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NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS

WAlmm Rlwolu’r

ORIGINALY ISSUEDkMay 192 aaA&ance ConfidentialReport

HIGH-SPEED TESTS OF RADZAL-lUfJG311ENACELLES

(N A THICK LGW-DR&2 WTNG

By John V. Beoker

.

Langley Memorial Aeronautical Laboratory.Langley Field.,Pa.

WASHINGTON

lJACAWARTItvIEREPORTS arereprintsofpapersoriginallyissuedtoproviderapiddistributionofadvanceresearchresultstoanauthorizedgrouprequiringthemforthewareffort.Theywerep?e-vfouslyheldunderasecuritystatusbutarenowunclassified.Someofthesereportswerenottech-nicallyedited.Allhavebeenreproducedwithoutchangeinordertoexpeditegeneraldistribution:..,,,

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31176013542197

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NATIOIUL ADV 1S03Y CCqMKVIYl?l?tE3?OR AER031AU9?ICX3

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Cola’IIJEN!IU#L 3.w?03m

By John P. Becker

Zests vere nade in the S—f00% high-speed ~~inatunnelto determiae the dra$ cha~acteristics of several conven-tional. types of radial-engine nacelle “on a Iow-dyag air-foil. Nodels , 1/8 full sca~e, simullating ins% allat ionsof the Vright 3350 engin,e in heav~ bom%er types wereemployed..

The drag coefficients of nacelles incorporatingcowling-nose sha.~es shown IV previous tests to be effi-cient and after bodies of ade,qua~e leagth were of aboutthe same nagnitude as commonly obtained for coin~arablei~staXZations on conventional wings. Nacelles that hadhigh drag coefficients at low speeds suffe~ed from largeincreases in drag with increasing Mach number. For thebest arrangements tested~ however , no serious increasesoccurred in drag coefficient within the limit of thetests, which covered a range of liach numbers up to 0.55.

In the d.esi:n of recent multiengined airplanes therehas been considerable conjecture regarding the drag andinterference of radi~l-engine nacelles on low-drag typesof wing. Zittle (&x~~ ob~aineil ur.aer the ~ecessary 1OV- .

turbulence testing conditions have been available.

~ke present test program was an outgrovth of testsin the NACA 8-foot high-speed wind tunnel of a l/8—scalenode3. boaber-type airplane in which an uausually high.drag occurre~ wi%h the original nacelles on the Iov-dragwing. Tests of improved nacelles showed that the ex-cessive drag was due to a poorly shaped cowling and a

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,“very blunt afterbody shape rather than to serious adverseint erfer ence with the 1ov-drag wing.

‘I!hepresent investigation included tests of furthermodifications to the nacelle of the airp~ane %est,ed andtests of severai “other typical nacelles of varying size, :location, a~d shape detail. The p~incipal aim was toprovide general information of immediate engineeringinterest on several types of nacelle rather than to studyin detail any isolated variables. The models tested were2/8-scale representations of inst-allations of the Wright “3350 engine in heavy bom%ers. A,pusher arrangement wasi)2ClU~Ledin the program. I!his type has the advantageof eliminating the increase in frictional drag of thewing due to the slipstream disturbance. Details of thepusher installation of the Wright 3350 engine were designedin cooperation with the IIACA pover-pl.ant installation grbup.

in addition to the usual force data, pressure-distribution data were obtained. a% the wing-naceile ju.nc-t-~~e of each mo~e~. ZG order to provide data frequentlyrequested for structural design, the pressure distribution.

. over the NAG.4 cowZing-C! profile (reference 1) of one ofthe models vas mer.su~c~ at high angles of attack.

The work was done by the NACA at the Langley MemorialAeronautical Laboratory,-Langley Tield, Va. - -

S3W301S

v free-stream velocity

P mass density of air in interna3. flow

Po free—stream

~ free—s+ream.

Q’ volune rate

&ensity

dynamic pressure (1/2 pow)

of flow through duct at density

z’ maximum cross-sectional area 02 nacelle

.

P

3

maximun cross-sectional area of engine (18.4sq ft for Vright 3350 engine)

velocity of souaa in air “

Mach number, v/a

pr es s7m e

pressure co-efficient ‘Plocal ‘/’- P~tr~~} ~

angle of attack of wing ,

external drag coefficient* of nacelle[(total drag of cou%ina%ion) - (drag of wing a%

.iZ’www -“ .,,

The $ests wei-e conducted. in.the 8–f oot high-speedtunnels in which the t-irlnalence level is considered tobe sufficiently low %0 permit significant results to be.obtained with models incorporating I?w-drag airfoils.

v2zLge- !Zhe wing on w~.ich’the na.cel.les were installedwas a 2~8-scale model .of & ~iing of NACA. low-drag sectiondesigned. for the airplane tested.. Z?he ~or%ion. of thewing reyresenteii inclut~ed.most of the left -panel and a,-small length of the right panel. Wlnen %otli inbbara andov.tboaad nacelles were represent ed, the nacelles we~eequi~is%aat from ‘the ‘center line of the tunnel- Theairfoil sect i-on “employed at the root was the ltACA65$2-223 and at the tip, the IYACA 66,2X-416. !i%e in-board nacelle was located 21,004 inches fron the root ata station where the ‘vifig chord ‘was 20.63 imches and thethickness ratio was 20.-’?‘percent. The outboard nacellevas situated. 45.96 tnches’ from the rQoi at a staticnvhere the ving chord. I?as 15.65 inches and the thicknessratio tras 19.9 p’erce:.t.

‘oThe ~;ing was set at 3 angle of inciii.ence to thethrust lines .of all of the nacelzes eycept the pushertype (nacelLe 5) , for ‘which the angle was 2°. Anglesof attack shown in- this repo?% are those of the wing.

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.Cooling-air flOy. – All the nacelles were tested with

internal air S1OW corresponding to the estimated requime-men%s of the Vright 3350 engine, and the internal pres-sure drops were simulated as closely as possible hy meansof perforated ~lates. !l?hevaZues assumed for the flowcharacteristics were as follows for full-throttle opera-tion at 400 miles ner hour and at 25,000 feet altitude:

(cu ft/min)

Engine cylinder cooling . . . . . . . . . . . 35,000

Accessory cooling ant! charg4”air . . . . . . 35,000

Total ‘70,000G

The value assumed for the pressure drop was 8 inches ofwater for the engine ba~fle anti also. for the accessorysystems ● I%e nondi~ensional pressure-drop ratio was,t?aerefoze, .

