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Wind Tunnel Investigation of Control Surface Characteristics - VIII - A Large Aerodynamic Balance of Two Nose Shapes Used with a 30% Chord Flap on an NACA 0015 Airfoil

SUMMARY

Force tests in two~dimensional flow have been made
in the HAGA 4— byJS—foot vertical tunnel of the character—
istics of an NACA 0015 airfoil with a balanced flap having
a chord 30 percent of the airfoil chord, a flap—nose over—
hang 50 percent of the flap chord. and a tab having a
chord 20 percent of the flap chord. The results are pre~
sented in the form of aerodynamic section characteristics
for a sealed and an unsealed gap at the flap nose.

The slope of the lift curve and the lift effective—
ness of the balanced flap were slightly less than those
for the HACA 0009 airfoil with the same flap. The aerody—
namic balance of 50 percent of the flap chord caused over—
balance through some range of deflections for both nose
shapes tested with gaps sealed and unsealed. The blunt
nose shape was more effective in reducing hinge moments
than the medium nose shape. Unsealing the gap at the nose
of the flap caused a decrease in the slope of the lift
curve and an increase in the effectiveness of the balance
for both nose shapes.

INTRODUCTION

The NACA has instituted an extensive investigation of
the aerodynamic section characteristics of control surfaces
in two—dimensional flow in an effort to determine the types
of flap arrangement best suited for use as control surfaces
and to provide experimental data for design purposes. The
first phase of the investigation consisted of the experi—
mental determination of the pressure distribution of the

NASA 0009 airfoil with many sizes of plain flaps and tabs.
The results of these tests haVe been presented in refer—
ence l in the form of parameters for determining the char~
scteristics 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 HACA 0009 airfoil with a 30—percent—
airfoil—chord (0.300) flap having various amounts of aero—
dynamic balance, various flap~nose shapes, various sizes
of gap at the flap nose, and Various beveled trailing
edges on a flap of thickened profile. The results of
these tests are reported in references 2 to 6.

A series of tests has been undertaken to provide data '
for the NAGA 0015 airfoil with a 0.30c flap and a 20—
percent—flap—chord~(0.Bch) plain tab, with various flap~
balance arrangements as previously tested on the NACA 0009
airfoil. The results of the'tests are presented in refer—
ence 7 for the plain flap, in reference 8 for the flap
with a 0.35cf aerodynamic balance, and in the present pa~

per for the flap with a 0.50cf aerodynamic balance.