Document
REPORT No. 677
WIND-TUNNEL INVESTIGATION OF AN N. A. C. A 23021 AIRFOIL WITH VARIOUS ARRANGEMENTS OF SLOTTED FLAPS By CARLJ. W&XZLXGEIR and THOMASA. HARRIS SUMMARY tion of an audiary slotted flap to the main fltip (ref- erence 2). Another type of slotted flap, nerodynami- An inwetigation hus been made in the A’. .4. C. .4.
eaIly superior but structudy more complicated, is the 7- by 10#oot un”ndtunnel of a large-chord A’. A. C. A.
-renet,ian-blindflap reported in referencc 3. Al these 230.21airfoil w“th ~ereralarrangementsof .26.66’-perce nt- flap arrangements were tested on the N. A. C. A. 23012 ckoro! slotted$apg to determine the eeetion aerodynamic airfoil.
characteristics as a$ected by slot shape, jlap shape, jiap In the present report, the results are given of the location, and jiap deflection. The jlap positions for tests of a relatively thick airfctiljthe N. A. C. A. 23021, maa”mum lifi, the polurs for arrangements conw”dered with several arrangements of 25.66-percent-chord farorable for take-qf and climb, and the complete section sIottecl flaps. This investigation included two flap aerodynamic character&tic8 for selected optimum arrange- shapes, each of which was tested ~ttith se~eral slot shupes.
tiient~ uwe determined. A discussion is g-ren oj the relatire merits of the WR’0U8 arrangementsfor certain MODELS .~electedcritem”ons. A comparison i8 made of a slotted PLAIN tiEFOIL flap on the N. A. C. A. 930.??1 airfoil uitli a corre~ponding The bmic wing, or the plain airfoiI, used in these elottd$ap preciously derelopedfor the LA’. A. C. A. 23012 tests was built to the N. A. C. A. 23021 pro~e nnd hm a airjoiL chord of 3 feet and a spzm of 7 feet; the ordinates for the The best slotted-$ap arrangement on the A’. A. C. A.
section are given in table I. The model was built with %70.21airfoil gare the same maximum lift coe~m”ent as solid laminated mahogany nose and traibg-edge the best slotted$ap on the Ar. A. C. A. .2?3012? airfoil.
pieces and solid mahogany ribs. The portion between Zie drag coefficients were higher with the AT. .4. C, .4.
the nose and the trailing edge n-ascovered with tempered 23021 airfoil, but the pitching-moment co@ient~ uwre wdboard. The trailing-edge section of this model was about egwdjor comparablearrangements.
easily removable so that the model could be quicldy altered for k.sts of different flap arrangements.
INTRODUCTION SLOTTEDFLAPS The A’ational Advisory Committee for Aeronautics is undertaking an extensive investigation of wn-ious The slotted flaps and the slot shapes were built of wing-flap combinations to furnish information appli- solid laminated mahogany. The slot shapes were bohed cable to the aerodpmnic design of high-lift de-rices for to the main airfoil in place of the solid trailing edge.
improving the safety and the performance of airphines.
The flaps were mounted on speoial hinges that permitted A high-lift device capable of producing high lift with considerable hititude in the location of the flaps with variable drag for landing and high lift with lovi drag respect to the main ffirfoil.
for take-off and initial climb is believed to be desirable.
Flaps.-Two flap shapes were tested. Flap 1 (fig. 1 Other desirable aerod~amic features are: no increase and table I), corresponding to flap 1 of reference 1, has in drag with the flap neutral; small change in pitching rt smaU nose radius and was designed to give only a moment with flap deflection; 10IVforces required to small break in the airfoil lower surface when unreflected.
operate the flap; and freedom from possible hazard due It also lends itself ta use with a door to seal the break in to icing.
the lower surface of the airfoil with the flap unreflected.
A very promising arrangement of a simple slotted flap Flap 2 corresponds to flap 2 of reference 1, which developed for the N. A. C. A. 23012 airfoil is reported gave the lowest drag at high and intermediate lift co- in reference 1. Further improvement, from a consider- efficients on the hT.A. C. A. 23012 airfoil. This flap is ation of high lift coef6cients and low drag at Mgh and shown in figure 2 and its ordinates are given in table I- intermediate lift coefficients, was obtained by the addi- Thie flap shape was obtained by combining the nose of 666 REPORT h’O. 677—NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS TESTS an N. A. C. A. 6330 airfoil with the trailing-edge portion of the main wing. It was designed h give low drag at The models were mounted in the closed teat section intermediate and high lift coefficients.
