Sikorsky Aircraft and it became a part of [[United Aircraft and Transport Corporation]] (now [[United Technologies Corporation]]) in July of that year. [[File:Sikorsky Aircraft Corporation ad Model S-42 Clipper Flying Boat 1937.jpg|thumb|left|upright|Advertisement for [[Sikorsky S-42]] Clipper flying boat from 1937]] In the United States, Igor Sikorsky originally concentrated on the development of multi-engined landplanes and then amphibious aircraft. In the late 1930s, sales declined and United Aircraft merged his division with [[Vought Aircraft]]. He then began work on developing a practical helicopter. After first flying the [[VS-300]] he developed the [[Sikorsky R-4]], the first stable, single-rotor, fully controllable [[helicopter]] to enter full-scale
Sikorsky S-7 The S-7 was entered in the international military competition at Saint Petersburg in August 1912. During a take-off attempt from a furrowed field the landing gear was severely damaged and the S-7 was unable to finish the completion. In 1913 the aircraft was repaired and served as a trainer. In 1914 Bulgaria purchased the S-7 and used it in operations during World War I. Sikorsky S-7 The Sikorsky S-7 was a Russian single engine experimental prototype aircraft built by the Russian Baltic Railroad Car Works shortly after Igor Sikorsky became chief engineer of the aircraft manufacturing division. The S-7 was