Flight investigation at high speeds of profile drag of wing of a P-47D airplane having production surfaces covered with ...

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Material Information

Title:
Flight investigation at high speeds of profile drag of wing of a P-47D airplane having production surfaces covered with camouflage paint
Alternate Title:
NACA wartime reports
Physical Description:
7, 7 p. : ill. ; 28 cm.
Language:
English
Creator:
Zalovcik, John A
Daum, Fred L
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Mach number   ( lcsh )
Fighter planes   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: A flight investigation was made at high speeds to determine the profile drag of a P-47D airplane wing having production surfaces covered with camouflage paint. The profile drag of a wing section somewhat out-board of the flap was determined by means of wake surveys in tests made over a range of airplane lift coefficients from 0.06 to 0.69 and airplane Mach numbers from 0.25 to 0.78. The results of the tests indicated that a minimum profile-drag coefficient of 0.0097 was attained for lift coefficients from 0.16 to 0.25 at Mach numbers less than 0.67. Below the Mach number at which compressibility shock occurred, variations in Mach number of as much as 0.2 appeared to have no effect on profile-drag coefficient. The variation in Reynolds number corresponding to this variation in Mach number, however, was appreciable and may have had some effect on the results obtained. Comparison of the Mach number at which shock losses were first evident in the wake with the critical Mach number indicated that shock was not evident until the critical Mach number was exceeded by at least 0.025.
Bibliography:
Includes bibliographic references (p. 6).
Statement of Responsibility:
by John A. Zalovcik and Fred L. Daum.
General Note:
"Report no. L-98."
General Note:
"Originally issued March 1946 as Advance Confidential Report L6B21."
General Note:
"Report date March 1946."
General Note:
"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 unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003613208
oclc - 71205552
sobekcm - AA00006249_00001
System ID:
AA00006249:00001

Full Text

ACR No. L6-21
ACR No. L6B21


NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS





WARTIMDIE REPORT
ORIGINALLY ISSUED
March 1946 as
Advance Confidential Report L6B21

FLIGHT INVESTIGATION AT HIGH SPEEDS OF PROFILE DRAG
OF WING OF A P-47D AIRPLANE HAVING PRODUCTION
SURFACES COVERED WITH CAMOUFLAGE PA3I2T


By John A. Zalovcik and Fred L. Daum

Langley Memorial Aeronautical Laboratory
Langley Field, Va.


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.


DOCUMENT S DEPART MEN [


*- .....


L 98











-.:,c: ',c :'!. L6321 3 / 3 U

I:-TI ";AL ADVISORY CC.i:.I'T.E FR' AIONAUTICS


ADVANCE CCfFID7rTIAL REPORT


F-T'IT Ii;i 3TIGATION AT HIGH SP3'EDSL OF PROFILE DRAG

CF '.lI7;' OF A P-1-17D AIRPLA-X'T HAVING PRh:DUCTION

SiRF'iCES COVTERD WITH C..:.J.LAGE P.IJl?

By John A. Zalovcik and.Fred L. Daum





A flight investigation was made at high speeds to
deterr.ine the profile dra, of a P-).L7D airplane wing
-avzrin production surfaces covered with camouflage
ga-it. The profile drag of a wing section somewhat out-
b,: crd of the flap was determined by means of wake surveys
in te:ts made over a range of airplane lift coefficients
frc: : .6 to 0.69 and airplane MTach nuiybers from 0.25
to '". ~. ..

The results of the tests indicated that a minimum
pr'.ofiie-drag coefficient of 0.0097 was attained for
lift coefficients from 0.'16 to 0.25 at ,aT-.h numbers less
tha, .17. Below the :i;ch number at which compressi-
L'-ll;- shock occurred, variations in Mach number of as
ul. L 0.2 appeared to have no effect on profile-drag
coef- _.fi' ent. The variation in Reynolds number corre-
spr'!,o:ni to this variation in 'tiach number, however, was
ap'ireciable and may have had some effect on the results
obL.a.-ed. Conuparison of the _Mach number at which shock
losses were first evident in the wale with the critical
iaci. niuaber indicated that shock was not evident until
t;'e cr-L.ical iach number was exceeded byT at least 0.025.


