Influence of Contact Points of Helicopter Skid Landing Gears on Ground Resonance Stability

Abstract

Soft-in-plane rotor systems are susceptible to a self-induced vibration phenomenon called ground resonance. This dynamic instability results from lag motions of the rotor blades coupling with airframe degrees of freedom while the helicopter is in ground contact. As an addition to slope landing studies in the past and investigations of non-linear landing gear effects, this work focuses on a systematic study of partial skid contact using different landing gear modelling approaches and contact definitions. Special focus is given to different methods of contact simulation, using 3D spring-damper elements and polygonal contact elements. This paper is part of a larger study to investigate the influences of partial ground contact and soft terrain on helicopter dynamic stability during landings. It is the long-range objective to reduce the necessity of extensive flight tests prior to helicopter certification processes.