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Wind Tunnel Investigation of Control Surface Characteristics - VII - A Medium Aerodynamic Balance of Two Nose Shapes Used with a 30% Chord Flap on an 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 NADA 0015 airfoil with a balanced'
flap having a chord 30 percent of the airfoil chord and a
flap—nose overhang 55 percent of the flap chord. The ef-
fect on the aerodynamic section characteristics of the
shape of the flap~nose overhang and the gap at the flap
nose was investigated. A few tests were made to deter-
mine the effectiveness of a 20—percent-f1ap~chord tab on
the balanced control surface.

The test results, presented in the form of aerody-
namic section coefficients, indicate that the lift effec—
tiveness of the flap was practically identical with that
of a similar flap previously tested on the NADA 0009 air;
foil and with that of a plain unbalanced flap of the same
chord On either airfoil. The slope of the curve of hinge-
moment coefficient as a function of angle of attack was
positive over a small range of angles of attack when the
gap at the flap nose was unsealed. With a blunt—nose
flap the variation of flap hingeumoment coefficient with
flap deflection was about one—third, and with a medium-
nose flap. about one—half that of a plain unbalanced flap
of the same chord on the same airfoil. The flap—nose
overhang was more effective as a balancing device when

the gap at the flap nose was unsealed than when it was
sealed.
IRTRODUCTIOH

The HACA has instituted an extensive two—dimensional—
flow investigation of the aerodynamic section characteris—
tics of centrol surfaces in an effort to provide experi-
mental data for design purpOses and to determine the types
of flap arrangement best suited-for use as a control sur—
face. In the first phase of this investigation the pres-
sure distribution of the NAGA 0009 airfoil with many sizes
of plain flap and tab was experimentally determined. The
results of these 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 two~dimensional~flow investi—
gatiOn consisted,of force~test measurements of the charac-
teristics of an NACA 0009 airfoil with a 30—percent—air-
foil—chord flap having various amounts of aerodynamic bal~
ance, various flap~nose shapes, and various sizes of gap
at the flap nose. The results of these tests are reported
in references 2, 3, 4, and 5. The effects of various cir-
cular, elliptical, and beveled trailing edges on the hinge
moment of a flap of thickened profile on the NACA 0009
airfoil were investigated and the results are‘presented
in reference 6. '