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NATIO.t+!AL ADVISORY COMMITTEE FOR AERONAUTICS,.—. . .

WA1tTIEill RIMWR”ORIGINALLY ISSUEDFebruary1941aa

Advanoe ConfidentialReport

WIND-TUNNELINVESTIGA!lZONOF AN NACA 23021 AIRFOIL

WITH TWO SIZE OF BALANCEDSPLITFLAPS

By RobertS, Swansonand MarvinJ. Schuldenfmi

LangleyMemorialAeronauticalLd30X%LtOiyLas@ey Field,Vaa

.NACA”“.”“..;

.>...

WASHINGTON

NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution ofadvance research results to an authorized group requiring them for the war effort. They were pre-viously held under a security status but are now unclassified. Some of thesnica.lly edited. All have been reproduced without change in order to expe (Neg&%23kBx&F~

... 4 ‘.$1-._.__—_ –.–.~_

LABoRATORY

LaWley Field, VA

mm~ —

...- —-.. —. .

3 1176013S56312—-—-—. . .— ___ .

. l’lIHD-T~Zl$$IIWES!CI(3ATIOH.- .-... .-+.,,..,..--., OF AX WiOA 23021 AIRFOIL. . . ..

SPLIT 3’LAPS -

J. Schuldenfrei

An”investigation has ‘beenmade in the HACA 7- b~ 10-foot wind tunael of a larqe-chord lLiCA23021 airfoil witha 15-percent-chord ,nnda 25-percent-chor& balanced splitflap of Olark Y prof’ile, to determine the aerotvnamio seo-tion characteristics cf tho airfoil-slap combinations’ asaffected ‘oythe size, moao location, nnd &eflectlon of theflaps. Section lift, dra~, and pitchia$-moment charmcter-Isticg are presanted iz the forz of contours of flap noselocation for ;Ivon vnlues of the lift, drnq, and pitchin%-moment coofflc?.ents acd conpleto aerodynnmlc section char-P.ctoristics nro Fresezted -‘or four rcpreeontatlve loca-tions of orch 5?-7.P.The two bnl~ncod split flaps aro com-parod with a slottod-flnp arran’;emont developed In .%pre-Tious invoatlqation.

Zhe optimum nerotynnmlc ~.rrnn:er.ent~f either ‘oal-~.need spl:t fln.p, from considqrr.tiono of minimum proflle-dr~zq coeff~clentfl for t~:=e-offand ~~imb, was ~.nmrrmqqementcomparable to the ~owler flmp. The i~-percent balnncedspltt flnp wnQ better over the mod.ernte lift rnz%e, whilethe 25-percent hr.lnnced spl~t Slap wns better over thehigh-lift rr.n~e. Both lmlr,nced eplit flaps were betterth?.n the “Destslottod fl?.pof a prev~ous investigation,except in tile Mqh-lift rnaqe, vhero the slotted flap de-yelopad n W.qhbr maximum Zlft coeffic+lentthan did the 15-parcont” ?mlr.need spl:t flop.

From considerations of mnx:mun lift coefficient, the~owlor arrangement of tho 25-peToent,balanoed spilt flapwas the optimum, %i~ing an Increment of maximum lift coef-ficient of a%out 1.8?. The ‘bestslotted flap of = previ-ous investigation qave an increment of 1.47, while theEowler arran~onont of tho 15-percent halancad spltt flap%ave an increment of 1-24. The opt~muc position for the15-percent balanced split fla~ was m high dra% posttionat 5 porcont ahead of the tr,aili.nqedgo n.nd3 pareont belowtho chord line, whoro tho incronont of naximum lift coef-fictont. 03tataod was 1.31.

.

L

2

. .. . .I

,

.In q~n~r~l, under comparable conditions, the provl -

OUSIF i!.ovolopodElottcd flnp had oqunl or so=owhat lowerpltchinq-nomont coefficients than either size of balancedsplit fla>.

