John Eacott:
I somehow think that despite Mr Robinson's Safety Course instructors dissertation, most helicopters aren't aware of whether they're departing or arriving when it comes to the HV diagram
John, I must respectfully disagree. I think it makes a big difference to the helicopter whether it is in a full-power climb at 100 feet and 20 knots or a low(er)-power descent with the same parameters.
In the climb you not only have more pitch in the blades, but must overcome the upward motion before you can get that autorotational thingee started. In the descent you're already coming down, and the pole certainly doesn't need to be lowered too much further to transition to the auto.
So yeah, BIG difference as far as the helicopter is concerned.
Let's remember too that the H-V curve is derived at max weight.
On landing, I don't worry much about the H-V curve. As long as I'm not a max gross, and as long as I've got "some" rate of descent going, and as long as I'm not pulling gobs of power, the H-V curve is simply not an issue. And I don't think that's a horribly unsafe mental attitude to have.
I'm not suggesting that pilots can come to an OGE hover at 100 or 200 feet with impunity. And if anyone doesn't want to say that the H-V curve is totally irrelevant to landings, fine, can we at least allow that it is smaller for landings than it would be for takeoff?