In 1973, the Hughes Model 77 was selected as the winner of the US Army's advanced attack helicopter ( AAH ) competition against the Bell 409 ( YAH-63 ).
The prototype made its first flight in 1975
as the YAH-64 , and in 1976 the company received a full-scale development
The AH-64D Longbow Apache designation was applied to near 600 upgraded AH-64A with 2 x 1800 hp T700-GE-701 turboshafts engines , the Westinghouse Longbow radar system for automatic detection and classification of targets and all weather fire-and-forget type weapons.
The Apache was also exported to Israel, Egypt, Greece, the Netherlands, Saudi Arabia, United Arab Emirates and the United Kingdom ( as WAH-64 to be assembly by Westland )