m-TuNNEL

REPORT No. 554

INVESTIGATION OF ORDINARY AND SPLIT FLAPS ON AIRFOILS OFDIFFERENT PROFILE

By CARLJ. WENZINGDR

SUMMARY

The Clurk Y, the N. A. C. A. .%012?,and the N. A. C.A. 2/?02?1airfoils equipped withfu.?l-epan ordinaq@p8and with fd!+?pan &hnpt?esplii j%ps were tested in theN. A. O. A. 7- by 10#oot wind tunnel. l%e principalobject of the tew%was to deiermine the ch.uracteridiceof theairfoil.owith ordina~fips and, in addition, to determinethe rekztwe m.en18 of the oarimu airfoi.?e when equipped

with ei#herordinu~fips or with timple spld&p8. TheClark Y airfoi? uxw teotedwith 3 w.MJuof ordinu~fip,10,20, and $30percent of the airfoil chord. The optimumwidth of the ordinu.ryand tlw timple spld~p bawi? onth maximum lift attained with the Clark Y airfoil wastlwn teotedon each of tb other two a~oi.b.

The optimum width of ordinu~~p for muoimum liftattuinuble was found to be the 8ame a-s thui of the qvli.tflap, 20 perceni of the airfoil cM. The eplit &pproduced 8omewhui greater in.creme8 in CL_ on theairfoils tested than did the ordinary &p of the 8amewidth, bti the L/D d muximum lift w praettiy th8amefor the two types of $ap. Any gap between theairfoil and the leuding edge of ordinaryj!up8 had a nayo?drimenta.1e$ect on the CL=a attainable. Breed p+n.-&p(@/ on faGtW8 a~ecting airplune performance, therelaiwe order of merit of the airfoils tated with eithrordinary or &plii&p8 h N. A. C. A. $3013, Clurk Y,and N. A. C. A. %02?1. The hinge-mti mej%ieni8(bad onjlzp chord and areu) of thefid.l+pan ordinary

$ap8 werepraetieaUyindependent of~p chord; t~ actualhinge moment8uaried approximdely a the 8quare of thechord. In addition, tlw hinge-momeni toe- of the8@ Jhp8 were PWhkid@ the 8ame as th08e of fd?-epanordi~fip8 of corresponding widihi?.

INTRODUCI’ION

Many experimental investigations have been madeof various types of flap for increasing, in particular,the maximum lift of airplanes as an aid to improvedperformance. Among the devices already investigatedin considerable detaiI by the N. A. C. A. are simple splitflaps, split flaps of the Zap type, Fowler flaps, andexternal-airfoil flaps. Some uncorrelated data are alsoavailable from various sources on sIotted flaps and on

130602-87-16

ordinary flaps. Because of the simplicity of ordinaryflaps and the lack of correlated data on them as a Iifbincreasing device, it appeared desirable to make a morecomplete invedigation of this type of flap.

Three basic airfoil sections were used in the presenttests to obtain an estimate of the ellect of airfoil sectionand thickmxw In addition to the Clark Y, theN. A. C. A. 23012 airfoil was selected as being repre-sentative of the best airfoils at present mailable foruse on conventional airplanes, and the N. A. C. A.23021 airfoil was selected as a representative thicksection. Three widths of ordinary flap ivere tested onthe Clark Y airfoil, and one width on each of the othertwo airfoils. For purposes of comparison one simplesplit flap was also tested on the N. A. C. A. 23012 and23021 airfoils, and data are included from previoustests of the Clark Y airfoil vvith a split flap. Theaerodynamic characteristics of the airfoils with all thediilerent flaps were measured and, in addition, hingemoments were obtained for the ordinary flaps on theClark Y airfoiL

MODELS AND TESTS

Models.-Mahogany models of the Clark Y, theN. A. C. A. 23012, and the N. A. C. A. 23021 airfoilsections were tested. The span of each model was60 inches and the chord 10 inches. The Clark Y air-foil with the 3 widths of ordinary flap tested (10,20, and 30 percent of the wing chord) is shown infigure 1. These flaps are arranged to lock rigidlyto the airfoil or to rotate hely about their respec-tive hinge axes. The other two airfoils are shownwith ordinary flaps in iigqre 2 and with split flapsin figure 3.

