 The whirling rotor blades of a helicopter can cause large electrical charges to build up on the airframe, large enough to cause injury to shipboard personnel should they touch any part of the helicopter as it approaches the deck.This was depicted in the 1990 film "The Hunt for Red October", when Jack Ryan is flown out to a submarine by helicopter.Ryan is lowered to the submarine, but brushes the officer charged with trying to hook him who receives a minor injury.