Document
----- 3y Tizonas A. Harris and Robert S. Svanaon Langley” Xemorial Aeronautical Laboratory ., l .. . . . .
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______ NATIONAL ADV.ISORY COMMITTEE 20R AERONAUTICS —- .
.— TECHNICAL NOTE NO, 782 . .
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l?IND-TUNliEL TESTS ox AN ~;ACA 23021 AIRFOIL EQUI’PPIID WITH A SLOTTED EXTENSIBLE AND A PLAIN EXTENSIBLE I?LAP 3y Thomas A, Harris and Robert S. Swanson _.
SUJWARY — An investigation has been made in the. NACA 7- by lo- foot wind +unnel of a larqe-chord XACA 23021 airfoil equinped with two arrangements Of a completely extended . .
15-pGrcent-chord extensible flap. One of the flaps had a faired juncture, without a qap; the other was provided .- with a slot between the trailing edge of the airfoil and .- the nose of the flap.
Complete aerodynamic section char- acteristics are presented for the various flap deflections for both flap arrangements in the completely extended po-- .+ . . .
sition.
—- The results showed that the “oasic airfoil gave the lowest profile-drag coefficients over the low lift rtinge, the airfoil wi”th the plain extensi-ole flap %ave the lowest profile-drag coefficients over the moderate iift range, and the, airfoil with the slotted extensible flap. q.ave the lowest profile-drag coefficients over the hiqh lift ranqe.
The airfoil with the slotted extensible flap had the same maximum lift at a flap deflection of 250 as the airfoil with the plain extensible flap had at a flap deflection of 600.’ The results of comparisons of the” “airfoil pitchinq- moment coefficients obtained with the two types of flap .
are dependeut upon the basis chosen for conph.risen.
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Ii{TRODUCTION + I The National Advisory Committee for Aeronautics h.ns undertaken an extensive investigation of various wing- flap cdmhinations to furnis’h information applicable to t_he aerodynamic design of high-lift devices for improving the safety and the performance of airplanes.
.Two characteris- ‘“.
‘i tics of high-lift devices considered d~sira-ble are hi~h lift with variable drag for la~dipg and high lift with low
.2-””
___ drag for take-off and .i~itial clipb. Other d.esirahl-e *.– aerodynamic features are : no increase in drag ‘.rLththe flap neutral; small chan~e in pitching noment with flap deflection; low forces required ho aperate the flap; and frocdom from possible hazard iluo to icing.
As part of an investigation ~f a %.danced split flap, tcs”ts havo been made of .an KACA 2,3021 r.irfoil equipped with two arrangame~ts Of’:e 0.15c ch~r.d cxten- zi.ble flap. Zho r.mangcmcnts wars t-osted only in the complctoly extended condition.. One of tke extensible flaps has a slot and is t.ha complqtel~ extezidcd Towlcr flap; iho other arra~ge~ent kas nQ slot an? iS somewhat . .
similar to tihc now Zap typo of flap. , MODEL .—-- !!J!io lIas5.cairfoil was built t.o the NACA 23021 pro- .-.
filo aud has a chord of 3 feet and: a span of 7 fcot; tkc section ordi~ates are Aiven in rcf~rcace 1. !Thc 15- t perceat-chord flap used was :.
built to the Clerk Y profile.
The flap was attached to tthe airfoil by special hinges -permitting c widu variation in the: location and the de- ~ s~~- flection of the i’l.ap-” with respect to the airfoil.
tion ‘view of the airfoil with the slotted extensible f-lap is shown in figure 1. The nose ‘of the flap wa”s lo- .- ‘cated “1.5 percent” of the airfoil chord below the tirailing edge of the airfoil for all flap deflection’s, ?he airfoil with the plaia ext&nsible flap is shown im figure 2. For this ifistallation tho nose point of the f~ap was locat-ed from the conditions that it be below the trailia~ ,qdgo –. .—— of the airfoil and that the upper- ‘Surftice’ of “tho flap bo approximately tangeat to the extended upper surface of the airf-oil. “The airf-oil-flap junction was soalcd aad ‘ smoothly faired with modeling clay “on both upper and lowor surfaces. The flap deflections for: both arrangements wero measured with respect “to”the airfoil chord line.