43 8 x 5.2—= .= 0.23q ~/2 x 0.00238 x ().448 (LLOO x 10~7)2

The perforated resistance plates vere designed to .“,pzoduce this pressure-d?op ratio at the required rate ofinteznal flow. .Z%e in>ernal mas s--flow rate is conven-iently expressed nondinens ionally as the ratio pQ/poAe~.7Jor t~e assuned flbw condition, the value of pQ/poAeVis 0.11. !I%e outlet openings were designed to producethis flo~; ratio, and it will be noted that the measured

.rates of flow closely approach the design tialue except,of course, in those runs in whit’h the outlet+ o~eningayea was ?educea.

Original nacelle desiEn.- I%e original nacelle

‘tested was a l/8—scale modeZ of a 7’2-inch-d5.amekercircular—section instiailation @ which ‘the engine t~aslocated .in the u~~~r -part of the naceile and the acces-sory air was carxiea underneath and. around the sides ofthe eag~ne. Z%e nacelle was desi~ned by a manufacturerand was subnit%e& to the NACA for tests in the 8-foothigh-speed wind tunnel. ~he co~~ling prOfil.e was Vn—symmetrical in si~e viev with a relatively sharp edgeat the top of the cowling. The blunt afterbbdy fairingwas the result of enclosing two 56-inch wheels in a lownacelle terminating at the trai~ing edge of the wing.

The model was tested with internal flow representingonly cylinder cooling.

The nacelle ordinates measured as in figure 1 aregiven in table 1. Sketches of each nacelJ,e are inclu@edin table II.

Nacelle 1.- 2Tace7_e 1 has the sane depth at each

afterbody station as the original design. A Much im-pvove@ after%od-y fairing was o%tained by making thenacelle symmetrical about its center line. The nacellewas also raised. above the original low position so that

‘ its center line passea %hrou@} the traillng edge of theYJi~~. The original cowLing nose was supplanted by covl-ing p~*ofile C of reference 1. In other respects nacelle1 was similar to the o~iginal design.

Nacelle lA.-. —— in order to compare the mei+its of thecentral position bf nacelle 2.with a IOV ~osition of ef-ficient aerodynamic shape, the origina3 low afterbody wasex.ten~ed, as shown in figure 1 and in tables Z and 11.lTacelle 1A was otherwise identical with nacelle 1.

lTacelle 2 - Eacelle 2 YJaS included to indicate the....— ●

effects of an improved nose shape. The conventional C-type couling of nacelles, l apd. 1A was replaced by anarrangement designated N.AGA cowliug E. !I?hisarrangementembodies a hollow-spinner through which all the requiredair is admitted at a velocity of about 0.4?J for the high-speed condition. The external lines of the spinner areobtained from nose B of reference 2.. The air for theauxiliai>ies was carried. by means of two ducts over andunder the resistance plate representing the engine.After passing through a resistance simulating the acces-sory pressure drops, the air was exhausted through anoutlet at the top of the nacelle. !l?heengine coolingair was e.xhaus%ed at either side of the nacelle. Theau.xili=ry air ducts r,eqnired a bump in the side-view can-

tour on top and bottom of the nacelle. In plan vievthenacelle contour was a continuation of the nose B contour(reference 2) of the spinner. I%e afierbod.y of nacelle2 was identical with ~hat of nace~le 3. except for thead?.ition of the auxiliary air outlet. The outlet open-ings of nacelle 2 “and all subs.equent moaels were under-cut bel OVJ the basic profile of the nacelle for some dis-tance back of the actual ,opening, as recommefidetl inreference 20 Details of a typical oVtlet are given in

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figure 2. As originally planned, the propeller bladeshanks within the outer syinner of cowling E in an actualinstallation were to be covered b“y fairings extendinghetveen the o-ater spinner and an inner spinner thatcovered the h~b. Yhe faii-ings wer e int endea to aid inground and climb cooling and to operate at zero lift inthe high-speed con,di%ion. On the model, this high-speedcond.ition was sirnul.q~ed by .sett ing the three-blade fair-ings with their axes ~aaallel to the thrust line, sincethe model spinner di$ not rotate. (See fig. 3.)

Nacelle 2A.- !Yhe opening on top of nacelle 2 wasfaired over for model 2A in order to indicate the effectof the opening. ‘

lTacelle 2B.- Nac .1le 2B was tested to permit evalua-tion =the improved Dose shape on a low nacelle. Thenacelle is a combination of the ,pacelle lA afterbody and.the nacelle 2A forebody.

Nacelle 2C*– ~jacelle 2C ~ras the s-e as nace13.e 2B

except, for en2axge@ (dee~ened) outlet openings. (Seefig. 3.)

~acelle 3.– The large size of the nacelles thus fardescrf.be~ (’72 in.~iameter, f-all sca~e) was necessary to .

permit enclosure of the landing gear. Nacelles 3 to 5and their modifications are types in whi.ck the maximumcross-sectional dimensions were made as small as possiblefrom considerations of only the engine size and the . ..~noling-.air requirements.

IiaceZle 3 was elliptical in cross section. Thedepth, 60 inches full s>ale, was I.imited.by the engine ,.

diameter-, and tb.e width, 7’2 inches, was chosen in orderto allow enouSh space

.on either side of the engine for

supplying air to the accessories. The O-cowling contourof reference 1, deriyed for a 4.50-inch radiusa was main-tained around. the nose. 9he maximum cross section was atrue ellipse as were the afterbody sections. The lineof symmetry of the nacelle passed through the trailingedge of the wing. Eour outlets were provided, one oneither sise for the en?ine cooling air and one each onthe top and on the bet. om for the accessory air.

~jace~~e 3&- The bottom outlet of nacelle 3 wasfaired over to form nacelle 3A.

7

Nacelle Li21.- In order to evaluate the effect of

shortening the a.fterbody, nacelle 33 was designed with ‘the afterbody terminating at the 50-percent-chord stationof the wing. It was otherwise identical with ~acelle 3A.

Nacelles 3C au?. fi-+.-Nacelles 30 afid 3D were identi-——— “.._cal with nacelle 3 e:~cept that the side outlets were ‘ .closed an@ faired over.on nacelle 3C and the top and

bottom outlets were closed and faired over oq nacelle 3D.

