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National Advisory Committee for Aeronautics, Technical Notes - Pressure Distribution Investigation of an NACA 0009 Airfoil with a 50% Chord Plain Flap and Three Tabs

Pressure—distribution tests of an N.A.C.A. 0009 air—
foil with a 50—percent—chord plain flap and three plain
tabs, having chords 10, 20, and 30 percent of the flap
chord, were made in the N.A.G.A. 4~ by 6—foot vertical
tunnel. The tests supplied aerodynamic section data that
may be applied to the design of horizontal and vertical
tail surfaces.

The results are presented as resultant—pressure dia—
grams for the airfoil with the flap and the 204percentej
chord tab. Plots are also given of increments of utensi—
force and hinge—moment coefficients for the airfoil, the
flap, and the three tabs. The experimental results and
values computed by analytical methods are in good agree—
ment for small flap and tab deflections. The results of
the tests indicated that the effectiveness of all three
tab sizes in reducing flap hinge moments decreased with
increasing flap deflection.

The recent increases in speed and size of airplanes
have produced excessive control forces. At the present
time, one of the most effective devices for reducing these
high control forces is the trailing-edge tab. (See refer-
ences l and 2.) Previous investigations have indicated
the effects of such factors as plan form, outuouts, end
plates, elevator nose shape, gap, and balance on the aero—
dynamic characteristics of some tail surfaces of. finite
span (references 3 and 4). Ho available data applicable
to tail~surface design, however, give the section aerody~
namic characteristics of a thin airfoil as affected by
flaps and tabs. The present investigation was therefore .
undertaken to supply information that would be applicable
for use in aerodynamic and structural design of tail sur—
faces with tabs.

The tests consisted of pressure—distribution measure~
ments over one section of an N.A.C.A. 0009 airfoil with a
50—percent-chord plain flap and with plain tabs 10, 20,
and 30 percent of the flap chord. From the data obtained,
normal—force and pitching—moment coefficients were calcu»
lated for the airfoil section complete with the flap and
the various tabs. In addition, normal—force and hinge—
moment coefficients were calculated for the flap with the
different tabs and for the tabs alone.