On the Autorotation of Monoplane Wing

Abstract

Making use of the results obtained by the measurement of pressure distribution over a rolling aerofoil in the wind tunnel, investigations were undertaken relating to the mechanism of autorotation at various angles of incidence and the justice of assumptions underlying the calculation based on the strip theory. Two quite different types of autorotation were discriminated by the condition of flow over the upper surface of rotating monoplane wing. Comparing the results of experiment and calculation, concerning the rolling moment due to each element of the wing, marked differences were recognised, especially at large angle of incidence. The causes of discrepancies were explained and the limit of applicability of calculating method was determined. Finally the importance of the relative position of the wing and the rolling axis was indicated as a cause of autorotation at large angle of incidence with large rolling speed, which corresponds to the “flat spin” of a monoplane.