INTRODUCTION

The National Advisory Oommitteo for Aeronautics hasunderto.ken an extensive invcstiqation of verioun airfoil-flap combinations to furatsh information applicable to thoaorodpnamic and structural deslqn of hiqh-ltft deviceswith the view tcward incrorsing the safet,yand porform-mnco cf nirplanen. A high-lift device cagahle of produc-In% hiqh lift with low drag for talco-offr.ndinitial climb,an~ high lift with varinblo drnq for lundin% is beliovoddosireble, Other important SontureG cre: no incroaso indra; r:itiflaps neutral”, small chanqo in pitchi~q moment~~ith flap Lcflcction, low oporating forcus, frocdom frompossiblo icing, and structural cimplicitp,

Somo promi~in% nirfoil-flnp combinations ha~e bocndovolo~od for the NACA 23C12 and 23021 airfoils. Aorod~-nam~c data for th~ WCA 2%021 airfoil oquippo~ rith nin%losloitod flr.psnrr :i*:onin roforoncoG 1 and 2, with splitflcpc in ro?ornnco 3, with plnir.and slottod oxtonsibloflapc iu rcforrnco 4, and \;ith double slotted Slaps inrofoz*cnco 59 Structural datn on thlo nirfoil oquippodwith a singlo ~lotted flap and with a split fl~p are givenin ret’eronce 6.

!Chetypn of flnp uost commonly used on modern air-pl.ants is Gomo form of split flr.p. In order to furuiohinformation on this typo of flrLp,an investigation hasbo~n made of .nnI?ACA23012 mirfoil equipped with two sizesof balanced split flnps, ana la reported in reforonco 79The invosti’;:.tionof br.lnnced split flr.pshas been extend-ed to tha thicker NACA ?3021 airfoil nnd tho results areprosontod horciin. 3y n brzl~-nc~dsplit flc.pis meant r.split flap of “~irfoil section rhich is &ioplacod rearwardas WO1l ao doflcctcd &omcard.

APPARATUS AND TESTS

Modols

Tho basic”~.irfollused In the tostg was built to theNACA 23021 profilo with a chord of 3 fcot and n span of

. .“.

3

7 feet: the ordinates for the eeotion are $Iven in ta%le I.-,. ,!.Tw5 sets of”lamiti~te’dmaho%any blocks were used.as removabletall piecee for the a:rfoil, one for each of the flaps test-ed. Tke 310cks rere cut out ae shows In :iwzre 1 RO that,in.the retracted position, the Slaps faired smoothly intothe u~n~.

The two Slipe tested rere ?nziltto the Clark”Y profile(ordinates table I). The fle~ chords rere, respectively,15 and 25 percent of the main atrfoi.1 chord an~ were of thesame span as the alr.foil. !l!heflaps rere built of lamSnatedmahoqany and were attached to the main airfoil with specialfit:inys. These fitti~?s allo”,~eda wide variation In thelocation cf the nose point of each flap and permitted flapdeflections of from Oo to 60° in 10° increments at each lo-cation. Figure 1 shows the location of the nose pointsteatoii. Yho noso po?.ntof the flap in defined es tie pointof tarqe%cy of the flap leadin;-~ d%o erc with a line yer-penilicular to the ~lr.pchord.. The ]Lodelswere nade to atol+rance of ZO.C315 i~ch.

. .

!casts

The nodel was mounted in the closed test section cfthe IiACA 7- %1’i%foot win? tunnel, r.othat it completel~epannod t>.ojet except for nmall clearances at each end(reforeaces 8 and 9). The m“ainairfoil was r2%idly at-tached to the balance franc b~ torque tubes which exten&ed throuqh the upper and the lower ‘boundaries of.the tun-nsl. The &nqZe of attack of the zcdel was set fron outsidethe tun~el by rotating the torque tubes ‘o:?means of a cal-ibrated drive. tSinceapproximately two-dimensional flowis o%taizte.d.w$ththis.t~pe.of Installation, the sectioncharaotartstics of tb.emodel under test nay he determined.

A d~.mic preascre of 15.37 pounds per square fcotWaa maintained for all tests, which corre~ponds to a veloa-.. It-w of a-oowt 60. miles per hour under standar~ con~itionsoand to a test Eeynolds nunber of about 2,190,000 based onthe chord of the airfoil’”with.t%e:flap retracted. !T!heef-

“ fectiye Ee~nolds num%er WmS about 3,600,000 based on a tur-bulence factor of 1.6 for the.tunpel.. (See reference 8.)

