Good point PPF#1, I recall that shot. Whilst it certainly looked slower than 40kts, I am not convinced that the trail was not simply downwash on the water rather than the pressure wave you can see under an aeroplane wing. Or maybe that is simply downwash of the voticies as well?
Lastly, PPF#1, au contraire to your earlier post, I reckon etnb is not as confused as you think. I can only find fault with his concept of a "forward glide". On the other hand, your quote that the disc of a helicopter acts like an aeroplane wing is frought with misconceptions. I cannot imagine a scenrio in which it behaves like the wing of an aeroplane. You say that:
"In forward flight it has the same characteristics as an aeroplane wing. Pull back on the stick to increase the angle of attack of the disk and you will get a corresponding increase in lift/drag. "
Pull back on which stick? Cyclic will have the effect of increasing pitch on the advancing blade, and decreasing it on the retreating blade. Collective will increase the pitch of all blades, but that doesnt necessarily cause the nose to pitch up. So how is this like a fixed wing?
Perhaps your understanding of the above also led you to say that:
"At the bottom of a fairly steep auto, ground effect will be minimal, and not felt until the pitch-pull.
But come in fast and round-out low. Like an airplane, the helicopter would take advantage of the same type of ground-effect."
It doesn't matter how low and fast you round out (isn't that the idea of an auto anyway??) I dont reckon you would get any ground effect, certainly no significant effect, and definately nothing approaching an aeroplane. Your descent rate and forward speed energy is being used mostly to turn the rotor blades, and secondly to produce relatively little lift, just enough lift to stop you free falling. During the flare and cushion, you are diverting the energy that was turning the balde stored as blade inertia, into lift to arrest your rate of descent, for the first time in the auto you are generating significant lift. No where during this process is there anything "aeroplane like" going on, not even a glide.