of the N. A. C. A. 7- by 10-foot wind tunnel so tlmt they Slot shapes,-slot shape a, which was used in com- completely apa.nnedthe jet except for smaII clearances bination with both flaps, is shown in figures 1 (a) and at each end. (We references 1 and 4.) The main airfoil 2 (a). This slot shape was designed to give a m.h@um was rigidly attached to the ba.hmce frame by torque break in the lower surface -of the wing and, conse- tubes, which extended through the upper and the lower quently, to have the smallest effect on the drag with the boundaries of the tunnel. The ang~e of attack of the flap neutral. Slot shape b is similar to slot shape h of model was set from outside the tunnel by rotating the reference 1, which gave the lowest drag at intermediate torque tubes with a calibrated drive. Approxhntitely two-dimensional flow is obtained with this type of in- stallation and the section characteristics of the model under test can be determined.
A dynamic pressure of 16.37 pounds per square foot was maintained for most of the tests, corresponding to s velocity of 80 miles per hour under standard atmospheric (a) { 56,2*
I
03 - (a) FIaPZ-a (b) FISP 2-b.
FIGURE-!2 -SeatIone of N. A. C. A. Z1021 akfoIl with armngwments of slotted flnp% %~ conditions and to an average test ReynoMs Number of k“.oo~ ; .Olcu J.02CW (c) about 2,190,000. Because of the turbulence in the wind tunnel, the effective Reynolds Number R, (reference 6) (a) FIw l-a (b) FlaP l-b. (r!) FlaP l-e.
was approximately 3,500,000. For all tests, R, is based Fmwm l.-awt.lone of N. L O. A. 29021alrfot$with am.ngemente of slottd Sap 1.
on the chord of the airfoil with the flap retracted and on and high lift coefliciente for take-oil. This slot shape a turhdence factor of 1.6 for the tunnel.
was also used in combination with both flaps and is Plain ahfoiL-Test.s were f~t made of tho plain ahown in figures 1 (b) and 2 (b). Slot shape c was espe- airfo~ over the complete angle-cf-attrtck range from cially d@qmd sc that a door could be used h close the –6° to the stall. In addition to this test, scab-effect break in the lower surface of the wing with the flap tests were made of maximum lift coefficient over the neutraL This slot shape was used only in combination range avai.Iablein the 7- by 10-foot wind tunnel.
with flap 1 and was similar to shape b except for the Slotted flaps.-With each slotted-flap arrangement, entry radius. Slot shape COhas a sharp entry, and tests were made to determine the effect on minimum shapes c1 and b have entry radii 1 and 2 percent of the drag of the breaks in the wing lower surface at the slot wing chord, respectively. All the slots were designed entrance with the flap retracted. Twts wero also made to be sealed by the eIot lip at the etit on the upper sur- to determine the effect of the flap hinges with the flaps face of the wing with the flaps neutral. in their retracted positions. The tests of slotted flaps The modeIs were made to a tolerance of 5=0,015 inch. I-a, l-b, 2+, and 2–b consisted in surveys of flap AN N.A. C. A. 23021 M133’OIL WITH SLOTTED 3zAE3 Position and deflection to determine the optimum path are not appreciably tiected because the mme hinge of the flap from a consideration of low drag throughout fittings were used with all the airfoil-flap combinations.
.
the complete lift range and of the highest maximum lift PLAIN AIRFOIL for each flap ddlection. TEsts were made of slotted Aerodynamic characteristics, -The complete section flaps l-cO, l-cl, and 1-G along the optimum path as aerodynamic characteristics of the plain ~. A. C. L determined for slotted flap l-b. Data were obtained 23021 airfoil are givrm in @e 3. Comparison with for alI tests throughout the angle-of-attack range from previously published data obtained from tests of a —6° to the stall at 10° increnmuts of flap deflection from 0° to 60°. No data were obtained above the stall flnite+pan model and corrected to kdinite aspect ratio because of the unsteady conditions of, the model.
Lift, drag, and pit&ing momenta were measured for all positions of the flap over the complete angle-of-attack range tasted.
Sch-efTect tests of maximum lift were also made of slotted flap 2-b at the optimum position for maximum ~ lift with the 60° flap deflection.
;- ..
RESULTS AND DISCUSSION COEFFICIENTS ~ All test results are given in standard section non- u b dimensional coeflicifmt form corrected as explained in $ reference 1.
t? 1, section Iift coefficient (t/gc.).
.* e c% section profiledrag coefficient (d~qc.).
L section pitching-moment coefhient about aero- %.c. )oj Q dynamic cent&rof phin &fOfi (m(=.6.1@m2).
~ where a 1 is section lift.
