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National Advisory Committee for Aeronautics, Report - The Small Angular Oscillations of Airplanes in Steady Flight

This investigation was carried out by the National Advisory Committee for Aeronautics at
the request of the Army Air Service to provide data concerning the small angular oscillations
of several types of airplanes in steady flight under various atmospheric conditions. The data are
of use in the design of bomb sights and other aircraft instruments. The method Used consisted
in flying the airplane steadily in one direction for at least one minute, While recording the angle
of the airplane with the sun by means of a kymograph. The results show that the oscillations
differ but little for airplanes of various types, but that the condition of the atmosphere is an
important factor. The average angular excursion from the mean in smooth air is 0.8° in pitch,
1.4" in roll, and 0.9° in yaw, Without special instruments to aid the pilot in holding steady con-
ditions. In bumpy air the values given above are increased about 50 per cent.

In the design of bombing and navigation instruments it is usually desired to provide a
reference platform which will hold as nearly as possible a constant horizontal position. For this
purpose it is necessary to know the character of the airplane motions, particularly the small
angular ones occurring in steady flight.

Apparently the oiily data previously available are those incorporated In R. & M. No 213 1
and R. & M. No. 422. 2 These tests are quite complete, but were made only 1n smooth air.
They will be referred to again as a means of comparison.

The present tests were made with four types of airplanes at speeds covering the usual flying
range and under all air conditions, giving data that should be sufficiently complete to cover
the required field.