Recent Tilt Rotor Flight Control Law Innovations

This paper describes three distinct control law functions recently developed in conjunction with full-scale development of the Bell-Boeing V-22 Osprey tilt rotor. Two of these are designed to improve the speed response of the aircraft. The first quickens thrust response to power lever inputs by varying proprotor RPM through a governor feedforward circuit. The second gives the power lever direct control of an aerodynamic brake formed by the aircraft's flaperon control surfaces. The third control law function is a model follower concept for mast torque control which protects against drive system overtorque and reduces thrust axis workload in all flight modes. The paper discusses the handling qualities of the aircraft that prompted the development of these functions, and the improvements resulting from each as determined by analysis and flight simulation.