The ordinates of the airfoil sections are includedwith the charts of their aerodynamic characteristics in ‘@.rea 4, 5, and 6. The size of flap that gave thehighest value of the maximum lift coefficient for theClark Y airfoil togethar with reasonable hinge moments(20-percent-chord flap) was used with the N. A. C. A.23012 and the N. A. C. A. 23021 airfoils.

Tests,—The tests “were made in the N. A. C. A.7- by 10-foot wind tunnel which, together with associ-

223

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.—————. —— A =_—

224 REPORT NO. 554 NATIONAL ADVISORY COMMI’ITEE FOR AERONA~CS

ated apparatus and standard test procedure, is described in reference 1. The dynamic pressure wumaintained constant at 16.37 pounds per square footwhich corresponds to amair speed of 80 miles per howunder standard sea-level conditions. The averag[Reynolds Number for the tests was 609,000, based 01

the air speed and on the lo-inch airfoil chord. Lift

1

I Gapaoo.z c-J.2’”yJr, removable secfion *

s, gap sealed‘.:..

~ 10-..,\ J

FmumL—l!ullq ordinary &p tested on the Clark Y airfoil.

drag, and pitching momem% were measured for all fhqarrangements with flap deflections from 0° to beyoncthose for maximum lift. The angle-of-attnck rang(covered waa horn below zero lift to beyond the stalof the airfoil. Hinge moments were also measured folthe three widths of ordinary flap on the Clark Y airfoil

.— ——

~Gum2-~ordhrg 13a~twledonthe N. LC. A.23013and N. A. O.A.ZJm FJrfom.

These moments ware obtained by the methods givenin reference 2, which present9 remits, of I@ge-momenttests on split flaps of various chords. .

RESULTS

Remdts of the investigation are given in standardnondimensional coefficient form for the following fourcoefficients:

c , pitching moment about quarter chordu~4 =

qsc

C,f=flap -lunge moment

qsfc,in which

s,airfoil lu-ea.S,, flap area.

c, airfoil chord.Cf,flap chord.g, dynamic pressure.

effects of thestatic-pressure

1+-o.2oc7

The data were corrected for theiet boundaries and for the tunnel

X4

——— —— ——

haom 3.—Full+zm spilt flem W on the Clark Y, the N. A. O. A. 23)1!2,andthe N. A. O. A. ?M41tiOiL%

radient. ” The standard jebboundary corrections,

u=#L’LX57.3, b degrees, and AC.=6~LZ, where 0

Jthe jet cross-sectional area, were used. The value ofictor 6=–0.165 was taken as being most nearlySpresentative of the boundary effect in the 7- by 10-Jotwind tunnel. (See reference 3.) The longitudinaltatic-presmre gradient in the 7- by 10-foot windunnelproduces an additional downstream force on thelodel. This force correaponda to a value of ~~D=.0015 for rectamguhw airfoils of thickness equal to2 percent of the chord and AeD= 0.0029 for an airfoilaving a thiclmess of 21 percent of the chord. Thesealues were obtained in accordance with methods given1reference 4.

DISCUSSION

PLAIN AIRFOILS

Complete aerodynamic characteristics of the threeplain airfoils are given in figures 4, 5, and 6. Thesecharacteristics include those for tie three airfoils of

ORDINARY AND SPLIT FLAPS ON ALRFOII.S OF DIFFEREN!r PROFILE 225

o~oo

.44

2.0 .40

1.8 .36

1.6 .32

ca~ oe

1.4 .28>-

I I I I I I I I I I I I I~ Cliikx ;ab

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.2+6-12-8-404812 IC?20Z428S k

-4

Angk of ottock;a(degrees)- ‘- ‘–

FmmE 4.—The Clark Y alrfo]l.

Jflol I I I Ill “’-WI-I IT/7

I I I I I I 48

.11 \ ! 44-P Te& Na2.382.

