�,

./ (

I�

- -.::;;:--- ) �' "

.'

-'

NATIONAL ADVISORY COMMITTEE FOR AERON�R.W /---

'ITl'llrl'I�KlI� IIJI"I)14)'· 'IlD'l' �W il llm "� "))t,:1 � / �: Jl1Jh, Ji

ORIGINALLY ISSUEr( June 1946 as

Memoramllm :Report W12

J'LIGB'l' MBAStJRI!MImLB BY VARICU3 MlLTHOIE

OF TBB DRAG OlIARAC'l!ImISTIOB

OJ' TBB XP-51 AIRPLAlIE

By Benr,r A. Pearson and Doro� E. Beadle

Ians181 Memorial Aeronaut1cal Laboratory IAnsley Field" Va.

�: � : ' .... . � . ,-- .. " ,r, ',. � . • ". _

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 pre­viously held under a security status but are now unclassiiied. Some of these reports were not tech­nically edited: .. All have been reproduced without change in order to expedite general distribution.

L- 741

.. 'po I

.. I • •

..

NACA LANGLgy M�ORIAL A�RONAUTICAL LABOR�TORY

M�ORASDUM REPORT

foX' the

AiX' Materie l Command, Army aiX' FcX'ces

MR. No. 'L6F12

FLIGb� M�AS���NTS BY VARIOUS M�THODS

or THE DR�G CEARACT�RI5TICS

OF TE� XP-51 AIRPLANE

By Henry A. Pearsr n and De- l"othy .1:. Beadle.

SUMMARY

The variat io n �f tha rver -all drag c�efflcisnt of the XP-51 airplane was measu�ad in dives up t� a Mach number of 0.8. ��ing the t�sts the airpl�ne was instru­mented s� that the ever-all drag val"iati�n was �btained by three methe-ds, each r.f which emplryad different c�m bi­natin�s cf instrum3ntatle-n. The metb�ds used are termad the accoler('rnater, the anergy, and tlJe diva ... angle me tr.ods.

A discussl�n �f the r�lative accuracy of'

the rasults obtainad with each �f the meth('ds is given both from the standp�int cf instrumsnt accuracy and C'f the accuracy with which the data mal be rdduced. It is concluded that with present instruments the accelercmater mathcd yields the most Accurate and censistent re sults.

A c�mparist"n r.tf th03 pX'·esant drag X'esults with those

obtained in the wind tunnel indicates that at supeX'­critical Mach numbers th� fli�ht values de not r.isa as rapidly as tht"ae fr�m the wind tunnel. � comparis on b3tw6en varirus sats cf flight data indicates that suf­ficient spX'ead of tha data 1s obtained with presdnt instru­m3ntation that a numbsr �f maasuremants may bs required 1n ordar to establish a drag variation ('f rdascnable ac curacy .

,. • I ..

. ME. No. L6F12

INTRODUCTION

In view �f ·the need f�� ob taining flight data at high speeds an XP-51 airplane was made available by the Air Materiel C�mmand, Army Air F�rces,for high-speed div'3 tes ts. Alt_h("�h the primary objective of the tests was to obi:Ci.�n /oS,;;naral lC"ad data that c�uld be applied to dxisting airplanes, a sdc�ndary objectivd was to e�mpare the flight r�sults where pcsslbls with wind-tunnel and other flieht mdasuraments. T� wind-tunn31 measurements were C'btained "'ti a. �-Se':lld mC"rial ('If thd XP-51 airnlane at the Ames aer('lnautical Lab('lratcry and the flight results frcm tasts made in En�land cn a similar m�del cf the XP-51.

.

- DurlnF th9 tasts at Langl�y Fiald, Va. , the XP-5l airolane was instrumdnt,�d so as te obtain data at high Mach numb3rs on such itams as: th3 prassure distribu­ti"'n �var thd wing and tail surfaces, the air�land pitchin�-m�m3nt variatt�n, tha oentrel c�araetdristics, the op�ration ('If spaelally ins talled divd-racovary rlaps, the pr�file, and over-all drag variations.

In sC"ma caSdS these quantitias Wcr3 t� be measurdd to the practical t3rrninal Mach numbar cf the e,lrpland. -Sined maaS1lrdIITdots c�uld n('lt b.:3 C'lbtaindd "n all �f the qua�1titi�s simultanaeusly, thd prC'gram was divIded illt� sevaral phas::ss. P1'9viC'uB l"clpt:'rts cn the XP-51 project (raferances 1 �nd 2) hava c�v�r�d thd �p�ration ('If thd dive-racC'v�ry fl&ps and the pr�fila drag, rasp�ctivdly.

Tha purpClSd �f this rap"rt is tCl pres�rit tht:l rdsults of the ovar-all d-rag c�dfficidn't variation with Mach numbdr up to 0. 80 f�r tha XP-51 airplane, and to discuss in sC'mo d3tail the accuracy of thd varicus mstheds that are availuble fC'lr d�t�rmining ths drag cndffician t in flight.

.

APPA�ATUS A�D TE5TS

Airolana.- A sid� VidW �f the XP-El airplana is shewn in figul"d 1 and a line drawing is giv�n in figure 2. During tl'J.a tasts th3 airplane was coat,;:,d with carncuf'lage paint; n� uttampt was mads to pr�pard atthur the wing or

2

"

I

MR No. L6F12

the fuselage to an Qsr�dynamically smooth oondition. Several minor medificaticns ware made to the airplane whoee etfeot 'on ' t-h8 drag "ira's unkD.cwn. Th:3se modifica­tions included l

(1) The installa tion �f a fixed pitot-static haad en a boom mcuntsd on the right wing near 'tho wing tip. The statio h�les were approximately l-ebord length for�ard of the leading edge.

(2) Tha ins tallation �f a shield cn the upper side nf th e !'uselaga aft �f th3 pilot to h�U5a a parisc�pe that was used in �th3r tasts.

(3) The ocvering of the six machina�gun openings in tha wing .

(4) The installation �f a Aeries �f six small automobile- type light bulbs (abcut 3/8 inches· high) acr�sa the span �f the horizental tail for usa in ether tests.

(5) The installati�n �f a rake f�� measuring pro­file draB on tha left wing at 51.3 paro�nt �f tha S-.;Im! .. span and thraa t�tal-haad tubes whioh pr�ju cta d 4 inches above the t�p sur faod of the ldft wing.

(6) Thd installation of dive-racovary fl aps , Thesd flaps f�rmed a bump 1/4 inch high an d 30 inch�s long on tha lowdr surfac 'd ('f thl3 wing. (5aa rdferilnoe I.) Some of thase m('dificati�ns may be sa �n ,in figures 1 and 2.

I Charaotdristios ef the airplana, a ng\na , pr�Pdlldr,

and axr�ust staoks ar� givan in tabla I.

Instruments.- amon g oth�rs, tha following instruments wera installed ; thos� list.3d ar� partin'3nt' tC" the rasults of this rapt:"rt.

