The Sikorsky R-6A (Hoverfly II) was an American built two-seat observation helicopter used during the Second World War. The Sikorsky R-6A had a three-blade main rotor powered by a Franklin O-405-9 6-cylinder horizontally-opposed fan-cooled engine providing a top speed of 160 kmh and carried fuel for five hours of flying time. The U.S. Navy designation was HOS-1, the British name Hoverfly II. Research Sikorsky R-6A
 
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