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1 1 I 1 1 I 36 u.44 .09

e“ :2.0 .40 ..08

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1.8 .36 ~.07 28$

1.6 .32 ● j.06 24 kQ ;

o 1.4 .28>. ~.05 20-2

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40

60

80

100

!+’=H+-l /.0 S.20; ?.(-I.3U-I-I

[ \ I .4<.08v~

h‘w-2 -04 .!+

.“

-.2 ‘~-r

1 I I I I I I I I 1-.- .#d fOinfiniiawpecf ~fi~ ’16-16 -12-8-4 0 4 8 /2162024283.2 ‘t s

Angle of affock,U [degre+:4 72 0 .2 .4 .6 .8 Lo IZ Li

liftcbeffikientG~GURE 6.—TheN. A. C. A. !iW12flilfOi]

.— —.—

226 REPORT NO. 554 NATIONAL ADVISORY COMMI’ITEE FOR AERONAUTICS

aspect ratio 6 corrected to free-air conditions, prcdilo-dragg coefficients, and angle of attack for intiniteaspect ratio.

AmFonsWrrHFLAPS

Clark Y airfoil with ordinary flap.-Lift, drag, andcenter-f-pressure characteristics for the airfoil withthe 10-percen&chord flap are given in figure 7. Theseresults are for the airfoil with the gap between the flapand main portion of the airfoil completely sealed withpkwticine. Values of L/D and C.441for the 10-percent+chord flap are given in iigure 8. Values of (?- andvalues of L/D and.CD at CL.= are given in figure 9 fordiflerent deflections of the 10-percentihord flap. Thelatter characteristics are given for the conditions inwhich the gap between the flaps and the main portion

horn references 5 and 6.) The effects on ULntiareshown and the effects on L/D and CL)at CL-O Fromthese results it may be concluded that split flaps ofthe ssme width give somewhat higher maximum liftsthan do ordinary flaps. Values of LID and (7D atCL- are nearly the Same for both @eS of flap.Practically no further gain in maximum lift is obtainedby increasing the flap chord beyond 20 percent of theairfoil chord, the data indicating that with wider splitflaps the mtium lift remains about the same butthat it drops off with wider ordinary flaps. Theoptimum width of either ordinary or split flaps for maxim-um lift appeara to be 20 percent of the airfoil chord.

Olark Y airfoil with a 20-percent-chord split flap.—For comparison with tests of the N. A. C. A. 23012and N. A. C. A. 23021 airfoils having split flaps, the

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/0 — T~feo!LiftU.-8

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o “: !J I II II MI m

I I I I I I I I I 1 00--- ,- e- -., . ..-. %-’H+W+H++

.Fmum 6.-The N. & O. & mxU afrfotl.

lift, the drag, and the center-of-pressure characteristicsfor a Chrk Y airfoil with a 20-percentihord splitflap are given in figure 16. These data were takenfrom reference 6 and have been corrected for a wingof aspect ratio 6 in free air. The L/D and 0~44’ forthe Clark Y airfoil with split flap are given in figure 17.A comparison of 20-percentihord ordinary and splitflaps on a Chink Y airfoil is given in figure 19. This

figure shows the variation of C&z and of L/D andCD at CL- for diiferent flap deflections. As pre-viously noted, the split flap gives a somewhat highermaximum lift than does the ordinary flap but has31ighteffect on the other factom.

of the airfoil is both open and sealed. It will be notedfrom figure 9 that even a small open gap had a verydetrimental effect on the maximum lift of the airfoil.It is therefore essential to keep the flap gaps com-pletely sealed to obtain the best characteristics withordinary flaps. Similar chart9 for the airfoil with a20-percentdord flap are shown in figures 10, 11, and12. Charts for the airfoil with a 30-percentiord&p are giVWl in @es 13, 14, and 15.

Optimum sizes of ordinary bd split flaps on theClark Y airfoik.-Figure 18 gives a comparison ofdifferent widths of ordinary and of split flaps on ClarkY airfoils. (The data for the split flaps are taken

0RD1NAR% AND SPLIT FIAPS ON AIRFOILS OF DD?FERDNT PROI?IILB 227

N, A. C. A. 23012 airfoil with 20-peroent-ohor(ordinary and split flaps.-Lift, drag, and center-ofpremure clmracteristic9 are given in i@re 20 for f

-40

-20 ,

L /

o 1) I

, , ,

,,01’-I-ML

I I r I I

/40

24

2,0

-z&b+. T- I I I I I I1.6

1.2

CL

.8

.4

c=

o

-.4

‘“:/6 -8 0 8 16 24 32 40d, degrees

Flaum 7.—Lift, drag, and centi Of PITSSIUW forthe Olark Yalrfoflwith O.Ioc~-~0-b. Flap gapSoled.

