In the mid-60’s, VTOL in all its forms was all the rage. In 1965, Lockheed answered a US Army Request For Proposals with the CL-945 concept, a stowed-rotor helicopter design. At low speeds and hover, it would operate as a helicopter; at higher speeds, aircraft-style propulsion systems would power it forward; and at much higher speeds than helicopters normally attain, the rotors would stop rotating and would fold back and be stowed for minimum drag. It was a great idea that had the little problem of being horribly complex, heavy and expensive.
At least three distinct designs were put forward. The First, the CL-945-1, used the rotors, pusher prop and tail rotor from the AH-56 Cheyenne were used with an all-new fuselage. The rotors folded backwards in flight, but were not covered.
The CL-945-2 designation was given to two slightly different designs. Both not only folded the rotors back, but also stowed them internally for minimum high-speed drag. One design featured turbofan engines, one under each small wing.
The other was similar, but used turboprops instead.
There were slight variations on the latter design shown publicly.
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