient of 2.86 as compared with ·2.54 for which may be called a profile-drag envelope polar, is ..

.3.2 I I I a60c plain flop of _ _ cffecft"ve fibt.naldS Number - EHective fteorOlds Number r- G

___ 8.200.0 O(appr~x.) .1 I I I I OG I 12 3,600.0 O(approx.) r-r-r-

o/.deg. 020304050 203040 I I 4- I 006 ... 0 ~"<l i 2.8 I ~ : ./ ~ 1.1'1"1 I I I I I J,{f 1,( ~ A !Si' I I

-

, I : ,({,M I ih' It 2.4 I I I;f I ~JI.{ '\: '\ ilJjlI I ~ I i ~ ~ .I' 1/ Ih ~ IP ~ If if' ~ Ii ~ 2.0 t( ~ ./ ~ 1/ 11/ I\. ~ ~ j, Ub'~

lh I ~ .. ~

.•. : ~i\, ~ 1/ a.

~ /.6 'f\~~ rl VJ l.

I), V- Iii ~

'-.l

~

I ,/1 I rf r-::~ rfC a...

Q, .......

(j, , rl II J r'"'

8 1.2

I 1'1.

it: " -1 / JJI I Q.

-.J I I J I I V~ ·1 VlV .8 ,.

il ) I A..!

II p I 1 II I II ! I /" f. 'f .4 jI I I II I J L ~ VJ

d I r

If ~ I II I / I

_.+- i-- -)-

I ( -.4 <II-' I j-

-1

i -24 -16 -8 /6 24 -32 o 8 16 24 32 0 8 32 Angle of attock. d ,deg.

l"Iovu 34.-LIft apIust mele of attack for N. A. C. A. 23012 alrfoO with O.2IMIec slotted llap 2-b, rectancuJar wine. aspect ratio 6.

the envelope of o.ll the polars for the wing with o.ll flap the split flap, 2.39 for the plain flap, and 2.37 for the external-airfoil flap. settings. A series of such curves for various flap types The deflection of the 0.60e plain flap had only a minor and arrangements shows the relative merit of each type effect on either the maximum lift or the shape of the lift for such an item of performance as take-off where, curve near the maximum (fig. 34). other things being equal, lower drag at high lift coeffi- cients is advantageous. Such a series of curves (fig.

PROFILE DRAG 39) shows the 0.2566e slotted flap 2-h to be definitely The wing with the slotted flap in the neutral position superior to the 0.20e plain and split flaps, as was also had 15 percent higher minimum drag than the plain shown by the 7- by 10-foot tunnel tests. Slotted flap 2-h is also slightly superior to the external-airfoil flap airfoil, as shown in figure 38. In order to find out to what extent this drag increment could be reduced by on the basis of low drag and is greatly superior to it on preventing flow through the slot, tests were made with the bo.sis of maximum lift. The data for these other the upper slot closed. The closing of the slot exit flap arrangements are taken from references 2 Rnd 19.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS -- .-'1' I l' I !

I I i I i .r I UY 1 I i-- !

· J

, ,

1>-

~ I

-

9>~ I

-

'"

--: .- - - -- !

--- -

--

-l-

.- -

i I T I I 4. \ , .024 \ I \ \ I \ 1 \ i 1\ I \ i I J !\ I \ II /' \ i !

/ .4'" \ \

1"'-

.020 ,/ , \ !

I \ I ~

"-

~ \ I/' I I / "\ "\ \ 1/ / \ \ \ \

V

r-..., /~ / I'-a.. I' A \

"'"

V· -a....

'\ l.% r-: r'\ / I

-

_10- 1\ \ !

/- ...,...

I ....,1-- V I ~ L \ ~ .......

..-' 0.... , V .....

" 1'""7 r-..... ~ V- 7 i>"'

"

, ...-'I '- ' . : J ~ -9 ,...- I- / ..

O.lcJ.

"

.... ;. - ~

- -

.t.'"

-- .004

....-

.J,.

'J1 )I' i 1 J..

, I-- 0-

-

o q i !

i I Q.. ~ I I i ~t I I I It ~

'"

I I \ ~il..

i I t?: ~

-

I V I , I ~ \ !j..