20-percenbchord ordinary flap on the N. A. C. A.23012 airfoil. The L/D and C=q( for the 20-percen&chord ordinary flap are given in iignre 21. Sim.hx

curves for 20-percent-chord split flaps me given infigures 22 and 23. A comparison of ordinary and

,, —— -- Q. -——- 0?, ~,, ---- +“ —___ x. -------- b. .— v4

1.2 . /.6 2.oc=

fi~~ 8.-~ I’atfoand PMohfng+noment OmfOofoutfor tb Clark Y afrfo1lWftbO.letfnaqkan m’dfnmytrap. map gapsad.

+, degrees

FIQUEE9.—Eff02tof flapdeflection on rnaxfmmn Ufb and on IffVdrogratio and dmgat maximum lifL The O.IOCfnllx ordlnwy flap on the Olark Y fdrfcdl.

split flaps on the N. A. C. A. 23012 airfoil is given infigure 24. This figure chows the effects of C* aswell as of L/D and CDat C’= for different flapde&c-

—.. ..— —.. .—

228 REPORT NO. 554 NATIONAL ADVISORY COMMJTPEE FOR AERONAUTICS

tions. As inthe case of the Clark Y airfoil, the splitflap gave a higher maximum lift on the N. A. C. A.

c=

f.2 I I I J-1,- /1,J4’)1 . I ./

.4

CD

o

-.4

F-.. ,

I I I

I I I I I I I 1 1

-:.& _8 Io 8 16

.—~

-_— n——._---~A_-— x“+----— D— ——-v

>

.

24 32 4

d, degrees

FI13cmE1O.—LHG&w, and m~ of P~ for the Cfruk Y OflfOnwfthOiUr fulma ordfmv ftap. Ffapgnp83dd-

23012 airfoil than did the ordinsry flap. h additiorthe two types of flap had almost the same effect othe other factor-aconsidered.

1?. A. G. A. 23021 airfoil with 20-peroent-chordrdinsry and split flaps.-Charts similar to those for

A-1--uu

E .&

hoD;~- .~” . -——- —1 Ib

4W

o I I I I I I I I

%.

I I I I-

I I I

q

MO= IL—LWIIW mtfo and plwg-mom~t fident for the Okk y akfooWfth on frdlsm OrdlrmrrfbP. ~P esP @~.

/0

8

6

&D

4

2

0tif, ~egrees

lrrcwrm 12.-Effwt of J&p de@n on nmxfmnm Uftj and on M-drag ratio and drauat rnaxfrnnm Mft- The O.Kkfnll-sran ordinary flapon the Olruk Y olrfoll.

the N. A. C. A. 23012 airfoil are given for the N. A.c. A. q3021 a~od fith fl~psh fiawes 25, 26, 27, 28,

ORDINARY AND SPLIT FLAP9 ON AEtFOILS OF D13?FERENT PROFILE 229

and 29. The ordinary and split flaps on the N. AC. A. 23021 airfoil also showed the same relatiw

--75”. ------- ;* = 90” m -—__v

140-

2.4

-,4- I

La “k%>? i I I I

I,

I

6= /*

-.4 -

-:76 _*o 8 16 24 32 40

d,degrees

F[owrm 13.—L1f~dIW, and mnti of p~ for the Oferk Y airfotl wfth 0.3wfrdI*pan ordbry ffep. l%p gep embi.

effects as they did on the Clark Y and on the N. A.C. A. 23012 airfoils.

Comparison of lift effeots of 20-peroent-chordordinary and split flaps on Clark Y, N. A. C. A. 29012,

20 P \

/ > \

L (. -’ -. L.f6

6: .

f2 t!//

4W\;~

//iifPIII III 1 1 YIJt

I I I

4

L.

7O“a’own5“ ● -.—---:

10” = ———- Q15” - -——. ❑

30° - ———A45” “ —--—+60” ● —-–—x75” * _______ Pgo= “ ——-~

“CL

‘Iaum 14.-Lfft4reg ratio and pltehing-monwt meffkfmt for the Clerk Y afrfoflwith 0.3W-n mdhmrg tip. Flap gap -cd.

