Vought-Sikorsky VS-300

The Vought-Sikorsky VS-300 was a single-engine helicopter designed by Igor Sikorsky. It had a single three-blade rotor originally powered by a 75 horsepower (56 kW) engine. The first "free" flight of the VS-300 was on 13 May 1940. While not the first successful single lifting rotor helicopter to fly, as the Yuriev/Cheremukhin TsAGI-1-EA machine was in the Soviet Union in 1931-32, the VS-300 was the first successful single lifting rotor helicopter in the United States and the first successful helicopter to use a single vertical tail rotor configuration for antitorque. With floats attached, it became the first practical amphibious helicopter.