* dUY section profile drag.
section pitching moment. ~ WUQ, dynamic pressure (1/2 pV2). $ % @- cm, chord of basic airfoil with the flap fully ~ retracted.
+3 < and 1$ is angle of attack for ir&nite aspect ratio.
c p~
0$
6: flap deflection.
-Q .+ “e
x
PRECISION j~g
@“au -4
The accuracy of the various measurements in the Secfion Iifi’coefficimf, cz tests is believed tmbe within the following limits: FIGUEE 8.-Saction aeroclynado oimacteristka of N. A. O.A. 25021 Pldu MoD.
.--------------------- .__ —-------- 50.1° % -------------------------------- (reference 5) shows significant differences in the &o. 03 ‘ales ------------------------------ results. The slope of the lift curve and the values of
&o.003
‘+a.c.)o drag coefimt are slightly higher for the minimum
C%*------------------------------- +0.0003
the present tests than for some of the resdta at a con- ---------------------------- +0. 0006 siderably higher ReynoMs Number given in reference 5.
c%q=.l .0)
The pitching-moment cceflicient and the vertical loca- --------------- _--- _—--------
+0.002
c~(c@ .6) tion of the aerodynamic center above the chord line are
ti,---------------------------------- ho. 2“
dightly lower. The chordwise location of the aerody- Flap position ------------------------ +0. OO1cm mmic center is the same for both sets of data. These No corrections for flap-hinge fittings have been IWrences are about the smne as those observed betweau appIied to the data because no etlect could be measured ~he results of previous two- and thredimenaional- with the flaps neutral. hTo attempt was made to 30Wtests of the N. A. G A. 23012 airfoil (reference 1).
determine the effect of the hinges with the fiaps deflected I’he data for the N. A. C. A. 23021 airfoil given herein because their effect was believed to be emsU and be- we directly comparable with the data for the N. A. C.
cause of the great number of tests reqyired. It is k. 23012 (references 1, 2, and 3]. When ccmpariscw believed that the ralative merits of the mwious flaps with other airfoils are made, it should be remembwed 668 REPORT NO. 677—NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS SLOTTED-FLAP ARRANGEMENT that no correction for tunnel effect has been applied to these data except for the lift; as explained in reference 1.
Determination of optimum arrangements for maxi- Effect on proffle drag of breaks in surface of airfoil mum lift,—The data presented in this section am the at slot entrance,—The effects of the breaks in the lower results of the masimundift investigation of the various surface of the airfoil with the flaps undefiected are flap-and+Iot combinations in which tile flap, at a given Ifo me&rable effect was etident shown in figure 4.
deflection, was located at points over a considcwddo from the breaks caused by the thickness of the sIot area with respect to the main airfoil Tho duta aro lip in the upper surface of the airfoil,_ .The increment presented as contours of the position of tho noso of profile-drag coeftlcient, AC%)was smallest for slotted point of the flap for a given lift coefficient, The mm flap l-a; Acd, varied from 0.0002 at zero Iift to 0.0006 point of the flap is defined as the point of tmgcncy of a line drawn perpendicuhw to tho airfofl C11O rd at a Iift coefficient of 1.0. Slotted flap Z-a had a and tangent to the leading-edge arc of the flup when constant increment of profile-drag co&cient of 0.0006 neutral, as shown in figures I and Z, L SYofted flop The complete maximum-lift data for slotted Ilaps # ~o l-u-.
1-s, l–b, 2–n, and Z-b deflected 10°, 20°, 30°, 40°, l-b ----- a 2-U —-— 50°, &d 60° are given in figures 5 to 8, respectivcdy.
w “2%-—” An inspection of these figures shows that tlm contoum $ —- ..
%. —-- are not closed with all combinations for flup deflections.
$.0032 I-C*—-- Iess than 30°. The position for maximum lift cocfE- --- -- ---- -- t --- cient is not ve~~ critical and only n sufficient number of __ --- -- positions were taken to cover any prmctiml path ulong &iA924 which the flap is likely to be opertitcd. l?urthcrmorc, k * it is probable that the optimum flap position for thcso G deflections wiU be chosen from a consideration of drag / /‘.
.
L,m[* -- / and ease of mechanical operation.
-- .-— .~- -y .$ ~, / The position of the flaps for maxtium lift coefficient ~ -; : -- /“” becomes much more critical for flap deflections from > am? 40° MO”. The maximum lift coefficient wos obt.aincd — .
for slotted flaps l-a and l-b with the flap deflected 60° — ~ $ — — and the nose point 1.5 percent of the wing chord directly s below the slot lip. With slotted flaps 2-rL and 2-b, k n P 4 .6 .8 Lo s- the maximum lift coefficient nt 50° flap ddleotion was iect?.m Iif# coefficient q obtained with the flap nose point about 2.5 percent of FIQUEE4-Eflect of dot opentngs In lower eurfeea of drfoll on prodfedmg CoefEcfent.