"

"""v

-c I'" , ~ -"V' ~ V ~ f.o'" ~ J>d.. B- , 'i I-'" ,/ ~'/ V -"C V, ~ La ~ u ~ IY' ,...;:V ! ~ I I l.:::<i ....

tl /' /fW' i.b!I ~ ....

,,/ 0 V ~ W' i ..:;.

I 6.1 .deg.

! -!!

V ~ 6 ~ 0- ~ ~ 0 0 I:: Ier"" ,....;;; ~ I----" ~ .; c 1 ..... ..-' /" ~ ~ 3() i to -8 v 40 ~ I-.a ~ ~ ;.c ,,/ .... ~ I;;" '7 ~ ....

p ........ v- JP/ -16 ,.....

A :64 ,J/: ::Q-'

-

I

- o .8 1.2 1.6 2.0 .4 .4 2.4 2.8 Section lift coefficient. c, PIO'I1B& ~.-Bection aerodynamic cbaracterlstir.os or N. A. C. A. 23012 IIlrroll wltb O.2M6e slotted flap 2-b and the O.6Oc plain flap neutral. Effective Reynolds Nllmber, approximately 8,200.000.

REPORT NO. 664.-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS a , !

, 1'\ , 4 I I , 1 I \.a... , , '\~ 1 I , I I ~

"-'

00;;: I f-- i ~ l>-

"'-

I, ['..

"'-.. ...

~ ~

.+--

'r--.... --

, , A. d"':: ...

I- :-- ~ ""'-

-

, , r- , i !

Q

c... ,\ : !

.024 : i

~ la-' \J

, ....

, ....D / ! \ I

"-

, ' 1 \j , I i"" 1 : Ia" , ,\ I .020 I "- : I : "- I 1 \ V ,

v

1>-' I 1\ \.

V I , '{ I'< ...0 rI , I, I \ t\ \\ I 1\ t--...

\ / f':.,'\ 1 II I [\ 1'\ , i \ / [\1\ \ \ ~ \ 1 I I 1L ~: : , 1\ ~ !

..... ~

'/ 'T P 'i" ~ I I I / "\ .-

- f-:I

!\ ...,~ ,..- rf I}J ~ ~

"'"

,.-, !\ IA: ~

"

.004 , , \ t-;-: 1\ ~ -' O.le ..

P'f!4.

V , '-... B.c: .-c I- I

o

I 1,\ 1 1 I , I I ~ : ~ I I ~ i I I I ~ , I ~ i ~ I , I f' I 1 ~ ~ 1 I 1 ~ b.

, lIT ,

-12

.f

b2' , V ~ ~ a I V l..;:; V , ~

i

/' ....

.s?

v IPt : ....

b-- {:) : ~v ~ i I '0 -8

v ~

~ ,/ ~v- !A" 'r'" ~

.f

4,deq.

,/ '.", ...... 1"'" Y 0 20 -16 ,.P V c 30 V ...-c v ~ 40 a"" .)l'V V / ,.a f(Y' .K ~ ~ ~ ./ -24 I

-r I

I -A- o .4 .8 1.2 1.6 20 24 28 Section lift coefficient. c, FIOURlI: 36.-Sectlon aerodynamic characteristics of N. A. C. A. 23012 nlrCoil with 0.256&: slotted lisp 2-h and the 0,60<: plain lisp dellected 12". Effective Reynolds Number, approximately 8,200,000.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTI'ED FLAPS 29

PITCWNG-MOMENT COEFFICIENT of attack, the pitching moments are the same for all three flaps.

The pitching-moment coefficient increased with flap deflection up to 40°. Tbe pitching moment for the .020 , I , : I I i same deflection is greater than that of the plain and , I , , i the split flaps but, when the comparison is made on the I , I i o SIot5 un!leoled , basis of deflections giving the same lift at the same angle o Upper 5/0t sealed I I i , i!~015 f v Plain airfoil I I I i i I I I I 4.8 I I ~ , . , , , ll:S'd~ II II , I I • , , , ~ t>4d' g'}111111111111111 , !

, ! i !

