 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 . 
