When the WWII started, all helicopter related jobs were concentrated in single OKB-3 headed by Ivan Pavlovich Bratukhin.
Involved in helicopter development since the late 1930s, I. P. Bratukhin first designed a twin-rotor helicopter, with an engine and related rotor mounted at each end of an outrigger. Designated 2MG Omega, this was completed in 1941. Vibration problems resulted in construction of Omega II in 1943. A series of similar twin-rotor helicopters were built up to 1948.