Airspaed reQ�rder

�r.essure 'altitude raccrder

aocalerometar for r� c�Tding aocelaraticn normal to thrust axis

3

. MR.. Nn. L6F12

Accelar��ter r��·rdccrding. aeoalaratlen parallel to thru�t axis "

. : . . (Tha abov� Instrum3nts w�re �f the c�ntlnuously rdc�rding

typa. ) . I Dir�ctlcnal gyre mcuntdd en pll�t's Instrum3nt panal

: �n,d t.l,iI.rn3d 900 'for m.:Jasurlng attl tud3 angle

Tlmar for synchronizing rdsults frcm abov� Instru­mont.s

Indica ting t hdrmcm�.tdr

Mach Q�ber Indicatcr

Indicating accdl�r�m�tur

16-millimdter camera fer phC"tographing 'pil�t·' s instrumant pan�l at 16 framdS par s�c�nd

Tasts.- The flight tclsts c�nsistdd of a numbdr of incrdasingly fast dLv�s starting from �tJady Ijv�l flight at a pilot's indicat�d SPddd �f 160 milJs pdr hrur and at a spacifidd · pr�ssurd altitude. Tha lav�l flight porticn, pri�r to thd d�va, was hald for about 4 mlnutds following which an abr upt PUsh-�vdr was mada te oith�r a sp�cifi�d divd angl,) C"r tC" a dlv� a.ngls ·which was cC"mfcrtabL:J to the:pilot. In thd lattdr cas� thd pilct pr�ce3dJd until a spacifiJQ Mach numbdr was rdachJd, aft3r which a 4g to 6g r�cC"vdry was made.

F�r thd mC"st part, the divas WJrd made with tha dngine throttled; in th3 thr�ttldd div�s trte mantf�ld prassure was below lowdst r�ading cn th3 gagd (10 inch�s �f m�rcury) thr�ughout thd d!v�. In all divas, hcwdvar, th� prC"p�ller was sst to g�vdrn at �600 rpm �nd th� small radiator spoiler flaps W4r';:, open. In SC"md of thd lat3r divdS, in an at tdmpt t� rJa.ch high Mach numbars at thd hIghest pcs­sible altttude, various am�unts �f p�wdr Wdrd used in the darliar parts ef th3 div�. P.3c�rds and m�ticn pictures wara taken during the paried from just prier tc th� push­ovar until tha pull-C"ut had bd·:m c�mpl,=,tjd.

. On tha w�y tc th3 .starting positi�n th� pilot obs�rvdd the outsidG air tampdratur3 at 1000-feet intarvals. The obsarvations Wjr& always takdn at an indicat�d sp�ad of

4

MR No. L6F12

160 miles per' hour atter conditions' were stabilised. ' In',order to establish tl1e temperature�pressure altItude

; variatian" to ",be- ",used wi th, t�· subs�quent, dIve the pilot's temperature observations were corrected for the small adiabatic temperature rise at 169 miles per hour •

"

. I · " · . . - . . � ,

METHOD, or Ri!DUCltlG DATA

The variation at the qver-all drag coefficient w1th Maoh number was evaluated for a number of the ,dives by each o:f three different me' thods. Each of the methods utilized measurements obtained from different combinations of instruments and are termed the "aooelerometer m.ethnd,

II the "energy method," and the "dive-angle mCtthod."

Accelar�mstCtr math�d.- The readings � btained from tbb accelerometers and the aIrspeed �ecorder were the prima�y measurements used 1n evaluating the over-all drag by the aocelerometer msth�d, �lthough the geometry ot the air­plane, rec�rded pressure altitude, and angle of attack were also usad. These quantItIes were Inserted in the following tias�,ly derived equati()n that expressas tha over­all drag co��flcl�nt:

COl = � (� cos a + n

v sin a)

In equat1en (1)

� ,

w

q

1s the �var-all airplane drag coefficient including effects �t pr�psllar and exhaust jet thrust and induced drag

reading of accdler�matar measuring accolerati�ns parallel to thrust axis, g uoit..s riih.en the, weight or Inartla forces on the accal�romatdr vane act r�Q�ard a negative,valuCt is r�corded,)

I'dading �f acceler"m'� ter measuring accelarations no�mal to the thrust axis, g units

wlng l�a�ing, wis. pounds per �quare f�ot , 1 2 dynamic p�ess�re, iPV , p�unds pdr square ,f�ct

5

MR No. L6F12

a. angle Clf ,attack 'Of', thrust ax1s 'and "f the" instrument bass ,relative ' to flight path' , degrees ' (The instru­

' menti board 'C'U which the: acceler'ometer was mounted was'par.allel, within ±O.'l°, ,to ths thrust axis.)

The dynamic pressure q used in equation (1) was derived from measurements �f the impact pressure qc and of the pressure al' tl tude botti "of which were correoted for the installation error eXisting at the static openings of the pitot-static head. No lag corrections wer� made to either' the airspeed or altitude measurements as studies now in'progress indicate that for the' lengths and sizes of tubing used 1n the, present tests lag effects would be well within other errors. .

The'angle Clf attack' a. used in equation, (1)" was,not measured directly but was determined from tha equation:

" nvw

a. = a� + q C ' o La.

where the add.! tiClnal. terms ara,:

. (2)

a.t airplane angld �f zero lift measurad from thrust o line, taken as _1.3°

,CL slope �f airplane lift curve, per degree, taken as a. 0.096

The choice of the abClve numerical values was based on an examination �f preliminary wind-tunnel data taken at Ames Laborat�ry'on the �-scale m�del at � �ch, number'of about 0.70.

Alth�ugh wind-tunnel 11ft-curve sl�pes and zero lift angles we�e-avai�able £�r the Macb number range of the flight tests t�Y'w9re not used becau�e any�ne confronted with the ' tp,sl:: l'f eV&.luating the drag frClm flight tasts would n�t ordinaI'ily have a�cess to such data. In such cases it w�uld be necessary either to st�rt fr�m a com­puted datum anq. apply a va.riation for Mach number or:to assume SOMa constant ' average value as wss done in the pre sent case.

Althrugh the use �f a. in equation (1) is in the nature of a correcti�n, it"is nedessary t� include it in the evaluation of the data since in nons �f the dives was

6

ME. No. LSF12

zero lift (that is nv = 0) maintained f�r any length of time. The. inolus.ion. of .. the. a.. , term �na'bles a time his­tOI'Y of the drag varia t i"n to be oaloula'teci ' -'thrc;ughout the dive even th�ugh the 11ft ooeffioient is oontinually vaI'ying. In the more or less steady portion nf the dive and at emaIl values �f load faotor the correotinns due to a weI'e generally small; during the push-over and in the pull-�ut the o�I'reoti�ns were largep and the evaluated I'aeults are influenced by the ohoioe of the values of CL and a� • .

a. 0

Energz method.- The readings obtained from 'the air­speed and pressure-altitude reoorder were the primary measurements usad in evaluating the over-all drag coef­ficient by tha energy method. The methnd is based on the assumption that tha rate of change of tha sum of the p�tantial and kinatic endrgy of the airplane during the dive is equal to the pow�r consumad in drag. The Pdrti­nent equations are:

Since

� (.I!n..rgy) = '1t (ha + �) = Drag * '" DV (3)

D = CD qS 1

CD - w d � + V2) = lL (:dha + V dV) (4) 1 - qV d t \ a 2g qV d t g d t

where the new terms not previously defined ara� V the true airspead, feet per second

g aoceleration of gravity, 32.2 feet par second2

ha the abscluta altItude, feet

t timd, ssconds

The true airspded V was obtained frcm tho' oorrected measurements of tha pressure altitude hp and the impaot pressure qc tog�thdr with the temperature observations taken at the various prdssure altitudes during the climb.

7

MR No._ L6F12

The abs�lute altitude used in equati�n (4) was determined by usual methods f9r corr&cting pressure altitude to absolute altitude • . It w�s f�und, how�ver� that in these tests while the absolute altitude varied . . . dh : a�m the pressure al. ti tude the quanti ties � . and

� varied. �Aly slightLY. .

