vertical autorotation
SEL,
Thanks for your interest and views.
I do have Prouty's Helicopter Performance Stability and Control, and his definition of vertical autorotation is: "At some rate of descent, the forward tilt of the lift vector is equal to the drag component. This is the condition of autorotation, since no torque need be applied to maintain rotor speed. In an actual rotor, some blade elements will have more drag than the forward component of lift; but on other elements the situation will be reversed".(ref. pages 96-97)
I note that Prouty has no mention of "driving-driven region" and hence my original question "is the driving- driven theory outdated"?
Your description is good up to the point when you said "as you close on the tip, the blade element velocity increasing, the total reaction moves past vertical and therefore acts to slow the rotor."
The forward lift vector would be maximum at the tip in my view, so I guess I disagree at that point.
As for the negative poster above, I feel that the discussion and debate of aero science is what this forum is all about.