Helicopter - I believe that you will find that helicopters are
sometimes able to self-rescue because the pitch of the blades can be
changed. As the helicopter falls through the air, the blades are
pitched to spin the blades rapidly in one direction. Just before the
helicopter crashes, the pilot adjusts the "collective" to switch the
blade pitch. The momentum of the spinning blades keeps them going for
a short time. With the blades now pitched to create lift, the
momentum-created lift can be enough to cushion the landing. If the
pilot adjusts the collective too soon, the helicopter will come almost
to a hover and then begin to fall rapidly to the ground.

Larry's physics strike me as correct -- up to a point. If just enough
power is applied to the shaft to turn the prop to match the water flow
past it, the drag ought to be zero. If more power is applied, the
"drag" would be negative. If less power is applied, the drag will
increase right up until the prop is almost stationary. When the prop
become completely stationary, however, a new condition is created.
The blades stall. Going back to an aircraft analogy, as the wings of
a fixed-wing aircraft are flown to take a bigger and bigger bite of
the air, the drag will significantly increase. But, once you go one
step too far and the wing stalls, the plane will drop like a stone.

While Larry's idea of the increasing drag as the prop slows its
rotation makes perfectly good sense, it misses the transition to less
drag when the blades stop moving and stall.

OK, so maybe it is BS. :-D But it is pretty good sounding BS.
And its my story and I'm sticking to it.

BTW, not only is Denmark a great country, Danes are very fine people.

Lee Huddleston
s/v Truelove