Document
REPORT No. 718
.-
DISTRIBUTION OVER AN NACA 23021 AIRFOIL WITH A SLOTTED AND A
SPIJTFLU?
By THOMAS A. HABBXS find JOHN G. Lowxtr slmfMARY the NACA 2212 (refenmoes 5, 6, and 7). The present A vre~edieti”bution investigation ha% been con- investigation will furnish load data for the split flap in
ducte~ in the IVACA 4- ~ 6~oot ;M”cal un”ndtunnel to
combination with a thiok airfoil.
detemine the air loads on an iVACA 4?30$1 airfoil in The present pressure-distribution tests vmre pmde of combind”on with a 5Y6.66-percen&ohord 810tted &p and a m NACA 23021 airfoil in combination with the 25.66- W-percent-chard @it @p. Preeeuree tie rneammd on peroenkhord slotted flap 2-b (referenoe 1) and the boih the upper and the lower eurfaoes of the main airfdil 20-peroent-chord split flap (reference 4). Teds were and the &pa for 8e?era.1trngle8 of attack and a4 8ecmd made at various angles of attaok and flap settings.
jfap 8e#ing8.
APPARATUS AND TESTS The data, presented aapressure diagmme and m graph% oj the 8ection coejlicient8for the @p alone and for the MODEM airfoil+lap combination, am applicable torib and&p de- The airfoil model used in three tests had a +Lfoot sign for a combindion of a thick ai@i.1 and a slotted or span md a 3-foot ohord; it conformed to the NACA a @it jfap. l%e re8u[t8 of prm”oue ieste of an NACA 23021 airfoil profle and was constructed of laroinated BOlfi ai&il with a slottedflap are mmpared with the . . .
mahogmy with a hollow seotion to accommodate the preeent results. ~i8 CO?IIpatiO?t 8houxd: l%e &p oopper pressure tuba. The baeio model, whioh eon- normal-force coejk+nt8 were approm”mateiythe same at sieted of the airfoil in combination with a fuil-epan high angle8 of atiack. lh jlap gn”tching-momentcoefi- slotted flap (fig. 1), was furnished with a mahogany m“entswe approximately the same for the range teeted.
tiller bloc-kwhioh fitted the slot entry in the lower sw 2’7ie chord-force coejtcient8 for tti jlap on the NACA face so that a smooth airfoil was formed. The slotted %9091 a@bil were genemll~ 8tight~~higher than for the flap was attmhed to the airfoil by tww hinges looated flap on the NACA 9S019 aitfd. Z%arwhfor the split on the tips of the airfoil. The full+pan split tip was &p Were about the 8mne CM for prm”ou8 ieet8 of 8plit constructed of quartsr-inoh plywood and was attached Jap8 on thinner ai~i.
to the airfoil by several braces equally spaced along INTRODUCTION the span.
The National Advisory Committee for Aeronautics The full-pan slotted flap (& 1 (a) ) was developed is undertaking an extezmive invWigation of various by the NACA and is designated 2-b in reference 1.
airfoiI-flap combinations to furnish information applic- It has a ohord of 9.238 inohes (26.66 peroent of the able to the aerodynamic and thestruotural design of high- over-all airfoil chord). A full+pan metal lip Iooated hft dsvioee intmded to rnorease the safety and the p- on the upper+wrface trailing edge of the &foil sots formanoe of Sir@nes.
One of the promising arrange as a partial seal when the flap is undsfleoted and direots ment.s is an airfoil in combination with a slotted flap. the flow of air over the dtieoted flap. The path of Data are available for aerodynamic and structural d- the flap nose (@g. 1) is the optimum one reported in sign of 12-paroen&tMok airfoils in combination with a refersnoe 1, where the nose of the ilap was defined as slotted flap, but little data are av&lable for the design the point of tengenoy of 8 line normal to the airfoil of oombinatione of thiok airfoils and flaps. The preemt ohord and tangent to the leading edge of the flap in investigation was oonduoted tQ add load data to the its neutral positiom The flap wes arranged for look- aerodynamic data already available (referenoe I) and to ing at downward, or positive, flap direoticme.
exhmd the data for loads on slotted flaps (references 2 The spIit flap (fig. 1 (b)) has a ohord of 7.2o inohee and 8). (2o peroent of the over-all airfoil ohord). The leading ‘“ Some form of split flap is cmnmordy used at present.
edge was sealed with plaetioine for all tests to prevent Aerodynsmio information ie available for the S@ flap any leakage. The flap waa arranged for looking at in oornbination mith airfoils of sevd thiolmesses (ref- downward, or positive, @p datleotions. The flap erenoe 4); but most of the load data for w@&p com- angle8 ware measured from the lower surfaoe of the binations are for thin airfoils, suoh as the Clark Y and airfoil as shown in @re 1 (b).
