The launch of a skid based Free Fall Lifeboat (FFL) typically consists of sliding on skid, rotation around skid tip, free fall, water impact, submergence, water exit and free sailing phases. The FFL's behavior after water exit is addressed in this paper.
Numerical simulations of the lifeboat's forward distance performance are performed in an irregular sea state and under constant wind and current velocities. In order to reproduce the behavior of the pilot, an autopilot is engaged in the simulations to keep the desired heading. First order wave forces are considered based on linear strip theory. Wind force coefficients are taken from measurements. The current forces are implemented as well. A numerical model of the nozzle propulsor is tuned according to captive model tests for the particular lifeboat under study. Maneuvering model of the lifeboat is first calculated based on strip theory and is further tuned so the simulated and measured turning circle and zigzag manoeuvers are in reasonable agreement, with the numerical nozzle propulsor model applied.
Three weather directions, two autopilot settings and different initial motion conditions of the lifeboat are considered in the simulations. Statistics of the simulation results are used to account for the variability of the lifeboat's forward distance performance in a seaway.