Dive-angle math�d.- The readings �btained fr�m the airspeed rec�rdar and the m�vies of the gyro w�re the primary measuraments uesd for evaluating .the drag cOdf­ficidnt by the dive-angle method alth�ugh the acceler-

. ometer readings ware used to obtain. the necessary secondary ccrreQtions for angle of attack . changes. Th� f�llowing equation was used in the rep.uction of the data:

CD ={� sin y - 1 .@¥, (5) : 1 \ g d�

wh�re Y ,"the flight-path angle rdlative to the hori­zontal, was obtained fr�m thd movies taken cf the instru­m3nt panel. In thd t�sts tha gyro· was uncaged .at 160 miles par hour just bdf�re the push-over. The initial gyro read­ing served as a datum and stibsdqudnt r�adings were cor� rdcted for the differancds in computad angle of attack existing at th.3 datum conditiC'n and the angla of attack computed f�r any other tlme. The partinant equation for dariving the dive angle y from the gyro readings wass

(6)

whera the subscrint 0 designates the readings in the datum position.

Corrdcti�ns for thrust and induced drag.- Corrections W3re madd to th� ovar-all dra� cceff1cidnts. CD cam-

1 putdd by tha various mdth�ds (dquati�ns (1), · (4), and (5» for thrust and induced drag in orddr tq �btaln the drag coefficient Cn fCl.r thd airplane alond. Thus:

o

+ !.J. + ::.e (7) qS qS TTA

8

f·

MR No." L8F12

where T" is the thrust in p�Unds and the subsoripts j and p rOarer to jet and propeller thrust, respectively. No-tests"-were" made to de te" rtnine" thEL span ""loading effi­ciency factor, thus the induced drag porti�n was computed from the elementary equation" CL

2/WA. The use of this equat10n is justified in the present case, since the usual 5 peroent correotion will hardly affect the �esults within the plotting accuracy.

where

N

The j�� thrust "was determined" from the equation:

v) (8)

average flow of exhaust gas, slugs par Bec�nd per cylinder

number of cylinders (12)

mean exhaust gas jet velocity, feet per sdoond .

flight sOded, feet per second •

In computing Me it was assumed that there was 0,0021 pound �f exhaust gas par second par brake horse­power. The value �f the brake horsepower was obtained from perf�rman�� charts f�r the Allison V 1710-81 engine. The" velocity Vj was obtained from r�sults givan in

, reference 3.

The pr�pe11er thrust. Tp (less c�mpressibility effects) was determined from the charts givan in refer­ence 4. In this determination, the "powar ooeffioient Cp and the V/nD ware first computed rr�m the engine manifold press�e, measu�ed airspa�d, and engine rpm. The, computed power c�efficient Cp was then converted to the propar activity fact�r in order to dntdr the charts. The thrust coe�ficlabt CT obtained from" the charts was

" tban reconverted to the proper activity factor following which the propeller thrust was computad �rom tha" equation:

(9)

9

I II I I .. 1.1 _I. I. •••• II. II 1.1 I I 1111 I I I. •• I 11_ III I

MR No • . L6F12

•

The above value �r pr�pal ldr thrust was c��ractgd for. comprassibility·effacts by �ult�ply"t].g·.aq�tion (9). •

by-a tip.speed· correction fac�or .�t· ap'd a . hub P��- .. t'action fact.or Fh ·" Ths valu.es of th�s� factC'rs w�I'e.

obtained fr�m references 5 and 6 and a�e stmilar t� . these givdn in reierdnce 7 •

• In the throttled dives when the manifold p,rassure

was 10 inches �f marcury �r below, the thrust and p�w�r were computed as th�ugh the prasaure were 10 .inches �� mercury. It will bd s�e·n la"tar · tha t this assumption will not affect tha, rdsults to any grdat extent,

RESULTS �ND ACCURACY

• ••• •

In this section r·esults are first pr<:;l'S.3nted for a seleoted div� in which the drag coefficient is determined by the various methods. following which the accuracy �f the rdsults obtainable with the various mathods Is brie�ly discussed, and finally. the average flight drag variation 1s given for all of the divss.

Results�

for a selected diva � - Figure 3 sh�ws a time history of s�ma of the measured. and oomput�d quantities for a dive in which a Mach number of 0.786 was �dachaQ. �his particular flight was .chosen for illustration because it was the highest Maoh number dive for which a c�mpldte set of instrum�nt racords was available for �valuating the drag .�y all thrae mdthC"ds. The diva wa� started from a push-ever at 31,200 �e �t and prccdeded for appr�ximately 20 second� at which time a 4.0g pull�out was initiated. The thrc-ttle was· set pri�r to th3 diva so as to ·govern at 19 ,000 fds€ and 160 miles pdr hour with a man�feld pressure of 37 inch9s of �.:tr.cuI'"1..

Table II lists. some of tha c�mputa.tions made in eva";luating CD and CD by each of these ma thods� In

o 1 . . . ord�r that an appraisal may be mado of the c�ntributions of thd varl�us drag components, table II also giVdS some of the computations for obtaining tho· J �t and propallar fur�t.

.

10

I

. MR .No, L6F1.2

.Figure 4(a) sh�ws the variatl�n �t the drag ooet� -1'lclant CD' with ·.Maoh number while figUl'd 4(b) shews

- : ... . 1. _ . . _ . . ·ths variation ef CD with Mach number. The values

o . givan in figure 4(a) ware obtained tr�m figurs 3 and table II. Tna values for figure 4(b), howaver , are takdn from lift c�erticient$ falling within the range from tO�2 1n order that tha effdot of any span effi­oiency faotor would be a minimum.

Acouracy .... The .wide variation and irregularity of the drag curvas shown in figuro 4 frr tha various methods indicatas the dasirability of some discussion of the aoouracy of measuramvnts and operations .

Tha major quantittas used in the e qua t ions for P3ducjng tha data ara bali�ved to be known to the following accuracy. .

Q.uantity Accuracy

w :1:0.005 or 1/2 p'jrcant

q ±l inch H20 �r 1 p3rcent �hich�ver is grodatar

V • Corrasp�nding to aocur3.C'Y of q above or 1/2 p�rcent

M to . Ol

Tj %20 pounds

Tp 'tlOO pounds

nh ±O.Olg

11

----------

Remarks

C�rresponds roughly to a we ight of ? gallons gasrlino

Corresponds roughly to 100 thrust horse� powa� at 20,000 teet

Corresponds to 79 pound!?, error in force acting along flight pa th ..

Ml1 Nc. L6F12

I).Uantity Acc. uracy . Remarks

nv to.05g Error e£ this amount in combination with an error in angle of 30 would. result

. in an error cf 20 lb acting along

. the flight. path par . .load :factor . ,

a tlO Due mainly to com-. bined errors in

a7, C"

and 07, a

.. Y ±20 DUd to combined

drrors in quanti-ti;;ls in equation 6

� dha Di:fficult to assess ,-dt dt

dV dha Errors in tha quantities d t and � are di1'ficult t� dstarmine sin�a part C'f tha arr�r may be attributad to th� measurements �f V and ha and part ·tC' the graphical dif£erantiatiC'n' that is required. Regardless . of method , th� absolute err�r in t� evaluated drag c�effici3nts, depends upon tha accuracy with which tha fC'rce acting aleng the flight path is kn�wn. Figure 5(a) shC"ws the variatiC'ln in ths width ('If the error enval�pa with Mach nurnbar and alti.tude due to an error Otf 100 p('Iunds f(')rce. Figure 5(b) s�ws a similar variation fer an error of 100 thrust hors�pC'lw�r.