10 2.

8/.

Ch

6 1.

gD

4.

2.

‘%

00 20 @ 60 80 100cfi, degrees

mum 15.—Effect of Sap dedmtlon on maxlmnm Ilfh and on lift-drag retlo anddrag at rneximmn ML The 02& fnlMIMI ordfnary flep on the OIark Y elrfefl

nd N. A, C. A, 23021 airfoils.-Table I shows theffects at a test Reynolds Number of 609,000 on the

—— —— .

230 REPORT NO. 554 NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

maximum lift coei3icient with tips neutral; on thmaximum lift coefficient with flaps deflected; on thincrement in maximum lift coefficient due to the tw

m..

. . / A //

.8g ‘ /’

,. /, ‘“ 7’

.4

c=

o

-.4

-.&3-16 -8 0 8 16 24 32

d,degrees

FIQURElo.-Ll& drag, and center of~ for Clark Y afrfoffwfth 02Ckfull-smus~t tip. (Data from mfemnce 6.)

typesof flaps on various airfoils; on the ratio of maxi-mum Jift to minimum drag; and on the ratio of lift todr~g at m~~ ~.

Somewhat l@her maximum lift coefficients andgreater increments in maximum lift were given by the

20 (f-..

/ x\

16 /

/ + \ \

if2 1 )

/ /k’

\

I8 ~ / I —

/4! #---------

4

LO5

? 6,- O“cfown o

-4 3 - . 15° N -—-—Q

/* -30° . ———A_ =45” * —--—+

\, /==60° m —---— x● =75” . —.---—-

-8D

0 i

?

c’.; /.. -.. “ . --.2

% ‘. -\\ ----.. - +. _ u= “

.h -

-2340 .4 .8 1.2 1.6 2.0

CL

XnmE 17.—Lfft-dragIWO and pltobing-moment oxzlhdent for the Olark Y cdrfollWfth oak fnu-qmnsplitllnp.

‘IQUREl&-Effwt of fiop ohm’dml nmxinom Ifftj and 011lfft~ l’OtfOorid drag atmaxiummllft for Mth ordlnmy and 6PM llaB on tho 018rk Y i?kfO~. .

plit flap than by ordinary flaps on the three airfoilsested. The highest mrd.nm.m lift coefficient and the

ORDINABY AND SPLIT FL&PS ON AIRFOI18 OF DIKFEItENT PROFILO 231

greMe.stincrement in maxinnun lift were both givenflaps on the N. A. C. A. 23021 airfoil. In this caae

A — -10 2.0

)-

/ NW “ \ *1

\ // “8 /.6 x— Ord@ory flUp

/ \ o — — Splliflop\\< ,

1 “ \6 1.2

gD

\\ g.K ~ D

4 .8

2 .4

G

00 20 40 60 80 100

byan

df, degrees

FIGURE19.—Efloct of !lnp detlwtkm on maxfmnm ~ and on U&drag ratio anddrag at moxfmom lift. The 0.21kMl-span ordinary and splft Sam on the Olnrk YBh’fou.

GF1OUMZ1.-Lfft-dragrotfo and pltchfng-mommt coefldmt for the N. A. O. & 2SOIZ

nfrfoff v?fth 0.’2OCfall-m mdfnary&p. FfaII9P s%akd.

increment in maximum lift coefficient of 1.193 wa9obtained, which represents an increase in the maximum

lift above that of the plain airfoil of more than 100percent. The highest speed-range ratio C._/aD=,~ wasgiven, however, by flaps on the N. A. .C. A. 23012 air-

o-f= O“down o—. - /5” u ._-_-~

120 m = 30” n ———A., =45° * —--—+n x 60° ~, —---— x,*= 75” - —---_-_-D—

140

2.4

2.0; CL

1.6 /

c=

12,..2

.8

,4

c=

o

-.8.‘=16 -8 0 8 16 24 32

d ,degrees

~OUREZ1.-Lif&dm& and c130ti OfplWSlU13for the N. A. O. A. 23X2 ofrfofIwfthOm fnU*p3n Ordfnmy flap. Rlap gap &5?lkl.

foil, which has a lower maximum lift but whioh alsobaa a considerably lower minimum drag. The steepest

___—.—— .- __— A. ..—

232 REPORT NO. 554 NATIONAL ADVISORY COMMI’ITEE FOR AERONAUTICS

gliding angle attainable (indicated by L/D at CLm=) k

the same with either type of flap on the particularairfoil considered.

bqoo i,. O “down —o —- . t5° * -——- a

4C

a =~o” a ———A,. = 45” = —--—+H . L70° * —.-—X

120 .. 75” . —— .--— P—

MO

24

J,G

2.D

1.6

c=.

