Yakovlev Yak-24 Horse. In 1965, the US Army launched the Uti lity Tactical Transport Aircraft System (UTTAS) program. The initial specification called for an aircraft able to carry a crew of three and eleven troops with the main goal of replacing the Bell UH-1 Huey. Requests for proposals were issued to the industries in 1972. All the designs proposed in response to the specification were required to use two G.E. turbo-shaft engines and wheeled landing gear. Bell , Boeing and Sikorsky submitted proposals. The Boeing model 237 and Sikorsky S-70 were selected to proceed to prototype construction as the YUH-61 and YUH-60. The Boeing YUH-61 made its maiden flight in 1974. It was Boeing's first design with a single main rotor. All the three YHU-61A prototypes were delivered to the Army in 1976. A UTTAS competitive evaluation was conducted over the next eight months, with finally the Sikorsky S-70 was declared the winner, as Sikorsky's design was less complex than Boeing's. The S-70 became the HH-60 BlackHawk.