If it is assumed that the errors in the major quanti­tiss used in thd equation for r�ducing thd data ard addi­tlya ths maximum possibla error in force along tha flight path from the dstimates given would be abnut 236 pounds. �t 20 ,000 feat the maximum width cf thJ arr�r dnvalopa for a lo�d factor of 1.0 wC'uld thdn be as sh�wn in figure 5(c) . The discussiC'n �f drr�rs in the prac6dding paragraphs has implied that the errC"rs are of accidental naturd. Thd pos� sibility of a ce rtain cC'psist�nt drror will bd tC"uchgd upon latar in th� discussien of rdsults.

12

� -"""

MR No. L6F12

Although it _is not readily seen from figure 4, since the results_given in this fig�e" a�e �C!.m ('nly ane dive. it may be stated that the snergy and dive angle methods yielded results with a c�nsiderably greater envelope band than that sh�wn in figure 5(c). In cont�ast, the accaler­�meter method gave b9ttar results consistently with an

" anval�pe band s�mewhat g�sater than that shown in figure 5(0). r " It;l" " gsperal" the band was smaller for th� fully throttled " divas t�an for the dives in which pow�r was usad.

Avarafe flight va�iati�n.- �n view �f the precading :' conSiderat ('ns the results from the acceler('mater mathod

were "deamed t� be" th� mest accurate " and th�refore only the rasults:nbtainad by this MQth�d ar� given 1n this r�port,. Figure 6 Ca) shows the rolsults obtained by the

"accalaromatar m3th�d f�r eight dives cf va�ious deg�ees of s�varity whdra ths ranga of airplana lift coefficient was to.2. Corr3cti�ns f�r propall�r thrust, j�t thrust, and induc�d drag w�rd mad� for aach diva as �utlined in table II.

Fr�m tha curv3s given in figUra 6(a) an avaraga curv� was " deriv(3d� Sincd th� numba� of curv.;,s to be avarag�d diffarad in vari�us rang�s tha final averagad curve of " figur3 6(b) has b�dn br�kan lnt� a number cf sdgmants, each sdgmdnt bding bas�d on thd numbdr of curv�s not�d. Th& dcttad linds rapr3ssnt tha maan daviaticns fr�m the maan and s�rVd dS an indication of thd rgliabillty of the avarage curva,

In order t�"SiV3 So�a idaB of tho correlation b�tween the rapid ris� in tha ovar�all drag curva and the critical Mach numbdrs, ths crlttcal sp3�ds as datarminsd from flight prassura distributions takdn OVdr thr�d'wing ribs located at 52, 114, and 185 inches fr�m tha airplnna centar line ar� noted on fig�re 6(b).

DISCUSSION

In connection with tha maan drag-coefficient curve 6f figure 6(b), it may be notsd that tha 1argast vaLue maasur�d was about twica thd low-spaed value and that tb� rapid risa in drag c03rficiant whare d(CD/M� = 0.1 fs associated with a Mach number which is about 0.05 gra'atar than the criti"crl.l Mach n�b3r r�r the w1ng s " dct1on at 52 inchas • • side fro� this 'general comment, it is of intarast to �r�Qdnt r�sults rrom ot�e� drag maas�eme nts

13

MR �o .. L6Fl2

pe�taining .to the P-51 ser�es of airplane and to discuss , ,the r.e quirements necessary to insure reasonable accuracy In flight me�surements nf drag.ooeff.lc1ent. .

, : Comparison.,ot the present measurements' "Wi th other

available results for"�he P-Sl series are sho,m in figure 7. Curve 1 show� the drag variation obtained at zero lift 'for a 1-scale model of the XP-SI,airplane

. " 3 ' , tested in the Ames l6-foot wind tunnel. The tunnel tests were made on a smooth propellerless model,w�ioh had same but not all of the protuberances that were present on the aotual airplane. A oo.mparison of the flight drag results with those obtained in the wind tunnel indicates that at the'supercrltical Mach numbers, even taking into consideratfon the mean deviations, the flight values do no�'r1se �s rnnidly as thoRe from thA'wind tunnel.

Curves numbers 2 and 6 ware obtainad fr�m fliFht tasts made in Graat Britain on an early versi�n �f the Mustang ' whIch was -eimilar in configuration tC'l tha XP-51. In the British �asts, ths drag variation was de t 3.rmined by the anergy meth�d . Curva 2 applie s with the small

.radiator spoiler flap up, while curve 3 applies with the radlat�r spoild!! flap dC"wn. The,' curvas shC"wn raprdse nt avarages of p�ints which w�re widely scattarad.

Curve 4 shows thd variation with Mach numb�r of the appare nt prcfile drag ccafficient C'lbtainad fr�m a rakd survey bahind a station 114 inchas 'out fr�m the wing cente r line on the XP-51. -This curve was taken from raferance 2 and repre se nts only Sacticn data.

It may be n�ta d that whdreas both curves 1 and 4 show eithdr no incra as9 or slight incraase in drag coef­ficient with Much number for M lass than 0.66 tha maan flight curve shows an opp�site trend which may be of sig­nificanca. All thd curvas in figure E(a) from which the maan curva was derived shC"w this samd t�ndsncy indicating tha possibility that s�ma consistdnt arr�r was introduced into the'computations. A c�nsistent trGnd �f the type sh�wn,cculd bs introd uced by 3mpl�ylng.aith�r Pfopa lldr charaete ristio �r engine-p�war curves which ware not directly applicabla tC" the �ngine pr�Pdllar combination useQ, �n the tasts. : It may ba sea n fr�m figure 3 and tabla II thut'in tha low-sp�3d range ( that is at the' baginning or the div�) small but consist3nt arrors In dithar the ,prddiction of the engine pcwe r or thd propaller

14

MR No. L6F12

thrust from the charts used would materially affect the results whereas In the higb�speed range this effect would' be much� le s s lmpc rt�n t. , . _ _ . _

In connectl�n with the Britlsh results (curves 2 and 3) a more recent British analysis of the data indicated that the instrumentation used was not adequate and recom­mended the use �f the accelerometer method for future evaluations �f flight dras - The same rao�mmendatlon is made in reference 9 whtch shnws that small errors in airspeed and altitude measurements give rise to large errors in. the drag c�efficiant as determined by the ene�gy lllathod.

Althoug� the comparis�ns o� figure ?(a) �re of prin­cipal interest slnce they partain to thd XP-5l, nther cC"mparisons. are c(" ntainad in figure ?(b) for (\th�r v.ers1ons of the P-51 airplana. Figura 7(b) sh("ws the comparison of tha XP ... 51 r�sults with wind-tunndl and flight rrh.1:�sur�m .. Hlts for the P-51B.alrplane. Curva 5 shows the-dr�g-codff1cLent-. variati("n obtainad at zero lift in the wind tunnal cf a �-sca13 Modal of the P-51B elrplan�, withnut a p�p�11ar. YSee ' rafarance B.) Curvas 6 and 7.arg thd dr�g v�riat1on �a6ur�d in flight naur zaro lift by the �ccdldromater mdthod .on a P-5lB wi thcut a prC"pellar : {Saa rtlfarance 8.} CurVd 6 rdpr�sentg thd varlatinn C"btuin�d in one flight in which it was st� t� d that thd Idast amnunt of dust was on tha a1rplane wh1la curV3 ? rapr�sdnts the casa of a diva with the most dust on the alrplan� . ..