242 mmoBT NO. 71*NAmoNAL AD-BY coyMyrrm FoE AEIRONA~Ct3
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COMBINATIONSTESTED.:”. ~ NACA S021!2121mI&# Whb m , “Lip20&% )hibk ‘. ‘ ,,<, ~ .Au% ix?” .- +yy,” .—. - *., .~” Orfw 0r15mramthr
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18 ......
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M INSTALLATION The model wss mounted in the olosed ted motion of ‘ be NACA 4- by 6-foot vortioal wind tunnel (referamms .
and. 10). Booause the modeI oomplet~ spanned the Tho modsl waa fitted with a shgle Ohordwb.mw of unnel exoept for small olesranoea at eaoh end (J&. 2), pressure osiiha at the midspan looated as shown in he iiides of the tunnel aoted as ad plates and approxi-:,- A single row was used beoause table I and figure 1.
IakJY Wudimtmaional flow ma obtained. Torauo the resuh of the teets of.refereuoe 8 &owed oqp to be ub&”att-aohed to the bslanoe fm.me held the mo&J. .
sufficient. Tubes leadjng from these otiow wore igidl~ and also smved ss a conduit for tbe prewro brought out through one ~d of Lhe wing (tig. 2) snd
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@tel sqqoiwt T .
., t
Press&e tti”es
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.-.
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4’ I t- — ...- ..-.
~, s.-.. . —— E’mum 2.-Wdelfnm Mfonlntbo4-by6hot?wtMwfnd4 unnm L PRllSSUIUl DIST~~ON O-AN NAOA 28021 AIRFOIL tubes. The angle of attack was set from outside the main portion of the airfoil. The section coei%ciente tunneI by rotating the torque tubes with a calibrated me defined as follows: electrio drive.
Cll”=ZJJQC normal-force codkient of airfoil with TmTs flap The tests were run at an average dynamio prwaura C.I=nffgcf normal-force coefficient of flap alone of 11.05 pounds per square foot, corresponding to an C%=mW/q& piu-mommt ccndlicient of airfoil .
aimpeed of approximately 66 miks per hour and to an with flap about quarter-chord point average Wt Reynolds number, based on the chord of of airfoil with flap neutral the airfoil with flap fully retracted, of about 1,840,000.
G,= mr[qc$s pitching-moment coe%icient of alotted The effeotive Reynolds number R, was about flap alone about quarter+hord point 3,660,000 and is equal to the ted Reynolds number of flap multiplied by the turbuhme factor, which is 1.93 for c.r=hf[qc~ hinge-moment codkient of split flap the 4-by 6-foot vertical tunnel.
alone about leading edge @nge axis) The model was tested with the slotted flap deflected of flap from 0° to 60° in increments of 10° and the split flap ce,=xf/gcf chord-force ocefMmt of slotted flap deflected from 0° to 76° in 15° hmmmnta. The tests alone were made through an angkwf-attaok range from zero to approximately maximum lift in 4° increments.
(c. g+= (Om~5-alXIO0 ~tmf-Pr=we hca- With the model at a given angle of attack and flap
tion of &foil with flap
setting, time was alIowed for conditions in the tunnel in percentage of airfoil and for the manometer to become stable before Lhe chord from Ieading presmwea were recorded.
edge of airfoil
(c. p.)~ 0.-: X1OO cent+x-of-pressure lcca-
PRESENTATIONOF DATA
()
tion of slotted flap P-UEE DIA(31UME alone in percentage of flap chord from lead- All the diagrams of pressure over the upper and the ing edge of flap lower surfaces of the combination me given as the ratio (c. p.),=– : )(100 oenter-of-pressure Iota- of the atatio prtwsure p at a point, or an orifice, on the r tion of split flap alone airfoil to the free+tresm dynamio pressure g for the
in pmcentage of flap
individual flap and angleof-attack settings. Presamw chord from leading over the airfoiI in combination with the slotted flap edge of flap are shown in figures 3 to 13, and premuree over the where the forces and moments per unit span are: splitdlap combination are shown in figures 14 to 19.
