Originally Posted by
PDR1
* although weren't the Sea Kings prone to transmission failures if they had an engine failure when hovering out of ground effect when doing things like mountain rescue? Something in my memory talks about it being very marginal and prone to over-torquing failures on the remaining engine, but I may have made it up
The problem in the Seaking and many other helicopters is not transmission failure once single engine so much as simply a shortage of power.
The power required curve for a helicopter is high power to hover, minimum at around 70ktsish for a decent size helicopter and high power again to go fast.
In the hover and light wind (even 15kts makes a huge difference) most/many twin cannot maintain a hover at a decent weight single engine.
Military SAR was allowed to practice without being safe single engine- ie in the event of an engine failure things were not going to be pretty.
In the Seaking we would brief the situation ie run and cut (winchman/SAR diver was going in the water immediately and we would attempt to gain enough speed to fly before impact) or safe single engine. I seem to remember 65% Tq was the magic figure.
The thing to realise is that rotary is very very different to fixed wing. There is an entirely different risk level at pretty much all times.