Helicopter Landing Trajectory Optimization after Tail Rotor Control Failure in Different Collective Pitch

直升机不同尾桨距卡滞后的着陆轨迹和操纵优化

¹ National Key Laboratory of Science and Technology on Rotorcraft Aeromechanics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
² China Helicopter Design and Research Institute, Tianjin 300000, China

Received: 2 November 2018

Abstract

This paper studies helicopter optimal landing and control procedure after tail rotor control failure (TRCF) in different collective pitch. The optimal control problem of landing after tail rotor control failure was solved numerically by direct multiple shooting method and sequential quadratic programming. A sample helicopter optimal landing procedures after tail rotor control failure in large collective pitch and small collective pitch were investigated respectively. As can be seen from the results, when the tail rotor is stuck at large collective pitch, the tail rotor provides a large lateral force, which facilitates landing with small forward speed and descent rate in a large power state. The pilot can maintain stability of heading by side slipping. When the tail rotor is stuck at small collective pitch, the tail rotor provides a small lateral force, which is favorable for flying near economic speed, but difficult for a safe landing. A normal landing maneuver will cause a high yaw rate at touchdown, which is dangerous. Therefore, autorotation is preferred during touchdown because the landing is more secure with small yaw rate. The trajectory optimization method of helicopter safe landing after tail rotor control failure can provide a reference for flight test.

摘要

计算并分析直升机遭遇不同尾桨距卡滞后的最优安全着陆和操纵过程。首先，将直升机不同尾桨距卡滞后的安全着陆问题表示成最优控制问题。然后，采用直接多重打靶法将最优控制问题离散为非线性规划问题，并进行数值求解。最后，分别计算样例直升机遭遇大尾桨距卡滞与小尾桨距卡滞后的最优安全着陆过程和操纵策略。结果表明：当尾桨卡滞在大桨距时，尾桨提供侧向力大，有利于使用较大的功率状态以较小的速度和下降率着陆，期间可以通过侧滑来保持航向稳定；当尾桨卡滞在小桨距时，尾桨提供侧向力小，有利于在经济速度附近飞行，但不利于着陆机动。若此时采用常规着陆，则触地时偏航角速度很大，容易造成危险。若此时采用自转着陆，则触地时偏航角速度很小，因此着陆更为安全。直升机尾桨距卡滞后安全着陆的轨迹优化方法可以得到直升机遭遇不同尾桨距卡滞后的最优着陆轨迹和操纵，从而为尾桨距卡滞飞行试验提供一定的参考。