.. Force tests..were made with each flap located in thepoeit.ions shown in figure 1 and for flap deflections from0° to 60° In 10°.increments. Lift”,drag, ahd pitching mo-ment mere measured thro-u~ht“~eanqle-of-attack range from-Go to the stall.

-—— .—. —- ., ..,,.. . . . ...—. —

4

RESULTS AND DISCUSSION

Coefficients

“All test results are given in standard nondimensionalsection coefficient form corrected as explained in refer-ence 8.

Czsection llft coefficient (1/qc)

cd section profile-drag coefficient (do/qo)o

‘in sectfon pltchinq-monent coefficient about aero-(m C.). dynamic center of plaia airfoil

where

t section lift

do section profile draq

‘(a. c.)o section pitch:nq moment

q dynanic preesure (* p v=)

c chord of baaic airfoil with flap retracted

and

‘O an%le of attack for ~nfin:te aspect ratio

%?flap deflection reasured between the airfoil

chord line and the fla~ chord line

Precision

The accuracy of the neasurer:outs in the tests is be-lleved to he within the follow~n% limits:

ao----- .+0.1 cd +0.0006‘(c~=l. o) : - - - -

cl - - - - +0.03 Cd 40.002nax

0(c~=2.5) - - - - -

.6

!,..-

. .

Cqa.c.)o - --*O- 8f---- ------+0.20

. . ...-

ca - - - --*(1.00(33 R’lKpposition - - - - +0.0010..“ ‘mill .... - .

Ro corrections have 5een applied to the data for theef:ect of flap hinges, as their effect 1s belleved to be“snail: The relative nerits of the various flap conlMna-

“’””tions are”proba%ly not appreciably affeoted because the.. . same hiaqe fittings were used i“nall tests.

,-

lib“attenpt wae ~ade to deternine the effect of thebreak in the loyer surface of the win% when the flap *Sretracted, aq it is believed that some comparatively sin-p.learranqeneat na~ be used to Seal the break on an actualZnstallatfon.

Platn Alrfoll

The conplete aerodynmnic section characteristic; of‘the piain NACA 23021 airfoil are qiTen in fiqure 2. Theeedata ere presented and discussed in reference 1.

Determination of OptirnuzFlap Arran%enente

MMnw 11$3 ● - Contou”rsof flap nose location fornaxtnua lift coefficient nrg presented in flqure 3 for the15-percect-chord balanced split,.flap..The optlnun Zoca-tions of the flap nose are direot~~ %elow the trailinq edqeof the airfoil for flap deflections “less than 25°: forwhich deflections, based on.info”rnation o-otalnedfron pre-v“iousInveeti%ations of low.drag arrangements, the flapwas unstalled. (Note that this is the R’owleror the slot-ted extensible flap arrcuu+enent.) The beet noqe looatlonwas 6 percent below the chord line for O0 flap deflection,3 percent below for 10° flap deflection, n?id1.5 percentbelow for 20° to 25° flap deflections. After the flap“stalls the optimzn location ie 5 percent ahead of the trail-ing &dqd and 3 pereent %e~ow the.chord llne for all flapdeflections. trom 30°”to 60°. The 13axihn lift coefficient,obt&l”qad””with ?Jxa”.fla~.locat~d at. the ~o~l~r position nndwith the compdr~tivo~y law drag flap:defl”ectloa of 25°,was 2.54” w%i@h’ tiss only i~creased to”2.59 at a flap deflec-tion of 60°. The maximum lift coeffld.ept obtained withthe 15-percent-chord Imln.need split flap tit the opt”imum lo-oatton was 2,66 with a flap deflection of 60° as eompnrea

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6

to the maximum llft coefficient of 2.82 obtained with the25.65-percent -ohord slotted flap 2b of re~erence 1.

The contours of flap location for maximum lift coef-ficient for the 25-percent-chord balamced split flap arepresented in fiqure 4. As for the smaller flap, the opti-mum locatione for the unstalled flap deflections are belowthe trail!ng edge of the airfoil, %e?ng 6 percent belowthe chord iine for 0° deflection, 3 perceat below for 10°and 20° deflections, from 3 to i.5 percent below for a 30°deflection, and 1.5 percent below the chord line for a 40°flap deflection. Note that the larqer flap went to a muc”hhigiaor defioction before it stalled. The boat locationsfor the 50C and 60° f~ap dcfloctions wore 3 percent belowthe chord lino and ~ porcont ahead of the trailinq edqo.