I I 4.0 o 30 Voriable-den~ity tunnel ...: i i i/I, o Plain winq I I I I I II I I i I LJ : t:: , x 30 } I ,I I I I I I! . /"/\ .S!

I ! !

foot + Pia n winq 7-b Y 10i tunnel -~ I ~3.2 I I I l~ VI i

I ,'I 1 I J

.....

I

L I I f./:~ i 6l:::l ! i I I ~ ~ I ~~ , (j2.4 ......

~ i i

i .. ~

..... Aci~~

-

.........

~ I

"'"

--

"'-- ~

- I

,...~ I

I

§ 1.5 I .~ I

~ .8

I I <:: I .0 I I ..::: 0 Q of 5 5 7 1,000.000 2 3 ... 5 10,000,000 o .4 .8 Jl Effective Reynolds Number, R.

Section lift cot!fficit!nt, Ct FIGUBJ: 37.-Sca1e eJlect one, for N. A. C. A. 23012alrfoll with and withoutO.2M&: Flavas 38.-E1!ect of slot open1q on prom. drac of N. A. C. A. 23012 alrfoU with - slotted llap 2-h. slotted llap 2-b neutral. EJlect!ve R8JllOIds Number, apprOximately 8,200,000.

, I . .zOe plain flap !

I I I i .20 i I I i I ~2Oc !Split flap I ! i , i I 1 ! I i I I ! !

I I I I I I I , I I I i I , I i I I I I I I , II ' 1/ I I j I / !

{y-40- " ; /1

V 1/ !

, / I / ~ !

, 1/ / J , ~2560c 5/0tted flap 2-n V

/ V

, / / / ~ , , , / 30" /.. r / / !

I ,/ I .,.1'/ !

v-:: , , :::.-- V~·-.20c", external-airfoil flop i ~ ,~ ...::i::="" ,D· i , o.~ 1 i -- , '-20° : , j i i I T o .8 1.2 1.5 2.0 2.4 3.6 o 2.8 3.2 Sec.-,an lift coefficient, C, FlQUlLJ: av.-Proflle-draa envelope polan, N. A. C. A. 23012 alrfoU witb various llaps. El!ectIve Reynolds Number, approximately 8,200,000.

30 REPORT NO. 664-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS CONCLUSIONS TABLE I-Continued 1. The optimum arrangement of the slotted flap ORDINATES FOR AIRFOIL AND SLOT SHAPES-Con.

tested was superior to the split, the plain, and the external-airfoil types of flap compared on the basis of Slot shape e maximum lift coefficient, low drag at moderate and at Station Ordlnate high lift coefficients, and high drag at high lift coeffi- cients. The slotted flap, however, gave slightly lower 74. 811 -0.18 76.41 .58 maximum lift coefficients than the Fowler flap. 76.93 1.18 76. 46 I.M 2. The increment of maximum lift due to the ~lotted 77.50 2.32 78.118 2.87 flap was found to be practically independent of the 80.00 2.97 Reynolds Number over the range investigated.

3. Openings in the lower surface of the airfoil for the slotted flaps tested had a measurable effect on the drag Slot shape 1 for high-speed flight conditions even when the slot was smoothly faired to maintain the contour of the upper Station Ordlnata surface and there was no air flow through the slot.

74. 811 -0.18 4. The slotted flap gave the highest maximum lift 76.41 .58 76.93 1.18 coefficients when the nose of the flap was located 78. 46 I.M 2.32 77.60 slightly ahead of and below the slot lip and with a slot 78.118 2.87 80.00 2.117 lip that directed the air down over the flap.

81.70 2.72 5. The lowest profile drags at moderate lift coeffi- cients were obtained by using a slotted flap with an airfoil nose shape and with an easy entrance to the slot.

Slot shape I 6. It appears that still further improvement may be obtained in low drag characteristics at moderate and Station Ordlnate high lift coefficients by the use of multiple flaps or by 74.0 ---::0:22--- slotted flaps with greater lip extensions.

74. 74 76.08 .13 76.eu .68 78.33 1.11 78.117 1.46 78.26 2.00 711.63 2.36 80.81 2.58 LANGLEY MEMORIAL AERONAUTICAL LABORATORY, 82.08 2.68 82.60 2.60 NATIONAL ADVISORY COMMITTEII FOR AERONAUTICS, LANGLEY FIELD, VA., February lS, 1998.

