^(\Cf\L-M\ ^ 
 
 NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 
 
 WARTIME REPORT 
 
 ORIGINALLY ISSUED 
 
 Octo'ber 19^1 as 
 Advance Restricted Report 
 
 DEVELOPMENT OF COVLIHG FOE LCWG-NOSE M3?-C00LED 
 ENGINE M THE KACA FULL-SCALE WIND TDMEL 
 By Abe Sllverstein and Eugene R. Guryanslsy 
 
 Langley Memorial Aeronautical Laboratory 
 Langley Field, Va. 
 
 UNIVERSITY OF FLORIDA 
 DOCUMENTS DEPARTMENT 
 120 MARSTON SCIENCE LIBRARY 
 P.O. BOX 117011 
 GAINESVILLE. FL 32611-7011 USA 
 
 NACA 
 
 WASHINGTON 
 
 NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of 
 advance research results to an authorized group requiring them for the war effort. They were pre- 
 viously held under a security status but are now unclassified. Some of these reports were not tech- 
 nically edited. All have been reproduced without change in order to expedite general distribution. 
 
 L - 2Ul 
 
\%"l 1 0\H^ o 
 
 3S6)5 ' ^7 
 
 31\lC-II\:Z IN THS EACii FULL-SCALE WIllD TUIJNEL 
 By Ate Silverstein and Bn^-ene H. Gr-ij.r--ansk:y 
 
 IKTROrUCTIOK 
 
 An investigation of co-A'lir.gs for long-nose radial 
 engines l:a s l"een made on the Ci.rtiss XP-42 airplane in 
 tne FaC \ full-scale vfind tunnel. The XF-42 airplane is 
 providei with a Fratt Sc '.Thitney ?.-l&c0-31 en^-ir.e, which 
 has a propeller s.iaft and tearing housing that is 2C 
 incl'es icnger ti;2.n the stared,- re short-nose engine cf the 
 same series » Tr.is fcrTrard tistension of the -nropeller en- 
 ahles the use of ftiselage nose sna-^es of higher fineness 
 ratio than are possible rith the olnnter short-nose en- 
 gine. In tha original C'-rtiss Co"nT,any design of the 
 Xp-42 airplane the pointed f-.sela,-^e nose y:bs used (fig. 
 1) and sharp-edge scco-os rer:^ addid at t^.e bottcn and top 
 of the corling for the engine- co ol ing and tne carburetor- 
 air inlets. Flight tests shoved i>, e high sr^eed of the 
 airplane to be co".i-^ara bl e rith, bnt not s'apericr to, that 
 of the I'-Sd, T«'hic-i is a ciiuilar airrlane ^ith a short- 
 nose eng: ne and a conventional KaCa celling installation. 
 Inspection of the covling scoops disclosed so\;rces of 
 drag, the existence of which rare substantiated by pre- 
 liminary I'ACa flight measurements. These tests shored 
 tha.t the engine cooling air enter-^d the lo^er scoop at 
 abou.t half the airrlane flight velocit^^ and that the 
 kinetic e n e r gy of this flow r a s d i s s i-c a t e d by the s ha tx> 
 change in the air-flow direction at the rear of the scoop 
 
 and. by the expansion fror.; the smai! 
 area ahead of the engine. '^3ee fij 
 
 scoop area to large 
 
 2.) 
 
 The existence of a large internal energy loss due to 
 the cooling-air flo^^ was establis.ied and experience led 
 to the belie'" tnat a f~i.rther subscantial external drag 
 wou.ld be add-ed by the flow over txie sharp scoop edges. 
 The full-scale tu..nel investigation was ti^en instiiS'ated 
 for the rV'.r~ose of Ie-d rovi n.; the original scjox; co'~ii:ig 
 
 or developing an efficient cowl 
 
 o: 
 
 another type. 
 
