Linear aerodynamic theory of rotor blades.

Abstract

A theory is developed for predicting the spanwise lift distribution of rotor blades in forward flight. The guiding thought of Reissner's theory for oscillating wings of finite span is followed, that is, the theory starts with the lifting-surf ace theory and then equations of the lifting-line theory are derived by mathematical approximation. The equation of the liftingsurface theory is exact within the scope of the linear theory. An approximation equivalent to that of Weissinger's L method is adopted rather than that of Prandtl's lifting-line theory. Numerical computations are carried out for the case of an NACA experiment. Fairly good agreements are obtained with the experimental values. However, the theory seems to fail to predict the abrupt lift changes, which are probably due to the nonlinear effect.