It is believed that m("st of the variation obtained in the form of the drag curves given in figures 7(a} and 7(b) may be attributed to dlffarences in the accuracy of tha measurements and methods usad In evaluating the data. On the basis of the presant exp�rienoe it may be stated that results obtained with the energy methnd are not as accurate as th�se obtainad with tha accel�romdter mathod. In support of this statemant it may be noted that tha wind­tunnel tests of the 1 �sca1a modal or the XP-5l indicatad that the small radia�or sp�11er flap had baraly a notice­able efrect on the airplane drag below an M of 0.75 and a slight effect up to 0.80, whereas the flight tests for the MU$tang (curves 2 and 3) showed that the radiat�r spoiler flap had a relatively large effect. It may also be noted fr�m figures 4 and 6 that drag variations as large as thC"se indicated by either curves 2 and 3 or curves 6 and 7 could be obtained between successive flights even

15

MR No. L6F12

though the airplane configurat1on had n�t been changed. This leads to �he conclusion that unless improvements are made in technique several flights may be required in order to establish the drag variation for a given con­figuration.

CONCLUDING REMARKS

The detailed computations given for the selected dive (figs. 3 and 4 and table II), as wall as results of computati�ns n�t included in this report, indicate that further gain in accuracy may be had by 1mpr�ving both the instruments and the flight technique. Lacking direct measurements of pr�peller thrust, an improvement in accuracy would be obtained by using less p�wer because t�e thrust could be more closely c�mputed. An improvement may also be obtained by further incr.easing the accuracy of

. ,the accelerometers and taking special precautions in their _ location with respect to 'the airplane. center of gravity and their orientation with raspact to the angle of zero lift. It 1s felt, unless such improveme nts ara accomplished, that (a) cnmputations for converting pressure altitud� to true .al ti tude, (b) determinations rtf span 3.f.ficiency .factol', and (c) correcti�ns for compressibility effects on propeller �ips and hub loss much �f their signi.ficance.

Langley Memnrial Aeronautical Laboratory National Advisory Ccmmittee .for Aeronautics

Langley Field, Va.

16

1m No. L6F12

REFERENCES

1. Beeler, De E., and Williams, Walter e.a Flight Tests of Dive-Control Flaps on an XP-5l Airplane. NACA ACR N�. L5D20a, 1944.

2. l3eeler, De E., a.nd Gerard, George: Wake M9asure:ments behind a lang Section of a Fighter Airplane in Fast Dives. NACA TN No& 1190, 1947.

�. Pinkel, Benjamin, Turner, L. Riohard, and Voss, Fred: Design of Nozzles for the Individual Cylinder EXhaust Jet Propulsion System. NACA ACR, April 19k1.

4. Gray, W. H. , and Gilman, Jean, Jr.: Characteristics of Several Single- and Dual-Rotating Propellers in Negative 'lhruot. NACA MR No. L5C07, 191+5.

5. Gray, W. H., and Mastrooola, Nicholas: Representa�· tive Qperating Charts of Pro�ellers Tested in the NACA 20-Foot Propeller-Research Tunnel. NACA ARR No. 3 I25, 191�3.

6. Hutton, P. A.: The Calculution of Airscre� Effi­ciencies at f!igh Speed. B. A. Dept. Note­Performance No. Ie, British R.A.E., Jan. 1940.

7. Gasich, �elko E., and Clousing, La�1rence A.: Fl!ght Investigation of the Variation of Drag eoerfi� aient with Maah liumber for the Bell P�39N-l Airplane. NACA ACR No. 5D04, 1945 .

8. Nissen, Jnmes M. , Gadeberg, Burnett L., and �lton, Williwm T: Correlation of the Dra� Characteristics

�ei-�� :i�����;�in�cir�R i�-4��� ����� 'I'

9. Keller, �omas L., and Keuper, Robert F.: Comparison of the Energy Method with the Accelerometer Nsthod of Computing Drng Coefficients from Plight Data. NACA CB No. 5H;1, 1945.

17

p'

MR Ne. L6F12

TABLE I

CHARACT�RISTICS OF XP�51 AIRPLANE

Airplane: 5 Over -all length • • • • • • • • • • • • • 32 ft 21l_in. Weight for tests, Ib • • • • • • • • • • • • • , .-7897 Wing span • • • • • • • • • • • • • • • '37 ft 5/16 in. Wing area, sq ft • • • • • • • • • • • • • • • • 235 . 75 Horizontal tai'!

Stabilizer area, sq ft • • • • • • • • • • • •

Elevat�r area (including 1.24 sq ft balance), sq ft • • • • • • • • •

Vertical tail F�n area, sq ft • • • • • • • • • • • • • • • •

Rudder area (includi� 0.63 sq ft balance), sq ft • • • • • • • • •

27.70

""13.76

9 .A4

11.16

Engine: • • • • • • • • • • • • • • • Allison V1710-81-99 N�rmal rating • • • • • • • • , . 1000 bhp at 2600 rpm

at sea lavel 955 bhp at 2600 rpm

at 15,700 feet Gear rat io. • • • • • • • • • • • • • • • • • • 2.00:1

Pr�peller: • • • • • • • • • • • • Curtiss ccnstant-speed Drawing number • • • • • • • • • • • • • 614CC1.5 - 18 Serial number • • • • • • • • • • • • • • • " AF 40-12646 Diameter • • • • • • • • • • • • • • • • • 10 . ft 6 In. Angle high at 42 in. station • • • • • • • • • • • 580 Angle low at 42 In. statton • • • • • • • • • • • • 230 Actlvity fact�r (t�tal ) • • • • • • • • • • • • , 265.5

Exhaust stacks: Area �r each stack, sq in . • • • • • • • • • • • • 4.95 Inclinatl�n to thrust axis • • • • • • • • • • 240 40' Incllnati�n t� plane of symmetry • • • • • • • 120 50'

NATIONAL ADVISORY CO�mITTEE FOR A£RONAUTICS

• u­lie .... f<":"" o 1.0 1.7 2.2 2.6 :5.1 4.0 4.t 5.0 6.0 6.6 7.0 8.0 8.7 9.0

10.0 11.0 11.4 12.0 1�.0 14.0 14.4 15.0 15.7 16.0 16.6 17.0 17.8 18.0 19.0 111.7 20.0 20.6 21.0 21.4 22.0 22.5 2�.0 2:5.5 2:5.8 24.0 24.4 24.5 24.7 25.0 25.1 25.5 25.65 211.0 26.1 26.5 211.9 27.0 27.2 27.5 28.0 28.5 29.0 211.5 211.7 :50.0 30.2 :50.5 150.11 31.0 :51.7 32.0 32.2 ��.o �Z.g :54.0 :55.0 156.0 157.0 38.0

"'C; :: ......... . ... .... ... -4

:592.7 :595.8 400.8 402.8 404.9 4011.9 419.0 424.3 429.t 446.0 457.5 464.0 4�.O 497.0 50�.0 52�.0 54�.5 552.5 565.2 585.6 606.8 616.5 630.5 1147.0 651.1 667.5 676.4 696.11 701.5 72�.O 7�8.0 745.0 757.0 767.7 773.0 784.0 792.5 600.0 807.0 810.1 812.5 816.5 817.5 819.0 821.5 822.0 824.0 824.5 8215.0 826.5 827.11 827.8 828.0 829.4 828.0 828.0 827.0 825.0 823.0 822.1 820.0 818.5 817.0 813.5 812.5 807.1 8Ol5.0 SOl.1 7114.2 78:5.11 78�.0 772.5 7112.4 750.5 741.11