Nacelle 4i-.—. Nacelle 4 represents about the minimum

size (60 inti diameter, full scale) that vill house theVright 3550 engine. NO provision was made for accessoryair on the model. Xi*her scoops or wing inlets would benecessary. The C-cowling contour (reference 1) was de-rived for the maximum radius of the nacelle. in sideview the after%ody contoui is identical with that of na-celle 3B. Yhe ““cross sectioas were c.ircttlar throughout,

~~~ce~le 5 - ~Tace~le 5,-—— ●the pusher type (figs. 1 and

4, wad tables i and 11), vas iLesigne@ around the install~tion shown in figure 5. All the required. internal airflow was admittea at the nose of the nacelle at ag inletvelocity of about 0.4V. The external. nose profile, wasthat of nose B of reference 2 car~ied back as far as theleading edge of ~he wing. .~he l,eading edge ‘f the na-celle was extended ah’eaa of the wing by about 13 percentof the chord in order to prevent interference effects dueto the low pressures on the forward part of the wing athigh aflgles of attack. 17he vertical position of the na-celle vas adjusted to allow e~u.al duct space above andbelow the wing for the engine cooling air. Z!he ducts(fig. 5) leading to the oil coolers, intercoolers, andsuperchargers were si: ~.~a~ed on the mod-cl by means” of asingle duct ia each wing term~na”ting in & outlet opening “on either side of %Le nacelle (fig. 4(_b)). Yhe rightopeniug vas ylaced close to the nacelle in order to permita comp,a~”isop of the interference effects at that locationwith the effects at the location of the left outlet fur- “. “ther outboard. The interaal f~ovi ve;s divided approxi-mately as follows% 50 perceat th%ough -the nacelle an~. .

25 percent through each ving duct. . “

~elle !5A.- ~?acel~e 5A ~ra~ the s~e a~. nacelle 5 ., .

except that the right outlet was closed. ,..’

l~acelle 5B.- The fillet sketch-ed ia figure 1 was—.. —added to nacelle 5A to nake nacelle 5B.

...-------- -.. ----

8

lTaceZle 5C. — Nacelle 5C was the same as nacelle 5-—except” that” the Zeft outlet was closed.

Outboard nacelZ&.- I?he outboard nacelle was the——man~facturer$s d.e.signfoz the airplane. It wa$ similarto the original inboard nacelle previously described ex-cept that the C-cowling contour was employed.

Pressure measurements.– Fressure-distribution datawere obtained on the cowling-C profile of nacelle 3 bymeans of flush orifices on the top and the side of thecowling. Pressures in the,wing juncture of each nacellewere measured ‘iy small po~tabie static tnibes. The tubeswere’’alined parallel to the flow direction as indicatedby tufts* The rate of internal flow.and the internal 1“pressure drops were measured, by surveys at several stationsin each outlet. opening$ taken with rakes of total-pressure’and static—pressure tu”Des.

ti~ce tests.–– qhe lift and drag c~haracteristics of

the wing alone and ia combination with each of the na-celles were measured for -the following conditions:

(1’)From a = –1° to 8° at 11 = 0.26

(2) From ~1.= 0.17 to 0.55 at b = 0° and 2°..

(c~ x 0.13 and 0.38)

Tests of..-&hoaid nacelle 1A were also na&e in the presenceof the outboard nacelle for the listeti conditions.

Pressure measurement s.- 2?ressure data at the wing-

nacelle junctures Tiere obtained for all configurations atN = 0.33 for amgles of attack of -1°, 2°$ and 6°. Pr es-sure &istrilmtions over cowling C of nacelle 3 wel*e ob-taine~ through an angle-of-at tac;k range of -1° to 16° atii = 0.26, a=d fron -1° to 3° for M = 0.17 to 0.55. Sur-

veys oi’ static and total pressure were made in each outletopening in order to determine the internal flow quantity,the pressure drop, ana the internal drag.

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9

Drag of the wing.- A specia3. effort vas radie througL=—.—out the tests to keep the wing surface ideally smooth andfai?. The drag of the wing alone was measured five timesduring the tests sad, was fouiit!to deviate from the origindl.values by not more than l+ percent (about 4 perceiit of av--erage nacelle drag incitement) . .

RESi3iI!i?S

Reduction. of data.- !i!hedrag increments due to the-—— .nacelles are given ill the form of coefficients based. onthe nacelle front+ai area. The calculated drag correspond-ing to the mone~tun loss of the internal flow has beendeducted from the total drag increnent, and the remainingex%e’rnal drag increue~s is presented in this report.Through the use of ih:s paraneter the effect of changes inexternal shape, ~~ith ~~hich this investigation iS IIlailllyconcerne&, .CC.Qbe studied directly. Drag-coefficientchaages associated with the internal flow are accowated for.‘I?hevalues of the internal--drag increments calculated from”,tho measu:red. internal-flow characteristics 3Y the methodof refere~ce 2’are sh-own in table 111 tor each nacelle.If it is desired to oltain the total nacelle drag+coefficientincrement , the values given in this table may be added tothe external-drag values shown ia the subsequent figures of

The total dra~-coefficient increment is ofthis re~orto .interest onZ~- at the design speed, because loi~er speedsvould require larger exit openings and highez internal @rag.