na normal force on airfoil with flap A comparison of the loads on the plain airfoiI and the nf normal force on flap alone normal to chord of flap loads on the airfoil-flap combinations for the same lift m= pitching moment of airfoil with flap and a~e of attack is shown for three flap eettinge in m~ pitahing moment of slotted flap alone &urea 20 and 21.
h, hing moment of spIit flap In@uree3t08, the pmsmres over the main airfoiI Zr chord force on slotted flap are plotted normal to the airfoil chord and the pressures q dynamic pressure of free air stream over the slotted flap are plottbd normal to the flap c chord of airfoil with flap neutral reference line. The flap reference line is a line through Cr chord of flap (measured from nose to tail) the nose point of the flap and parallel to the main airfoil and chord line with flap neutral. In figures 14 to 19, the 4 angle of attack for *t-s aspect ratio preeeur~ over the airfoil and the split flap me plotted & @of flap deflection . ..
normal to the airfoil chord but the flap preesuros are The coeflhienta for the combination were derived plotted from an imagina~ flap chord line. This ima- from the normaI forces alone, the chord forces on the ginary &p chord line is the deilscted-flap chord line flaps being neglected. Ih the case of the slotted flap, moved normaI to the airfoil chord line until the lead- however, neglecting the normal-force component of the ing edge intersects the airfoil chord line. The ima- chord force of the flap in the calculations for the com- gina~ flap chord line is not ehowm because it would bination reduced the values by an average amount of only complicate the figures.
0.04. Because the skin friction of the flap wilI enter coEmKmwrs into any correction for this discrepancy, no attempt The pressure diagram were mechanically integrated was made to include a correction for flap chord force to obtain data from whioh standard section codiciente in the &al results. Incsmuch as the model complete~y were computed. Where the term “flap alone’J is used, spanned the jet, the integrated reeulta, which are in it refers to the forces on the flap in the presence of the coef%cientform, may be used as section characteristics.
244 REPORT NO. 7 l&NATIONAL ADVISORY C@MlTJ31El R(IR AERONAUITCS
IHguma 22 to 27 chow the motion chara.oteriatica of flap, h figure 28 (b), the ioroes on the split flap when the combination and of the flap alono for the slotted neutral were fetid by aeauming that the only leakage flap; &urea 28 b 33 ahow @e eeoticm ohara@@.im betwean flap and airfoil was at the trailing +ge; the of the combination and. of the flap alone for the split loads were computed on that baeia.
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PRWSUR21 DISTRIBUTION O= AN NACA 28021 AIBFOIL ..-
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RmoRT NO. 718-NATIONAL ADVZ60RY cohwdrrrm FOR MRONAUTICS —.
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PRESSUR31 DISTRIBUTION OVER AN NACA 2802 I AIRFOIL . ..— . .
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REPORT NO. 718-NATIONAL ADVISORY CO@M’TEBl FOR UONAU’1’X~
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PREESURII DISTIUBUTION OVER AN.NAOA 28.021AIRFOIL ,.
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Q FREISSUR31 DIBTBIBUTION O- A?.? NACA 28021 AIRFOIL --- ---- ,.
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onao9ssM dottednnpracmtdon the Flmmu.-o lmdprauredwfbnthm Onaosm?cdottd tipmounbdotltb FWStL 11.-Ohad misma dMrlWtb NACA=mlrfOIL m6Btd Xl”. NACA MEl alrfoll RhP =t d W.
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262 “ s RIUPORT N“O. 71t+NATION~ ADVISORY COMMI’M’EEI FOR AERONAUTICS . PRCCISION --~ --.
~- - -=a~ NoZi.Pflow alinement tests were made in the tunnel
/’0 \
.
with the test arrangement ua8d in the present investi- ..
“\ — ....
/- gation,__The ab@h angle of attack may therefore be in error, but the relative angles of attack of the modd.
