The investigation was made to determine the effects of full-span and of partial-span split flaps on the aerodynamic characteristics of a tapered wing. Aerodynamic force tests were made in the N.A.C.A. 7 by 10 foot wind tunnel on a highly tapered Clark Y wing equipped with various split flaps. Two sizes of tapered-chord flaps were tested as full-span flaps, and a narrow tapered-chord flap was tested as a partial-span flap by cutting off portions first from the tip and then from the center. The investigation showed that with full-span split flaps the lift and drag characteristics of the tapered wing up to the stall are similar to those of a rectangular wing with flaps of comparable size, but that the stall of the tapered wing with full-span flaps occurs at progressively lower angles of attack with increasing flap deflection up to that for maximum lift. For partial-span tapered split flaps on a tapered wing it was found that the maximum lift is greater, and the lift-drag ratio at maximum lift is less, when the partial-span flap is located at the center of the wing than when it is located at the tip portion

Wenzinger, Carl J

English

NASA Technical Reports Server

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TECHNICAL NOTES
ITATI02TAL ADVISCIRY COl!MITTZIE FOR AEROFIAU~t CS
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TEE AERODYNAMIC CHARACT3R1STICS OF
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By Carl J. Wen~ingOr
Lahgley Memorial Aeronautical
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NATIONAL ADVISORY COMMITTEE I’OR AERONAU!i!ICS
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TECHNICAL NOTE NO. 505
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THE EFFECTS OF I!’ULL-SPAN .4NJ3PARTIAL-SPAN SPLIT FLAPS ON
TIiE AS!!RODYNAMIC CHARACTERISTICS OF A TAPER3D fiN&
By Carl J. Wenzinger
SUMMARY .
The investigation was made to determine the effects
of full-span and of partial-span split flaps on the aero-
dynamic characteristics of a tapered wing. Aerodynamic
force tests were made in the N.A,C.A. 7 hy 10 foot wind
tunnel on a highly tapered Clark Y wing equfpped with va-
rious split flaps. Two sizes of tapered-chord and two
sizes of constant-chord flaps were tested as full-span
flaps, and a narrow tapered-chord flap was tested as a
partial-span flap by cutting off portions first from the
tip and then from the center.
The investigation showed that with full-span split
flaps the lift and drag characteristics of the tapered
wing up to the stall are similar to those of a rectangu-
lar wing with flaps of comparable size, but that the stall
of the tapered wing with full-span flaps occurs at pro-
gressively lower angles of attack with increasing flap de- .
flection up to that for maximum lift.
.-
For partial-span tapered split flaps on a tapered
wing it was found that the maximum lift and the drag at
maximum lift is greater, and the lift-drag ratio at maxi-
mum lift is less, when the partial-span flap “is ~ocat6&
at ‘the center of the wing than when it is located at the
tip portion. .- , ..
INTRODUCTION ., —. .
Split trailing-edge flaps are being used to a consid-
erable extent for improving the landing properties of air-
planes by increasing the maximum lift and also the “drag.
Airplanes so equipped are enabled to land more easily in
restricted areas because of their wide range of gliding
angles and because of shorter ground runs. The split
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2 l?.AaCsA.o Technical Note No. 505
trailing-edge flap is farmed by snlittiag the rear portion
of the wing into upper ,and lovor ;~ctions and deflecting
the lowor section downward for u’se as a flap. This typo
of flap may be used over the ~Vtiro spqn of ~hg. wlngl or
may have portions of the flap near the t“ip”cut off for the
use of lateral control devices,. or it ‘may have a section
cut out at the center “for the fuselage.
.
e
l-
The aerodynamic charactorietics of rectangular wings
with full-span and with partial-span split flaps have been
previously reported in ref~rencos 1, 2, and 3. Tho pres-
e~t investigation was made to determine the ch&ractcrie-
tics of a tapered wing with full-span and with partial-
span split flaps. Two sizes of flapsl mod~um and narrow
chord, and twQ typ’os, tapered e,nd constant chord, were
teste-d on a highly tapered Clark-Y ~ing. All. the tests
were conducted in the N.A,C.A. ? by 10 foot wind tunnel.
AI?PARATUS AND TESTS
.
ModeQ.- Th.e.wing model.?l~ed in these tests was ta-.
——.—
pered 5:2, the slope of the leading and trailing edge8 be-
ing the same {fig. l). The Clark Y profile was used at
all sections along the span, and the maximum ofiin~tes .of
all sections were in a horizontal plane on the upper s’ur-
face. The model was constructed of lamltiated mahogany,
with a span of. 60 inches and an aspect ratio of 6.0.
The tapered flaps were tapered with ‘the vfing6, the
chord of the narrow ones (A, fig. 1) at any longitudinal
section being 15 percent of the wing chord at the same sec-
tion, and the chord of the medium-”si.ze.dones (C, fig. 1)
being 25 percent of the wirig chord, The flaps with con-
stant chords (B and D, fig. 1) had the same chord dimen-
sions as the average chords Of the respect- tapered flaps.
