Post-Failure Control Reconfiguration on a High-Speed Lift-Offset Coaxial Helicopter

An elastic blade trim model of a coaxial-pusher helicopter with aerodynamic interference between the rotors is described and validated against existing experimental data for coaxial rotor systems and helicopters. With the trim model in place, parametric sweeps of trim controls are performed to examine different allowable control settings in terms of the swashplate actuator positions on a generalized swashplate geometry at 3 different flight speeds representing a low speed, moderate speed, and high speed flight condition. The effective allowable ranges of locked-in-place positions are established for the 3 actuators on each swashplate, and explanations for the relative ranges are discussed. In low speed, differential moment variation between the rotors allows for actuator settings accounting for approximately 30% of the total range. In moderate and high speed these ranges change due to the moment balance between the rotor and aerosurfaces of the vehicle, with the aft actuator on each rotor trimmable over the entire allowable range, whereas the forward and lateral actuator on the two rotors have allowable ranges accounting for 40-60% and 20-25% of the total range, respectively.