The flaps were set at are acc.urfite ti within +0.1’.
specfied angles to within + 0.6°. The results from check tests, in which both the angle of attack and the flap setting were independently changed, show that the ofice pressures agree within +2 percegt, with tho exception of upper-surface pressures near the leading dgm yhich, at _high angles of attack, chctcked wifhh! _ .
about +6 percent. The individual free-stream dy- namic p~ures are accurate to within + 1 percent. A t~el-w.dl correction (reference 11) has been applied --”-
\
. “\ ~c,.afi \ 6-4” only to. the normal-force coefficients of the airfoil-flap
,.%\ \
C* -+44 . . \
N combination. This correction tads to. reduce the
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f I .\ magnitude of the preaau&; the other results, which are uncorrected, should therefore be conservative.
DISCUSSION 13EOTION PR-UEE DL13TEIBUTION The pressure curves (figs. 3 to 21) show .&e didribu- . . .,.
tion of load over the upper and the lower eurfacee of the airfoil-flap combinations for several flap defections.
These curves may be appbd to the design of ribs and -\ flaps and are also useful for ahowing the change in ‘\\ distribution of pressure over the airfoil as the flap is t \ \ deflected. In ganeral, theee curves are similar in ahapo \ \ and magnitude to the on.ea .obtaimi from presauro- \ \.
\ diatribution, inv4gations of the thinner airfoil-flap \ \ combirititioris (refarances 3 and 6).
;, -, t \ The shapes of the pre8aure ourvea for the slotted flap a-o” t,
‘\
\ C*--a@ \ (@s. 3 to 8) ~egenerally similar to those of the curves ~.-.
\ ‘.
f f’ . for the I!TACA23012 airfoil tith a slotted flap (reference \ I I ‘\ 3); this similarity shows that the flape have the same ticteristice aa to extent of peak pressures , occurrence of douhls peak pressures on the upper surface, and magnitude of peak negative preaeuma. In the preeent investigation, the double peak disappeared at flap defleotioxwof 30°.
Figuree 3”to S ahow an inoreaae in velocity at the slot entry. b some oases, this velmity exceeds the free+tream velocity; however, the area of increased velooi@ is small because the deflected flap retards the Flaw.x ls.-ckd mmlTedbirlblltIou c4aaos9ssednttd ikplnonOtd Lqltbl flow to the rem of the slot.
NAOAaldrU1. tiaiiat~,
PR.PlSSUR21 DIS~UTION OVHJRAN NACA 23021 AIRFOIL 253
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RMPORT NO. 718—NATIONAL ADVISORY ”CO~MTEE FOR JU&ONAUTICE!
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PRKl@EIURll DISTRIBUTION OYKB AN NACA 28021AIRFOIL ,
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r - -- ------ —---------- ---- .-.
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ord flap -- —---- _ _—-—.
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* -202 ..- -. . .- ~POIKC NO. 718-NATIONAL ADVISORY CCWMHTEM FOR AEIRONAU’FICS .
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264 REPORT NO. 71S-NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS .
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S@!cm&umteMa oftMNACA_atrRiff withm09k@.Itf@x PRJISSITIUil DIS~UTION OV21R AN NAOA 28021 ~OIL The chord-pressure diagrams (figs. 9 to 12) were Figures 20 and 21 show that the main dleot of either inc~udd to show that rebtively high forces existed flap on the airfoil is its abtity to ohange the flow whioh would tend to retraot the flap from the maximum- around the airfoil in suoh a manner as to decrease the lift setting, as was found for the NACA 23012 airfoil adverse pressure gradient and to oause the airfoil to -.
with slotted flap. (See reference 3.) The negative mrry a mmih greater load without stalling.
components overbalance the positive ones for almost AERODYNAMIC SEtX’xON OHABA(XEEISTI~ all flap settings, which creates a form forward. The A compsxieon of the seotion characteristiea of the skin-friction force, if taken into account, will reduce flap alone and of the combination (figs. 22 to 33) shows all negative values and increase all positive values ..
that the loads on the flap build up more slowly thin because it acts nemly parallel to the chord and to the do the loads. on the combination. The loads OR @e rear.
slotted flap (figs. 22 to 27) build up more rapidly with No tests were made to determine the efleot of a E@t flap deflection than do the Ioade on the split flap (@e.
deviation from the optimum nose path for the alotted 28 to 33) md reach a higher maximum value. The flap but, es pointed out in reference 1, a alight deviation should only slightly change the charactmistics. If the change in characteristics is small, there should be little change in the pressure distribution.