8f, (r. the wing chord directly below the slot lip, From these contours, it should be possible for tho for all lift coefficients from zero lift to a lift coeilicient designer to choose the best path for tho flnp to follow of 1.0. Slotted flaps l-q and l–cL gave approximately from a consideration of masimum Iift coefficient done.
constant increments of profile-drag ccdlicient of about If, from structural considerations, it is not pmsiblc to 0.0010 and 0.0012, respectively, up to a ]ift coefficient use the bcwtaerodynamic path, the loss caused by using of 0.6, beyond which the increments increased to 0.001S a compromise. path cnn be immediatcly evaluated.
and 0.0022 at a lift coefEcient of 1.0. Slotted flaps CompIete section aerodynamic characteristics of select- l-ca and 2–b ga~e about the same increment of profile- ed optimum arrangements for each fkp deflection are drag coefficient, 0.0014 to 0.0015, for lift coefficients given in a later section of this report.
less than 0.6, beyond which the increments increased Determination of optimum arrangements for profile to 0.0022 and 0.0018, respectively, at a lift coefficient drag.-Optimum positions of the several flaps for tho of 1.0. Slotted flap I–b was inferior to all other conditions of low drag for take+ff und initial climb arrangements, the increment of proflklrag coef6cient to clear an obstacle were determined. Tho sole crite- increasing nearly linearly from 0.0026 at zero lift to rion for a given lift coefficient is the drag coefllcient.
0.0030 at a lift coefficient of 1.0, It is probable that a door could be fitted to any of The most important singIe factor in unassisted tukc- the arrangements in such a manner as to seal the off distance is the value of the lift coefficient for tukc-ofl break in the airfofl lower surface without measurably because the higher the lift coefficient, the lowcr tho increasing the profile-drag coefficient of the wing with take-off speed and, other conditions being equal, the the flap neutral over that of the phin wing.
shorter the distance”required to clear a given obstaclo.
-- 64.?02 0) (a] 64202 Percenf wiq chortf Percenf wi~ chord (a} 6,-lm (d) 64202 (c j Percenf wing chord (d) fv==”.
(c) h====”.
— >>......:. .... ... +.: ..:.+.
(e] 64Zoz Percenf wing chord (0 a-w.
(e) d+”.
209142-4W4 670 REPORT_ NO. 677—NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 6~ (b) - ““ Perceni wing chord Percenf wing chore’ (8) d/-W.
b) t!=mo.
(c) ,.
Percenf wi~ chord (c) &-w.
(d) af=40*.
~ (e) (f) \\ Percenf wing chord Percent whg chord (d a~w.
(!) df=W’.
FIGUEE O.-c%tbrm Of flql h?utbnfor C, - . Slotted tip I-b.
.U AN N. A. C. A. 23021 AIRFOIL WITH SLOTTED FLAPS . .
Rrced wiq chord (a) 8I-10”. (b) af-zo”.
.
(c) (d) 8/40”.
(c) itf-m.
64202 f e) Percenf wtng chod (f) af -w.
REPORT No. 677—NATIONAL Dvn3013Y cm3nifmE FOR AxRoNAtmIcs (n) 8/-llY.
(b) af=w.
(d} a+w.
. .
Percen+ wing chord J (0) &=m”.
(f) 6f-l?Q”.
FmUFIE8.—Contours of flap katlon for Ci=a=. Slotted flap 2-).).
AN N. A. C. A. 23021 AIRFOIL WITH MOTTED ELAPS 673 — The limiting conditions are the power available to o-rer- Section aerodynamic characteristics of selected op- timum arrangements.-The complete section aero- come the drag at the higher lift coefficients and the excess awdable lift required from considerations of dynamic characteristics of selected optimum arrange- safety. The data are given, therefore, as contours of ments of slotted flaps l–a, l–b, 2-s, and 2–b are given the nose position of the flap for constant drag coeffi- in figures 13 to 16, respectively. The optimum arrange- cients at certain selected lift coefficients, cl= 1.0, 1.5, ments were chosen from a consideration of low drag” -- coefficients at the specified lift coefficients for flap 2.0, and 2.5, and for flap deflections thtit cover the range for which the drag coefficient is decreased by deflections from 10° to 30° and from a consideration of maximum lift coefficient alone for flap deflections from dei3ecting the i?ap.