.Tests with fixed transition on the vin g.– In previous—.tests of nacelles on conventional vings$ it has been founddesirable to fix the trans~ti.on point near the leaaingedge of the wing in order to ~ake the boundary-layer con—d.itions coiarespond to t’hosa of i~ight. Eor the low-dragt-y-peof’ ?7illa$however, the full-scale flight transitionlocation is noii definitely known an~ therefore cannot ‘oesimulated. in model tests. In addition, ii has been foun~that the metk~ds used. to fix the transition location 3ringabout a type of transition consiilera%ly different frou the%ype that occurs natu:-ally on a smooth low-drag ving. Af’w runs weve made during the present investigation withthe transition fixed. on both the upper and the lowe”r sur-faces of t;~e wing at the 15-pe~cen+ci~ord- station in orderto detei’mine the r.ace:.”.edrag for this extreme of the‘iiou-ndary-layer con.ditior.. It was .fou:a&that the nacelle

.- . . -.

10

drag was of the order of half the value obtained. on thesmooth wing. Because the fixed transition data w&?e ofdOu~~fu~ sigai~ica~ce. sad. ~a~icated very low nacelledrags, no further fi~ed-transition tests were made. Al 1the data presented in this report were obtained with thesmooth wing.

. .

Yorce-test data.— The external drag coefficients of

the nacelles$ gro-a>e& acccrdi~g to type, are shorn infi.g.zres6 to 9 as functions of M and a. The small in-.e~ference drag between~

the inboard aiid the outboard na-celles is shown in fig-ire ZOe A comparison of the drag

7 of each type is made in figure 11.of nacell-es t:~pica-Tahle Ii affords a comparison of all. the naceiles. Inaddi%i,on to the dra,~ c efficient , the drag in yotin?.sat253000 feet altitude .j;adat K = 0.50 .is tabulated toshow the over-all. drag changes including the effect ofchanges iti the nacelle frontal area. Favorable interfer-ence effects associated with the outlet flow are shown infigur es 12 an& 13. Figi~re 14 sho~~s the lift coefficientsof the king-nacel~e combinations.

Pressure daia.- The pressure d.is;ributions over cowl- “

ing C (nacelle 3) are presented in f“igures 15 and 16.t~he~e ~.aia are given in considerable detailas regards angle-of—attack range,

s particularlybecause a number of re–

quests have been received for aata applicable to structuraldesign at high angles of attack. , .“

Pressure d.istri.in.ziions a% the juncture of the winganit nacelle 3 are shown in figure 1’7. Thes& results were .typical of the juncture pressu?es obtained with the othernacelles.

NAC3LLE ‘DRAG

Qe~tical location.- In a series of preliminary tests

not described in tk.is report, it was found that shout tvo-thirds of the large drag reduction that occurred when theaanufacturerts original naceile was replaced ‘by the cen-trally located nacelle 1 (table 11 ana fig. 6) was theresult of raising the nacelle to the central. position.Yhe resi of tk.e reduction in drag occurred through the useof cowling Co A separated flow condition that existed.over the original afterboay did not occu:r with nacelle 1

becavse of the greatly inprcwed afterbody shape madepossible by the central location. The same result wasobtained by Ieugtheni-ng the after’bod.y of the originallow nace~le. ~(~i ;afelles 1 ana 1A, 2A anti 2B of table11 EI.13C~fi~ss The uacelle in the IOW positionvith the exteufi.eaaf{erbody gave lower drags than the na-celle in the central ~osition for angles of atiack greaterthan 5° (figs. 6(c) ana 17(c)). It thus appears that thecentral location offers no advantage except in the caseswheye a large nacelle m-ast be terminated near the t~ail-ing cage.

&fiend.ed o.fterhod~:.- The adverse pressure gradient

over a nacelle af%erb’ .y is superimposed. on the adversegi’adiezlt of the vins if the nacelle is terminated. at ornear the trailing e?.ge of the wing. - l?he resulting pres-sure gradient will tie‘more severe than for either wing ornacelle al.o-neand seyara%~on effects will be encouraged.This result is Particularly true of lov~-iiragwing sectionsthat comaonly have steeper ativerse gradients than con-ventiona~ sections ana is one of the reasons that nacelledrags on low--drag wings teztl to be greater than on con-ventional wings. The difficulty can be circumvente~ byextendi~g the nacelle a.fterl?otiysa procedure which notonly moves the adverse gra~ient on the nacelle ava~ fromthat of the wing but vhich also red-uces the magnitude of ‘the gra.3ient on the nacelle. The ‘beneficial effect inthe case of nacelles 1A and. 23 was very large~ as previ–Ously shown, because of the critically poor shape of theoriginal nacelleb In this instance a.nacelle extensionof only 15 percent of the wing chord was sufficient toprevent serious separation. The amount by which the na-,cel.lc should be extendea is a function of a large numberof variables; tests to aeterrnine the optimum length inindividual cases will probably be required.

&l~* shs@&.- The reduction of the drag of theoriginal nacelle by one-third through the use of covling-profile C (reference 2) was due “to elimination of localseparation of the flow oveqt,,thetop of the original bluntprofile. A comparison of cowling C with the high-speetlcovling 3 shoved that ;he mininum drags at moderate speedswere about the sine. (Cf. nacelle i with 2A. or nacelle1A with 213, table 11. ) At Biach numbers beyond 0.62, how-evers the drag with cowling C has been found to increaseprecipitously (reference 1) owing to the compressibilityburble; whereas the drag of coviing E remains low up toMach numbers of the order of 0.70. to 0.30, &epending -on

. . .. —-. . . ..- .-. .. .. . ..-

.,

. . . . .: .,,. .:;.,.. . ..-. ,.-,.~.__*.: 2X.,. A2 ..>... AA.--L-----..... ...-. --,— —,——- ,-------—.-

.,

12

~~e magnitude of ~~e pro~uber~nces due tO the accessory

