Tilt-Wing eVTOL Takeoff Trajectory Optimization

Technological advances in areas such as battery technology, autonomous control, and ride-hailing services, combined with the scale-free nature of electric motors, have sparked significant interest in electric vertical takeoff and landing (eVTOL) aircraft for urban air mobility. In this work, we use simplified models for the aerodynamics, propulsion, propeller-wing flow interaction, and flight mechanics to carry out gradient-based optimization studies for the takeoff-to-cruise trajectory of a tandem tilt-wing eVTOL aircraft. We present results for optimizations with and without stall and acceleration constraints, with varying levels of flow augmentation from propellers, and find that the optimal takeoffs involve stalling the wings or flying near the stall angle of attack. However, we find that the energy penalty for avoiding stall is practically negligible. Additionally, we find that without acceleration constraints, the optimized trajectories involve rapidly transitioning to forward flight and accelerating, followed by climbing at roughly constant speed, and then accelerating to the required cruise speed. With an acceleration constraint for passenger comfort, the transition, climb, and acceleration phases are more gradual and less distinct. We also present results showing the impact of wing loading and available power on the optimized trajectories.