ABSTRACT
This chapter addresses the helicopter undercarriage strength in a helicopter-landing-ship (HLS) situation using probabilistic modeling and the extreme value distribution (EVD) technique. Safe landing could be expected if the probability that it occurs during the lull time is sufficiently high. The probability that the helicopter's undercarriage strength is not compromised can be evaluated as a product of the probability that landing occurs during the lull time and the probability that the relative velocity of the helicopter undercarriage with respect to the ship's deck at the moment of landing does not exceed the allowable level. The highest safety, in terms of the helicopter undercarriage strength, when landing on a ship deck, could be expected, if such landing occurs during the lull period of the seas. Typically, the officer on ship board, using the information from the on-board surveillance systems, signals to the helicopter pilot, when the lull period ("wave window") commences.
