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-16 delivered in early 1916. Although highly maneuverable, the S-XVI possessed a comparatively poor performance due to insufficient power. A further small batch were completed in 1917, with the aircraft being used during the Russian Revolution and staying in service until 1923. At least one aircraft have been used by the Ukrainian People's Republic after 1917. Sikorsky S-16 The Sikorsky S-16, or RBVZ S-XVI (named after its manufacturer), was a Russian equi-span single-bay two-seat biplane designed by Igor Sikorsky in 1914-15. Conceived in response to demand for an escort fighter for the Ilya Muromets bombers, it was noteworthy in that it