Pitch Link Loads Analysis of a Variable Speed Rotor

An aeroelastic simulation is employed to analyze the pitch link loads of a hingeless stiff in-plane variable speed rotor based on the generalized force formulation, including a moderate deflection beam model, Leishman-Beddoes unsteady aerodynamics and Pitt-Peters dynamic inflow. The dynamics in the flapwise and lagwise directions are strongly coupled with the torsional dynamics. Lagwise resonance has a critical influence on the pitch link loads. The rotor should avoid speeds near lagwise resonant frequencies. Increasing the flap stiffness can significantly decrease the 1/rev and 2/rev pitch link loads. The higher harmonic pitch link loads increase, however, especially at low rotor speeds. Shifting the torsional frequency far from the loads is shown to significantly decrease the higher harmonic pitch link loads, especially the loads near the lagwise resonance crossing. The influence on the lower harmonic pitch link loads is small. Increasing lagwise damping can significantly reduce pitch link loads around lagwise resonant frequency.