152.7 8:5.1 SI5.8 1515.11 157 .. 0 88.2 71 •• -7:5 •• 75.' 82.4 815 .8 89.0 911.8

1015.8 107.2 1111.7 132.5 1;54.1 141.2 Hi�.4 168.1 175.11 1811.8 197.0 200.5 212.8 2111.15 2157.11 2�1I.1I 259.t 275.0 281.5 2117.t �07.1 313.:5 ;52:5.11 �32.4 :!-45.3 358.0 3511.11 364.3 370.2 �71.e �74�" 377,8

��::� 38!S.!S ZIIO.O

3111.2 :511.11 400.1 400.t 402.7 404.8 40B�' 412.' 41t.l 4De�' 411�0 411.1 410.11 tl0.' 4De •• 408 •• 4015.0 402 •• 400�' :504.' 384.8 384 •• 157t.4 Z64.4 35:5.11 3t4.1

TABLI! II

COMPUTATIONS FOR BVALUATION OF DRAG COEPFICIEIT OF XP-51

PLIGHT 4&

r.

i .... .cI u • ..

0.:5811 .:5112 .&117 .:51111 .401 .4011 .nei .420 .t25 .4n

•• 4ei& .457 .475 .4110 .4116 .514 .ei4& .545 .555 .574 .594 .604 .620 .f53:5 .1535 .650 .658 .678 .681 .6911 .7115 .722 .7:S4 .740 .746 .748 .7M .768 .770 .774 .775 .'778 .779 .780 .780 .780 .782 .7815

-35.t -:511.4 -35a -35.t -155.t -35.4 -l!5.4 -�4.9 -� •• 5 -33.8 -��.6

-28.1

-24.8

-23.1

-20.6

-17.11

-15.4 -15.0

-11.0

-7.3

-2.1

-1.6

-.7

.5 .784 -----.784 .7 .78;5 -----.785 3.2 .765 -----.7815 3.8 .784 --- -­.784 -----.786 6.2 .780 7.8 .774 -----.'M5 8.7 .772 -----.71111 11.8 .7118 -----.71515 10.5 .765 ----­.7511 11.1 .755 ----­.'153 11.5 .7411 ----­.7311 1 12•2 .735 -----.727 --__ _ .716 1 12.3 .706 -----.15117 11.8

� -or. . �.8 � ... <>.r" J� " .. '" o -... 0.86

.5& • til .06

-.18 .06

-.511 -.41 -.80 -.67 -.59 -.67 -.67 -.61 -.10 -.�7

.49

.59

.15

.72 1.10

.60

.6.:5

.19

.67

.15

.10

.49

.:35

.06 1.14

.44

.5�

.49 1.58 1.21 1.29 1.�1 1.50 1.80 1.48 1.99 2.12 1.99 2.46 2.70 1.24

.86 1.117 2.07 2.111 2.13 2.27 2.47 2.20 2.511 2.711 .:5.3:S 3.57 3.40 3.711 4.02 .:5.72 .:5.98 15.91 4.02 .:5.47

-15.40 :5.47 3.67 3.60 3.38 2.10 1.50 1.19

-0.086 -.070 -.0I5l5 -.055 _.04-0 -.Oei1 -.Os:» -.073 -.085 -.075 -.mo

o

.0150

.045

.080

.105

.110

.160

.100

.1110

•• 0 .2110

.&25

.:5150

.370

.425

.:575

.:550

.:500

.:525

.2150

.200

.170

� � ... -. ... ... (� .. .. .. .. ""

31,200 151,200 31,200 31,190 31,1110 31,190 151,190 151,040 30,950 �O,760 ;50,700

�O,220

29,360

27,930

27.440

26,970

26,440

25,750 25,310

24,810

2�,660

22,850

22,450

22,310

22,060

21,740

21,500

21,070

20,940

20,:5150 19,960

19,730

19,170

19,040

18,900

18,880

18,990

32,.00 �2,"OO 32,400 152,400 32,3110 :52.350 32,2150 152,200 32,110 32,000 31,800

31,1520

�O.3:50

28,990

28,310

27,870

27,270

26,600 26,210

�5, 700

25,200

24,500

2�,700

2.:5,300

23,100

22,8150

22,470

22,1110

21,6110

21,500

20,87. 20,610

20,400 20,240

20,0110

19,sao

19,7M

19,500

19,470

19,1100

� '" -" '" . ... " ..'" " -;; '"

27.0 &11.0

41.0 t7.5

52.ei 511.0 150.0

58.5

110.5 61.0

82.0

110.5

6008 511.0

57.5

55.0

5:5.0

61.0

50.0

48.0

411.5 45.0 4:5.5 42.0 38.0

:50.0

22.5

co ;; .., .. '" -" .. ... " .. <> ... '" . ..... r. c .. . o <.>

10.5

18.8 28.0

:51.0 37.7

44.7 47.5 53.8

52.4 54.6 53.8

52.7

52.2

53.6 53.6

55.6

55.1

54.3

53.9 53.0

51.4

50.0

49.8

46.7

42.5

40.11 39.7 38.4 37.3 :53.5

29.7

27.1

25.8

18.0

13.1

8.8 1.11

-4.0 -6.0 -7.8

MR No. LSF12

... <> !l ... . .. ...... o '" .. ... '" � :!.;5S 1.53 1.24

__ -.911 -2.22--1.01 -4.12

r. .. • o ... .. :: 11 .= �

-3.20...

1.7:5 1.7" 1.711 1.77 1.78 1.80 1.St 1.87 1.811 1.1111 2.01 2.04 2.13 2.111 2.21 2.30 2.39 2.43 2.49 2.58 2.67-2.71 2.77 2.85 2.86 2.94 2.98 3.06 3.09 3.18 3.25 3.28 3.315 3.38 3.40 3.45 3.49 3.52 3.55 3.56 3.58 3.59 3.60 3.60 3.61 3.62 3.6:5 15.63 3.6Z 3.64 15.64 3.6t 3.64 3.65 15.64 3.64 :5.64 :5.113 :5.62 3.112 3.61 15.150 15.511 15.58 15.58 :5.55 15.5:5 :5.52 :5.411 15.t5 :5.45 :5.tO 15.:55 3.:50 3.211

20.0 20.0 20.1 20.2 20.3

-20.5 20.8

-20.11 21.0 21.2 21.5 21.8 22.0 22.2 22.5 215.0 2.:5.7 23.9 2t.l 25.0 26.0 26.4 27.0 27.7 28.0 28.7 29.0 30.0 30.2 .:51.4 32.2 32.7 33.3 34.0 34.4 35.0 35.7 36.1 36.8 o'37.l 0'37.2 37.7 157.9 38.0 38.3 38.5 �9.0 311.0 311.'5 1511.e 311.11 40.0 40.2 40.2 to.5 41.0 41.1 41.5 U.8 tl.8 41.11 42.0 t2.0 t2.0 42.0 42.0 42.0 42.0 42.0 42.0 t2.0 42.0 41.11 41.8 41.6

500 500 505 510 515 520 5:50 535 5tO 545 550 560 570 580 585 5115 610 615 625 640 670 680 6115 710 720 740 750 780 7110 815 835 850 670 890 1100 1115 930 gl;O 1165 975 980 9110 11115