I. T'rT .DUCT ION


A flight investigation was made to determine the
pr'_.fl'ie-drag characteristics of a P-47D airplane








CO!NFIDE TIFAL


wilng with various surface finishes. T'o phases of this
investigation were reported in references 1 and 2, and
the third and last phase is reported herein. In refer-
ence 1 results were reported of tests made to determine
boundary-layer-transition locations and profile dr9g of
a wing section with faired and smoothed surfaces. In
reference 2 results were reported of tests made to de-
termine the effect of surface roughness on the profile
drag of the faired surfaces with transition fixed far
forward. The results reported herein are of tests made
to determine the profile drag of a wing section having
unfaired production surfaces covered with camouflage paint.
The present tests and those of references 1 and 2 included
Mach numbers !-.rough the critical values; in the present
tests, however, the :.cach number range was extended to
somewhat hig-her suoercritical values than those of ref-
erences 1 and 2.

Profile drag was determined by means of wake surveys.
The tests were ma-de for conditions in which airplane lift
coefficients from 0.06 to 0.69, Reynolds numbers from
8.4 x 106 to 25.1 x 106, and ,1ach numbers from 0.25 to 0.78
were obtained.


APPARATUS A:ID TESTS


The investigation was conducted on a right wing sec-
tion of a P-47D airplane (fig. 1). This wing section,
a Republic S-5 section, had a chord of 86.05 inches, a
thickness of 11 percent of the chord, and was located at
65 percent of the semispan from the plane of symmetry, or
about 2 feet outboard of the flap. At this spanwise sta-
tion the test section included the aileron but was out-
board of the propeller slipstream, the gun ports in the
leading edge, ani the shell ejector slots in the lower
surface. 1:P3 measured ordinates of the test section are
given in fractions of the chord in table I. The Republic S-5
section tested has pressure-distribution characteristics
similar to those of the :IA.CA 25011 airfoil.

T:ie surfaces of the test section were prepared by
covering the production surfaces with one coat of zinc
chromate primer, one coat of gray surface, and two coats
of olive-trab cam ouflage paint. eoacurements of surface
r-oueiiness made by means of a sh.p microscope (described
in reference 2) indicated that the surface roughness con-


C O. F-.ITI AL


ACA AR ;r,-.. Lu321








C .iC:: L6E21 CONFIDENTIAL 3

slited of particles of about 0.0012 inch in height and
n.-berling roughly 10,000 per square inch.

An indication of surface waviness was obtained by
:ne ns of a curvature gage (fig. 2) with legs spaced
S-,erc!eit of the test section chord. The waviness con-
Jition of the unfaired and roughened production surfaces
and also of the faired and smoothed surfaces of refer-
ence 1 is indicated in figure 4 by the plot of the
*w.-iiness index d/c against s/c, where d is the de-
flection of the curvature gage, s is the distance along
the surface from the leading edge, and c is the test sec-
tion chord.

Profile-drag measurements were made with a wake-survey
rak!e (fit. 5) located 19 percent of the'chord behind the
tr-ilin: edge of the test section. The rake was the same
as that used in references 1 and 2 except that two tubes
spaced four inches were added to each end of the rake (mak-
ing a total width of 23.9 inches) in order to permit a
survey of more of the wake at supercritical speeds than
in references 1 and 2. Wake total and static pressures,
free-stream impact pressure, and the position of the right
a'leron were measured with NACA recording instruments.
The section profile-drag coefficients cdo were determined
by the integrating method of reference 3; that is, the
total-pressure loss was integrated across the wake and
then multi-lied by factors dependin.-, on free-stream im-
pact 2ressu-re, maximum total-pressure loss, static pressure
in the wake, and flight Mach number.

The tests were made in level flight, dives, and turns
at 20,000 feet and over a range of calibrated airspeeds
from 150 to 415 miles per hour. The airplane lift co-
efficient CL obtain. in the tests ranged from 0.06 to 0.69,
the Reynolds number R from 8.4 x 106 to 23.1 x 106 and the
;ac. number M from 0.25 to 0.78.


