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-3 early in December. The S-3 made its last flight on December 13, 1910 when at an altitude of 90 feet the engines distributor shifted to a retarded position and lost power. The aircraft landed hard on a frozen pond, broke through the ice and sank causing serious damage. The S-3 was salvaged and some parts including the engine were used in the construction of the S-4. Sikorsky S-3 The Sikorsky S-3 was an early Russian single seat biplane design by Igor Sikorsky. Work on the machine started in July 1910 and was completed in late November. The S-3 was a