Non-PC Plod,
The principal reason for using floats is to ensure that the helicopter remains in an upright position during the period in which an evacuation takes place.
Helicopters which have been certificated for ditching have a specified sea state for which entry procedures and stability have been established (usually modelled). The advisory material indicates that this sea state should be the 'reasonably probable' conditions over which the helicopter is flown - it is indicated in the text that this might be sea state 4.
Helicopters which are not certificated for ditching can also be equipped with flotation equipment but entry procedures and sea state are not established by the manufacturer (it is likely that the floats used on these helicopters are the same).
More modern helicopters have obtained ditching approval for sea states up to 6; analysis indicates that the North Sea has a sea state higher than 4 for 30% of the time in winter.
Because it is reasonably probably that the helicopter will invert following a ditching in high sea states, all helicopters operating for oil support in the North Sea have a 'pop-out-window' at each seat row. These windows help to ensure that all passengers and crew members can evacuate within 'breath hold' time following an inversion.
The UK CAA are about to publish a paper which fully discusses the issue of ditching; it will contain a number of previously published and unpublished papers on the subject.
Recovery of the helicopter is an economic issue and has nothing to do with the provision of flotation equipment.
Jim
Last edited by JimL; 31st May 2005 at 07:06.