An optimization for alleviating pilot workload during tilt rotor aircraft conversion and reconversion maneuvers

Abstract

This work was focused on the conversion and reconversion maneuvers of XV-15 tilt rotor aircraft between helicopter and airplane modes. To alleviate pilot workload and improve safety, we proposed a multi-objective optimization method. Firstly, an augmented dynamics model has been developed and validated. Then, the transition maneuver was formulated as a proper optimization problem. The cost function consisted of several factors including transitional time, pilot workload, the power required, control allocation and pitch attitude. The constraints included not only the trajectory constraints and control rate limits, but also safety conditions of the conversion corridor and flight height. Finally, we analyzed the optimization results of two typical nacelle tilting schedules for both maneuvers using the wavelet analysis method to compare the pilot workload. Based on the results, in order to alleviate the pilot workload, it was recommended that during the conversion maneuver nacelles should initially tilt with much slower rate before aircraft reaches a certain forward speed at which the nacelle can tilt with normal rate. While during the reconversion maneuver nacelles were recommended to tilt under a normal rate. The nacelle tilting schedules in both maneuvers should be restricted inside the conversion corridors. As a result, the presented optimization method could identify the pros and cons between the two typical nacelle tilting schedules successfully. The obtained results could be used to provide a better reference for pilots and automatic conversion control systems.