Aeroelastic stability of an advanced bearingless rotor with consideration of a lag pin

Nonlinear strain-displacement relations were presented using Green-Lagrange strain tensor and an advanced bearingless rotor was modeled with multiple-load-path. Two-dimensional quasi-steady strip theory was used to evaluate aerodynamic forces. Unsteady effects were simulated by a dynamic inflow model. The finite element equations of a blade motion were obtained from Hamilton's principle. Effects of a lag pin on aeroelastic stability of an advanced bearingless rotor in hover were investigated. Numerical results show that up-location of the lag pin introduces a negative pitch-lag kinematic coupling and improves the lag mode damping of a blade effectively. Vertical offset of the lag pin has a substantial influence on the lag mode damping of the blade. Moving the lag pin attachment point to the higher position increases the aeroelastic stability boundary of the bearingless rotor.