Novel Approach to Interaction Between Engine-Drive Train System and Deformable Rotorcraft Airframes

In this paper a procedure to restore the torque load path between the drive system and the airframe is proposed. The load path is modeled starting from the rotors to the engines, through the drive train system. The torsional loads are transferred to a detailed finite element model of the airframe through connections constraining the gearboxes to the airframe structure. At the same time, the torques generated by the airframe deformations are fed back into the drive system. The procedure to restore the torque load path is firstly validated with a benchmark model, in which the gearboxes are introduced as rigid bodies and connected to the ground by means of elastic springs to represent the airframe elasticity. Overall stability analyses are performed on a complete aeroservoelastic helicopter model to investigate possible aeromechanical phenomena due to airframe and drive train system coupling. A comparison of the results obtained by the classical decoupled approach and the fully coupled approach is presented to highlight cases where significant differences arise between the two approaches.