40° to 60°. In addition to the optimum mmmgeme.nte, The complete drag data for slotted flaps l-a, l-b, 11 11 \\ \ N&x I f - .- ,._. _— .. . ... ..:.
(a) 64Z0 . .
Percenf wing chord Percenf w~ng chord - (a) CI=ILI; af=lo”. 03) CJ=l.* 61-ILY s=- .. _:--- ~/0
q++-1. ‘~
(d] 642 (c) 6 2 . .
Percehf wing chord Percenf wtng chord (c) Cl-z.@ 61-2.V.
(d) c1-2.IJ &40°.
FIGURE9.—Contonrs of tip location fore+ Slotted Sap k% z–a, and 2–b are given in figures 9 to 12, respectively.
data me also gken for certain arrangements that minimum drag coefhcients were approxi- Where the appear structurally simpler. A table inc.ludcd in each mately the same for a given lift coefficient at two flap figure shows the nose position of the flap for the various settings, both sets of data are given. From these data, deflections and the points me plotted on the diagrams.
optimum paths for the nose points of the several flaps The selected optimum path referred to hereirmftor is may be chosen from a consideration of drag coefficients shown by the broken Iine through the points and is a at the various lift coficients. If it is structurally compromise between aerodynamic nnd structural wn- impossible to follow the optimum path, the additiomd eiderations. The aerodynamic characteristics shown drag coeilicient caused by the deviation will be available.
in these figures are typical; complete data for other Insufficient data were obtained to close all the contoum, positions of the various flaps at the several flap defleg- but most of the practicable arrangements are believed t.ionsare avaiIable upon request.
to be within the range covered.
— REPORT NO. 677—NATIONAL ADVISORY CO.MMltiE FOR AERONAUTICS
L._&&
+-=--s
Percent wing c} ‘d (a) C1= 1.0 ar-lo”.
(0} cl-w 6P1O”.
(d) CI=l.& 6f-2JP.
(e) (e) CZ-2Q af=w.
(0 ct=2.ix at-w.
Fnxw 10.-C!ont0um of fipj~ti~ fcmCdr EUottad flap l-b, AN N. A. C. A. 22021 eOIL WITH S~ F- o ... ........
2~ $ 4.$ 6~ ~.
o L # to (h) 6 42 02 ,—, 64202 (a) Pereent wiq chord “ percent wing chord (b) Cl-l* 8{=10°.
(a) Cl=l.& J31=.lo”.
(d) (c) 64202 Percent wing chord percent W7hg C#Iord (d) c1-2.ti ar-w.
(0) Cl-l.@ Jr-m.
o (e) t++ Percent wiq chord [e) cI-2.0 af-w.
Fmum 11.—CUntolucof flap locctkm for C%. mttcd flap %3.
REPORT hrO. 677—NATIONti ADVISORY” &MITTEE FOR AERONAUTICS.
(a) (a) CI-LO; 8f-10°.
(b) et-l G &+OO.
/ (d) At-cent wing chord Perc8ni wing chod (d) CI-I.M ar-rn”.
(8) CI-2.U dp=m’d (f) CI-2.S :&f-w.
FIGURE12.-Uontours of @ locatkm frx”cdr Slotted llnp 2-b.
AN N. A. C. A. 23021 AIRFOIL WITH SLOTTED FLAPS .— ..—
-lUL—u—Mu
I 1 1 1 I I I I I I i I I I I AN N. A. C. A. 23021 MRI?OIIJ WITH SLOTTED FLAPS -..— I I I
11111
Ill
II
I I 1 I \ I I 1 I 1 I I I I I I I I I I I I I I 1 I I 1 ., Sec+ion Mf coefficient+, c~ EIQUU l&-&J2tb3n a9zO~ ObUMIt@dSk of N.A.O.A.23(!21 alrfd with dOtted @.8p 2-A.
—, 680 ~PORTJO. 677—NATIONAL mvIsORY &iWfI~EE FOR AERONAUTICS _.. - t t t II I 1 I I [ I 1 :316 ./ I I I I I I I I i 1 1 I t 1 I 11 —I I I M-7 —.-— t t J- 1 I I I I ..L I < * p Y -8 2.8 -.4 0 .4 .8 [2 ““” 1.6 2.0 2.4 Sec7%n Iiff Coefficient, c, FIGURE16.-&etton aerodynamic characteristics of N. A. C. & ZS6Zlekfoil wltb dotted flap 2-b.
AN N. A. C. A. 2i1021 AIRFOIL WITH SLOTTED FLAPS .- .-. , -..
..
i..
. .—.
. ..
. .
