Validation of a Ground Dynamics Model Formulation By use of Landing Data

In this paper, a new formulation for a ground dynamics model for a commercial two engines helicopter is validated after touchdown. The inputs of the ground dynamics model are the velocities and angles at touchdown, while its outputs are the forces and moments produced by the ground on the helicopter. Expressions for forces and moments depending on the friction coefficient between the skids and the ground and the system stiffness and damping are presented. The system stiffness and damping are defined between the touchdown point and the center of mass in each of the helicopter degree of freedom. Expressions for the stiffness, damping and friction coefficients are derived to validate one engine inoperative and autorotation landing cases. The ground dynamics model is validated by use of landing flight test data collected on the B-427 helicopter and is further used in the building and in the certification of a level D simulator.