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• April 23, 2016 Create Date
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National Advisory Committee for Aeronautics, Technical Notes - Aerodynamic Effects of a Split Flap on the Spinning Characteristics of a Monoplane Model

The investigation described in this report was made
to determine the change in aerodynamic forces and moments
produced by split flaps in a steady spin. The tests were
made with the spinning balance in the N. A. C. A. 5—foot ver—
tical wind tunnel. A low-wing monoplane model was tested
with and without the split flaps in 12 spinning attitudes
chosen to cover the probable spinning range. The changes
in coefficients produced by adding the split flaps are
given for longitudinal force, normal force, and rolling
and yawing moments about body axes. '
The results obtained indicate that the use of split
flaps on an airplane is unlikely, in any case, to have
much beneficial effect on a spin, and it might make the
spin dangerous. The change in the spin will depend upon
the aerodynamic and inertia characteristics of the partic—
ular airplane. A dangerous condition is most likely to be
attained with airplanes which are statically stable in yaw
in the spinning attitude and which have large weights dis—
tributed along the wings.
Split flaps are being used on airplanes to decrease
the landing speed, to increase the range of possible glide
angles, and to shorten the landing run. Since they are
used at slow flying speeds where the airplane may possibly
spin. some data on their effects on the spin seemed desira—
ble. Regular windatunnel tests of split flaps have been
reported in references 1 to 5 and rotation tests with
2V = 0.05 in reference 4.
In order to determine the effects olf split flaps on
the forces and moments in spinning attitude--s, the present
investigation was made with a monoplane model on the spin—
ning balance in the NACA. 5~foot-vertical wind tunnel.