Optimization of critical trajectories for rotorcraft vehicles

This paper focuses on the development of computational procedures trajectory optimization of maneuvering rotorcraft vehicles. The flight mechanics models are based on classic blade element theory, and are applicable to both helicopters and tilt-rotors. Maneuvers are formulated here as optimal control problems, whose solution minimizes an appropriate cost function subjected to constraints that translate the flight envelope limitations of the aircraft and all the necessary safety and operational requirements. A finite element based transcription process is used for discretizing the problem, leading to a finite dimensional parameter optimization. Procedures are proposed for ensuring flyable solutions and realistic control time histories that are compatible with the hidden (unmodelled) actuator dynamics. The methodology is used for studying the take-off of helicopters and tilt-rotors in the one-engine failure case under Category-A certification requirements.