 •°'a' 
 
 Tne wind-tunnel program included an initial investi- 
 ■ ion of the original F- 42 cowling, wnich was follo'^ed 
 
"by tests of several modified arrangements v;ith iniproved 
 scoops. The general v.nsat i sf ac to ry eerod"namic charac- 
 teristics of all the con'lings with scoop inlets led to 
 the development of the annular high-velocity inlet coal- 
 ing. Since it ras tl.e pv.Tpose of the wind- tunnel i^^vesti- 
 gi.atiOi. to develop an o-ctir.mm covlin^i; that could he later 
 constructed for fli.:ht tests, the various cc^'line- -oaram- 
 eters, such as inlet velocity ratio, exit area, etc., 
 were studied in consideraole detail. This cowling has 
 teen constnctec! and is c'^rrently undergoing flight tests 
 on the F-43 airplane. Tne res'^Tlts of tne flight investi- 
 gation will be reported at a later date. 
 
 METHOD AUD AFFASATUS 
 
 The iTACA full-scale wind-tunnel halance equi-pment 
 used for tne force inet?. surenent s is described in reference 
 1. Tne method of mounting the airplane on the br.lance is 
 shown in figure 1. The sr;ecial tec.'Uiique and apparatus 
 used for the monentun measurements are described in ref- 
 erence 2. Static-pressure ceasur ement s vere obtained 
 either by the use of static orifices or l/l 5-inch diam- 
 eter s ta.t ic-p r es r.ur e tubes mounted near the airrlana sur- 
 faces. Tne air flo"/ through the engine cQv,'lin^ r.as meas- 
 ured by total-pressure and sta t ic-pre r sur e tubes placed 
 in tne diffii.sers aneyd of t"ne en{^ine baffles, and in the 
 CO wl or t let s . 
 
 KssuLis a:^td discus 3 lors 
 
 ^Li^i^-?-l._ikll~l2 _cp_wl vnj2.«- -A photograph of the instal- 
 lation of t;.e original scoop coriing on the Xp-42 airplane 
 is shovTn in figure 1; a s;<etch with a rnoro detailed view 
 of the engine air scTop is shov^n in fig^ure 2. The cool- 
 ing air is turncvd ^^ith a snort radius through 90° and dis- 
 charged into the cor.vca rt K^nt anet^d of the engine cylinders. 
 As a result of the energy losser- occii.rring in the turn and 
 the exjansicn, the total pressure at i^he front of the 
 engine baffles rvas found to be only about 0.4 the free- 
 strean total pressure. This large inlet loss was cniefly 
 responsible for the -..it:h drag of the co'vling installation 
 and tne dra^ coefficient for the air-nisne ecuipped with 
 the original cooli ng-r.i r scoop "^a s 0.0C40 higher than for 
 
the smooth airplane v/ith the scoop removed and the cowling 
 sealed. Although tae internal losses largely accounted 
 for the drng of the original cov.l, a substantial incre- 
 ment was also added "by tne srxarp scoop edges. The drag 
 coefficient for the airplane in the smooth condition (fig. 
 3) served as a base value for deteruiining the drags of 
 all tne modifications tested. 
 
 Or i^g_ir^a]^_co_wl i^n^_wit_h_m^ij^]^t^ In order to 
 
 avoid, the large internal cov;l losses, the single ori^,inal 
 sharj.-edge scoop rtas rep'la.ced with four smaller rounded 
 inlet scoops (fig. 4). Tne use of m-i.ltiple scoops rather 
 than a single scoop v/as advantageous both in obtaining 
 better diffuser j^as sages ax.d in avoiding the sharp bend 
 required in the single-scoop arrangement. a si:etch show- 
 ing the detailed dimensions of the ducts is contained in 
 figure 5(a). Tne results obtained with tnis arrangement, 
 wh i en 
 
 was designated cowl 
 
 are s ho wn in table I. 
 