air ducts around the engine. in the absence of the pro-tuberances, no pressure peak occurs on the E--cowling~rofile (reference 2).

~he drag ~~ith covr~~n~E was consid~ral)iy leSS than

with cowling C at. the &.igher angles of attack. (cf.nacelles 1 and 3A with. 2 and 2A in figs. 6(c) and 7( c).) .The entrance and duct losses with cowling E were foundto be r-egligible throughout the entire range of angles ofattack$ indicating that higher front pressures would %eavailable with cowling E than with cowling C, for whichthe entrance losses are appreciable at the higher angles.Unfortnnat ely, this result cannot be translated ,direct;ly ‘into flight ~erfOrmance because the effect of the propel=wShank fe,irings with a rotating propeller is not included.The entrance and duct losses in the pusher arrangementwere likewise fo-tind-to be negligitile throughout the angle-of-aitaek range. This design also employed the cowlingE profile at the entra~ce.

~a.c.elle s5.ze.– Nacelles smaller than ‘?2 inches in.—...—diameter are feasible vheze provision for lzr~o wheelsis rLot requi:cecl; for ex~-a~le, in flying ??oavs cr in theoutboard nac~lles of four- engine ie.lld~l%~.z~s-. Large dragrediictioas can be made -oartly as a result cf the reducedcross-sectional and we:,ed areas and partly through thereduced interference dvag of the smaller nacelles. The’72– by 6C–inch elliptical nacelle has 83 percent of thefrontal area of the V2-inch-diameter model but only 54percent of the drag. (See nacelle 3 of table 11. The .d-rag coefficients shown in table II and in fig, 8, beingbased on frontal area, show only the changes d-ue to varia-tions in interference effects; hence, a column is incltidedin table 11 showing the drag of each na”celle in pounds “fora typical operating condition. ) The reduced interferenceeffects probably result from the fact that a larger pro-portion 01 t3-e vetted area of the smaller nacelle iscovered by the wing. !l!heimproved after body fairing an~increased fineness ratzo are probably also %eneficial. Anafterbody extending only to the 50—percent-chord stationof the ving resulted in a%out the same drag as the longerafter body. (Cf. nacelles 3A and 33, fig. 8, and table II. )

. .Ihzrther decrease in the nacelle dimensions to 60

inches diameter, the ninimmi size that will enclose theVright 3350 engine, permitted still further reductions in,the nacelle drag (nacelle 4, fig. 8, and table XI), l?his

13

,1 model had no Fro-?ision for the introduction of a~Lxiliaryair, however$ and it is not likely that any net saving

T-” over nacelle3--wou-ld occur ?.f scoops were added or if any,$inlets were employed.

?1.) ?%sher nacelle.- With the pusher-nacelle-arrangement3 —A.——;/: it was possible to a< .-it all the required air through an

/’ efficient inlet opening at ~he nose o? the nace2.le (cowlingpE profile, nose B of reference 2) and? at the same time,Iemploy the mi,nii~lvnpossible diameter of 60 inches. sUf fi-cient space was available for efficient ducts fjo the in-tercoolers and turbosuperchargers carried in the wing oneither side of the nacelle (fig. 5). This naceIle had thelowest drag of any model tested. (See nacelle 5, fig. 9,and table IX.) T?he drag at M = 0.50, for the flow condi-tion corresponding to 25~000 feet altitude, was 33 percentof the drag of na,celle 1 aitd 61 percent of the drag of theelli~tical nace?.le 3, As previously mentioned, the pusherarrangement would not suffer as would the tractor typefrom increases in wing drag due to disturbance of laminarflow on the wing hy the slipstream.

Interference betveen inboard and outboard nacelles.-——..—-..— ____________ —— ——-._..___In the minimum drag condition the interference was neg2i-~il)le (fig. 10(a)). At hi~h angles of attack a favorableinterference effect occurred (fig. 1O(C)), probably as aresult of reduction of the separated flow over the bluntafterbocly of tile outbop.rd nacelle.

Conip~~isoa with conventional w=.- Drag results.— — .—previously obtained for nacelle iA on a wing of mere con–ventional section are unfortunately not directly comparab-le with the present results: first, I)ecause the thicknessof the conventional w!ng was greater (22.7’-percent-thicksection) and, seco,nd, because the data with the conven–,tional wing were measured in the presence of a large fuse-lage. Z%Le results of reference 3, although not strictlycomparable with the results presented herein %ecause awing of l&percent thickness ratio was employed, permita comparison, of good conventional nacelles at identicalvalues of the ratio of’ nacelle diameter to wing thickness.The following table compares the minimum external dragcoefficients of these- tests with those obtained in refer-ence 3 at a~proximately the same Reynolds number. It iSpointed out that the comparison tends to be unfavorableto the low-ira~wing data in that the liach number was 0.30a.nclthe lift coefficient .0.4 in the present tests as com-pared with a llach nuaber of 0.08 and a lift coefficient ofO in the full-~cale-tunnsl tests.

14

1“i —–-—— -

Nacelle diametel”— ———. — iWing thickness lTacelle on

conventional wing———.—...—-..——.——— t--- --———----

2.10 G.055

2.10

2.10

● 055

.055

1.75 I

I.050

1.’75 .05G

1.75 !.o~o

I

I——— ..——.-—— ... ..-—————— ——..

J!

——.

Nacelle onlow-drag wing

0.067

.070

.058

.049

.043

.04.1

—-——.

-—.

Nacelle.—— ——

1

2-A

2

z

4

5

——-.——