1 I d I I I I I J I 1 J I I I I i I I I I I 1 I 1 I I I I I 1:1 I I I — 1 1 H ,, I I [ I t I I I I !
— ,5 ,Z?
—.-r 2.4 28 u .-f .0 t.c 1.0 2.0 Seci%n /if? coefi%im~ ~ FIGm 17.-Eectt0n aerodxc aharackrfstfre of N. A. U. 4.. .23&Zafrfoll with slottd fk~ l%.
— ~PORT NO. 677—NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS -.
I 1 I I 1 1 r 1 ! 1 I I t I I I As 1 1 1 r I 1 1 1 1 1 I 1 6 -, I I I I I I I I I -% .
$ 8 -k’ u ~o ~ tn -8 -.4 0 .4 ,8 1.2 }.6 2.0 2.4 2.8 Secffbn lift coe%cienf, cz FIQVBX 18.-&mtIon mxdymmfcOhmcteKMfCU of N.A.CLA.2W21 drfdl with S101W fbp I-oi.
684 REPORT No. 677—NATIONAL mTUE40RY COM311~EE FOR AERONATJWCS The compIete section aerodynamic characteristics 10-foot wind tunnel is shown in figure 24, where the.
WI siotted flnps l-co, l–cl, and I-cz are given in &ures ~ lmz for the pIain airfoil and the cl~u for sIotted flap 17 to 19, respectively.
These data are all that were Z-b at the optimum deflection (~J=500) are plot.tcd obtained for these slotted flaps. The path of the flap ~ainst efbctive ReynoIds Number. A comparison of nose used for all three mran~ements was the sume as the two curves shows a slight increase in Acl~~z with ml for slotted flap l-b. - ncrease in scale but it is probable thnt; if the incrc- Comparison of selected optimum arrangements,—In nent were considered to be independent of scalo in orcler to compare the drags of the various flap arrange- ipplying the remdts at higher vrdues of the Reynolds ments, enveIope poIars are given in figure 20 for the Yumber, the result would be conservative. lt shouhl slotted-flap arrangements of figures 13 to 16. This ]e r&nembered, however, that the maximum lifts pre- figure shows slotted flap 2-b to be superior for take-off ;enteclin this report are section, or infil]it%~~)cc[-ratio, at any lift coefficient from 1.0 up to the maximum Iift :hmacteristics and wiIInot be renlized on a finite-mpcct- coefficient. SIotted flap l–b is only slightIy inferior to ‘atio wing except for one with an elliptic lift distribu- slotted ffap 2-b over the saiii” lift range. Slotted ff&ps tion.
l–a and 2–a are both inferior to l–b throughout the A further comparison of the various slotM-fiup rw- lift range from lift coefficients of 1.0 to that for maximum ‘angements is gi&n in the following tublc: lift, flap 2-a being slightly superior to flap l-a. A com- parison of slotted flaps l–b, l%, l-c,, and la for the Ctmm, — wdy.qm,, cm” take-off condition is given in figure 21 as envelope polms.
%,-w) Slotted flap l-b, which has a.n 8-percent radius at the —— sIot entry, is superior to the others. The slot entry ?JOnc .... 1.35 111 324 -o. Ow l-e...- . 218 1: lti 18.6 -.300 with the sharp edge (slotted flap l–cJ appears to be the l-b-.. .
:!! 165 14e 19.I -.s5 2=0... . . 271 ;!! IN M* la [ -.325 Ieast desirable ahhough there is Iittle dillerence among 2+----- 282 207 1% 161 10,a -. (m!
l-ci ----- 2t?a Zol 1s2 Iris Ml,2 -.355 the three.
l-c[ . . ..- 2U9 200 17Q 17.8 -. aas 1*..-.. 21i9 197 17!; % 18.6 -. ?J5a
For lift coefficients less than 1.0, the pkin wing has T
I Ii I J.
lower drag coefficients than any of the arrangements Tl~e maximum eflicicncy for a tiven kmdimr spoccl with the flaps deflected; therefore, if a door were used ril.1be obtained with the ~irfoil t~at gives the~ighest to seal the break in the Iower surface of the wing at the atio of maximum lift coefficient-to the drag meflcien t slot entrance, W the slotted-flap arrangements would or cruising. A comparison on this basis of the sevoml be of equal merit for lift coefficients less than 1.0. The lotted-flap arrangements showwslotted flap 1-a to bc use of a door would probably be more complicated with uperior to any of the other mrangements for the coa- sIotted flaps l–b and 2–b than with l-co, l-cl, or 1-cZ; litions assumed. VJhen the cruisiug speed is obtuiued becrmee of structural considerations, no definite con- ,t a Liftcoeflkient of 0.6, flap Z-a is equalIy as good m :Iusion can therefore be drawn M to which sIotted flap –a, and 2–b is ordy slightly inferior to either.
