Effect of dynamic stall on helicopter trim and flap-lag response

A unified lift model is used in the derivation of elastic blade equations. The resultant mathematical model predicts the aerodynamic forces on the helicopter blade and the flap-lag response before and after stall occurs. An ordering scheme is applied during the derivation so that only important terms are retained. The time history solution is obtained using Galerkin's method. The results agree qualitatively with the linear model for small angles of attack, and give a reasonable prediction of the flap-lag response including stall.