Helicopter Pilots Synchronize Their Altitude with Ship Heave to Minimize Energy When Landing on a Ship’s Deck

Objective: This study aims at investigating helicopter pilots’ strategies to achieve ship deck landing. Background: Helicopter maritime operations are challenging, especially when it comes to landing on the moving decks of small ships, such as frigates, which can lead to dramatic accidents. Method: Expert pilots were requested to fly the full ship landing maneuver from approach to touchdown in an immersive simulator. Two sea states (3 and 4 on the Douglas Sea scale) and their resulting deck movements were used. Changes in helicopter altitude were correlated with deck heave movements throughout the maneuvers in order to scrutinize the helicopter-deck coupling. The energy at impact was measured. Results: The dynamics of helicopter-deck coupling evolved through two phases during the maneuver: Initially, no coupling then, coupling in phase between the helicopter vertical displacements and deck heave displacements. Moreover, the coupling reached higher values within the last 15 m to landing, corresponding to a hover phase and touchdown, and the correlation increased with sea level. This coupling might help in improving pilots’ safety since the greater the coupling at touchdown, the lesser the kinetic energy at impact. Conclusion: Coupling the helicopter vertical displacements with ship heave movements seems to be an efficient strategy to minimize energy at impact. Questions arise on both the rationale and the perceptual invariant behind such behavior and indicate the necessity of further investigation.

研究目的：本研究旨在探究直升机飞行员完成舰船甲板着陆的操作策略。
研究背景：直升机海上作业极具挑战性，尤其在护卫舰等小型舰船的移动甲板上着陆时，极易引发严重事故。
研究方法：邀请资深飞行员在沉浸式模拟器中完成从进近到触地的完整舰船着陆机动动作。实验设置了道格拉斯海况等级（Douglas Sea scale）3级和4级两种海况，并模拟了对应海况下的甲板运动。在整个机动过程中，通过将直升机高度变化与甲板垂荡运动相关联，以细致分析直升机与甲板的耦合效应，并测量了触地时的冲击能量。
研究结果：直升机-甲板耦合动力学在着陆机动过程中分为两个阶段：初始阶段无耦合，随后进入直升机垂直位移与甲板垂荡位移同相耦合的阶段。此外，在距离着陆最后15米的阶段（对应悬停与触地阶段），耦合效应达到更高水平，且相关性随海况升高而增强。该耦合效应有助于提升飞行员作业安全：触地时的耦合效应越强，冲击动能则越小。
研究结论：将直升机垂直位移与舰船垂荡运动进行耦合，似乎是降低触地冲击能量的高效策略。但此类操作背后的理论依据与感知不变量仍存在疑问，这也凸显了进一步开展相关研究的必要性。