A comparison of the pressure distribution over a Fowler, a pkin, and an exterqrd-airfoil fklp with a slotted flap is given in reference 3. k no great difhrences esist between the mrves in reference 3 and those of the present investigation, no comparison with other types of flap is made.
The shapes of the presauie curves for the split flap (figs. 14 to 19) are verysimilarto *eshapesof themrvee Shown in references 6, 6, and 7. This agreement was expected because reference 4 shows that, with & 0.20c split flap, the maximum lift is prmtically independent of the airfoil thickness.
Comparison of thi pressure &grams for the plain airfoil with hose for the airfoil-tip combinations at the same lift (figs. 20 (a) and 21 (a) ) shorn hat decrea@ng the angle of attack and increasing the flap angle had the following effects: The pressure at the nose of the airfoil decreased as the flap @e was iuoreased. The negative pressures at the trailing edge were increased for both flap combinations. The positive prwsures on the rear part of the splitAlap combination irmreused, but there was little variation in the same region for the slotted-flap combination. The flap loads on both rmmx MAhwrbm afaecuonXrJmJ-fwm and Smchfwmcmmlt MeEtcbnb combinations inoreased with flap angle.
IX09W3calotted EwOn NAOA9Wlmnd MO19MrMb.
Comparison of the pressure diagams for the pkiin greatw part of the inorement of section normal-force - _ uhfoil with those for the @foil-flap combinations at the same angle of attack (@s. 20 (b) and 21 (b) ) shows coefficient ori the combination is the result of the that increasing the flap angIe had the folIowing effects: rnoreesed load taken by the airfoil. For the elotted- The pressure over the entire oombiition increased, Eap oombkation, approximately 75 percent of the load oausiug the airfoil to mrry a much greater load. The increment is taken by the airfoil.
pressure gradient remained @out the same throughout The chord-force omfficienta of the slotted flap (&e. 22 to 27) me praotimlly all negative in sign; that k, the the rang~ of flap angles shown. The loads on the flap force acting parallel to the flap referenoe line is direotad increased with flap deflection.
The shapes of the prwmre curves for the slotted flap forward. The magnitude of these foroes is greater are similar to the shapes of the pressure curves for the ihan for the NACA 23012 airfoil-flap combination airfoil alone. The wake of the flap as well as of the cOm- (reference 3). Jn the mhmlation of the rwltent force bmtion should hmsfore be narrow, which accounts for m the slotted flap, the ohord foroee should be taken into the low drag of the slotted-flap combination as shown MOouut but it should be remembered that these foroea in the reeulta reported in reference ‘1. 10 not include akin friotion.
REPORT NO. 71&NA!HONAL ADVISORY ~ FOE ~ONAUTICZl - Tlw hinge-moment ooefficieuls for the split flap on b have lees ohord foroe in almost all comlitioua t.astexi.
the NACA 23021 Sil’fOfl”SrO Slightly greater tian thOSS At the high angle of attack, tho ohord-force coefficionl.
found for the split flap on the thinner airfoils (rdwenoea of the slotted flap on the NACA 23021 riirfoiI is pro- 5, 6, and 7). In addition, for both thin and thick air- portional to the flap deflection.
foils, tlm hinge-moment ooeflioienta for the split flaps COLLUSIONS “ me muoh greater than the pithing-moment .mticienta A camparieon of the results foi the alottcd flap on for tho a~otted flap, which are about the flap quartar- an NACA 23021 airfoil with” the results of pressure-. .- ohord point.
distribution’teata.of an NACA 23o12 airfoil in oomhina- The comparison of the dotted flap on the NACA tiog with a alottad flap showed: The flap normal- 23021 airfoil and a eimilar dotted flap on the NACA foroe cOMcienta were approximately the same at a 23012 airfoil given in figures 84 end 36 should be useful ~ %@s of atti ovar thQ useful range of ,flap d+ fkoticme. The flap pitahing:moment ooeflicients wore .
about he samo for the range tested. The ohord-foroe cmlhi@t was higher for moat conditions tested for the fla~ on, the NACA 23021 airfoil. The results for the split flap ware qbout the same as previous reaulb for sp~t flaps on ,thinnur airfoils.