The maximum lift-coefficients obtnlned were 3.16 at 40°deflection aad 3.CC at 60° deflections, so there is noreason to use the hiqher deflections unless added dra;for lending is Lesired along with a sacri~ice of ~aximumlift coefficient.

From the contourc given in figures 3 and 4 the de-siqner can deternine the maximum lift coefficient to heexpected at any flap location and deflection within theran%e in~esti%ated. The contours do not all close ~at itis believed that a sufficient range was investigated tocover an~ prohahle installation.

“Mtninur.nrgfile Lraq.- The contours of flap nose lo-cation for constant profile-drag coefficients for the 15-percqnt-c~ord balanced split flap are presented in figures5, 5, and 7. The contours are qiven for lift coefficientsof 1.0, 1.5, and 2.0 $or each flap deflection from 0° to60°. The alnimum profile-drag coefficierit obtained at allft coefficient of 1.0 was 0.0218 for the Fowler arrange-ment.deflected 10° as compared to a profile-dreg coeffi-cient of 0.0248 for the plain mimq. At n lift coefficientof 1.5, the R’owler arran?omcnt deflected either 10° or 20°qave a minimum profile-draq coefficient of 0.0306, and ata lift cooffi.cient of 2.0 the I’owlerarranqoment doflocted20° was also the optinum, givinq n minimun profile-dragcoe~ficioat of 0.0446. !?hoFowlor arrangonent of tho 15-percent-chord ‘~r.lanced spilt flap his a lower profile draqthan slotted i’lcp2b of roforoncc 1 fcr all lift coeffi-cients below 2.0, but has higher profilo-drag coefficientsat llft coefficients cbove 2..0.

7

The contours of flap nose loaation for oonstmnt..-, profile-draq coefficients for tti.e25-percent-chord balanced

split flapocre presented in fiqures 8, 9, and 10. “Th@”op-timum location of the nose of the flap for n lift coe fi-cient of 1.0 wns 3 percent be-lowthe ohord llne and

dper-

cent dead of the trnllinq edqe at 10° deflection for the25-percent-chord flap. However, the mintmum p~ofile-~raqooefficlent of 0.0231 wag only increased to 0.0237 whenthe flr..pwas moved hnck to the 3’owler”position. Both ar-ran~er.ents are better than either the plain airfoil oralottod flap 2b ,of referohce 1, but are inferior to theoptinum arran~emqnt of the 15-percent-chord balanced splitflap. The Z’owler arrangement uas the optimum at a liftcoefficient of 1.5, nnd the piofile-dra% coefficient wasthe sr.meas for the 15-percent-chord balanced split flapat the same list coe~fi.cient. At a lift ooefficfent of2.0, the optimum arran~emont was the Eowler, deflected 20°.The profilo-draq coofsicient of 0.0495 obtained was lowerthan that of either slotted flap 2% of reference 1 orthe 15-porccnt-chord.balnnoed split flap. The 25-percont-chord balanced split flap locatod at tho Forler poeltlonhad a cia$mum profile-draq cogfficiont of 0.064 ct a liftcoef:icteat of 2.5 as coinpr.redto a profilo-draq coeffi-cient cf 2.(?83 fdr slotted flap 2b of reference 1 nnd0.110 for the 15-percemt-chord bnlanced split flnp nt theFowler pos~tion. -

The locatlon of the nose of the flapmced spilt flr.pfor minimum profile-drm%not extreaely criticnl, but the dra% doesrapidly as the flap nose is moved forward

for either lml-coefficients isincrease .rntheror downward from

the optimum posfti;n. The optimum arrangement 5.sone com-parable to tha Yowler flap from considerations of minimumprof:le-dra% coefficients.

Pitching moment.- The contours of flap nose locationfor pitchj.n~-moment coefficients shout.the r.erodynamio cen-ter of t~e plain nirfoll nre presented In figures 11 to 16for both sizes of bnk.need split flaps. Xn %eneral, theoptimum location of the flaps to give minimum pitchlng-monent coefftcionts nt n qiven lift coefficient rmd flapdefloctio~ is tho simplo split-flr.p arranqemont, while thelocntion which qlves the mmximum pltchin$-moment coeffi-cients is the Fowler arran~emont. For tho 15-percent-chord

,balanced split flap tho pltchlnq moments for tho 3’owlerarran%enent are mbout 35 poraont hiqher than for the sim-ple split-flap arrangement, and for the 25-percent-chordbalanoed split flnp they are mbout 90 peroent higher for .

