To:rwm
The Cheyenne had a lot of new and untested ideas on it. The shape of its blades was the least of the problem.
If you are addressing the use of gyroscopic forces to control blade pitch (cyclic) the concept was well proven on three levels of prototypes. The concept adopted by Lockheed was to scale up a smaller design using a similar airfoil section that was not asymmetrical as described by Nick Lappos. The original design had the same cross section at each of the blade stations. The Army kept adding weight to the design and soon the helicopter could not perform to the specs. Lockheed requested that they be allowed to increase the blade length to accommodate the increased weight. The Army refused so Lockheed (Ray Prouty) was forced to come up with a blade design that would accommodate the increase in weight while still remaining within the design planform approved by the Army. That is when the problems started to manifest themselves.
The propeller at the rear of the helicopter,which was used for forward propulsion or to retard the speed in a dive was basically proven by attaching a small turbojet engine to one of the smaller prototypes. This engine could not retard forward speed but it was capable of providing forward thrust. It was one of the first compound helicopters.
If I haven’t addressed the shortcomings you alluded to please post again and we can continue this discussion.
