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-35 Sikorsky S-35 The Sikorsky S-35 was an American twin-engined sesquiplane transport later modified to use three-engines. It was designed and built by the Sikorsky Manufacturing Company for an attempt by Rene Fonck on a non-stop Atlantic crossing for the Orteig Prize. It was destroyed in the attempt. The S-35 was designed as a twin-engined transport with a range. During 1926 Rene Fonck, a French First World War fighter ace, was looking for a multi-engine aircraft to enter a competition to be the first to fly non-stop from New York to Paris. The prize was $25,000, offered by Raymond Orteig. Fonck