!Ph.is comparison shows that , in slpite of the factorstending to increase the nacelle drag on a low-drag wing(disturbance of the laminar flow on the wing by the na-celle a.nilincreased separation tendencies), the drag ofsuitable nacelles is 1:-otgreatly different from the dragof, similar nacelles on a conventional wing.

Effect of an operating propeller.- The %rag coeffi———-----.—-——-. -— —-. .-— .———..cients. of the tractor nacelles On the ~o~’~drag wing wovldbe somewhat increased if an operating propeller were pres-ent ‘oecause the propeller vould create a disturbance of -the laminar flOT~JOn the ~rin~. AU estimate of this effectfor the original nacelle on the 20.7-percent–thick wingcan be made on the assumption that the boundary-layer flowchanges from the laninar to the turbulent type over 40 per-cent of tile airfoil surface as a result of the propelleraction, The dimensions used and the calculation are asfollows:

Propeller &iaQeter, feet . . . . . . . . . . . . 16+

‘Nacelle diameter, feet . . . . . . . . . . . . . “6

Wingchord, feet . . . . . . . . . . . . . . . . ~~:

.

Increase in section drag coefficient of wing due “to Fropel.ler action,” Ace . . . . .. . . . . .0020

ftJcDF=(0.0G20)(wing area exposed to sli~stream)..——.—.- —.—.

nacelle cross-sectional area

;(’-’)(q ,“0.002 ~=.— . -.

28.2

= ().010

This value represents shout 12 yercent of the drag of the~~-il-,Ch-~Liameter nacelles and about 21 percent of the dragof the 60- hy 72-inch nacelle.

Variation vith if,acQ_~t:mbero - Figure 11 shows that the ‘-—.-—..-+...,-.drag of the original nacel~, e increased very rapidly withMach number, p:cohab].y becaxse the flow separation becomesmore inteuse as the speed increases. If the nacelle dragcoefficient is high at lov~ speefis, a much higher value~Lay be expected at high syeeds. If the chag is small at :low ‘speeds, ho~t~ever$ int!ice.ting satisfactory flow condi-tions, no serious iilcreases with speed occur until thecritical compressibility speed is reached. It will benoted in figure il that the maximum test Mach number,0.55, was considerably lover than the critical Ma,ch numberof any of the nacelles (cowling C, critical i.i= 0.62).

.li&neficial effec&& of air outlet .- The outlet open-ings on nacelles 2 to 5 wei-e “designed in accordance withthe suggestion of reference 2 that the outlet flow shouldcause ‘a minimum of disturbance to the static pressuresover the bzsic boCy, which, condition requires that the out-let ~rofile be cut below the basic body profile for somedistance ‘lack of the actual o~ening (fig. ‘2). It was fdundin s~veral cases that the drag wa,s less when tile outlets :were open than’ when f ?..iredover. The “to~~outlet of nacelle2 had a large favor a?~le effect (see fig. 12), apparentlythe result of decreasing a local separation on the upperwin-nacelle juncture. The top and bottom outlets of na-CeZle 3 had a similar effect, but the side outlets, locatedin the positive pressure field of the ‘wing,”added somewhatto the drag; {Cf. “figs. 8 and i~. ) Alternate fairingover of the wing o’utletsof nacelle,’5 (fig. 12) showed that

16u

..

both had a favorable effect. The left outlet was more ef-fective than the right, which was located in the wing-nacelle juncture (fig. 4(b)).

EFFECT OF NACELLES ON LIFT

At a given a,ngle of attack, all the nacelles testeddecreased the lift when added to the ~Jing. None changedthe slope of the lift curve (fig’. 14). The low naceiles1A, 23, ancl 2C caused tb.e largest lift decreases. Inorder to aaintaia the required flet lift coefficient, itwould “oe necessary to increase the angle of attack of thewing, a yrocedm-e that would result in increased wing drag%ecause of operation of the wiag at higher than its designlift coefficient In the clesign of the wing, therefore,the design lift coefficient should be determined from aconsideration of the effects of nacel?.es and fuselage aswell as of the wing loadin~.

YEXSSURES AT VIXG-?XACIZLLE .7UNCI!UR3

Tlte results shovn in figu~e 1’7 are typical of allthe nacelles tested. It will he noticed that the after-l)ocliesof the so–called centrally located nacelles werelarger on the uader side of the wing than on the upperside because of the camber and the 3° angle of incidenceof the wins. The pressures on the lower surface were thusdisturbed to a greater extent tha,n on the upper surface.As shown iil figure 1’7, the local pressures became morenegative on the lower surf?ce at tlhe wing-nacelle juncturethan on the wing alone, ~r~hereasthe upper-surface pressuresbecame more positive. The contractiilg lines of the upper-surface junctures and the decreased circulation in thevicinity of the nacelle are probably jointly responsiblefor the reduced negative ;Oressure peaks on the upper sur-face. This result is desirable because on a lifting wingthe negative pressure peak on the up:~er surface determinesthe critical liach number, and this peak should not be aug-mented by the presence of the nacelle. The pressure peakon the lower surface, even though increased by the nacelle,is not liliely to exce d the upljer-surfa,ce peak. (See fig. ~17,) Cn tile basis of these results, it is evident thatnone of the nacelle installations tested would reduce thecritical syeed he10’;J that of t~.e wing.

1?

:!

1!,!

l==- ..Although no attempt was made, to do so in the presentttists$ it appears possi%le to dt3sign a wine-n acell.e junc-ture that t?ill not augment either the upper- or the Iolrer..

surface peaks.