 The results were unsatisfactory since it was found 
 that the flo?.- was separating from the inner wall of the 
 duct passages and owing to the negative pressures over 
 the top of the co?-l in the climb condition, the flow 
 through the upuer scoop wa a reversed. As a result of the 
 flow brea:<do','i'n in tns ducts, the pressr.re in front of the 
 engine averaged only about 0.6 the free- stream pressure 
 (fig. 8). The air-flow quantities measured for three 
 exit areas of 57, 84, and 98 squ.are inches were S,370, 
 8,610, and 10,280 cubic feet per m.inute, respectively. 
 The drag coefficient corresponding to the 57- square- inch 
 outlet area v/as 0.0023. Tne drag of the airplane v;ith 
 the scoop outlets sealed and with the inlets unsealed, was 
 increased 0.0017 abo'/e the drag of the smooth airj/lane. 
 
 As a result of the difficulties encountered with the 
 four- scoop arrangement, the top scoop was removed and the 
 scoop inlets were extended forward along the cowl about 
 11 inches (see fig. 7); with these changes the duct inlet 
 area v^'es considerably reduced. (See fig. 5(b).) The 
 modifications served to locate the inlet more nearly 
 normal to the local flow direction and to lengthen the 
 diffusing passage. The results were somewhat m^ore satis- 
 factory and the total pressures in front of the engine 
 were higher than for t'ne former arranf^ement . (See fig. 
 6.) 
 
since 
 t her 
 st rai 
 ment , 
 f ic i e 
 quant 
 inlet 
 ■eras i 
 the p 
 
 f 
 
 m.o 
 
 w 
 nt 
 it 
 s 
 
 nc 
 
 TO 
 
 s diffuser pass 
 lO'-v treakawa^ o 
 dification was 
 tenedo (See fi 
 ith an outlet a 
 increment of 
 :/ of 12,700 cut 
 and outlets sea 
 rea sed .0005 , 
 truding scoops 
 
 age, however, was still inefficient, 
 ccurred on its inner rail and a fur- 
 made in wi-ich the duct -oassages were 
 g. 5(c).) For this improved arrange- 
 rea of 91 square inches, a drag coef- 
 .0024 was measured with nn air-flow 
 ic feet per minute. With the scoop 
 led, the airplane drag coefficient 
 which is a measure of the effect of 
 on the external drag of the airplane. 
 
 Annular in le t c o v 1 . 
 
 arrangeme.it £ tssted v/a s 
 recteri toward developing 
 vas introduced ti^rough a 
 of the airplane, with a 
 huh and the blade shanks 
 which is designated cowl 
 the velocity at the cool 
 of the free-stream veloc 
 exit sealed and the airp 
 owing to the cowl form d 
 the cowl opening. 7vith 
 plans drag was increa^jed 
 outlet areas, the. airp la 
 0.0022 ?7ith an nir flow 
 and was increassd 0.0027 
 feet ver minute. 
 
 - Since the drag of all the scoop 
 high, the investigation was di- 
 a cowl in which the cooling air 
 narrow annular inlet at the nose 
 spinner fairing for the propeller 
 (figs. 8 and 9). This cowl, 
 2 (taole I), v.-a s designed so that 
 ing-air inlet was atout one-fourth 
 ity. It was tested first with the 
 lane drag was increased 0.0012, 
 rag and the circulation of air in 
 the inlet also sealed, the air- 
 D7 only C.0002. For different 
 ne drag coefficient was increased 
 of 12,0 50 cubic feet per minute 
 v-ith an air flow of 17,000 cubic 
 
 These drag in 
 large and since dr 
 pected owing to im 
 not fully realized 
 was unsatisfactory 
 the original cov/l 
 showed that air wa 
 exhaust collector 
 flow over the fuse 
 modified, as shown 
 tiongl flap gear a 
 engine and install 
 this modification, 
 and the cowl drag 
 a flow of 12,040 c 
 v»as continued by s 
 outlet and providi 
 
 fig. 
 
