The Germans did not place an order, but the United States Army placed an initial order for six S-64A helicopters (with the designation YCH-54A Tarhe). The prototype S-64 first flew on and was followed by two further examples for evaluation by the German armed forces. The S-64 had a six-blade main rotor and was powered by two 4,050 shaft horsepower (3,020 kW) Pratt & Whitney JFTD12A turboshaft engines. The Sikorsky S-64 was designed as an enlarged version of the prototype flying crane helicopter, the Sikorsky S-60. Skycrane 'Olga' lifting a CN Tower antenna segment