—— .—

__— —..>.*. -1

8

the Yowler arrangement than for the simple split-flaparranqersent.... .

An exact analysis of pitohinq-~onent data’.lequite,complicated and a qreat nan~”difforent factors nust he...considered. In this report the pitch?ng-moment coeffl-Cle=zits of the t~o sizes of halaneed split flaps will beco~paretl only on. the basis .of equal naxit:un lift coeffi-cientso Thts conyarimon is given in the following tablefor b“oth SiSBS O: talanced uplj.tflapflat several”loca-

. tions r.ndfor.slotted flap ~b of rsference 1, all ar-ran?bd to g5~e a raximzn lift coefficient of 2.3 and at

.lift coefficients, of 70, 80; and 9C percent of the Haxi-hu~ lift ooefflcicnt. Profile-dimaq”-coefficioatand Slap-deflection @.ataare included in the ta%le.

-—.——.—— -—. --——. .——.—- — ——— --

JI cd ato [

Cn(a.c-)o at “.—-...-———-— _____________ —.—--—--——-———

25-percsnt-chord balanced “split flap, . Cl___.= .2.3 “---—- ——.---...-—--.—.——— -

0.0833 0.06

1 I15.5° a.oE?6 0.075 0.067

.1667 .9s 86 .054 .042 .035

.25 0 10.50 .055 ● 044 .036

.25 .015 50 .058 .042 .C35

.—----

0.9

c%max-—-—

-0:295-q313-.330-.300.—--- .

!s-~

0.8

c%max

-0.292-.302.-m3~5-.278

—-

0.7

a%max—.

-0.285-.286-.305-.260— .-——

15-percent-chord ‘balanced spltt flag, CT = 2.3”.

:IH13EBE=:25.56-perce:~-chord slotted flap ?b of reference

cl = 2.”3mix

-——

-0;279.-.295-.349-.352

1,

z-EgIEEI!!,zlE!_zEEEEI_ijEI... ..The tabla ~how.sthat slotted flap 2b of referen~e 1

has”.sliqhtl~ lower pitching-moment coefficients tharithe15-pe.rcent-chord balanoed split flap except for the hiqherd.ra%arranqeme.nt.of the balanced split flap, and has ap-

.-..

9

.,

t-- prox~qda$ely.j~e same pitchl~g-monehti coefficients as ‘theIow-draq arranserniri~iof the ..25-p.eicent-chord halanbedsplit flag. . .“ ..

llffectof semlln% ~au.- Incomplete teste”were made ..“trlth both the 15- and the 25-percent-chord balanced’ spiltflr.ps to determine the effect of sealing srmll qaps be-’tween the airfoil and the flap nose. Results are in aqree-me?rt with reference 7 where it.vas found that semlinq smallgaps of about 1 percent or less was beneficial to the max-imum li$t coefficient, whtle sealing qaps qreater than~.bout 1 percent was detrimental to the maximum lift coef-ficient. 3’romthis it would mpponr that the small qnpswere c,ctinqas leaks rrhllethe la,r~e~aps were acting asslots; hoyever, $-t s’houldhe noted that in nll crises seal-ing tho %ap increased the profile-drag coefficient. l?hedata obtained on the effects of sealin$ the gaps were notsufficient to be prementea in the fern of cur’resin thisreport .

Aerodynamic Section Characteristics

Complete aerodynamic section characteristics are pre-sented In fiquros 17 to 24 for four different noso locm-tions of both the 15- and the 25-percent-ciord bnlancedsplit flaps. These locations are belloved to lie on ornear any probable path taken by the flap in movinq fromits retracted position to its position for maxlmzm lift.These fiquros, In conjunction with the contours of figures3 to 16, should allow tho dosiqners to preaict tho per-formance of any a,trfoil-flap arr~nqemont within the ranqoinvostiqatod.

