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National Advisory Committee for Aeronautics, Technical Notes - Spiral Tendency in Blind Flying

The flight path followed by an airplane which was being
flown by a blindfolded pilot was obseIVed and recorded for a
number of pilots. When the pilot attempted to make a straight—
away flight there usually developed a tendency to deviate from
the straight path and to take up a spiral one.

Tradition says that the normal tendency of man who is walk—
ing without a visual reference, as when lost in a forest or in
a dense fogjis to take a circular path. This traditional ten—-
dency has been investigated experimentally and reported upon
exhaustively by Dr. Asa A. Schaeffer, of the Zoological Laborar
tory of the University of Kansas, in a paper entitled "Spiral
Movement in Man," (Journal of Morphology and Physiology, Vol. 45,
No. 1, March, 1988). He finds that whether walking, swimming,
rowing a boat, or driving an automobile, the tendency of a blind—
folded person is always to follow a spiral path. Such a tendency
would naturally be of greater importance in flight.than perhaps
anywhere else, and it was the intention of these experiments,
carried on by the National Advisory Committee for Aeronautics
at Langley Field, Virginia, to determine whether the same ten—
dency normally appeared in the piloting of aircraft.

For the purpose of these experiments, a dual control VE—7
airplane was used. The subject pilot Was placed in the front
seat, which was located approximately at the center of gravity
of the airplane. In this position the subject pilot was less
influenced in piloting by the accelerations. A safety pilot,
who also served as observer, occupied the rear seat.

A face mask type of goggles, in which the glasses were re—
placed by light—tight pieces of cardboard and black paint, was
used as a very effective blindfold; they are shown in Figure l.

The subject pilot was usually directed to take off and fly
to some safe altitude at which steady air conditions existed, in
the meantime getting accustomed to the flying qualities of the
airplane. At this point the observer took over the controls,
and the subject pilot assumed the “blind condition” by putting
on the goggles. The airplane was then brought into position
for straightaway flight by the observer and turned over to the
subject pilot, who then attempted to maintain straight flight