If a vouId be superior. From a pureIy aerodymmnic con- [oouvere used to close the break in the Iowcr surfnco sideration, however, slotted flap 2–b is superior for f the wing when the flaps me neutral, the speed-rtingo conditions of take-off and initial climb to clear a atio (c,Jctio~,J ~ould be highest for slotted flap 2-b given obstacle.
A compmison of slotted flaps l-a, l-b, 2-a, and 2-b ~ecause it has the highest maximum Iift coefficient.. Tho as Iift-increrwing devices is shown in figure 22 where the ptimum sIotted fkLpfrom conaidemtion of speed-range increments of maximum lift coefficient Ackcz are pIotted batio will, therefore, depend upon whether a door is ~ed” to close the break in the Iower surface of the wing against flap deflection when the flap is moved along the vith the flap neutral, optimum path previously mentioned. Slotted flap 2–b The ratio of lift to drag at 0.!3cl~=Z, (1/d)p.w,_], is a is superior as a lif&increasing device, and the maximum increase in AcZ~u is obtained with a flap deflection of tit erion of the masimum gliding angle; the Iower the ‘atio, the steeper the angle of glicle, The ratios tab- 50° with only a sIight loss at a flap deflection of 60°.
dated in the table were obtained by dividing 0.9cl~oz, The other slotted-flap arrangements are all somewhat inferior to 2–b, the maximum lift coefficient being from vith the respective flaps deflected 60°, by the drag 3 percent less for sIotted flap l–b to about 4 percent Iess :oefiicient at 0.9cbU.
Slotted flaps 2-a and 2-J will for slotted flaps l-a and 2-a, ~vg the steepest gliding angle on this basis.
The change in slohentl~ radius had a negligible effect h“order to control the gIide-path angIe, it is desirablo on the nmximum increments of maximum Iift coefh- o have avaiIable not onIy a low ratio of Z/d at a hiih cient as shown in figure 23, where Ac l~~z is pIotted ift coefficient but also a high ratio of Z/d. Slotted flap against.flap deflection for slotted flaps l-b, 1%, l-cl, &b is superior in this respect, for the maximum lift is and l–cZ, all flaps being deflected along the optimum practically the same for flap deflections from 40° to path selected for flap l–b.
10” but the profile-drag coefficient for 13~=40°is onIy The scale effect for the range available in the 7- by ,bout onehalf of its value for 6~=60°. (See fig. 20.)
AN N. A. C. A. 23021 AIRFOIL WITH SLOTTED FT.APS
:,,1-H-I-F
‘L?
a) ,- fllilllllllttl .-
1!1
-.4 0 .4 .8 /.6 2.0 2.4 ZB Section lift co~+fici~t, cl FIGURE2rl.-Compacimn of pm~edrog Mclents for dotted flaw I-& l-b, %aj and 2-b.
.24 ..5V # ti- .5 !’6 i * ./2 I ~ y9 u $ .04 .Secfion Iiff co@fkient c, FIQUEE21.—Effect of sIot-entry mdne on prm!.kdrog mefflcfent of afrfofl.
REPoRT NO. 677—NATIoNfi Amu3013Y COMMITPEE FOR AERONAUTICS FmuBE !M-Oompgrison of fncmmenti of maxfmum ltftmeflloient for dottal ihm l-a, I-b, 2+ and >b when moved find Mleoted along the seloctod optimum path% FIGURE ‘2&-Etit of EIot.an~ mdbm on jnoromgnt 04maxlmmn Ifft eoaf3Mmt of afrfoil when thsflapg ~movti and dedlmtw along tha sobxkl optlmumpathfor flap l-b. – WITH W#r’lmO FLAPS 687 AN N. A. C. A. 23021 AIRFOIL 4.2 Reference h &ure 16 also sho-iys that, beyond this range of flap ddections, there is practically no change 3.9 in the pitding-moment coeflhient md only about a 1° shift in the angle of attack at a lift coefficient 3.5 - of 2.6 with a 20° change in flap deflection from 60° to 40”.
3.3 The tabulated maximum pitching-moment coefficient 4? - 50~ — 3.0 ruge.
C*==is the maximum obtained in the useful-~ht I / - Slotted flaps 2-a and 2-b have the highest, and nearly & # < .2.7 — - 6 percent equal, values of c~m=j these valuee being ~ higher than any of those for arrangements of flap 1.