TABLE I TABLE II ORDINATES FOR AIRFOIL AND SLOT SHAPES ORDINATES FOR FLAP SHAPES [StatioDi and ordlnatelltn percent of wtnr chord) [StatioDl and ordlnatelltn percent 01 wlDl chord] N. A. C. A. 23012 AlrfoQ Flap 1 Lo .....

Station aurr- La_

= Station

surfaoII 0 0

=

-----i-67--- -1.23 1.2& 0 -1.61 -1.61 2.6 3.61 -1.71 -.18 .52 --._-- 6 4. 91 -2.211 -2.41 1.04 .58 7.5 5.80 -2.61 -2.43 1.156 1.16 10 6.43 -2.92 -2.42 2.00 1.63 15 7.19 -3.50 -2.37 3.13 2.30 20 . 7.50 -3.97 2.84 4.61.

2& 7.60 -4.28 ------ 2. 97 -2.16 6.63 7.56 -4.46 ~ 2.88 11.82 7.14 -4. is ::i:23 16.63 1.68 -4.17 50 6.41 20.63 .II'J -.70 5.47 -3.67 26.63 .13 -.13 4.38 -3.00 3.08 -2.16 1.68 -1.23 Center 01 L. E. arc .92 -.70 .13 -.13 0.72 -1.61

E. radius: US. Slope 01 I

L.

through end 01 chord: radius L. E. radius: 0.72 0.305.

AN N. A. C. A. 23012 AIRFOIL WITH SLOTTED FLAPS TABLES II-Continued 6. Irving, H. B., and Batson, A. S.: Summary of Data on Slotted Wings Obtained in the Wind Tunnel of Messrs.

ORDINATES FOR FLAP SHAPES-Continued Handley Page, Ltd. R. & M. No. 930, British A. R. C., 1926.

Flsp2 7. Anon.: Re.sum6 of Investigations Made on Handley Page Slota and Flaps. A. C. I. C., vol. VII, no. 639, MaMriel Low.

BtatIoD ;:&: IIurfaoe Div., Army Air Corps, 1929.

8. Clark, K. W., and Kirkby, F. W.: Wind Tunnel Tests of the -1.211 -1. 211.

Characteristics of Wing Flaps and Their Wakes. R. & -.32 -2. 011 .to .72 • 04 -2.21 M. No. 1698, British A. R. C., 1936.

1.38 .81 -2.38 2.00 1.04 -2.t1 9. Higgins, George J.: An Airfoil Fitted with a Slotted Flap.

-2.-U 2.M 1. to Jour. Aero. Sci., vol. 3, no. 12, Oct. 1936, pp. 431-433.

3.112 1.~ ......

6.20 2.30 10. Harris, Thomas A.: The 7 by 10 Foot Wind Tunnel of the ::2." is 6.M --2."M National Advisory Committee for Aeronautics. T. R.

8.~ .... ---- 7.76 2.63 ------ No. 412, N. A. C. A., 1931.

9.03 2.511 ... - ..... - 10. 31 2.46 11. Glauert, H.: Wind Tunnel Interference on Wings, Bodies.

::i:23 16.M 1.68 and Airscrews. R. &; M. No. 1566, British A. R. C., 1933.

200M .92 -.70 2A.M .13 -.13 12. Tomotika, Susumu: The Lift on a Flat Plate Placed in a Stream between Two Parallel Walls and Some Allied CeDter of L. E. arc Problema. Report No. 101 (vol. VIII, 5), Aero. Res.

Inst., Tokyo Imperial Univ., Jan. 1934.

0. D1 -1.211

I

13. Platt, Robert C.: Turbulence Faciors of N. A. C. A. Wind Tunnels as Determined by Sphere Tests. T. R. No. 558, L. E. radlus: O.Dl N. A. C. A., 1936.

14. Jacobe, Eastman N., and Sherman Albert: Airfoil Section CbaraoteristiOll as Affected by Variations of the Reynolds RElERENCES Number. T. R. No. 586, N. A. C. A., 1937.

