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National Advisory Committee for Aeronautics, Technical Notes - Spin Tests of a Low Wing Monoplane in Flight and in the Free Spinning Wind Tunnel

Comparative full~scale and model spin tests were made
with a low-wing monoplane in order to extend the available
information as to the utility of the free-spinning wind
tunnel as an aid in predicting full~scale spin character»
isties.

For a given control disposition the model indicated
steeper spins than were actually obtained with the air:
plane, the difference being most pronounced for spins With
elevators up. Recovery characteristics for the model, on
the whole, agreed with those for the airplane, but a dis—
agreement was noted for the case of recovery with elevators
held full up. Free-spinning wind-tunnel tests are a useful
aid in estimating spin characteristics of airplanes, but
it must be appreciated that model results can give only
general indications of full-scale behavior.

Because of lack of detail on the model and such wind-
tunnel effects as low Reynolds Number, the model spin—test
results from the N.A.C.A. free-spinning wind tunnel might
be expected to differ somewhat from the correspondingufull-
scale results. The reasons for these differences are dis-
cussed in reference 1. In order to assist in the predic-
tion of spin characteristics in flight, a study is being
made of the agreement between model and flight results.

Reference 2 gives a fairly complete comparison between
model and full-scale spin characteristics for twombiplahes.
From the comparison it was felt that, although the tests
of the models of the two biplanes gave good approximations
to the spin characteristics of the full-scale airplanes.
definite conclusions should be reserved until similar
tests had been made of other models. particularly of
various monOplane types.

The present paper gives the results of similar,
though less extensive, tests of a low-wing monoplane fur-
nished by the Army Air Corps. The wind-tunnel tests were
made with a l/lS-scale dynamic model of the airplane.