Effect of Structural Parameters on the Flap-Lag Response of a Rotor Blade in Forward Flight.

A study is made of the effect of structural coupling on the vibrations of rigid, centrally hinged rotor blades. In particular, if the parameter combinations that result in desirable stability characteristics might also result in good vibrational characteristics. In order to determine the stability and vibrations simultaneously, a new analytical method, based on eigenvalue and modal decoupling, is developed to solve for the eigenvalues and forced response of systems of equations with periodic coefficients. This method is then applied to the linearized equations of motion for rotor flap-lag in forward flight. Unlike conventional linear analyses, however, this analysis retains the nonlinear terms as added forcing functions.