All the flaps were made of 71=
-inch” steel plate and wore
screwed to the wing, They ‘were doflegted about the axes
Silownj the angles being measured in a plane normal to tho
axis of deflection.
Wind tunnel - The .7 by JO foot wiad .tuqnol h&s an ‘open
——— l
jet and a single. closed re.t’urnpassage. The tunnel, togeth- ,-
er with the regular -balance and associated apparatus, iS
described in detail in ref%rence 4.
.
H.A. C.A. Technical Note Nb”. 505 3
“1
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Tet3ts,. - The tests were made-at a dynamic pressure of
16,37 pounds per square foot, co”rres-pending to an air
speed of 80 miles per hour at standard density, and the
Reynolds Number was 609,000, based on the average wing
chord. The data were not corrected for tunnel-wall” effect.
The wings with full-span split flaps were tested with
the flaps having deflections from 0° to beyond those for
the maximum CLmax obtainable. The angle-of-attack range
was from zero lift to beyond the stall, an~ readings of
CL, CD, and Cm were taken at sufficient points to define
the curves. The junction of the flaps at the center of the
wing Wa-s-tia”decontinuous by covering the srna~ zap ivith””
thin paper for each different flap deflection. Check’t68ts
with these gaEs open showed that-the effect was to :reduce
the maximum lift and increase the drag at maximum lift %y
about 1 percent. ..
The wing with narrow tapered-chord flaps was tested
‘ also with these flaps as partial-spaa split flaps~ with a
deflection of 60° down. These flaps were used since they
appeared to” be the most practical of those tested as full-
span flaps. The wing Was tested first with the partial-
span flape having sections of equal length rmoved from
the ttpe, and then with sections of the same total Ien&”th
removed from the center of the span, The flap length wap
reducud. by cutting off portions of the flap in steps of 209
40, 60, and 80 percent of the span.
-.
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RESULTS AND DISCUSSION
Full-Span Split Flaps
Lift, dra~,.-q.nd c@.- Curves of lift and drag coeffi-
cients, and center-of-pressure loca-tion are given in fig-
ures 2, 3, 4, and 5 for the wings, with the various full-
span split flaps tested. Flap deflections are included
for each flap up to the angle giving the maximum CLmax
obtainable. The shapes of the curves for the arramgemerits
tested exhihit no unusual characteristics up to the” stall,
and are similar to those given in reference 2 for flaps of
comparable sizes on rectangular wings. ‘- – - J “’- ~;
— ::==
—
—
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4 Y.A.C.A. Technical Note XO. .5O5
:One Feint of interest that-ma:’- be noted is that the
stall occurs at pro~res’sively lower angles of attack with
i.nereasing flap deflection for the tapered wing with the
flaps tested. Thee ffect is most noticeable for tho 0.25c
com~tant-chord flap in which case the angle. of attack of
the stall was reduced from 17° with flaps neutral to 13°
with flaps down only 30°. The rectangular wings with split
flaps did not show this characteristic but stalled at about
the’ same angle of attack with flaps either neutral or de-
flected. (See reference 3.)
L/D atcLmex ______and CLnax*” The maxtmum lift coefff.-
..-— ——— ---....=-... .
.—.— .- --- -
cients obtained with the tapered wing with the variou6
‘ flaps, and the flap deflections required are shown on fl.g-
ure 66 Both tapered-chord flaps give tl~g wing somewhat
higher maximum lifts than the const-ant-c?~ord flaps, and
the tapered-chord flaps %oth give the ving about the same
maximum lift although with different flap deflections.
Curves of L/D at ‘Lmax are also given on figure 6
for the wing with the different flaps and flap deflections
~“the steepest glidingtested, This factor is a measure o.
anCle attainable with the wing for use in the landing con-
dition, the smaller the value the steeper the glide. The
medium-sized flaps would gl.ve the wing shaper angles of-
glide than-”the narrow f~aps-”,the difference being about 2°.
The angle is steepened from 7° with flaps neutral to about
13° with the medium-sized flaps deflected.
Partial-Span STlit Flaps ‘
Tip sections removed.- Curves of CL, CD, and C*PS—— —
are given on ~iguro 7 for the 5:1 tapered tvifig having
0.15c- tapered flaps with difforoat equal-length sections
removed from both tipe. The lift ctirves do not havo as
sharp a drop just after the, stall as those for partial-
span flaps on a rectangular wing (rofErenc@ 3) . lt should
also bo mentioned that the .drkg doe~ not fall of-f nearly
so fast when shor”t sections -of “the tiap”e~ed‘flaps aro re-
moved from the tips as it does in tho Ca~O of a rectangu-
lar wing with split flaps of the same longt”h.
Qenter sections rexoved.- !?igure 8 :;ives curves of-——— ——— -.—
CL, CD, and c,,p. for tlie 5:1 tapered wing having split
flaps with different amounts removed from the center of the
span. In this case the drag variation is more like that
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IIS-A-A.C.A. Technical Note No. 505 5
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for the rectan@lar wing with split flap’s”. ~~-cent%r Of
pressure moves forwart% quite rapidly when short sectio~,s’”
