Ditching is when a non-float equipped helicopter must be landed in the
water. Ditching might be performed power off if the engine fails, and
power on if some emergency makes it necessary to land (such as impending
If the helicopter is not within gliding distance of shore and the engine
quits, the pilot will have to ditch the aircraft.
Normally the helicopter would enter autorotation. Passengers would be briefed
in the use of emergency equipment, and often the doors will be unlatched
while in flight. The pilot would normally make any emergency communications
possible, and then switch off the electrical power.
A normal flare is performed, and then as the helicopter settles into the
water the pilot decreases rotor RPM to minimum and uses lateral cyclic to
roll the aircraft on its side. This causes the blades to strike the water
and immediately stop turning, so that people are not hit by turning blades
while evacuating from the aircraft. Most helicopters will sink fairly
quickly since there are not normally large spaces to trap air in a helicopter.
This makes it critical that everyone is briefed in how to get clear of the
helicopter and get to the surface of the water.
A precautionary ditching would normally only be performed if some catestrophic
problem with the helicopter makes continued flight dangerous. A failing main
rotor transmission would be a good example of this. So would running out of
fuel. The major difference is that the pilot can come to a hover and offload
passengers, crew, and survival equipment. He can then hover away and perform
a ditching as described above. By allowing people to egress the aircraft while
it is still flying, chances of someone drowning are reduced.
paul at copters.com
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