,9

I 1 I I I

1

-.4 w/ / /

& “;.

J

-.8-16 -8 0 8 16 24 32

d, degrees

~CVJEEZZ.-LW drns, end centi of P1’fSOi%ferthe N. LC. A.2X112efrfoJ.lwfthOa)c fnuq SW tiP-

Some tests in the full-scale tunnel and in the variable-density tunnel (reference 7) indicate that the maximnm

24

f \

20 /

I /

/6

f2

8

4

r

I l-l+- J4-- -+ I

1 v 1 ! I I I I

4“- - !? a -——-n ~

%MWEE !2S.-LIft-dregretio end pftchhg-moment codfchnt for the N. A. C. A.

‘zXmfdrfoifWfthO.mfnlkpan .@t Jlap.

~, degrees

hmJBE 2L-Effwt of tip detlectbn on mexlnmm lfft, end on M-drag ratio ondding at mdmnm lffL Theo.mcfuU~ordinw endmlItfler@onthe N.A. 0. A.mu &fen.

ORDINARY AND SPLIT FLAPS ON

lift of the N. A. C. A. 23012 airfoil is equal to or slightlygreater than that of the Clark Y airfoil in the normalfull-scale range of the Reynolds Number. l?urther-

H-l-i ‘d$L i’O 80 ,’ I

1

, ,6f- O“down o

.. = 15” * -—-— u- .II =30° M ———A

i

Ko

8/00 !4G “

120“ .45* * —--—+,,-60” . —- .-— x-t-l* = 75” ~t -----— bI

/40

2.4

1 I 1 1 I 1 1

2.0

L6

/.2

c=

.8

,4

c=

o

-.4 ““~ ,

2 / ‘/

-.8 ~j

-16 -8 Q 8 I@ 24 30d ,degrees

FIOIJEWZ5.-Lff~ ~, end canta of prexmre fortho N. LO. A. X021 eMoilwltb0S% Ml-span Ordlnmy 13ap. Flep gep 8mM.

more, recent tests in the variable-density tunnel showthnt at large as well as at small Reynolds Numbemthe N. A. C. A. 23021 a,irfoil has considerably lower

AIRFOIM OF DIFFERDNT PROFILE 233

maximum lift than the Clark Y. Thus, it appears thatthe N. A. C. A. 23012 plain wing will have some ad-

16 \

\

12

4~!, J.Ilf *1—

8

4

L= 0u

,/

4“ ! crf=’1 i 1 ,

O“a’own 0

-4 /y

== 15”- -— —0“ = 30” ● ___A

/ t - - 45” “ —--—+J

/

-=60* ti_x,● . 75- H . —--—-_-_~

-8c‘

) {

o— ~ *

0

w ~/

-.1 a-- ‘-0-+ q *

F

%AC .- .

L.z- ‘\ /

-.2x h,! ---- - -“ 4 -— - yd -

-.3’-.4 0 .4 .8 1.2 1.6 20

CL

FIGUEE10.-LUt.drW ratfo end pitohfng+nomeot KMlcfent for the N. A. O. A.28021flfrfoflWfthoak fuu+pl mdinery flap. F19p gap SmM.