are removed from the ce’~ter of the span, compared with a
small movement when corresponding sections are removed
from the tips.
Comparison of effect of removing
.— .——— ——
sections from the
—— ——.——
tip’ a~~ from the center.- Curves of CLmax, and of CD———— ———-
and L/Ii at CL-X are given on figure 9 for different
flap lengths, both for tip sections removed and for center
sections removed. It should be mentioned that a consider-
ation of the flap effects on the basis of flap areas would
probably lead to somewhat different conclusions, but in the
present case the flap lengths seemed to he of the gfeate’r
interest and hence are the only ones discussed. Figure 9
shows, as for partial-span flaps on a rectangular wing
(reference 3) , that a sommhat smaller part of the maximum—-
lift is lost by cutting off the tip sections than by remo-i+-
ing center sections of the same total length.
The drag at maxinrum lift, however, is also affected
by the location of the portion of the flap removed from
the tapered wing, which was not the case w$th the rectan-
gular wing. It will be noted that, as in the case of the
.maxim~m lift of the tapered wing, a smaller part of the
drag at maximum lift is lost %y cutting off the tip sec-
tions than %y removing center sections bf the same total
length.
The foregoing characteristics are also indicated by
the curves of L/D at maximum lift shown on figure 9. . A
steeper angle of glide could. be obtained with the tapered
wing and flap combination tested by removing sections of
the same length from the tip rather than from the center
if partial-span flaps were required. !This characteristic
Zs just opposite to that of a rectangular wing with.par-
tial-span split flaps.
.,
CONCLUSIONS
1. The lift and drag characteristics of a tapered
wing with full-span split flaps up to the stall are simi-
lar to those of a rectangular wing with fla~s of compara-
ble sizes.
.
——. ._. _
.,’
6 N.A.d. A, Technical Note Eo. 505
2. The stall .of a tapered wing with full-span split
flaps occurs at progressively lower ang2es of attack with
increasing flap deflection up to that for CLmax.
3. On a tamered wing, full-span tapered flaps give
higher maximum l_ift coefficients than constant-chordf laps
of comparable sizes.
4. The maximum lift and the drag at irtaximun lift of
a tapered wing with a tapered flap extendlkg, over part of
,the span is greater, and the L/D at maximum lift is lese,
when the partial-span flap is located at the center of the
wing than. when it is located at the tip portion,
Langley Memorial Aeronautical Laboratory,
.’ National Advisory ComWittee Xor Aeronautics,
Langley Field, Va. , September 6, 1934.
..
REFERENCES
l, Weick,. I?red l!., and Harris,, Thomas A.: The Aerodynamic
Characteristics of a liodel Winq Having. a Split I?lap
Dbflected Downward and koved to tire Rear. T.N. No,
422,’ ~~.,AOCiA,, 1’932.
I
2, Wenzinger, Carl J.: Wind.-Tunnel Measurements of Air
~ Loads on Spiit Ylaps. T,No Kc). 498, N,A.C.A. , 1934.
3. Wenzinger, Carl J.: The Effect of Partial-Span Split
Fl&ps on’ the Aerodynamic Characteristics of a Clark
.. Y Wing. T,Ni ~~, 472, N.A.C.A. , 1.933,
,,
4,. Harris’, Thomas A,: The 7 by l@ l?oot‘Wind Tunnel of the
,’
National Advisory Committee for Aeronautics. T.R.
.
~0, 412, N.A.C.A,, .1931. *
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N.A.C.A. Technical Note No.505 G.‘
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Elevation
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Fig. 1
;-Section showing flap
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B
Figure 1.- ‘-
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on 5:1,
ta~rea . ‘:
Clark Y
wing.
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N.A.C,A. TechniczilNote No. 505
-. Figs.2,3
Figure 2.-The 0.15ctapered- Figure 3--The 0.15cconstant-
chord splitflaps along chbrd splitflapsalong
entirespan of 5:1tapered wing. entire span of 5:1tapered wing.
.
N.A.C.A. TechnicalNote No. 505 F5gs.4,5.
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Angle of attack,d,egrees,:4
Figure 4.-The 0:Z5Ctapered- Figure 5.-The 0.25c constant-
chord splitflapsalong chord splitflapsalong ‘-–
entirespan of 5:1tapered wing. entire span of 5:1tapered wing.
-
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“Figure6.- Effect of flapshape and deflectionoh
c~tiX andon L/Dat CLm~fOr 5:1
tapered wing1
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Hap le;-gth,percentagewing span
CD
at
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“~,T@uFe 9.- Effect of partial-sPansP lt
flapa ~CLmu andon%~a
l@atCL~X. ~ 0.15ctapered-&ord,i;
flaps On s:ltaperedwing,%- 60°.
.N.A.C.A. TechnicalNote No. 505 Figs.7,8
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flaP,6F= 60°
If ~-- —O. OObflap– –
;1//, --—0.60 u “
-—0.40 u’ # :
x-------0.20” “— –
+— Plain wing—
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Splitflapswith tip Figure 8.-Splitflapswithcenter
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Figure 7.-
s~ctions removed
on 5:1tapered wing.
—


The effects of full-span and partial-span split flaps on the aerodynamic characteristics of a tapered wing

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