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-18 leave the ground. Sikorsky S-18 The Sikorsky S-18 was a Russian twin engine aircraft designed by Igor Sikorsky and built by the Russian Baltic Railroad Car Works aviation division at Petrograd during World War I. The S-18 was a large three bay biplane fighter/interceptor powered by two Sunbeam Crusader V-8 water-cooled engines mounted on the lower wing in a pusher configuration. The aircraft featured armor protection for both crew members with the gunner/observer seated in the nose and armed with a single machine gun. The aircraft was very heavy and with the less than reliable Sunbeam engines neither example built