Support System (AAFSS). The development objectives document (QMDO) for the AAFSS was approved in April 1964, and on 1 August 1964, the Transportation Research and Engineering Command contacted 148 prospective contractors with a request for proposals (RFP). Bell submitted the D-262, a modification of the D-255, but still a conventional helicopter design. Sikorsky submitted the S-66, which featured a "Rotorprop" that would serve as a tail rotor but as speeds increased would rotate 90° to act as pusher propeller. Lockheed submitted the CL-840 design, a rigid-rotor compound helicopter with both a pushing propeller and a conventional tail rotor mounted at the end of the tail. The Army announced Lockheed and Sikorsky as winners of Project Definition Phase contracts on 19 February 1965. Meanwhile, the Army also continued to pursue an interim aircraft for combat in Vietnam until the AAFSS could be fielded, resulting in development of the Bell AH-1 Cobra which would become the backbone of the Army's attack helicopter fleet during and after the Vietnam War. Lockheed and Sikorsky developed proposals for their respective designs, establishing three configurations to satisfy both the development objectives and a revised RFP based on a draft requirements document. An evaluation board studied each company's proposal and then submitted its recommendation to a selection authority council on 6 October 1965. On 3 November 1965, the Army announced Lockheed as the winner of the AAFSS program. The Army perceived Lockheed's design as less expensive, able to be delivered sooner, and a lower technical risk than Sikorsky's Rotorprop. On 17 December 1965, the Army released the final requirements document. The document added fourteen requirements that were not previously addressed by Lockheed's proposal, including the addition of an aerial rocket armament subsystem. On 23 March 1966, the Army awarded Lockheed an engineering and development contract for 10 prototypes, designating the aircraft AH-56A. Initial operating capability was planned for 1972 with an optimistic target of late 1970. Lockheed began construction of the aircraft at its Van Nuys, California facility, and on 3 May 1967, Lockheed held a roll-out ceremony for the AH-56A. The aircraft was christened Cheyenne by the Army. The first flight of the AH-56 occurred on 21 September 1967. The Secretary of Defense approved pre-production funding to support an initial production order for 375 aircraft on 8 January 1968. Manufacture of the 10 Cheyenne prototypes was completed by 1969. Design Lockheed designed the Cheyenne as a