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, LANGti”Y. ~fE&iIiL AERONAUTICAL LABORATORY, ‘ NAiIONA~ Anvmony COMMITrJSBFOR A E. RON#UTIW, ‘- GLEY WELD, VA., Ma~ 88, 1/?40; - ‘ ,., , .,.
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lZKFBItENCES ; ,_ . ..
. .
., ..” 1. Wepdnger, Csri J., mad H- Thomas A.: Wii&TLU]ni4 @eat&a@on “d an N. A. C. L 28021 Akfoil wfth Varlouq =E@I of SIottad Flaw. ~p. No. 677; NACA, . . . .
K~~”&rg: Premmm Diatrhutioh on a Wing Seo&m wik ““ ?.
SIotted F18p in Free. ~t TM&.. T. M. -No. 886, ‘- ~C& 1087.
8. Wednger, Carl J., and De4no, JamoEB,: Pm&e Diw .
@butfon over an N. A. C. A. 28012 “Airfoil. with a Slottad . ~d a Plain Flap. Rep. No. 688, NACA, 1988.
4. Wm@nger, @rl J., and Harria, Thoma8 A.: Wind-’flmnd Invdgatlon_,of N, A. C. A: 2@2, @l, and 28o9O A@oila with Variouo $Ia~ of Split F18p. Rep. No. 068, -, ,, NACA, 1989; 5. Wallace, RudoW Inwstigaticm of FuL&xde SpIit Trailh)g- Flwlauaa.-conl@B0nofmctkln dumMarm OmmOhtl lMo9tUWslourd fiWoll Edge. Wtng Fiaps with Various Church al!d Hinge k NACA ~snd~drblls Idom. Rep. No. 589, NACA, 1.985.
6. Wanzing~, Carl J.: Pressure DMbution over a Clark Y-H “” for. th interpolation of flap oharaoteristics for similar AfrfoU Seotion with a Split F1ap. T. N. No. &, NACA, lfi~.
slotted fkips on other NACA airfoils of the 280 ties.
7. Wenzinger, CM J., and Harria, ThomaE A.: Premuru DIs- Figure 34 show+ the relation between section normal- trfhutlon over a Iteotaogular Airfoil wfth a Partial-Span force and pitddng-moment tieflioisnts. of the flaps for S@t F18p. kp. No. 871, NACA, 1886.
the two combinations ut a low wgle of attack, aO=OO, s. Wenzbger, Carl J.: Prwure IMrfbution over an N. A. d. A.
and at a high angle of attack, ~= 12°. “ The normal- 23UI?4 AidoiI-ivith an N.”A. C. A. 28012 )ikternal-Atrfoi] ~p. kp. No. 614, NAC& 1988.
force ooticienta me approximately tho mine for the 9. Wensinger, Carl J., and Hairis,. Thomaa A.: The Vcrtioal two flaps untiI tbe flap deflection exceeds 26°. At low Wind Tunnel of the Natknud Adv!sory Commit& for angk of attack, the slotted flap on the NACA Z3012 Aeronautics. Rep. No. 867, NACA 1981.
airfoil oairiea more load for flap deflootions greater 10. _ William (1., and &a, Milton B., Jr.: Pmaum- ‘“ ‘– than 26° but, at high anglea of attmk, tlw loads remain Distribution Investigation of an N. A. C. L 0002 Mrfofl with a 50-Percent-Chord Plain Flap and Thtwe “T@@.
about the same throughout the useful range for the T. N. No: 784 NACA, 1989, flaps on either airfol The ourvee of pitching-moment 11.
Wermfnger, Cad J., and HarrfE, Thomaa A.:”Wfnd-Tunuel ‘-”- coeflhient show little difference throughout the range .ti@d@@% of a!! N. L C. A. 23012MM with VariOUB teateil. A campmiaon of the section ohord-foroe 00’ Arrangement of Slotted Flspa Rep. No. 664, .NACA, e.flioienta (fig. 86} shows the fihp”on We thi.nndr airfoil 1989. .