To: tacks
The Apache would most likely never have been built if it were not for the intransigence of the US Army. Early on in the program the Army asked Lockheed to add on additional equipment increasing the gross weight. This taxed the lifting capabilities of the rotor system and Lockheed requested that the Army allow them to increase the rotor diameter along with attendant design changes. The Army refused so the aerodynamicist (Ray Prouty) had to redesign the blades to increase lift. This lead to the multiple aerodynamic shapes at the different blade stations. This coupled with the blade stiffness had a severe impact on blade stability and the shifting of the phase angle. The rest is history.