 (a).) 
 
 crenents caus^^id by air flow were too 
 ag reductions that should have been ex- 
 proved internal flo'" (see fig. 6) were 
 Lt was suspected that the cowl outlet 
 Tuft investigation of the flow from 
 outlet on the XF-42 airplane (fig. 10) 
 s b&ing discnarged over and around the 
 and flap gear in such a manner that the 
 lage was disturbed. The oirtlet was 
 
 in figure 10, by removing the conven- 
 nd exraust collector from behind the 
 ing a smooth unrestricted outlet. ^ith 
 
 th=i drag coefficient was reduced 0.0C07 
 coefficient of 0.0015 was measured with 
 ubic feet per m.ir.ute. The investigation 
 ealing- the conventional radial cowling 
 ng a bottom, outlet on the cowl. (See 
 This bottom outlet was too small becaiise 
 
the measured air flor T?as lover than required and a larger 
 ■bottom outlet ra s constructed (fig. 11(Td;). The corl drag 
 coefficient for this arrangement r7as O.OOll Trith air flow 
 of 12,800 cubic feet per minute. This drag is 0.0004 
 lower taan for the cowlint:' with the smooth radial outlet 
 and is O.CCll loT/er than the conventional flap outlet. 
 
 The large drag reductions effected with the improved 
 outlets emphasize the importance of providing a smooth 
 outlet on production airplanes. Although the single bot- 
 tom outlet will proDahiy "be insufficient to provide tmi- 
 form cooling for all the engine cylinders, the result oc- 
 tal ned with this arran.^enent is of particular intsrest as 
 a reference for evaluating the drag of the outlets. 
 
 From "cressure measurements in the diffuser of the 
 ann-aiar cowl 3 (fig. 5), it was noted that tne total pres- 
 sure was less tuan O.S the free-stream dynamic pressure. 
 Since it was expected tnat this value would he close to 
 stream pressure, the flo^v over the spinner was investi- 
 gated with tufts. It was fouac^ that flow reversal was 
 occurring on the upper part of the spinner at the inlet. 
 This phenomenon was further investigated ty measurements 
 of pressures along the spinner, which are snown in fig- 
 ures 12 and 13. In thess figures the magnitude of the 
 pressure is indicated as the length of the vector normal 
 to the spinner surface. It ^^ill he noted that a large 
 adverse pressure gradie.it exists in the direction of air 
 flow, the value of which is indicated hy the slope of the 
 pressure plots. For the climh condition the slops is 
 high forward on the spinner and shows a jagged peak ahead 
 of the cowl inlet. For the high-speed lift coefficient 
 ( Ct = 0.150) the adverse r^ressure gradient is high toward 
 
 the forward part of the spinner and decreases several 
 inches ahead of the nose of the inlet. In agreement with 
 usual houndary-layer phenomena, the extent of tuft rever- 
 sal could te coordinat ed .with, the slope of the pressure 
 gradient along the spinner. Further modification was then 
 made to cowl 2 (fig. 14) to reduce the pressure gradient 
 along the spinner. The inlet area for the cowling was re- 
 duced hy increasing the spinner size (spinner B, fig. 9) 
 so that the inlet-veloc it;- ratio (Vj_/v) was increased 
 ahove 0.5. With the higher inlet velocities, the diffuser 
 pressures were increased to approximately 0.970^. The 
 
 pressures on the spinner corresp-onding to the two outlet 
 conditions tested are sho\'?n in figures 15 and I'd. 
 
For. the high-speed condition the rise in press^Are 
 along the modified spinner is cons iderahly lovrer than for 
 the or iginal . spinner . In the climo condition, the same 
 irregularities in the pressure distribution occurred and 
 these irregularities were found to te associated with a 
 tuft reversal even for the higher inlet velocity obtained 
 with the spinner modification. The pressures at the face 
 of the engine in the clinh condition were, however, uni- 
 form and high. 
 
