Shipboard landing period based on dynamic rollover risk prediction

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Dang-Vu, B.
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While SHOLs (Ship/Helicopter Operating Limitations) provide acceptable wind velocities and orientation and ship motion limits, limited attention has been given to the real-time determination of windows in which ship motions are likely to be safe for helicopter landings and deck handling operations. Existing operational systems developed to indicate periods of quiescence usually combine a specific set of ship motions into a scalar quantity, e.g. an energy index. The contribution of the present paper is to associate forbidden landing windows with the conditions of a control departure when the helicopter landing gear touches the deck of the ship. Among the well-known losses of control, dynamic rollover is particularly critical and hard to recover. A method to determine shipboard landing periods based on dynamic rollover risk prediction is proposed. The objective is to reduce the helicopter hover time and to provide the pilot with a safe go-ahead signal to start the hovering descent to the deck. A simulation tool has been developed, capable of modelling the complex interactions in the dynamic interface between ship and helicopter. Simulation results as well as sensitivity analysis with respect to uncertainties are presented.