Mart,
Dave, my "threadjacking" light just came on.
. The three unfulfilled requirements mentioned in post #400 are directly related to the 'Sikorsky X2 coaxial heli development' and its ability to achieve high speed flight.
Interestingly, all three of these unfulfilled requirements are also directly related to; a rotating airfoil, where the axis of rotation is normal to the free stream velocity.
Is Darwin trying to tell us something?
Dave