1. !l?heminimum drags of conventional uacelles ofvarious types ant!.,sizes installed on a 20.7-percent-thicklow-clrag wing were of the same ortier of magnitude as theminijilu.mnacelle drags obtained in a previous investigationemplo$ing an 18-pe.rcent —thi ck con.vent: onal wing-

2. The esti.i7.ated effect of the disturb e.nce of the .lminar boundary layer on the w:.n.g by the slipstream of atractor propeller is to iilcrease the nacelle drag fro~ 12to 22 percent, depending on the l~acelle size.

z. The drag coefficients of nacelles that were un-sat isf actoi”y at low syeeds inci-eased very ra,pidiy with in-creasing Mach n-~mber. For the lest arrangements tested,however , nO Sericus i~cr eases occurred within the limitof the tests, for which the hii~liestMach number was 0.55.

A. Decreases in nacelle size resulted in large dragX’educ.’;;oilsboth thro_cLflhtll”ereduced frontal area andthrongh decreased interference effects.

5. A 60-inch-diameter pusher arrangement w~th pro-visions for handling all the air requirements of theWright 3350 engine , hut with no provision for housing alanding gear ~ had the lowest drag coefficient oX’any na-celle tested.

6. The miilimum drags obtained with NACA cowlings Cand 3, as tested with the syinner stationary, were aboutequal at Mach numbers below 0.55. At higher angles of .,attack, cowling i? had less drag and higher pressuresavail a%le for cooling than cowling C.

‘7. I?acelles in the low yosition with the top of thenacelle flush with upper surface of wing had about thesame drag as nacelles y;hose center lines passed throughthe trailing edge of wing, provided thet the low after-body was extended far enough beyond the trailing edge toprevent flow separation.

18

8. Low nacelles appearedcentrs3 nacelles in designing

to present less of a pro’blemthanfor a high critical Mach number

at’the wing-nacelle juncture lecause only the relatively lowlocal velocities on the under surface of the wing were augmentedbythe afterbody. With either the low or the central location itappears that the critical !fi.chnumber at the Juncture can be made toexceed that of the wing alone by proper shaping of the nacelleafterbody.

9. The effect of air outlet through efficient openingsresulted in reduced external drag in several cases. Thiseffect was large enough:”towarrant.further investigation. Ns,cal!la-development programs should include tests to d.etertinethe mosteffective outlet location.

Lan@ey Memorial Aeronautical LaboratoryNational Advisory Committee for Aeronautics

Langley Field, Va.

1. Robinson, Russell G., and Becker, John V.: Hi@-Speed Tests ofConventional Radial-Engine Cowlings. NACARoI). ~0. 745, 1942.

2. Becker, JohnV.: Wind-Tunnel Tasts of Air Inlet and OutletO~enings on a Streamline Body. NACA ACR, Nov. 1940.

3. Wilson, Her?)ertA., Jr., a.ndLehr, Robert R.: Drag andlko-pulsive Characterist~.csof Air-Cooled Engine-Nacelle Instal-lations for Two-En@ne Air@anes. NACA ACRJ Dec. 1940.

I Manufactworta orlglnalnacelle

r.___—.—x l%XYL

II-I

—-. — .. .-— -—

0 3.650 0 3.065.011 7.676 .02& 3.125.03..066.Ml.289.4%.587.m+.8031.1051.4751.8452.2162.6396.5506.550

I7.0508.25012.060I

---.u6 3.273.240 3.405.M?93.590.7363.731.~o 3*8411.2333.9401.M1 &.&3

--- ,—4.361i+.lga4.lb75L.500&.5oo4.120Il.3?0

2.1.- –,.3.7114.4216.5506.5507.050

i.4511+.5cQ4.5001+.120b.330.-.

IIri.~o ~;gi:;% 12.C60

17.220ll:270

.—-X Ye

—-

0 3.36.0183.365.o&5j.45~.W3 5..523.1935.631.3945.185.59L3.834.79L 3.984.9% k.Q6J~1.195 4.1331.h95&.21b1.9984.3312.108L.&o2.9901,.4803.570L5Q06.5504.5006.5501$.12Q7.050L.3308.250L.50Q12.043 1+.5oo17.220 4.42022.0604.01027.0602.2703Q.620o

TA8U 1.- 00J1ttiWd

2ACELLE 02DINAT2S Ill Illmt2 - Oolltinl=d

.

NAc2ug 1 EAOKLBIA

x(radLu3) ‘ (rd:a,) ‘ % ‘= ‘=

3.15 0 3.15 12.c64048Id&lL.@0.043 3@ .243 3*4I 16.b54A8 I@ I@.086 3.48 .086 3A8 21.95----3*733.73.173 .173 3*59 27.95---.346

2.302.30% .346 3*75 30.541.lF91.50l.~

.519 3.88

.@.519 3.88 31.501.281,111:%

3.97.W L.07

3.97 32.471000:% Ib*07

1.039 h.11$33.06 .n :r7 .33

l.o~ 4.14 33.660 0 01.210 k.21 1.210 lh211.383 1+.27 1.383 Jb271.73 4.37 1.73 4.372.08 4.44 ;.g 4.442042 4.48 M@2.77 4.50 ;:g6.55 l@6.55

t% ‘6:55

7.05 4:33 7*O5 k%8,25 4.50 8.25 4.5013.50 4.5016.50 ~:;18.50

3:75,,

20.5022.50 3.2124.50 2.5626.50 1.83.28.50 *98X.62 o

*

“~= –--===--======.._.”._“.-_= .__-. —

~.~.

TABLE1.- Cantinuod

MACBLLEOSWJINATESIN IHCKES. continmd

[HACELLE2

1

% x

~

Y?J YL Ys(raiius)

1“.032I 1.89 I U%It% I!250,1.87.050

?.21.I

I I 1 ! I I #

‘J!ABLE1. - continued

NACELLE oRDI1$ATESIN J.NCHSS- OtXl%Ud

NACELLE3 I

o 2.30 3.15“GJ432.55 3.40.086 2.63 3.48.175 2,-/L3.59.3M ~w 3.75.518 3.05 3.&3.@ 3.12 3.97.865 3.22 f4.071.039 3.29 I.1.llj1.210 3,36 lb211.30 J.42 4.271.?3 3.52 4s37:.: ;.:; :.$

2;77 3:65L:503.373.654.506.6253.651+.506.6255.653.857.6253,65J_l.128.6?53.654.3510.0003,6511.4510.OOO3.054.4511.5003.20MO4.cco3.45!+2818.0003.133.0922.0002.49~.cQ26.OCQ1.1$71.8330.6250 0

10.035*O-R.13$

.279

.418

.558●W.8%.9761.1151.3$iJ1.6731.9522.2302.2512.%

:6257.6258.62510.0001.4.wo18.00020.00022eow26.ooo30.@

Mu 4 1

(rulk) “

2.537

‘2%2.8933.0183.1233.1993.2%3.323*387304363.520:57;

3:6253.6253.6?53.&?53.6253.&52.934I;.g g.g

3:5803:5803.4503.1302.8502.@o1.4Po

o 1.78.Qjo 1.8$.Oyj L.g.1.301.*.320 2.13.43 2.5.96a2.1#11.~ 2.611.932.a2.502.*3.003.oe4.003.275.003.ld6.w 3.527*OO3.68.OO3.6610.003.7112.003.75llb.oo3.7516.003A918.003*5520.003.3122.002.9624.002.5025.V ;:g25.7526.251.5727.001.3628.W 1:%~oo30.050

