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
Igor Sikorsky 1912. In early 1912, Igor Sikorsky became Chief Engineer of the aircraft division for the Russian Baltic Railroad Car Works ("Russko-Baltiisky Vagonny Zavod" or "R-BVZ") in Saint Petersburg. His work at R-BVZ included the construction of the first four-engine aircraft, the S-21 "Russky Vityaz", which he initially called "Le Grand" when fitted with just two engines, then as the "Bolshoi Baltisky" (The Great Baltic) when fitted with four engines for the first time, each wing panel's pair of powerplants in a "push-pull" tandem configuration previous to the four tractor-engined "Russki Vityaz". He also served as the test pilot for its