RESULTS AND DISCUSSION


The investigation of flow conditions indicated by
surface tufts located over a portion of the upper sur-
face of the P-47D airplane wirng, reported in reference 4,
showed that somewhat inboard of the test section, at 65
percent semispan, cross flow was present at Mach numbers
greater than 0.70 at a lift coefficient of 0.40 and


CONFIDENTIAL








4 CONFIDENTIAL I.-.A ACR :. L6B21

---ater than 0.76 at a lift coefficient of 0.15. Be-
cause of this flow condition and the fact that the wake
at ?:a.h numbers greater than 0.66 at a lift coefficient
of 0.40 and greater than 0.72 at a lift coefficient of
0.15 extended beyond the limits of the wake-survey rake,
the wake surveys for these flight conditions were not
evaluated.

Profile-drag coefficients selected for several lift
coefficients for which the data were most complete are
plotted against Mach number in figure 5. The correspond-
ing Reynolds numbers are plotted above the profile-drag
curves.

Figure 5 shows that the profile-drag coefficient de-
creased with lift coefficient and attained a minimum
value of 0.0097 over a range of lift coefficients from
at least 0.16 to 0.25 at Mach numbers below 0.67. The
minimum value of the profile-drag coefficient of the
faired and smoothed surfaces reported in reference 1 was
0.0062. At Mach numbers below that at which compressibil-
ity shock was evident, as indicated by the rapid in-
crease in profile-rrag coefficient, variation in Mlach num-
ber of as much as 0.2 appeared to have no effect on the
profile-drag coefficient. This variation in MIach number,
however, was accompani-ed by an appreciable variation in
Reynolds number, which may have had some effect on the re-
sults obtained. In the tests of references 1 and 2 var-
iations in Mach number of as much as 0.16, with negligible
variation in Reynolds number, had no effect on the profile-
dria coefficient for the wing section with smooth surfaces
and for the wing section with smooth and rough surfaces
with transition fixed far forward.

The flight Mach number and airplane lift coefficient
at which compressibility shock losses became evident in
the wake are shown by figure 6. The rapidly increasing
with of wake with :.'ach number is shown in figure 7 as an
indication of the presence of compressibility shock losses
in the wake. In this figure the total-pressure loss across
the wake is presented for several Mach numbers at a lift
coefficient of about 0.16 as a plot of AH/qc against y/c,
where AH is the loss in total pressure at position y in
the wake, qc is the free-strcam iar-act pressure, and c
is the chord of the wing section. (Position y/c = 0 cor-
responds to the top tube of the rake.) Wake profiles for
Mach numbers 0.64 and 0.67 showed no evidence of shock, but
profiles for 'ach numbers 0.68, 0.70, and 0.78 indicated
shock of increasing intensity on the upper surface.


CO:;FI Di.TI AL










..:-' ACR :-". L6:21 CONFIDENTIAL 5


In filure 6 the demarcation of flight conditions-
with res-ect to the presence or absence of shock losses
in the wake is well definel. At lift coefficients of
0.13. a.s 0.50, shock was first indica-ed at Mach numbers
0.-. an' 0.62, respectively. Ter first indications of
shock in the wake as shown by fi'--re 6 correspond to the
be,: n:i'.n of the rapid increase in profile-drag coef-
ficients in figure 5.

rTe critical :.ach number for the wing section having
production si.zrfaces covered with camouflage paint was not
determined. Tle critical Mach number, for the corres-oin lin
left wing section with faired and smoothed surfaces,how-
ever, was determined in tests reported in reference 1.
This critical T'ach number, shown plotted in figure 6, may
be as much as 0.05 too high for the present tests because
of the method of :-easuring the chordwise pressure distri-
bution anf because the left aileron was deflected u.-.ard
about 30 and the right aileron was deflected downward
about 10. .Cormarison of the :Ach number at which shock
was first evident in the wake with this critical MIach
number indicates that shock losses were not evident in
the wake until the critical Mach number was exceeded by
at least 0.025. A similar result was obtained in refer-
ences 1 and 2 except that, in reference 1 for the faired
and smooth wing section, the critical ich number was
exceeded by at least 0.0i. The appearance of shock in
the wake of the unfaired and roughened production sur-
faces at a lower .a'ch number than for the faired and
smooth surfaces \:. be associated with a lower critical
.:'ach number for the unfaired and roughened :. :,duction
surfaces than for the faired and smooth surfaces.