2

c=

o

“ 12 2.4

10 2.0

@ /.6

%naX

6 1.2

&D

4 .8

.4

0 20 40 60 80 1006f, degrees

FIGIJM m.-Eflect O( ilep dedlwtfon on mndmnm Ifftj ond on Ilft-ding ratio anddrag at mexfmnm IfIl. The 0.2Wftdf-upao ordfnary arid splft fiem on the N. A.c. A.!au?lakfOfL

vantagea over the Clark Y or N. A. C. A. 23021 wingsin the full-scale range of the Reynolds Number that

234 REPORT NO. 554 NATIONAL ADVISORY COMMITI’E E FOR AERONAUTICS

me not shown by low-scale tests if the lift incrementsdue to the flaps are not adversely ailected. Experi-mental data (unpublished) have shown that actuallythe increments in maximum lift due to split flaps onmedium-thick airfoils vary but little with ReynoldsNumber. In connection with +e present inve-stiga-tion, a few tests were made in the variable-densitytunnel to detarmine the scxde tiect on 6’L_ at h.kh

; 40 I I 1 1/X_&i=+@

H-HQi6100

2.0

1.6

1.2I I I

Q

.8

.4

G

o

-.4

-.8-1

RX,degrees

FIGURE =—I-W da% ad -~ ~ P~ fortheN. AO. LZJEIakfOUtiti

O.!m fnlP@3n Splh ftap.

Reynolds Numbers of the N. A. C. A. 23021 airfoil (8thick section) with a 20-percent-chord split flap. Thtremdt.sof the scale-effect tests are given in figure 3(in which CL_ for the N. A. C. A. 23021 airfoil with thfflap neutral and with the flap dellected downward 75’is plotted against “fiective” Reynolds Number botifor the 7- by 10-foot and the variable-density winetunnels.

critical R free air.~ectiveReyno]& Number=test RX ~~tic~ B tunnel

3ss reference 7.) The value of the factor is 1.4 forhe 7-by 10-foot wind tunnel and 2.6 for the variable-kmsity wind tunnel. The data show that the scalelffect is about the same for the N. A. C. A. 23021 air-oil with the flap deflected downward 75° m it is for

/ Y - -Ou. . ———~b

/- --75” = -. -—-- - D* . go” “ ——-v

\ J/

-f6

FIGURE 2’&-L.lftaw rfth~d dtiw-mom~t -tit for t~N. & C. A. !MQ1akfoilwfth0.2kfoil-sw 6PM fiP.

the plti drfod and that thO hCU3RM3fIt k (?&m,z dUO

to the deflected split flap is, therefore, practicallyindependent of scale effect. It seems fairly well edab-lished that increments of 6’L@ due to split flaps onmedium-thick and thick airfoils are independent of scalogffect, so that values of the increments obtained atthe relatively low scale of the present te.sta moy brdirectly applied to full-scale wings.

.

ORDINABY AND SPLIT FLAPS ON AIRFOJM OF DD?FERENT PROFILE

TABLE I

CO~PARISON OF CLARK Y, N. A. C. A. 23012 ANIN. A. C. A. 23021 AIRFOILI3 WITH BOTH ORD~NAR1AND SPLIT 0.20cFLAPS

nhe 7-by lllfmt wind trmnd R, 6Q3,@M]

I I Flaprlmtrnf I FlqldellwtajI T~ d @l ==lcL--CL- ‘cL-u●CL-’CD={=‘fl~I Clnrk Y

Ordhu-y..... L 260 K9.4 2 m 0.705 144sput______ L.250 m.4 4,82 lls .M$ 151 48

I N. A. O.A. Z.012

I%ik!l:::: :2 107 ‘L@) 0.374107

191 4.62 lm .S74 m 46

I,, ,, t

N. A. (J.A. z3c21

i’p%5z::::tM 73.2 21s7 1.01773.2 2353

4.6L I’m ;Z 46

—. CD.,. volne3 for fhp nmtmf.

, , ,I

I I I 1111

3.0

2,5

2.0

,J###mC&x

1.0

.5

0 2 4 68106 2 4 6810Effecf!.veReynolds Number - - -

FIOIJBEW.-Scale effmt on maxfmnm ffft oMTioient of tke N. A 0. A. 23021wfth O.’illc8PM tlap neutral and dalti 7&.

‘7

afrfoff

Hinge moments of ordinary flaps.-The hingemomenta were obtained for the three widths of ordinaryflrLpon the Chrk Y airfoil. These results are givenin figures 31, 32, and 33 as coefficients of flap hinge

moment against flap deflection for

235

various anfzkw ofuttack. Comparison of hinge-moment coeffici&ts forthe three widths of ordinary flap indicatas that theyare practically independent of the flap chord. Com-parison of the hinge-moment coeilioients of ordinaryflaps with those of the split flrLpsgiven in reference

-.40

–s0

–.80Ill

o 10 20 30 ’40 50 60 70 60 90~ , degrees

FIotmE 3L-Hlngemomont cmfthlentsofOIOcfnff~ordInary SapontkeCfarkYrlkfoa. Ffap gapSwdd

f%,

n

-.