Compnrisnn of Flap Arrangmnonts,

Envelope polmrs of profile-drag coefficient for boths3ses of lmlnnced split flaps are ~iven in fiqures 25 and26, for the four positions for whtch complete aerodynamicsection characteristics wege qiven. These polars show .that the I’owler arrangement qlves the lowest profile-dragcoefficient for a qiven llft coefflcia”nt for either sizeof flap, exoe~t at the maximum llft of the 15-porcmentachord bnlancsad split flap, where a higher maximum lift co-efficlont is o%talned with tho flap locatod 5 .percen”tahead of the trailing odgo and 3 porcont below tho chordline. E’ron consideration of rmxintm llft coefficient andninimun profllo-drm$ ooofficlont, tho Yowler location Istho best for the 25-porcont-chord bnlmnaed split flap.

.- — —.

—.— ——I

10

Fron consideration of raxinw lift cooffictont, the opti-mum location of the 15-percent -ellordbalanced spit.t flapis 5 percent ahead of the traillng edge and 3 percent belowthe chord”iine: while. from considerationti of Minimumprofile-dra~ coefficient, -themFowler location is tho opti-mum .

Comparison of I’omlerArranTe~euts of the 3alancod

Split Flaps a,ndSlotted 171ap2b of Rgfermce 1

Envelope pclars for the Fowler arranqonents of thetwo sizes of.balonood split flaps and for the 25.66-percent-chord slottod flz~ 2b of roferenco 1 aro ~~ivenin fi~~re 27. This fiqure shows that the basic airfoilhad the lowest profile-drag coefficients over the low liftranqe: the Fowiar arrangement of the 15-perceat-chord bal-anced split flap had the lowest profile-draq coefficientsover the moderate lift range: and the Fowler arrangementof the 25-percent-chord balanced split flap had the lowestprofile-drag coefficients over the hlqh lift ranqe.

The I’owler arranqeaent of the 25-percent-chord bal-anced split flap was %etter than slotted flap 2h of ref-erence 1 over the whole lift ranqe; while the Fowler ar-rangement of the 15-percent-chord balanced split flap wasbetter than slotted flap 2b over the low an~ moderatelift ranqee, but had hiqher profile-drag coefficients overthe high llft ranqe.

A comparison of the increments of maximum lift coef-ficient for the two s~zes of balanced spilt flaps at thel’owler position and for slotted fl&p 2b of reference 1Is given in fi%ure 28. This i’l%ure shows that little tn-crease in maximum lift coefficient :S obtained by deflect-ing the balanced split flap %eyond the angle at which theflap stqlls. The 25-percent-chord balanoed split flapgave the lar%est increment of mnximun lift coefficient,about 1.82; slotted flap 2b of reference 1 qave an inter-mediate increment of maximum lift coefficient, about 1.47:while the 15-percent-chord bulnnced split flap gave thesmallest incromont of maximum lift coefficient, .nbout 124.

I

11

. . . . ... ,. .,- “ ,-““”-CbHCLUDIlH3RIXARXS . -“.. .

The ~ptimun aerodynamic nrrangeaent of either size ofbalmnced split flap, iron consideration of Elninum profile-draq coefficients for take-off nnd initial clint, was anmrran~;e~ent conparabio to the X’owlorflap. The resultsshowed th.ntthe %asic airfoil h~d tho lowest profile-dra$coofficieats over the low lift mn$o; the optimm mrrange-mont of the 15-~orcent-chord balanced.split flap had thelowest profile-drn.g cocfflci’onts over tho r!oderato liftranze: end the optlnun arranqenent of the 25-percent-chord balanced split flap had the lowest profile-drag co-efficients over tke ‘al%hiift rnnqe. On the basis of lowpro~ile-draq coefficients, the ~ptinun arrangement of the25-aercent-chord balanced srlit flap WEASbetter than the.best slotted flnp, dsvoloped In a previous investigation,over the whole lift range, Trhile tha o:~tinunarranzer?entof t-no 15-:~orc~nt-chord balanced eplit flap was betterthan the ~rovi.ous:y developed slotted flap over the lowacd aodorato ltft ran-qos,hut handhi%hor profilo-draq co-efficlonts over the hi~h lift rnmqe.

