matelot asked:
"Do those things with the whirly bits on top ever experience crosswinds on t/o or landing? Can't they always point into wind and in reality don't even know what a crosswind is?"
And muffin replied:
"Yes they do. Actually you always try to land and take off into wind which is normally easy. However, if the site restricts you it is quite possible to do so out of wind but you have to be careful as it is trickier. The crosswind limit is actually determined by the amount of cyclic authority available, as you obviously have to be stationary as you let it down on to the ground. If you don't have enough sideways cyclic control available to hold it in one place as you touch down, then you have to turn into wind where the control range availability is much greater."
You also have to consider the effects of the wind on the tail rotor. If you're landing with a crosswind from the left, you can get "tail rotor breakaway", which roughly means the tail rotor stops working properly, so that the pedals won't keep you straight! I always thought this was LTE (loss of tail rotor effectiveness), but I've recently been told the two phenomena are slightly different...for those who understand about this or care. The R22 doesn't seem to suffer from this much, and I've never experienced it. But I've been told that it can definitely be a problem in other helicopters. So yes, as Muffin said, you always try to land into wind. However, you can make your approach crosswind, and then turn into wind as you come to a hover...which you can't do with f/w really!
You also need to be careful starting up in a strong crosswind, as you can get blade sailing and chop off your tail! The direction the helicopter is facing and the way the rotor blades turn makes a difference as to whether this happens, but if I think about that too much my head hurts.
Anyway, to avoid all these nasty unpleasantnesses, and having to work out the likelihood of them occurring, we hover-lovers take off and land into wind if we can.
And why not? After all, we don't need runways.