$2.4 The pitching-moment coefficients obtained with the # . Ah . .
slotted flaps on the N. A. C. A. 23021 airfoil me about the g same as those obtained for corresponding flap arrange- ments on the hT. A. C. A. 23012 airfoil reported in 1 ‘“8 reference 1.
~.5 Comparison with slotted flap on N, A, C, A. 2S012 i!
& - -- airfoil.-The envelope polars for slotted flap 2-b on the g /.2 , P&i~ airf~il N. A.~C. A. 23021 airfoil and for the corresponding Q fig slotted flap 2-h on the N. A. C. A. 23012 airfoil (refer- ence 1) are plotted in figure 25 for comparison. The .6 two curves are quite similar,with the curve for the N. A.
C. A. 23021 airfoil consistently showing a somewhat .3 higher drag coefficient for all lift coefficients throughout The maximum lift for either the normal-tight range.
/
3 4X /06
The final seIection of airfoil arrangement is the same.
Effective Reynolds Afumbeq R= thiclmess will probably be a compromise between aerodynamic and structural requirements.
dotted flap S-b at optimum location, FIIWM? !25.-Comparisan o[glotted tips on N. A. C. A. ZJM!2 and N. A. 0. A. 28021akfoils.
— REPORT NO. 677—NATIONAL ADYISORY t!ObfMITTEE FOR AERONAUTICS CONCLUDING REMARKS 3. VTenainger, WA J., and Harris, Thomas A.: Preliminary Wind-Tunnel Investigation of an N. A. C. A. 23012 Airfoil If a door were used to close the break in the lower with Various Arrangements of Venetian-Mind I?lws. T. R.
surface of the wing with the flaps neutral, sIotted flap (to be published), N. A. C. A., 1940.
4. Harris, Thomas A.: The 7 by 10 Foot Wiud TUIHIC1 of the fl-b would be superior to any of the flaps tested on the National Advfsory Commitke for Aeronautics. T. R.
bask of maximum Iift coefficient, speed-range ratio, NO. 412,N. A. C. A., 1931.
control of the angle of glide, and low drag for take-off and 6. Jaoobs, Eastman N., and Sherman, Albert: Airfoil Scctkrn initial climb. Of the other combinations without a door, Characteristics ss Affected by. Variations of tha Reynolds slotted flap l-a gave the highest speed-range ratio, but Number. T. R. No. SS6, N. A. C. A., 1040.
slotted flap 2-b is stfi superior in other respects. The TABLE I pitching-moment coefficients were about the same for ORDINATES FOR AIRFOIL AND FLAP SHAPES the slotted flap on the hT.A. C. A. 23021 airfoil as for the corresponding arrangements on the N. A. C. A. 23012 16WOIIS and ordinate-q h Percaot ofwingchordl airfoil. The final selection of the optimum slotted flap W probably be a compromise in which structural considerations will be the deciding factor.
Jpm krlt[or wars ..--— o .. .----- :: g .82 -1. LB 4.67 –i m 6.14 -a 14 .64 –. a –k 62 LANGLEY LhlEMORW AERONAUTICAL LABORATORY, 7.93 -462 1.% -467 9.13 –6. 56 i~ –L 76 hTAmoNAL ADVISORY COMMI~EE FOR AEILONAUTICS, 10.w -6.32 H! 1.96 ~g u 19 –7. 61 6.14 LANGLEY FIE~D, V~,, F;bruaty I?J,1939. “ IL S2 7.70 M -’i 79 -& 30 –S. 76 3.90 –a 34 W &42 -z 64 W -8.96 11.49 lh 46 ;3J -2.36 –S. 83 REFERENCES 10.40 –s. 14 17.99 -1. s6 ~: g g$ L50 -1.36 .s.m 7.69 –. 81 1. Wenzingm, Carl J.,” and Harris, “Thomas” A.: Wind-Tunnel 4K? :% –, 22 6.05 tio6 Investigation of an N. A. C. “A..23012”Airfoil R?th .Vti.OM —2.20 I z 76 I L 62 –L 66 - Arrangements of Slotted Ffaps. T. R. No. 664, N. A. C. A., z Center ofL. E.8ro Cartet of L E. era .22 -.
1939.
-0.56 2. Wenzinger, CarI J., and Gauvain, Wflliam E.: WincI-TunneI L. EJWua: 4#.6. 610P6 2.W of radlua through end ~ c1 Investigation of an K. A. C. A. 28012 Airfoil with a Slotted of chord: 0.30S L. E. radiua: LOO L. E. mdhrs: 2.S9 Flap and Three Types of Auxiliarv Ffam T. R. No. 679, N. A. C. A., 1939.