On 26 March 1964, the Army Chief of Staff redesignated the FAS program as the Advanced Aerial Fire 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.