The risk of a helicopter capsizing during a controlled ditching is “considerably higher” than targets set by the UK Civil Aviation Authority. “Means should be sought to reduce this risk,” says a study by the CAA of ditching tests and operational experience, particularly involving North Sea oil support flights.
Greater knowledge of helicopter behaviour after a controlled ditching could result in better certification guidelines for helicopters themselves and for their flotation equipment, the CAA hopes.
The authority’s Summary report on helicopter ditching and crashworthiness research recommends that new tests should extend existing knowledge to establish a reliable computer model of the motion of a helicopter floating on waves, and that this should include the helicopter’s behaviour in different sea states starting with “regular” waves.
Meanwhile, there are some relatively low-technology solutions that could be exploited more extensively than they are now because they are proven to be effective under most circumstances. These include the use of float-scoops attached to flotation equipment. The CAA adds that more work should be done to establish precisely why float scoops are effective so they might be better designed. Any means of causing the helicopter to “weathercock” nose into wind – like a sea anchor – are beneficial, the CAA reports, because it reduces the likelihood of capsizing.
More detailed investigation should be done into the “wet floor” concept of flotation – where the aircraft is allowed to sink deeper before it stabilises in an upright attitude – on specific helicopter types before determining whether raising floats on any individual machine would be beneficial.
Finally, the CAA recommends “more serious attention should be given” to measures that prevent a helicopter from rolling completely inverted when it capsizes – like engine-cowling floats. These have the potential to stabilise the helicopter on its side in the water, allowing crew to escape from an exit that is not submerged.
DAVID LEARMOUNT/LONDON
Source: Flight International