The models w~rc’ mo”untvd in “the.closed tes”t section of tho NACA 7- by 10-i’oot wind tuniol .(roforencc- 2) so that they c“omplete.l~-sparin”ed the”je$ exce’pt-for $m.al~ clearances at each .“er.-di “Yhe “m:?,in airf%i”l “was rigidl~ NACA Technical Jfots Xo. 782 ,, attached to the balance frame hy torque tubes, which ex- v and tb.s lower, ‘ocundaries of t-he teaded through the upper tunnel. The’ angle of attack of the model was set from outside the tunr,el by rotati=g thn torque tubes with a calibrated drive. Sinco approximately twc-di~ensional flow 2s obtained with this type of installation, the sec- tion chr.ractcrt.sties of the uodel under test ccn 30 de- termined.
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All the tests ”were “na.de at a dynanic pressure of 16.37 pounds per square foot, which- corresponds to a ve- locity of about 80 nilcs per hour under stah~ard atmos- pheric conditions and to nz a~erage test Reyaolds n-anber Because of the wind-tunnel turbu- of a-bout 2,130,000.
lence, the effectivo Reynclds nuaber was approx~gately 3,500,000. For all tests, the Reynolds nmbe~ AS 3ascd on the chord of the airfoil with ihc flap retrc,cted and on a turbuleaca factor of 1.5 for the tnn=cl. Fcr each arraiigonent of wing and flc.p, tests were Gad3 through an angle-o f-attack range fron -6° to the stal”l.
--’1.
-~ Thc test results are gi~~ea in standard section non- . ,“ dine~sional coefficient fern corrocted. as e~laiaed “in=- refereaco 2S cl section lift C“OeffiCiCnt (1/qC) * section profile-drag coefficient (do/qc) ‘d.
section pitchir~g-norLcnt coefficient zbout tk.e C%.C.)O aorodycafii.c center of tlie plain airf-oil n(cl.c. o )
(
) qca where .- ..,” -.
1 Saction lift do section profile drag.
section pitching nonent %oc.)o .- -- dynanic pressure (>~rz) ~ c chord of basic airfoil with flap r“ctracted . .
—— and.
— . .
&Lr. glo of attack for iaficitc aspect ratio ao r . .
flap deflection with rcspoct -to airfoil chord 6f line —.
*O.1O ~o- “ -- - - - — *0.C02 —
c~(zbc. )o- - - -* G”003 af ‘;- - - - - - - ‘0”3”
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---- Flap_~fisftion - - - *0,002c c .1 - *0.00G3 .. ..
., ni.n i;.~ corrections have heon ap~lied to the data for the .(-- flap hinge fittings. Yhe relati~e reri.ts of &he vartius arrangements are probably inappreciably affected because .-- -.
the sane hinge-fittings were used thro-aghout the tests.
The results of the tests aro presented as aerodyna~ic section charzcteristtcs in figares3 to 6.
DISCUSSION:; I.t should be renculerod thnt the flaps were ‘tested only tn tho conplotely extend.ed condition. Extending tho flap for either flap ”arrangenont incroasod the wing chord, and, since the Ii.ft coefficients .a.r~ b~.sod on the wine chord with tho flap rctractod, the S1OFO of tho lift curve and the naxinun lift coefficient ware considerably incrcasod~ (S13C figs, 3 and 4.) A comparison of the slopes of tho lift curves given in flgurcs 3 and 4 shows that for flap deflections less than 25° tho slopes are greater for tho airfoil with the slotted extensible flap than for the air- foil with the plain extensible flap; probally because tho slotted extensible flap is unstalled for the low deflec= %ions. For deflections fireator t-ban 25°, tho slopes of the lift curves. are alout the same for both airfoil-flap arrangements, In general, thoro is less change in the q- =.
anglo of attack for maximum lift with changes in flap dG- . _ -. ._ flcc!tion for iho slotted oxtcnsible flap arrangornont than — for the plain extensible flap arran~cm~ut.
i— The plain exte~sible fla.~ must. he: ~eflected approxi- mately twice” as much as the slotted extensible flap to ASI shown in fig- give the same maximum lift. coefficient.
ure 5, this fact is true for only slotted extensible flap deflections less-than 25°, b-at,ei.ace almost the same max- ‘ imum lift coefficient is obtained for a.25° deflection of the slotted extensible flap As for a’. .60-0, deflection of the plain extensible flap,. there wo.tildbe n-o~nee.d to use higher slotted extensible fl~p iieflections:for take-off.
Increased drag may he desired, however, for landing and higher flap ”dcflections may be used for the landing con- dition.
