First flight of the S-64 was on May 9, 1962, only 13 months from program go-ahead. Only two months later, in July 1962 the aircraft was flown to Ft. Benning Georgia for Army evaluation. Up to this time, everything was company funded.
The U.S. Army bought six S-64s for evaluation at a cost of $13 million. They designated it the CH-54A Tarhe. Four of these aircraft eventually went to Vietnam to assist in the war effort. The German government also bought two for evaluation. A U.S. Army production order followed the initial Vietnam evaluation. The Germans did not buy any Skycranes, preferring the CH-53A with its internal cabin.
Initially the aircraft were designated the S-64A. With a production order from the Army, including numerous configuration and performance changes, including wider chord blades, the aircraft were designated the CH-54A by the Army and the S-64E in Sikorsky terminology. After a number of years of production, the mission capabilities were expanded again with the CH-54B/S-64F configuration.
