Sikorsky VS-300

The Vought-Sikorsky VS-300 was an American single engine helicopter designed by Igor Sikorsky, making its first free flight in May 1940. It was the first successful single main rotor helicopter built in the United States, establishing the single vertical tail rotor arrangement for countering the main rotor's torque that became the standard helicopter layout for decades afterward. Fitted with floats, a later version of the VS-300 also became the first practical amphibious helicopter.