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-19 Sikorsky S-19 The Sikorsky S-19 was a Russian twin engine experimental prototype aircraft built late in 1916 by the Russian Baltic Railroad Car Works while Igor Sikorsky was chief engineer of the aircraft manufacturing division. The S-19 was a two bay sesquiplane powered by two Sunbeam Crusader water-cooled V-8 engines installed in push-pull configuration. Arranged as a twin-boom aircraft, it had a large rudder located in the center of the empenage. Two crewmembers occupied cockpits in the foreword most section of the booms in front of the lower wing and served as pilot and machine gunner. Flight testing revealed sluggish