Application of 2GCHAS to the Investigation of Aeromechanical Stability of Hingeless and Bearingless Rotor Helicopters

Selected aspects of analytical modeling of aeromechanical stability of hingeless and bearingless rotors are addressed. The Second Generation Helicopter Analysis System (2GCHAS) is used to investigate hingeless rotor helicopter air resonance with several unsteady inflow models, structural dynamics of bearingless rotor blades, and air resonance of a five-bladed bearingless rotor helicopter. Comparisons of air resonance predictions with experimental data for both the hingeless and bearingless configurations are included. Modeling considerations for nonlinear elastomeric dampers are addressed with an emphasis on limit cycle oscillation behavior. The results of these investigations illustrate a broad range of 2GCHAS capabilities for addressing the aeroelastic stability characteristics of advanced state-of-the-art rotor systems.