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National Advisory Committee for Aeronautics, Technical Notes - The Aileron as an Aid to Recovery from the Spin

As part of a generalrinvestigationnhy~the NACAnef
factors that affect the spin, the use of the aileron as
an aid to recovery-from the spin was studied. Tests of
10 different models, covering a wide range of mass dis-
tribution, were madewin the NACA_free-spinning tunnel to
determine the effects of a large downward deflection of
the outboard aileron-and of normal angular deflections'
of the ailerons upon recovery characteristics.

The results indicate that the direction ofuaileron
setting, with or against the spin, which.will aid‘recovery
from the spinidepends upon the airplane weight distribu-
tion. For moneplanes and for biplanes with lower—wing
ailerons,-ailerons with the spin will bc‘favorable when
the weight is distributed chiefly-along the fuselage
(single—engine airplanes) and ailerons-against the spin
will be favorable-when the weight is distributed chiefly
along the wings (multiengine airplanes). Downwardnmove—
ment of the outboard aileron through a large angle will
not always be effective in—aidingqrecovery, the effective~
ness of such a.movement also being dependent upon_the
weight distributfen of the airplane.

HumdrousFSPecial devices to insure recovery from the—
spin have-been developed from time,to time. Except for
the tail chute, none has been widely.adopted.

A method of expediting recovery from the spin that
showed particular promise on the basis of past experience
consisted in deflecting the outboard aileron (left aileron
in a right spin) downward'through a large angle to assist
the rudder in recovery. At large deflections, the outboard
aileron should provide considerable antispin yawing moment
to augment the' moment obtainable by reversal of the rudder.
A study of this method of improving spin recoveries was
accordingly undertaken infthe NADA. free-s pinning tunnel.
In order to afford a means of comparison and to obtain a
clear understanding of the results, a study of the effects
of normal angular deflections of the ailerons, with and
against the spin, was included in the investigation.
Ailerons deflected with the spin means that the ailerons
are deflected with right aileron up and left aileron down
in a right spin. The results of the investigation are
discussed in this paper.