The Fowler nr~aa;enent of the 25-percent7chord bal-anced split fl~p ~avo the Y.i%hest increment of maximumlift coefficient, about 1.92 as compared to 1.47 for thepreviously developed slotted flap, and 1.24 for the I’owlerarran%oment of the 15-percent-chord balanced split flap.The optimum arran~ement o: the 15-percentechord balancedspilt flap from considerations of max~mum lift coefficientwas 5 percent ahead of the trailing edge and 3 percentbelow the chord line, whe?e the increment of m~imum liftcoefficient wag 1.31.

In general, under comparable condition, the Preti-.OUSIF developed slotted flap had equal or somewhat lowerpitching moments than either size of balanced split flap.

Lanqley I!emorlal Aeronautlce.1 Laboratory,- National Advisory .Oommittee for Aeronautics,

Langley Yiel&, Va.

12

REl?l!!HEIVOES

1. Wonzlnger, Carl J., and Harris, Thomas A.s Find-TunnelInvestigation of an K.A. C.A. 23021 Airfoil w+th Var-ious Arrangomonts of Slotted Ylaps. NACA Rep, ~0. 677,1939.

2. Duschik, Yrank: Find-Tunnel Investlqation of anlf.A.C.A. 23021 Air50il with Y170Arranqorcnts of a49-Porcont-Chord Slotted Flap. mc4imn0. 728, “1939 ●

7Lm T?onzj.aqor, Oarl J., and Harris, Thomas A.: Find-Tun~olInvostisntion of H.A~O..i. 23f)12,23021, and 23030$;rf 11s with Various Slzos of Split Flap.

&WA Rep.

. ,,1939.

4. Harris, Thoncs A., and Swanson, Robort S.: ~ind-Tunnel.Tests of an lLiOA23021 Airfoil Equipped with a Slot-tod Extor.slhlo and a Plain Extonsiblo 3’lap. 19ACA!/3?Ho. 7~2, lg40.

. .5”. I?8rris, Thonas .4.,azd Rocnnt, Isadoro G.: lHnd-TunaelInvosti%ation of NACA 23012, 23021, and 23030 Air-foils Equi~p”od wit% 40-Porce~t Double Slottod Flaps.NACA RW. NO. 723, 1~1.

6. Harris, Thonas A., and LonrF, John G.: Prossuro.Dlstri-bution over -m NACA 23021 Airfoil rith a Slotted anda split rl.ap. NACA Rep. No. 718, 1X1.

7. Ha~rls, Thonas A., mnd Purser, Paul 3.: l?ind-Tun~ol. Invo:sti%ation of z::?IACA 23012 Airfoil rith Two

Sizes OS Bnlancod Split Flap. i9AOA ACR.. , mov..lg4o.

8. Fen!zic%or, Carl J., and Harris, !i!honasA.: Find-TunnelInvosti%ation of an I?ACA23012 Airfcil with VariousA=rcnyonocts of Slotted Zlaps. N.l!!AReP.HO. w,1939,

9. Harris, Thomns A.: Tho 7 by 10 Foot Find Tunnel of*he Hation.%1 Adtisory Oonrtitteefor Aeronautics.lQACARep; HO. 412, 1931.

10. Jaco?Is,Eastman H., nnd Sliernan,Albert: Airfoil Sec-tion Characteristics as Affected by Variations ofthe Reynolds Number. lCWA Rep. No. x, 1937.

.. . . . ., -,.. . .TA3Ll!lI ” ”.......-

Ordinates for Air20i.1 and Flap Shapes

(Stations and ordinates in percent of airfoil chord)

-——. -——.

NACA 23021 airfoil

StatIon

o“1-252*557.5101520253040506070809095

100-—-——

—.——-

Uppersurfac43

4.876.147.935,13

ZG,9311.1911.8012,0512.0611.4910.408,907.095,052.761.53.22—.

L.E. radius: 4.85

- .—

Lowersurf=ce-———-

0-2.08-3-14-4-52-5.55-6.32-7.51-0.30-8.76-8.95-8.83-8.14-7.07-5 .7?-4.13-2,30-1.70-.22

Slope of radiusOt;~gughend of choad:

●-——-——

-———.

Clark Y flaps-— -.

Station

o“1.252.557.5

101520PO40506070809095

100———-L.E.

--

—.