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A compartsoa of the optimum arranger,ents of the two types of flap, from considerations of low profile drag at This fig- a giVen lift coefficient, ‘is made in .fi,gure 6.
ure shows that the kasic airfoil has the lowest profile drag for lift coefficients’ less than 0.8. For lift “coef- ficients between 0.8 and 1.4, the airfoil with the plain extensible flap 3eSlected.10Q has the lowest profile drag.
It should %s noted that the airfoil with tha plain exten- sible fla~ deflected 0° might have had somewhat lower profile-drag characteristics ‘if it had been poss’ible to fair the lower surface to a better profile.
For lift coefficients greater than 1.4, the e.irfo:l with the -slot- ted extensible flay has the lower profflG drtig, provided it is not deflecte~ more than 25°.
A comparison of tie pitchi~g-.momoat coefficients corresponding to the envelope pol.ars of figur”e 6 shows that the airfoil with the plain extensible fl~j has” lower pitching-momeat coefficients than the airf~il with the slotted extensible flaa.
It should be remembered, how- ever, that this comparison is made solely on tk.e 3asis of low profile drag for take-off and no account is taken of the added safety factor afforded by the 610tt-ed extensible flap, :vti-ich would be operating at a lo;fer percentage of -- the maximum l:ft coefficl.ent.
Th.o pitching-moment coefficients of the two arrange- ments may also be compared at such flap deflections that each arrangement has the same maxtmti lift coefficient,” and tharofore the take-off lift coefficient wil’1 be td same percentage of the mo,ximun lift coefficient for each wing-flap arrange:.lent.
in this case ~ho slottod extbn- sible flap has the- lower pitching-n~ne”ni c.o-officiontsc b Probab13- an even sore critical criterion for a comparison of pitching-noment coefficients is the land-~ng conditions r l .
6 NAC.A Technical Note No. 782 both f;lapswculd probably For this condition, however, be dcflec.tcd full downward and thb would havo “very nearly { equal pitching-moncnt coefficients. Other effects, such as stability and br.lcincb chcn&es ‘&uc to powor, the sp2n of the flaps, the ch~racteristics of ttio tail, rind, In general,, all of the other factors, connocted with the in- dividual design of each airplane, would haTo to be con- sidered in nc.king a vn.lid conp,arison of the pitching- aonont coefficients obtai’nod with different wing-flap coubiuations, , CO:{CLUDING REMARKS !lhc basic airfoil gavo -the lowest profilc~drag coof- ficieat~ o~~r the low lift =mge, t-he airfofl with t+e plain oxte:lsiblc flap gave the lowest profile-~rcg coof- ficio-dts over the moderate lift ra~ge, and. the airfoil . .
with t’hc slotted cxtcnsiblc fla”p g:avc tho lGwost profilo- “-” drag cocfficien.ts over tho high lift range. The airfoil with the slotted extensible f,lap had the sane nnxinua lift . .
&r!. t“z flap &cflectiaa of 25° ‘as “the’airfoil with tire ylain cxtc~sible flap had at a flap dcflcctic?n of 60°. Z’ho re- sults of conDarisons @f the airfoil pitching-nonon t coef- ficients obtained with tho two types of flap are dopondent .
upon the basis ckoson for c.onpnrison.
Langley Memorial Aeroqauti”cal &nboratory, ~;ational Advisory Cormittec for Acroaautics, Lailgle7 Field, Tn., Octo%~r 1, 1940.
-=.l — “.
RE.FM.XITCZS ~ 1. Wenziager, Cn.rl J. , and I+Io,rr”is, Thonns. A. : Wind- !R.znaclInvestigation of CUN.A.C.A. 23021 Airfoil with various Arrangonents of SLotted Flaps. ,Ilep.
No. 677, NACA, 1939. .
, 2. Wonzin~er, Carl J., and Harris, flhonas A.: Wind- !Mnnol Investigation of on IT..A;C.A. 23012 AirfGil with various Arrangcnonts cf..Slotted Ylaps.
Rep.
No l EACA, 1939. ~ 664, XACA TeohnloalSot. k. ?S2 rig8. 1,8.
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Figure l.- 8eotion of IAOA 23021 airfoil
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I 1~ m- Wl 1 I I I I I I I I I I f 1 i [ Q o .4 .0 1.2 1.6 a.o 2.4 8eotion Mft oqeffioient,ol rigura 3.- 8eotion aerodynamicoharaoteriatioe of the SAOA 23021 airfoil witha 0.150 slotted extensibleflap. (Olark--T motion).
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F@us. 6.- Compazisgm of the,, protlle~ oMrmtoxlat~08 d the *VO &pe8 Of fhp Om an XAOA 23021 aiffoil.