CON CLUS I~-


Th-e ilit in-etigation of the profile drag of
a F-ID73 -ir-iani .e .I -li havingg production surfaces covered
with cI.'-ouflag ;-aint indicated the followi.:- results:

1. .A miLir-.ul: .rofile-d'r-. coefficient of 0.0097
was Lttoi:;;ed for airil-ne lift coefficients from 0.16
t3 '.25 .-t :.:a -h nm-iers below 0.67.

2. 3elo" the ,:Scih number at which compressibility
shock .kas e.viL:;t, Cas indicated by rapil rise in profile-
dra coefficient, va.ri.ation in ":1;h number of as much as


CO:7F r.-E::T:-.L









6 COC'VITT I TIAL K.i'A ACR Ho. L6B21


0.2 e- ear-.J to ir'.v no effect on profile-dr: g cceffi-
cient. The variation in ':--n:olds number that corres.l:n.cc.
to this variation in iLl.c. ntober was:... :re c iab le and :.:v.
h:.'.A h ..., some effect on the results obtained.

5. Comparison of the ach nu.:ber at .hiich shock
losses were first evident in theo ake with the critical
ITach inumLber of t.e v.w-:i section s:ith f aired and snroot-
t faces indic. ;l-. that colpressiobili shodc losses
wesre not evident until the critical Mach munuber was
exceeded by at least 0.02,.


Lar..71; j '..::?rial oniarltical Laboratory
1-.'-ional Advisoory Co;m.ittee for Aeronautics
Lan!rgle Field, Va.





1. Zalovcik, John A.: F ".it Investigation of _- ary-
Layer and Profile-Dr Characteristics of S:mooth
i:.- Sections of a P-47D Airplane. IACA ACR
5--. L5-E -a, 1'45.

2. Zacvcik, John .'., and 7ood, Clotaire: Flight
InvestiU:tion of the Effect of .,i..rface noushness
on ,Ting Profile DrL- with 4 .ansition 71::ed.
-'ACA :>. LlT2L l l41..

3. Silverstein, A., and Katzoff, S.: A 3 1 lified .thod
for Deter- :.i.- 7..:-. Prr"'ie ;. in P1. ..t. Jour.
Aero. Sci., vol. 7, no. 7, ay I I., ;? :"5-7--1

. '.,.>,od, Clotaire, and Zalovcik, John A.: Fli _' Inves-
tigation at iigh .: ?-,:ds of Flo. Conditions over an
Airplane -i. as Indicated -:- .iuface T-'ts. ;..CA
CB No. L52- ..


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OEDI ..'T-r O0 -:" ULLIC S-5 :.I0 "'ICTIO T._i rT
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ll values giver in fractions of clhod;
or:dinates ;aic-ur;ed rel'ativ to an arbi-

ec, o:e o il ro in line wv:1 .L trail.ing
';dJ of flapj



: t ion --
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CONFIDENTIAL
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NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


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CONFIDENTIAL


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NACA ACR No. L6B21


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CONFIDENTIAL


NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


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Figure 5.- Profile-drag coefficient of P-47D wing section having
production surfaces covered with camouflage paint. Reynolds
number is plotted above drag curves.


Fig. 5







NACA ACR No. L6B21


CONFIDENTIAL

o No evidence of shock in wake
+ Evidence of shock in wake
--First indication of shock in wake
---Critical Mach number for section with faired
and smoothed surfaces (reference 1)


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NATIONAL ADVISORY
COMMITTEE FOR AERONAUTICS


Figure 6.- Variation with airplane lift coefficient of
critical Mach number and Mach number at which shock
became evident in wake.


CONFIDENTIAL


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Fig. 7 NACA ACR No. L6B21






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