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

ABSTRACT 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.