1. Platt, Robert C.: Aerodynamio CharaoteristiOll of Wings 15. Wenzinger, Carl J.: Wind-Tunnel Investigation of Ordinary with Cambered External-Airfoil Flaps, Including Lateral and Split Flaps on Airfoils of Different Profile. T. R.

Control with a Full-Span Flap. T. R. No. 1541, N. A.

No. 554, N. A. C. A., 1936.

C. A., 1935.

16. Wenzinger, Carl J., and Anderl!lon, Walter B.: Pressure 2. Platt, Robert C., and Abbott, Ira H.: Aerodynamio Char- Dlatribution over Airfoils with Fowler Flaps. T. R. No.

acteristlOll of N. A. C. A. 23012 and 23021 Airfoila with 620, N. A. C. A., 1938.

20-Percent-Chord External-Airfoil Flaps of N. A. C. A.

17. Jacobs, Eastman N., and Abbott, Ira H.: The N. A. C. A.

23012 Section. T. R. No. 1573, N. A. C. A., 1936.

Variable-Density Wind Tunnl'l. T. R. No. 416, N. A. C.

3. Weick, Fred E., and Platt, Robert C.: Wind-Tunnel Testa A.,1932. .

of the Fowler Variable-Area Wing. T. N. No. 419, 18. Jacobs, Eastman N., Il.nd Abbott, Ira H.: Airfoil Section N. A. C. A., 1932. - Data Obtained in the N. A. C. A. Variable-Density Tunnel 4. Platt, Robert C.: Aerodynamio Charaoteristioa of a Wing &8 Affected by Support Interference and Other Correc· with Fowler Flaps Including Flap Loads, DOWDwaah, and tions. T. R. No. 669, ~. A. C. A., 1939.

Caloulated Effect on Take-OtY. T. R. No. 534, N. A.

C. A., 1931i.

19. Abbott, Ira H., and Greenberg, Harry: Tests in the Variable- 5. Glauert, H.: The Handley Page Slotted Wing. R. &: M.

Density Tunnel of the N. A. C. A. 23012 Airfoil with Plain No. 834, British A. R. C., 1923. and Split Flaps. T. R. No. 661, N. A. C. A., 1939.

U. I. GOVl"NMINT '.'"T1N' oPPle.: list (J

"-

"-

"

z

Positive directions of axes and angles (fo rc es and moments) are shown by arrows Velocities Axis Moment about axis Angle Forc e (parallel Linear Sym- to axi s) Sym- Positive D es igna - Sym - (compo- De s ignation Designation Angular bol s ymbol bol direction tion bol nenta l ong axis) - - Rolling _ __ __ Roll ___ __ LongitudinaL ____ Y --) Z q, X X L u p La te raL _________ y Pitch __ __ y Pitching __ __ Z --) X M IJ v q NormaL _ ___ _____ yawing __ __ X--)Y yaw ___ __ Z Z N w T

'"

Absolute coefficients of moment Angle of set of control surface (re lati ve to neutral L }vI po sition) , o. (Indicate surface by proper subscri pt .)

t m C = qbS C = qcS (rolling) (pitching) 4. PROPELLER SYMBOLS Di ameter D, P,

Power, absolute coefficient O p= ~ D 5

Geometric pitch pn p, Pit ch ratio p/D, c., Speed-power coefficient = \I~~ : V ', Inflow ve lo city Efficiency 'f/, V., Slipstream velocity Revolutions per second, r.p.s.

n,

. T

T, Thru st, abso lu te coefficient C = 2 D4 T pn Effective helix ang le=tan-{2!n) Q, Tor que, absolute coefficient OQ= 9 n.

pn LF 5. NUMERICAL RELATIONS 1 hp. =76.04 kg - m/s=550 ft-Ib. /sec. 1 1b. = 0.4536 kg .

1 metric horsepower = l.0132 hp.

1 kg=2.2046 lb.

1 m.p.h. = 0.4470 m.p.s. 1 mi. = 1,609.35 m=5,280 ft.

1 m.p.s. =2.2369 m .p.h.

1 m=3.2808 ft.