-.

-.

0 1020.30405060 70 L1090I+ . degrees

?IOWRE3Z-Hfngemoment coeflidents ofOXkfnU~ ordfnory flap on tke fJlark Yafrfoa. Flap gBpsmkwl.

G,

-.

-.

-.

-.

-.-.

~ , degreeshouEE23.-HfngemornentWOJTMentsof0.30cfnll-spmordk?nrgfip on tlM ObrkY

afrfou. Flapgopmakl.

! indioatea also that the hinge-moment coefficient arenautically the same for the lm-o types of flap. The~ctual h.hqge moments in inch-pounds me plottedgainst flap chord to a logarithmic male in figure M

or diilerent deflections of the ordinary ilaps and foreveral angks of attack. The slope of these curves isapproximately 2, indicating that the actual hinge

,— ---

.

236 ICEPORT NO. 554 NATIONAL ADVIEORY COMMITTEE FOR AERONAUTICS

moment varies as the square of the flap chord for agiven flap deflection.

100

80

60

40

I ,$r-

.?’.+—H—H++I I Wll f / I 1/’

/I I /% / / ● A

AX/ / I y – –-.z

2

IFlop chord,percen+ wing chord

Fmum 34.-V fub3tlon ol hingO monmnt with tip M for U- ~fim cmthe Olark Y airfoil. Q-1637 IIJJw. k

CONCLUSIONS

1. Full-span split flaps produced somewhat greatertiti~es ti CL_ of the three airfoils tested than didfull-span ordinary flaps of the same width, but the L/Dd C!_ was practicfdly the same for the two type9 offlap.

2. Based principally on the speed-range ratioCL~CDm,nY the relative order of merit of the airfoilstested with either ordinary or split flaps is N. A. C. A.23012, Clark Y, and N. A. C. A. 23021.

3. Any gap between the wing and the leading edgeof ordinary flaps had a very detrimental effect on thoc._ attainable.

4. The hinge-moment coefficients of the full-spanordinary flaps were practically independent of fkpchord; the actual hinge moments varied approximatdyas the square of the flap chord. Both of these fidiRgsaccord with theory.

5. The hinge-moment coefficients of the full-spanordinary flaps were practically the same as those ofsplit flaps of similarsize.

LANGLEY MEMORIAL AERONAUTICAL LABORATORY,

NATIONAL ADVISORY COMMI~B FOR AERONAUTICS,

LANGLEY FIELD, VA., Ocfolwr 25, 1936.

REFERENCES

1. Harris, Thomae A.: The 7 by 10 Foot Wind Tunnel of theNational Advisory Committee for Aeronautics. T. R. No.412, N. A. C. A., 1931.

2. Wenzfnger, Carl J.: Wind-Tunnel Meaeurementa of Air Loads

on Split Flaps. T. N. NO. 498, N. A. C. A., 1934.

3. Theodomn, Theodore.: Interference on an Airfoilof FinitaSpan in an Open Rectangular Wind TunmJ. T. R. IQo.461, N. A. C. A., 1933.

4. Glauert, H.: Wind Tunnel Interference on Wings, Bodies.and Aii%Cl?3W0. R. & M. No. 1566,Britieh A. R. C., 1933,

5. Grumhwitz, Eugen, and f%brenk, OSkar: A Simple Methodfor Increaein g the Lift of Airplane Wings by Means ofFlaps. T. M. No. 714, N. A. C. A., 1933.

6. Weiok, Fred E., and Harrie, Thornaa A.: The AerodynamfoCharacterktke of a Model Wing Having a Split Flap Dc-fleet.ed Downward and Moved to the Rear. T. N. No. 422,N. A. C. A., 1932. 0

T. Jacobs, Eastman N., and Clay, William C.: Charaobmlstkw

of the N. A. C. A. 23012 Airfoil from Tests in the Full-Scale and Variable-Dendy Tunnels. T. R. No. 530,N. A. C. A., 1935.