 The dragcoef 
 the rr.o dified botto 
 of 15, 870 cubic fe 
 ing the inlet velo 
 sure in the diffus 
 ficient of O.OOOS, 
 lowest that aas be 
 on radial-air-cool 
 the cowl is most c 
 sure measurements 
 sive modifications 
 creased from an av 
 
 more than . Bqg wi 
 
 internal drag loss 
 
 ficieat for cowl 2 a 
 m outlet, was 0.000 6 
 et rer mimite. The 
 city and recovering 
 er amour tei to 0.000 
 
 meas^ai ?d for this a 
 en obtained in f Till- 
 ed engine covi-lings. 
 learly deraoiistrated 
 at the outlet (fig* 
 
 the outlet total pr 
 erage of about 0.3qg 
 
 th co'vl 2 arid spinr.e 
 
 es are a direct func 
 
 nd spinner 
 
 ^- i t h an a i 
 gain due to 
 the full to 
 5. The dra 
 rrangement , 
 scale tunne 
 The effici 
 by the tota 
 17) . , 3y pr 
 essure was 
 with cowl 
 
 r B. Since 
 
 tion of the 
 
 B, with 
 r flow 
 
 increas- 
 tal pre-o- 
 g coef- 
 
 i s the 
 1 tests 
 ency of 
 1-pr es- 
 ogr es- 
 in- 
 1, to 
 
 the 
 
 factor 
 
 1 - /— , Increasing the value of ^/Qq s^ ^^i® outlet 
 V /lo 
 
 from 0.3 to 0.8 corresponds to reducing the internal drag 
 losses to almost one-fifth. 
 
 In- order, rto determine whether the high efficiency of 
 this cowl could be preserved with greater air flows, the 
 outlet area was increased about 50 percent by partly open- 
 ing the smooth radial . out let . A cowl drag coefficient of 
 0.0012 was measured with an air flow of 21,140 cubic feet 
 per. minute. This air' flow is sufficient not only for the 
 engine air but also for the carburetor and oil cooler. 
 An investigation of ducts for handling the oil and the car- 
 buretor air was not isade. 
 
 In order to a.id in the est imat ion' o f the compressi- 
 bility . eff ect s and to study the flow within the annular 
 .diffuser passages, pressure measurements were made over 
 'the inside 'and the outsicie of the cowl for several dif- 
 ferent air-flow conditions. These plots are shown in fig- 
 ures 18 to. 21. The maximum negative pressure of approxi- 
 mately 0'.4q Was measured at the nose of the cowl, which 
 
indicatss that the critical ccmpres sitil it y speed will 
 occvr a'oove 500 miles per hour at 20,000 feet altitude. 
 The tiniforni recovery pressure on the inside of the dtict 
 is demonstrated in figures 13 and 21, 
 
 COITCLUSIONS 
 
 1. The long-aose en^^ina enables the design of an 
 efficient annular inlet cowling, owing to the length avail- 
 atle for a diffusing passage. 
 
 2. li;.e ratio of the cooling-air velocity at the 
 cowling inlet to the stream velocity is one of the most 
 imr)ortanc design variables for tne annular inlet coaling 
 and this ratio should not t 3 less than about 0.5. 
 
 3. The critical co:."ir re ss 1 til ity speed for the long- 
 nose engine cowlin;:, can be extended to above 500 miles 
 per hour at 20,000 feet altitude. 
 
 4. Important dra^ losses occur due to the flo?; of 
 cooling air out of conventional co^^'lins; outlets with flap 
 gear and erhaust collectors to disturb the flow. 
 
 Langley Memorial Aeronaiit ical Laboratory, 
 
 Fational Advisory Conmittee for Aeronautics, 
 Langley Field, Va. 
 
 EEJE2SKC3S 
 
 1. DeFrance, Sniith J.: The I'.a.C.a.. Ftill- Scale tTind 
 
 Tunnel. Kep. l"o . 459, ITaC^j., 1953. 
 
 2. G-oett, Earry J.: Experimental Invest ifat ion of the 
 
 Momentum Method for Eetemining profile Drag. Rep. 
 ¥o. 660, 11 AC A, 19 39. 
 
NACA 
 
 TABLE I. - SUMMARY OF RESULTS 
 
 Table 1 
 
 Oowl 
 
 
 
 
 Cooling a; stem 
 
 En It 
 
 area 
 
 aqln. ) 
 
 Drag coefficient 
 (at 100 mph) 
 
 Air quantity 
 (cu ft per 
 
 mln at 
 350 mph) 
 
 Inlet 
 
 velocity 
 
 ratio 
 
 Sketch 
 
 Width 
 
 outlet 
 
 opening 
 
 (in.) 
 
