Sikorsky S-72 Sikorsky S-72 The Sikorsky S-72 was an experimental hybrid helicopter/fixed-wing aircraft developed by helicopter manufacturer Sikorsky Aircraft. The Rotor Systems Research Aircraft (RSRA) was developed by Sikorsky for NASA and the Army. The RSRA was developed to allow the inflight measurement of helicopter rotor characteristics. The airframe was developed using an existing Sikorsky S-61 main rotor, an S-61 roller gearbox, and a highly modified Sikorsky S-67 airframe. The RSRA could be fitted with TF34 turbofans and wings to allow compound helicopter configurations to be experimentally investigated at speeds up to . In addition, it could fly as a fixed-wing aircraft
Igor Sikorsky No. 64 issued by the Imperial Aero Club of Russia in 1911. During a demonstration of the S-5, the engine quit and Sikorsky was forced to make a crash landing to avoid a wall. It was discovered that a mosquito in the gasoline had been drawn into the carburetor, starving the engine of fuel. The close call convinced Sikorsky of the need for an aircraft that could continue flying if it lost an engine. His next aircraft, the S-6 held three passengers and was selected as the winner of the Moscow aircraft exhibition held by the Russian Army in February