-4.91 -4.08 -�.5�

.21

.07 -1.06

-.60

-1.22 .12

-.69 -.75

.42

.03 o

.40

.55

.53

1.15

.52

.5:5

.79

1.00 1.46

1.51

2.015

2.11

1.62

1.116

.67

-.13

1000 1005 1010 1020 1020 1025 10150-10155 1040 1045 Iota 10150 1065 1070 1080 10110 10110 10115 1100 poo 1100 1100 1100 1100 1100 1100 1100 1100 1100 1095 10110 1065

NATIONAl. ADVISORY COIIIImu fOl �ICS

MR N o . L 5 F 1 2

u ... . f<-

o 1 . 0 1 . 7 2.2 2.6 �.1 4.0 4 .' S .O 15 . 0 6 .6 7 . 0 8 . 0 8 . 7 11 . 0

10.0 11.0 1 1 . 4 12.0 1�.0 14 . 0 14 . 4 15.0 15 . 7 16.0 16 .15 17 .0 17.9 18.0 19 .0 111.7 20.0 20.15 21.0 21.4 22 .0 22.5 2:5.0 2:5.5 23.8 24.0 24 . 4 24.5 24.7 25.0 25.1 25.5 25.65

_ 215.0 26 .1 26.5 26.9 27.0 27.2 2'7 . 5 28 .0 28.5 29.0 29 .5 29.7 30.0 30.2 �O.5 30 . 9 :n .o 31.7 �2 .0 �2 .2 �� .O ��.9 �4.0 35.0 .:56 .0 .:57 .0 38 .0

S81.6 5'7'7 ,., 590.11 567 .0 585 .3 578 . 3 5'75 . 0 575.:1 55'7 .0 :146.7 620.0 550.0 5e7 . 0 521.3 5011 . 8 516 . 0 500 . 0 488.8 482 .0 46� . 4 44'7 . 1 430.8 428 . 3 3711 . 2 :5 '7'7 . 7 361 .6 354 .'7 330.8 304 .3 28:5 .9 268.9 240.1 210 . 2 213 . 11 18'7 . 4 166.6 171 . 0 141.11 126 • • 120 . :1 112 . 2 102 .11 103 . 3 103 .'7

95.5 115.11 96 .'7 96.15 87 . 6 88 .:1 88. 1 99 ." 119." 98.8 811 .5 90.15

102 .5 91.6

111.2 110.8 11 1 . 6 121 . '7 12 1 . 8 140.3 140 . 5 150.6 169 . 3 169.15 207 . 5 2M.'7 246 .1 260.2 293 .15 336.11 34"6.11

44,,11 4 4 . 11 45 .'7 46.1 46.7 47.4 48 .2 48.7 411 .� 49 .0 411 .5 50.2 50.'1 51 . 4 51 . 8 51.11 52. 5 52 . 9 53 . 2 5� .9 56 .4 56 . 9 58 . 0 58 .7 59 .11 61 . 1 6 1 . 7 63 . 8 . 65.2 66 .4 67 .2 68.' '70.1 71.3 72 . 1 72.4 73.5 75 . 1 75.e 76.4 711 .15 77 .2 77 . 5 77 . 8 78 . 1 7 8 . :5 79.1 79.0 78 . 9 79.7 79 . 3 79.7 79 .8 711.11 80 . 5 81.6 82 . 1 82 .5 8�.4 � . 1 83.7 94 . 2 94 . 3 84 .2 84 . :5 84 . 7 84 . 6 94 . 8 8 4 . 11 85.2 85 .3 86 . 8 86 . 4 815 . 4 86.7

.. � .... .. '" o .. '"

'" o ...

0.05115 .058e .0575 . 051511 .05711 .0568 .0541 .05�1 .05115 .01'711 .01&:1 .0165 .0255 .'0215 .02011 .01'711 .0182 .0115'7 .0146 .012' .0111 .01oe .001II .0084 .0082 .00'71 .001511 .0057 . 00511 .001' .0040 .0055 .0050 .00;50 .00215 .0023 .0021 .001'7 . 00115 .0014 �0015 .0012 .0012 .0012 .0011 .0011 .0011 .0011 .0010 .0010 .0010 .0010 .0010 . 0010 .0010 .0010 .0010 �0010 .0012 .0012 .0012 .001:5 .0013 .00115 . 0015 .00111 .0019 .0019 .0022 .002:1 .0026 .0050 .0054 .OO�II .0044

'fABL& II - Concl�.

COKPO'fATIOKS lOR KYALUATIOI or DRAG COIPPIC1II7 01 JP-Sl

PLIGHT 4� - Concluda4

0 . 0050 . 00;50 .00211 . 00:50 . 0030 .0030 .00211 . 9628 .0028 .00215 .0024 .0024 . 0022 . 0021 .0021 . 0018 .0017 .0017 .0016 .0015 . 0014 .0014 .0013 .001:5 .001:5 .0012 .0012 .0011 .0012 .0011 .0010 .0010 .0010 .0010 .0010 . 0010 .00011 . 00011 . 00011 .00011 . 00011 .00011 . 00011 . 00011 .00011 .0009 .00011 . 0009 .00011 . 00011 .00011 .0008 .0008 .0009 .0009 .00011 .0008 .0009 .00011 .000\1 . 00011 . 00011 .0009 .00011 .00011 .00011 .00\l.1I .00011 . 0009 .00011 .00011 .0010 .0010 .0010 .0011

..:I u • c • .... '" .. �

0. 4:1'7 .2'7'7 .2151 .O�

-. 0110 . 052

-.2'7'7 - . 187 -.5:14 -.270 -.2215 -.2:11 -.218 -. 200 -.052 - .0118

. 122

.148

. 0511

.154

.2111

. 116

. 105

.l�&

. 109

.026

.013

.071

. 045

.006

.142

.046

.058

.051

.167

. 1011

.1211

. 1211

.122

. 1118

. 117

. 180

. 165

. 178

.188

.239

.121 • on; .146 . 177 . 160 . 178 . 1153 .8015 . 182 .212 ;225 .2611 .292 .2'7'7 .267 .328 .26:5 .525 .278 .333 .251 .294 .295 .3111 .1274 .263 . 19� . 126 .116

0.0115 .0041 .OOM .0001 . 0004 .0001 .0041 .00111 .0068 .00511 .002'7 .IIOM .002tI .0022 .0001 .oooa .0008 .0012 .0001 .0011 .00211 .000'7 .coee .0010 .coee .0001 .0000 .00015 .0001 . 0000 .0011 .00()1 . � .0001 .OOJ,I .oooe .0009 .00011 .00» .001& .000'7 .0018 .00111 .0017 .00lP .OO�U .0008 .� .0012 .001' .0014 .001'1 .0014 .0021 .0018 .oo:u .002'7 .00511 .000t .0041 . 00511 .0058 .00�'7 .005'7 .0041 .coeo .OOM .0044 .0047 .0056 .0041 .005' .0020 .00011

. • 000'7

-0.01�· _.02112 - . 026'7 -.02� - . 0165 - . 0245 - . 0105 - . 0228 - .0072 - . 0010 - . 01211

.0001

. 0005

. 0055

. 00'78

. 0090

. 0175 • Qall .02111

.0065

. 0281

. 0!151

• 0404 .041:5

.0401

.0426

.0401

. 0372

. 0162

r< tl �j' .... .. <=I • o c •

-0. 014'7

.0051

.014'

-·:Oi� .01'71

.01111

.0210

. 0211

.02'7'

.0llS'

.0441

.048'7

. 0521

. 011..,

.0511

.01121

.0521

.0522

.0514

. 0501

.04911

.042'7

.03511

. 0261 ---�---

.0171

-0.0014 .0180

.orr4 .024'

.01'72

.coee

.0100 .OUII

.CIa .. '7

.0106

.08'r4

.�

.04811

.048'7

.0Ii0'1 .OUII

.0611

.01&1

.�

.06'7 •

.0618

.�

.011111

.01l1iS

.04811

.04154

.041'

.052f.

