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Wind Tunnel Investigation of Control Surface Characteristics - VI - A 30% Chord Plain Flap on the NACA 0015 Airfoil

SUMMARY

Force-test measurements in two—dimensional flow have
been made in the NACA 4- by 6-foot vertical tunnel-of the
characteristics of an NAOA 0015 airfoil equipped with a
plain flap having a chord 30.percent of the airfoil chord
and a plain tab having a chord 20 percent of the flap
chord. The results are presented in the form of aerody—
namic section characteristics for several flap and tab de-
flections and for a sealed and an unsealed gap at the flap
nose.

The slope of the lift curve of the NADA 0015 airfoil
Was slightly less than the slope of the corresponding
curve for the previously tested NAGA 0009 airfoil, but
the effectiveness of the plain flap in producing.incre~
ments of lift was practically the same for both airfoils.
For the thicker airfoil the variation of flap hinge moment
with angle of attack was about one~third and with flap de-
flection about one-half. of that for the similar flap on
the thinner airfoil. Unsealing the gap at the flap hinge
axis had a greater effect on the characteristics of the
lB-percent—thick airfoil than on thOse of the 9—percent-
thick'airfoil.

INTRODUCTION

The NADA has instituted an extensive investigation
of the aerodynamic characteristics of control snrfaces in
an effort to determine the types of fla'p arrangement best
suited for use as control surfaces and to supply experi-
mental data for design purposes. The first phase of this
investigation consisted of the experimental determination
of the pressure distribution en the NACA 0009 airfoil with
many sizes of plain flaps and tabs. The results of these
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2

tests have been summarized in reference 1, which presents
parameters for determining some of the characteristics of
a thin symmetrical airfoil with a plain flap of any chord.

The second phase of the investigation consisted of
force—test measurements in two—dimensional flow of the
characteristics of an NACA 0009 airfoil with a 0.30c flap
having variations in aerodynamic balance, in the shape of
the flap nnse, in the size of the gap at the flap nose,
and in the trailing~edge shape of a flap of thickened
profile. The results of these tests are reported is ref-
erences 2 and 3 and in the papers listed in the bibliog~
raphy.

As a OOntinuation of the investigation, tests have
been made to provide data for the NACA 0015 airfoil with
flap arrangements similar to thOBe already tested on the
NACA_0009 airfoil. The present paper presents the aero~
dynamic section characteristics of an NAGA 0015 airfoil
with a 0.300 plain flap and a 0.20cf plain tab.