 Teat condltlona 
 
 '°mln 
 
 % at 
 0^=0.15 
 
 A Od at 
 Ol=0.15 
 
 (b) 
 
 Smooth 
 without 
 original 
 acoop 
 
 
 - 
 
 D> 
 
 Sealed 
 
 
 
 0.0192 
 
 0.0203 
 
 
 
 
 Smooth 
 with 
 original 
 acoop 
 
 - 
 
 :^ 
 
 > 
 
 \A3 
 
 Standard 
 
 167 
 
 0.0232 
 
 0.0243 
 
 0.0040 
 
 16,100 
 
 0.69 
 
 Cowl 1 
 
 
 Sealed 
 
 
 
 0.0209 
 
 0.0220 
 
 0. 0017 
 
 
 
 
 - 
 
 ^~~^^==i.^^ 
 
 5/S 
 
 
 67 
 
 .0212 
 
 .0226 
 
 .0023 
 
 6,970 
 
 0.15 
 
 
 - 
 
 aj 
 
 > 
 
 3A 
 7/8 
 
 
 98 
 
 
 
 
 8,810 
 10,280 
 
 .19 
 .23 
 
 
 ' ===^ 
 
 Sealed 
 
 311 oooler open 
 
 
 .0210 
 
 .0224 
 
 .0021 
 
 
 
 Oowl 1 
 modified 
 
 >T 
 
 r~-^-> 
 
 Sealed 
 5/8 
 
 Sooopa sealed 
 
 
 0.0194 
 .0196 
 
 0.0209 
 .0209 
 
 0. 0006 
 
 .0006 
 
 
 
 
 - 
 
 C3 
 
 > 
 
 5/8 
 J/"* 
 
 Scoops open 
 
 It n 
 
 63 
 
 .0206 
 .0208 
 
 .0221 
 .0224 
 
 .0018 
 .0021 
 
 7,330 
 
 a23 
 
 
 
 
 7/8 
 5/8 
 
 II n 
 
 98 
 65 
 
 .0210 
 .0211 
 
 .0225 
 .0224 
 
 .0022 
 .0021 
 
 10,900 
 9,160 
 
 .3'* 
 .28 
 
 
 
 Duct atralghtened. 
 expansion reduced. 
 
 
 
 7/8 
 
 Same aa 5/8 
 
 91 
 
 .021b 
 
 .0227 
 
 .0024 
 
 12,700 
 
 .39 
 
 Oowl 2 
 
 
 Sealed 
 
 
 
 0.0200 
 
 0.0215 
 
 0.0012 
 
 
 
