Dynamic conversion corridor of tiltrotor aircraft under accelerating and decelerating conditions

The development of electric Vertical Take-Off and Landing (eVTOL) aircraft is increasingly linked to the low-altitude economy, with tiltrotor configurations gaining industry favor. Precisely defining the conversion corridor is key to ensuring the safe completion of transition flights for such configurations. Traditional conversion corridors are determined by solving for speed ranges of steady-level flight at different rotor tilt angles (static conversion corridor). However, this method inadequately reflects the dynamic process where configuration and speed change synchronously between helicopter and airplane modes, posing safety risks. To address this issue, boundary conditions for both low-speed and high-speed segments of the conversion corridor are formulated based on a nonlinear flight dynamics model of a tiltrotor aircraft. The effects of different accelerations and climb/descent rates on the dynamic conversion corridor are systematically analyzed and compared with the static conversion corridor. Results show that as acceleration increases, the maximum flight speed corresponding to various rotor tilt angles decreases linearly, while the reduction in minimum flight speed slows as the rotor tilt angle decreases. In specific flight states involving accelerated climbing, the dynamic conversion corridor area is reduced by about 52% compared to the static conversion corridor. Flight simulation results of different transition paths further indicate that relying solely on static conversion corridor designs may introduce flight safety hazards such as power exceedance and wing stall. Consequently, this paper proposes using the overlapping region of dynamic and static conversion corridors as the safety boundary for path design, thereby, improving the safety of transition flights.