Comparison of the Effect of Structural Coupling Parameters on Flap-Lag Forced Response and Stability of a Helicopter Rotor Blade in Forward Flight,

An eigenvalue and modal decoupling method to predict helicopter rotor stability and forced response has been successfully developed. The advantages of this method are: Stability and forced response are obtained from the same method, thus allowing direct comparison of parametric effects; Only one rotor revolution of numerical integration for an initial condition of unity imposed on each degree of freedom is necessary to define the Floquet Transition Matrix, therefore, the ambiguous interpretation of time history response data over many rotor revolutions and the separation of transient and forced response is no longer necessary; and Additional degrees of freedom such as hub and airframe motions, inflow feedback, etc. in both the fixed and rotating systems can be included since Floquet theory is applicable to equations with periodic coefficients.