 Spinner 
 A 
 
 
 - ~~~--^ 
 
 5/8 
 
 
 70 
 
 .0213 
 
 .0225 
 
 .0022 
 
 12,050 
 
 0.32 
 
 
 ^ 
 
 3/"^ 
 
 
 7S 
 
 
 
 
 13,750 
 
 .36 
 
 
 
 ^ 
 
 7/S 
 
 
 98 
 
 .0216 
 .0209 
 
 .0230 
 .0222 
 
 .0027 
 .0019 
 
 17,000 
 
 .44 
 
 
 
 
 
 
 
 
 
 
 5/8 
 
 («) 
 
 63 
 
 .0201* 
 
 .0218 
 
 .0015 
 
 12,040 
 
 .31 
 
 
 
 Sealed 
 
 Nose aealed * 
 
 
 .0192 
 
 .0206 
 
 .0003 
 
 
 
 
 
 n 
 
 Bottom e)tlt open ^ 
 
 72 
 
 .0198 
 
 .0214 
 
 .0011 
 
 9,940 
 
 ,26 
 
 
 
 " 
 
 Modified bottom exlt^ 
 
 91 
 
 .0199 
 
 .0214 
 
 .0011 
 
 12,800 
 
 .33 
 
 
 . 
 
 " 
 
 Modified bottom exlt^ 
 upper Inlet sealed. 
 
 91 
 
 .0199 
 
 .0212 
 
 .0009 
 
 13,550 
 
 .35 
 
 
 
 Partial 5/8 
 
 Modified bottom exit* 
 
 136 
 
 .0202 
 
 .0216 
 
 .0013 
 
 
 
 
 
 . 5/8 
 
 Bottom aealed * 
 
 "^5 
 
 
 
 
 8,150 
 
 .21 
 
 
 
 " 7/8 
 
 II n a 
 
 63 
 
 
 
 
 12,100 
 
 .32 
 
 
 
 » 1-1/U 
 
 n n a 
 
 90 
 
 .0209 
 
 .0224 
 
 .0021 
 
 18,600 
 
 .49 
 
 Oowl 2 
 modified 
 Spinner 
 B 
 
 t~ 
 
 
 ) 
 
 Sealed 
 Partial 5/« 
 
 Modified bottom * 
 
 91 
 131 
 
 0.0199 
 .0204 
 
 0.0209 
 .0215 
 
 0.0006 
 .0012 
 
 13,870 
 21,l40 
 
 0.55 
 .83 
 
 \- 
 
 — ^^ 
 
 
 
 
 
 
 
 
 
 Cowl flap gear reraoved and smooth exit Installed. 
 
 Baaed on smooth condition with original scoop off; landing gear fairing reraoved; control surfaces unsealed; 
 and antenna on. 
 
MCA 
 
 Figs. 1,14 
 
 ^ ' ' F HiKci 5. 
 
 ■fz: 
 
 
 Figure 1.- Ths XP-42 airplane in the standard condition, 
 
 'I' 
 
 Figure 14.- Tlie XP-42 airplane in the smcoth condition with 
 cowl 2 modified and smooth cowl flaps. 
 
NACA 
 
 Figs. 2,10 
 
 k 
 
 
 
 Q^ 
 
 c, k 
 n O 
 
 <0 
 
 
 *3 
 
 
 On 
 
 c 
 
 
 
 
 <^ 
 
 
MCA 
 
 FigB. 3,4 
 
 Figure 3.- The XP-42 airplane in the completely smooth condition 
 Tnoijnted in the full-scale tunnel. 
 
 a-xiCvxe 4.- The XP-42 airplane in the smooth condition with covd 1 
 and original cowl flaps. 
 
NACA 
 
 F,'q.-5 
 
 u 
 
 ''Xl 
 
KUCA 
 
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 3 
 
 (y/p//M ~J3SnjJip J.O IU3D-J3d 'SUOI^OfS^ ID3l.f-i3/l 
 
MCA 
 
 Figs. I ,'d, 
 
 Figure 7.- The XP-42 airplane in the smooth condition with cowl 1 
 modified and original cov>l flaps. 
 
 Fi£-'are S.- The XF-42 airplane in the scocth condition with ccv/1 2, 
 spinner A, and original co\vl flaps. 
 
NACA 
 
 Fig. 
 
 12 
 
 
 
 
 to 
 
 
 
 1 --; — • -; t>J rsl n~ ■53- <* IT) Ol 
 
 3 
 o 
 o 
 
 
 H 
 
 ■ — ■ l:^i ri v;)^ IT) O 
 
mcA 
 
 Fife. 11 
 
 
 
 
 
 ^ 
 
 
 
 !**»■ 
 
 ^"V 
 
 >i 
 
 Ml 
 
 ■ ^ 
 
 
 • 
 
 1 
 
 L 'JI^^H 
 
 1 
 
 
 sssill 
 
 a 
 
 
 (a) Bottom outlet 
 
 (t) Modified bottom outlet 
 Figure 11.- Cowl outlet on XP-42 airplane. 
 
MACA 
 
 /■Ks ir.!3 
 
 .2 A 6 .fl 1.0 
 
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UNIVERSITY OF FLORIDA 
 
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 DOCUMENTS DEPARTMENT 
 120 MARSTON SCIENCE LIBRARY 
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