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
Sikorsky S-34 Sikorsky S-34 The Sikorsky S-34 was a 1920s American six-seat sesquiplane, designed and built by the Sikorsky Manufacturing Corporation. Only one was built but the design led to the successful Sikorsky S-38. The S-34 was a sesquiplane amphibian with a boat hull, being powered by two tractor Wright Whirlwind J-4 engines. It had a boom-mounted twin-rudder tail unit and room inside the hull for five passengers. During a test flight in November 1927 one engine failed and the S-34 crashed and sank. Igor Sikorksy and the others onboard escaped without injury but the S-34 was destroyed. It was the first