Hummingbirds perform a variety of agile maneuvers, and one of them is the escape maneuver, in which the birds can steer away from threats using only 3–4 wingbeats in less than 150 ms. A distinct kinematic feature that enables the escape maneuver is the rapid backward tilt of the wing stroke plane at the beginning of the maneuver. This feature results in a simultaneous nose-up pitching and backward acceleration. In this work, we investigated how the magnitude and timing of the wing stroke-plane tilt (relative to the phase of flapping cycle) affected the generation of backward thrust, lift, and pitching moment and therefore the maneuverability of escape flight. Investigations were performed using experiments on dynamically scaled robotic wings and computational fluid dynamic simulation based on a simplified harmonic wing stroke and rotation kinematics at Re = 1000 and hummingbird wing kinematics at Re ≈ 10 000. Results showed that the wing stroke-plane tilt timing exerted a strong influence on the aerodynamic force generation. Independent of the tilt magnitude, the averaged backward thrust and pitching moment were maximized when the stroke plane tilt occurred near the end of the half strokes (e.g., upstroke and downstroke). Relative to the other timings of stroke-plane tilt, the ‘optimal’ timings led to a maximal backward tilt of the total aerodynamic force during the wing upstroke; hence, the backward thrust and nose-up pitching moment increased. The ‘optimal’ timings found in this work were in good agreement with those identified in the escape maneuvers of four species of hummingbirds. Therefore, hummingbirds may use a similar strategy in the beginning of their escape maneuver.

蜂鸟执行各种敏捷机动，其中之一是逃生机动，在这种机动中，鸟类可以在不到 150 毫秒的时间内仅使用 3-4 次翼拍就可以避开威胁。实现逃生机动的一个独特的运动学特征是在机动开始时机翼行程平面的快速向后倾斜。此功能导致同时向上俯仰和向后加速。在这项工作中，我们研究了机翼冲程平面倾斜的幅度和时间（相对于扑动周期的阶段）如何影响向后推力、升力和俯仰力矩的产生，从而影响逃生飞行的机动性。使用动态缩放机器人机翼的实验和基于 Re = 1000 的简化谐波机翼冲程和旋转运动学以及 Re ≈ 10 000 的蜂鸟机翼运动学的计算流体动力学模拟进行了研究。结果表明，机翼冲程平面倾斜时间施加对气动力产生的影响很大。与倾斜幅度无关，当行程平面倾斜发生在半行程结束附近（例如，上行程和下行程）时，平均向后推力和俯仰力矩最大化。相对于其他行程平面倾斜时间，“最佳”时间导致机翼向上行程期间总气动力的最大向后倾斜；因此，向后推力和机头向上俯仰力矩增加。在这项工作中发现的“最佳”时间与在四种蜂鸟的逃生演习中确定的时间非常一致。因此，蜂鸟在开始逃跑时可能会使用类似的策略。