1.*l.~1.’/5

1.*L.v1●8O1,83L.tyJL.Mi.921.95?.17?.64)~●975,205*379.52

10rdlnntesrorwnr~of10-~nchstationoamenonacelle3.

NACA Table Z

TABLE 11DRAG OF NACELLES TE-SHD

I ... . . . .

r//A

2

2A

H3

Zc

1<COWL C

‘+ E#5zo,

COWLc

1(- b’----

TOP OUTLET CLO.XD

.—

-E+-—- -—-—-—.3AME A.5 24, LOW POS/T/O/V

//VTERNALFLOW

%ii’

Qo5/

.05/

.05/

.//6

.053

.053

.07+

/l/f”L?

Q+-

9/74

.08c5

.080

.06/

.08E

088

090

335

3/5

2?’0

3+5

3’45

350

/t!/5.lJ “w T9- 30-w

Table Z(concludecf)

7A HI D -Cone/uded~H’AG Uf NACELLES TESTED -

M6’’Ez!. ARRANGEMENT

3

3A

3B

5

7./5

COWL c M/Lv?7S/T/O/V

_-

IL ,ELLIPTICAL CR055 SEC T!ON

<AFTER50D Y

i=—t- –-—-

1 -E-~ ,-

-“-_______—___———-.

—-— -.—-—-.-–--– .- —–.- .J----

.5MALL FILLET 0NLEFT5/DE

9/26

.055

.003

.065

.//3

.089

.089

“05+.

.053

.04-0

.052

2%OOOFT(76- .—

/80

200

/55

//0

/40

/20

(Es. 8%5 T/0 -/-+/‘for IY=Q.7

Nacelle

Origins’111A22A,2B2C‘33A3B3C3D4

. 55A535C

———.——

,,.TABLE -III

INTERINAL-DRAG INOREMENZ!S

[a = 2“; M = 0.50]

—,—- .. . . ..

Flow condition

Engine cooling air only.. *.* do . . . . .. . . . . do ...,.Complete. air requirementsEngine cooling ~,ir Only

..*. . do. ● . . ●

Enlarged side outletsComplete air requirementsBottom ou.tict closed. . . . . do. . . . .Auxiliary air oniyl!lngine cooling air only1.25 X engine cooling airComplete air requirementsRight outlet closed

do. . . . .;e;t”o;tlet closed

—._— —_.—._.

.——

ACDm——.

0.006.006*006.020.011.011.023.024010:010.003.003.016.!)17.014.014.014

I

k--x ++

F@re

PU5HER NACELLF

L- Generu/ arrungemenf of nuce//es.

NACA

qa..

491

I

t-Di2L.—.

e ,, ... . .//’[/ /

-—-—7 ‘-

A/‘i/.— -—f~

f/GURE 2 – 7_YP/CAL AIR OUTLET.o 6-

(rOPLWTLE~ NACELLE # SCALE

.-

1

-= —

.—

w I’.4?w (w/Au Lvx7fio’r s?iaw)

Fiqure 5.- Prqmsed ins +ullvfion d?toils, nacelle 5. w

*

. ..-, ..-. ..-.. -—. ..— .—— _-

NACA Figs. Sa, Sb

Figure 3a. - Nacelle 2C. Three quarter viewi

Figure Sb.- Nacelle 2c. Top Viewe

NACA Figs. 4a, 4b

Figure 4a. - Nacelle s. Front view.

Figure Lb.- Nacelle 5. Rear view.

km-., ,,,n,,, I11111—mlllllwm

(a)Variation Or drag with mad numb.r; a . P.

Figure 6.-Oharaoteristicaof the 72-inch-dimetor

MO.1198; oonventlonal oowlbh

‘1

./2 -❑

N ACELLE iA,/0 - ~ p

\

CD\

f“ El-c.J—f \

.08

.M o ,/0 .20 30 w ,s0 .aM

(b)Variationof riragwith Maoh number;a . &o

Figure6e--.comt4w~

‘b //--[.,

./0 /1

&

!

/,

,08\

\

r

/

.06-/ o /

2GG.A7 f ; 5 6

(c)Variationofdragwith’angle’ofattack;H= 0.26Figure6..Concluded,

m

,/8 P/

./6 C??&/& 4?L-.

~- -)

./+-+<.J--J ‘--

.12

,/0 /L4CEL8LE’2C x

c 2B \‘f

2AJ

.08 \2\

$+?— \ +

.196

.o?~ ./0 .20 .30 .+@ ..50

(a)Vartitionof drag with Maeb mmbcr; a . Z@,.

?- 7.-Oharaotarlmt&o# of tho 72-inch4iametor

./2

NJWE./0

L&

CD+7

F,.

.06

,o+- /Y./0 .20 .30 +

..1 .,..

+

(b) Variationof drag with Maohnudmr; a . d.

riguro7.-oontinua&

!NACELLE 2 c\

,/0

c’ 2 B\DF- k

\

\‘ A\

1T - \1~ _ 1;I

06 1=% ‘@r--

— --’ ‘/

ti,deq +4.0+

+ 0 / 2 3 P 5 6:(c) Variationor drag with anglo●f attaok;M = 0.26.

aaeollon;HAOAoowl$rng &Flguro’ 7.-Oonolu40&

NACA Fig, 8

.08

,

.06

M ““ “-- “--(8) Varlatlon of drag with Mch numb.r;a . 20.

Flguro 8.- CharaOtorlstlom Of tha ’72- by 604noh ●l.liptloalawI

At@ 60-lnoh-diaaotornaoolloa,ITACAoowllng00

,/0

NACELLE ,3B,.08-

3A

s./ h

Io ./0

1.20

1.30

I.40

I I [

M.50 .60 .70

(b) Variationof daag with IA&h nmb.r; a - W.

Flgura 8.- Oontlxw~

./0?

./0

.08

(c)\

.0+-1 0 / 2 a!, deg 3 4 5 6

(o)Variationd dIW with angle of atta6k;M= 0.26.

Figurg & - conolud~e

*

It

MAOA rig.9

,oa~

NAGELLE 5?

.06-‘ ‘- ““““

5\f’. \ \

t I 1

0 ,

0 ./0 .zf2 .3DM

,40 ,50 .60

.06 - /VACEZ L E 5B,

A=

,0+ -

C+ I

( b) VU’ iau on ef, drag WIUJ H80h numb.r; a = d,.02.. rlgum 9.- Gontlnu&

o0 ./0 .Zo .30

M ‘*” .5i9 .60

08

.06

coF

7

.02 ~,o / i? 3 4 5

d, deg

—

3JACA Fig. 10

./0 ,I I I

7

cI

//l/ PR.&5ENCE OF “@Zi90ARD - N4CEbLE‘?

.08-~

(a)- .06’0 ./0 .20 .30’M .40 .50 .60 .70

(a) Varlatlonof ~ with ~ah mbor; u = @e.

~lguro 10.- Interforonoobotwoon inbeord and outboard

Meollom. moollo u

(b) Variationof drag with Mob aumbor;a . 00.

Flguro 10.- Contlmod.

a, deg

(o)Variationof drag with angle os attaok;M . 0.26.

Flguro10.- Conoludod,

,, , ,,,..,., , ,,, .,,, ... ..——.—

.;6 o

I I IORIGINF?L NAcELLE / “

,/6 - L x)

v/(

,/4

,/2 - “

C’F

Jo -.

I #4C&Q/5 /A, y.m. “-

1-

<.06-..

04.P+-- “~b

,. Ib Ib.0+- b 4,v

\#

o .10“0 M ‘m ‘m

.50

Figure //. - Cofnparison of the drag coef-ficients of typicaj ndcelle

arrangements. a= 2°.

I !5.08 JXe” wXAef’x

NACELLE 3D\ Y— ~m?)

3c\.06- “ m \

%F % 11- > 4 1

1’

.0+ -‘ 7*. c?07d 4h!4xn —

dwA4efx o+’

.02 -—I

Figure /3.-Cornprison of +op and boj+om ouf /e +s

L wijh side ouflejs. -1

(a) (0) & .200 1- I I I I I I I I 1 I I I 1

.0+1.’”’ i I I I I I I 1“ I I I I :W

-/ o / 2 3 + .5 6.:d. deg

Figure /3.- Cortc/uded. (b) M= 0.26. u

I

I

I

I

\

,/0 . - l?.

1>

.08. .NACELLE 2A /L

Gl~ }}2\

.06 -L+: ~

t

.02-,

0 --

0 ./0 ,28 ,SW,.

.4’0 ,50 i60 O ./0 .20 ,.30 .4’0 .s0 ,60

I

.9

“-” :8

,6

,5

CL

.+

.3

.2

.1

0

-,I

Fi9~re 14, - The effect zf the nace//es on fhe /if f churocteristics. M= 9.26

-1.0

-.8

P

-h

-.2

aI

F@x-e /.5- Concbhd.

15b

NACA Fig 15a

●

P

‘k

–i2I I

–Lo--- -—. ——.

/-.8

P -,6./

/-,4

(-.2 /

/B\< ~\

i /aver sffr&ce.

o- f

11 (\

\.\

.2 () -

.4 >

,,

I

1..,b

JIlllllllllllihilimlinI3 1176013542197_———-

#/---