.02411

.020'7

.0140

.. • .. I • 0 .. .. ... o . · '" .... <1 0 • .. u • u "'" .

0.0127 .0083 .010:5 .0116 .023'1 .0150 .02211 .0112 .0204 . 0255 .0124

.021�

. 016'7

.0168

.01115

.0172

. 0171

. 01112

. 01'76

. 0211

.0250 .

. 0257

.0522

.0348

.036'7 · .ozeo

.O�

.0395

. 0:5113

.0�81

. 03110

.0:568

. 0557

.0:514

.0231

. 0210

0 . 01�

.0170

.0218

.02:51

.0251

.0240

. 0265 .02411

.04111

. 0514

. 0564

.05011

. 05111

. Oli1'7

.0516

.0502

.04114

. 04611

.0452

. 0418

.ono

. 02811

.02211

... • .:; . · i .. . ... 0 · '" . . 0 � .. .. · ... '"

.04M .�'18 .02'71

.02011

.0168

. • 02114

.05111

.041.

.0440

.04611

.0487

. 0514

.0542

.0552

.0560

.0567

. 05.,2 · . 0556

.05:57

•. 0482 '

.O�

.0410

.o� .02611

.0247

.0188

NATIONAL ADVISORY

COMMITTEE FOI AEIIOIIAUTICS

� ......

. ,;

' ;" .;":: or:I

/arqe total head

Fi gu r e 1 . - Th e N o r t h Ame r i can XP- 5 1 ai rp l an e .

SIalic

Iit"" T

r---- ��I ----+-H

1---------- .11-'-./"---------------1

Rib I I�

A IIpptr a6 U Lowr Qj

B � o LOMK 0

e tA- at ""- a6

Tlt;:pw a? '-�

»'M , . � ��l llib T , • • II

Orifice /a:u/;(YJ //7 percelJ/ chr"o' Orillce mOlDer

2 4 ,J 4 5 6 7 " 9 J() II " O K IS /if U .J.S 9.6 J( ;/.1 � J4.Ul.l f4! sz;a., W I.! 2.S 9.6 iJt' U 71. '-aT uil"- .J.7 .1:4 !l.S JI. �4 ar. 4USIlI O. 12.01 ,U 9.S J('�I J(I. 1M , I ... u .1:"- !6NJ az ill' Ii,A' 1M, I"" '" " U 5. ... �6JV <I2.I;>;!' �. I ... I ... 1..-. lZII.!I J.O 1If·? J( HI. .� J ,J.O 16� v. lSO .1U 1«'" � \17.1 'l

17 II /' 10 21

1-------�---J2:cr ----------i

I �

( I \ I I

NATIONAL ADVISORY COMMITTEE FOI AElDllAUTICS

riiure 2 . - L ine d rawi n'i o f XP- 5 1 airp l ane showi n g I O .cat ion o f vari ous i tem •.•

MR No . L 6 F 1 2

MR N o . L 6 F 1 2

I

MR N o . L 6 F 1 2

" b, , I' i � '

" , i , ' r ' , ' " ,

, ! ,

, ; ,'iif ' i : , ' , , i �� : , '�

I

: 1 "

j '

, " I .' niL ' , ' , ' Pi:

• l ' : ' " I ! . � . i ! : : i , , , ' I�, : i : ' i"l : , i , A�i ::�:;;: '"'reT,' i , l ' . .

I i � blii U�;:'jjU ,q:", 1"1'" ' v

i kl:�h'g k, F' '

: 1'''_' " , �,: , 'l",

I I. " � :

" '

I�: :: ' 1' " , ' ' , i i IF ill 1''' n: I�: , " IL:;; ! E:: ; : !

' " V' �' " � '

, I tW , ! I , ' I 'it, I : ' ; ' , � "'fPT I , , ' ,

, I , , ' , , :ji1F: TI l ' I> :i ' ; : : iI+

' . ! i o t:�. !

, I ' I : · ' : 1 I i

" " I e;; ' ' . t : "

Iii::!:" , ! ! . 1 . l' I I " ' i :'('I " �'" : I:�I: : :

' i : ,n: : ' I ! I : :� ' i ' ! i :

i j , I g:;

' . . . ! . ! ; , " : , I'i

, i

! : :

' I ' I '

I , : ! : ! 1 : ! . : i : '

, 'I if ' ." : " : i ' I':

, ,

: : : I ' :

t :

I I

! !

i ! 1 . : 1 i ! ; . i l ; . !

. ! I '

, !

. �I[tj 2 : ; . r ibl�. : " ; . . . . . Ii ! : : i !! I : : ! ! . i l i ! : ! L ! ii ! I .

: 1 '

l ! : " " i' 'I�f ";j: , , T:+: f ! I FY= I ' " :U�: : liii! , " , I ' , i ' , : I I , ' I ! ' ! I 1 I I , i ' ! ! ' : ' I 'j l�!;ii t;� ' jiH''i}:: ' ' , , ' ri l'::' ' ' ' , : ' 1 : : '1 ' 1 , : i : ' i I , ' ; , I , , ' , I I : i i ' I " I : ' i ' l ": k:r � 1i' 0: ' : f!'J:' : ' i , : " ,c;kJf,: : j!�I , " , : C1': I " , , , , " , " , ! , ' ! I ' r '!!'::I I ' : ' , : ji'1LtlU ' , " ' : 1< : I ' I ' ! " , i I Hi !� I I " ! ! I I HI , I ; , ' : i ' ! ! ' , " ; , I : " : , , ' " ; ' "":['i ""f : : : I f , ' : : II:l 'Ii!" : I i : :: : ' , " I," ' , , : 1 ' I " , i ' i ' ' , 1 :

, , : " I :ic , (,: I:' ' : ' " " : I: ' : ' " I:i;' f ' f i , 1 ; '" :: " . . , , , , I i , : , , ' I ' , , , ' i: ' : j;:' ' I : ' ; r il 1 ' , ' 1 " " " ' : '1': ' ' f ' I, , : ",r': i l :: : l i :,i '[i:-;; : f : " 1 im 15' ; 1 : " ; ! : I I I " '":" ' , , " , : " ,' " L , : , , :, : f :1: : : : : " l':¥ : ' ;, i f f f ' ' I f l f!' ; i : , , : 1 ' : J" i " "

" ', " I" in",1 " f' J J' 2 < ': 1':: ' I> ', iY:: i ' i ' , !)i'i'f ' , 'H'" , , ill : ! ' i , ' I " ' I I '

f-f-t-

I ! I � ,

t i

li H I'li'I 'lL' ' L; rl:lJ I t : Ii" ,j,,- :

II ,.)-,5 ..... .... (r...,.. 'I-Val�1 �.; , , " ,' : I--II-+-+-+-l--I--i-+--+-f-++ l i '" I ' 'Iu , r:':LlFIC , .' " 1 ''1 i- l --'i -f-+--j-,-j, '.,,-, ' '+-" +'1 1:"'1, C-+-+C+ .. :-;.-"'": ,�-+-"l

3: :::0 Z o .

MR N o . L6 F 1 2

MR N o . L 6 F 1 2