The Sikorsky S-67 Blackhawk was a private-venture, prototype attack helicopter built in 1970 with Sikorsky Aircraft research and development (R&D) funds. A tandem, two-seat aircraft designed around the dynamic drive and rotor systems of the Sikorsky S-61, it was designed to serve as an attack helicopter or to transport up to eight troops into combat.
Its armament included a Tactical Armament Turret (TAT-140) with a three barrel 20 mm (0.79 in) cannon, and could carry 16 TOW missiles, 2.75-inch (70 mm) rockets, or AIM-9 Sidewinder air-to-air missiles.[3] The Blackhawk was powered by two General Electric T58-GE-5 1,500 shaft horsepower (1,100 kW) engines.
As part of internal Sikorsky R&D efforts, in 1974, the S-67 had a 3.5-foot-diameter (1.1 m) ducted fan fitted instead of its original conventional tail rotor.
Sikorsky S-67 Blackhawk - Wikipedia
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