Uppersurface

3.505.456.507q908.859,60

10,6911,3611.7011,4010.529.157.355,222.801.49.12.———

:adius:1..-——-

Lowersurface.—

3:501.931.4?.93.63.42.15.03

0“00000000.——

0.--—

!.“i IT

{

qi-.UJ

.

“N

Su2A-”’“-- ““-

$‘Q

J-,=+4-

rig.3

O/i s& 0.2//,%2’ “ ‘r

s* .40”

,Ed &- caw&% @ 27”.iiwsv?!10/? G C’2 .

a:iSc A#anced sp/lf flop?’

— . — ——

“=

/==,-.en+ 0,,- +.;/ Ohe,+

J, =30”

Flgwc 4.- Cmtwr~ 0 f f+ A04fmn fer

Cl_ ;O 2Fc ho/on.ed split #Ap.

&=60” ~

II

b

“l?.ACA Fig.5

P ..<..1 t 0,, /0,/ c/,o,d

J-- = /o-Pecc e“, 0,,,%/ -,.-.,7

CJ+ 20’

Ffj?u?w5.- Contours of /70p hcotion

O. 15c balonced

,,,. ,-, ,,,, ,, , .,,.-—

rig. 6

. .. . . ... . ....

f.r e .“7- .7;,f.;l =h.r d

——- VA.* “ *..S-./. d ‘~.,p+s $3. 0“

-./..==.+ ‘?,r&/ ‘+.,-&

~ -/fin

Agure 6.- Contours of f/op /ocotion

~. /5 C bu/unce d

Fig.?NACA

—. -.

--- 4/”.s“*.F

s.. /,d /4 t. + =/0-

F,g.re 7- Con)’ours of f/op /ocQflon

0./5c balonce d

for cd 0/ Cz =20;

Sp //”f f/op.

NACAFigs. 8,9

>-..

&’ .0”

—-— V.Au n...Jf ./0”

. a.1.d pDt.7ta

-–- V’.I”** “e.r+=0”

sealed pi.? ta

a

+ --7 /0

d# = +0”

L-4.49

B..ent Oirf.t/ ctid “

4=30;. t+=z.cl

1“

%ACA Jig. H

J-j.6’”-

&sb”

1

XACA ““Fig. 12

.> .,, .,,“

~~ A /1 /1/1 L-d .;0,

--- V.I.*. .?..-o/.d PO,.-

J&37’

0

2

t

. ...-—

XMA

,>— . .

/ I ‘2”m ‘i7“ K &

/ / ?8 6~

I 1111-■ 1m mm—.——.. , , ,m . . . . . . . .——— . .

EACA

>. .,,

‘++? ‘-’”

-..

Figs. 14,15

+./o-

+ ./0”

W%gama-cm?k~ .f

,o.as&

II

“Y-. d-, = 30” cj .<.

( D) J-, =2.0 ~..?.o

—

—---l

4/,/,

1-

W

Angle o .f offock, da , deg5ec??on p;tching-momenf

.Sect;on profile-drag coeftic~ent C<O coeffic;en~ c~(a,q,

! m cl. . n, n, h, c., t .1 I

02’61 “@?J V3VN,

.—

/

4[

Ii,. ,-.. Section pitching-moment

drug coefficient c~O coe fficien~ cm~aa,

I I I I I 16;--l

I

22’12“@J V9VN

.m!a-

+—

Section pitching-momentAngle of ottock, dO , deg Seci’ion ,orofi/e - drag coefficient c~O coe fficien~ c,. ~a,)0

~

0~.

>>$

l-)Clm$0$

w-l

--

NACA Figs. 25,26

.,

.

Section fift coefficient, cl

Figure 25. -Coolparisonofprofile-dragcoefficients●fvariousarrangements●f0.15Cbalancedsplitflapon

NACA23G21airfoil.

Figime 26. -ComparisonofprOfile-dragcoefficientsofvariousarrangementsofO.25cbalancedsplitflapontheNACA23021airfoil.

FiglJ. 27,26

. . . . . . . ,,

Figure 27. - Comp=iaen of beat slotted with best balancedeplit-flap arrangements on NACA 23021 airfoil.

Figure 28. -Compari30nofincrementsofmaximum

section

liftcoefficient.

o

,,

. . ...

IlllllllllllllflflwmllllllllllllI3 1176013655312 ~— .— ,, —

..,.,

L 1