Helicopter pilots synchronize their altitude with ship heave to minimize energy when landing on a ship's deck

International audienceBackground: Helicopter maritime operations are challenging, especially when it comes to landing on the moving decks of small ships, such as frigates. In order to understand how pilots achieve such a demanding task, we scrutinized the coupling between the helicopter's altitude and the deck during landing maneuvers.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 into 7 bins throughout the maneuvers. 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 15m to landing, corresponding to a hover phase and touchdown, and the correlation increased with sea level. This coupling might help in improving pilot's safety since the greater the coupling at touchdown, the lesser the kinetic energy at impact.Discussion: Results are discussed from a Gibsonian perspective and emphasize the role of motion vision for goal aimed behavior. Questions arise on both the rationale and the perceptual invariant behind such coupling behavior and indicate the necessity of further investigation