Page "History of aviation" Paragraph 77

Less than a decade after the development of the first practical rotorcraft of any type with the autogyro, in the Soviet Union, Boris N. Yuriev and Alexei M. Cheremukhin, two aeronautical engineers working at the Tsentralniy Aerogidrodinamicheskiy Institut ( TsAGI,, ), constructed and flew the TsAGI 1-EA single rotor helicopter, which used an open tubing framework, a four blade main rotor, and twin sets of 1. 8-meter ( 6-foot ) diameter anti-torque rotors ; one set of two at the nose and one set of two at the tail.

Powered by two M-2 powerplants, up-rated copies of the Gnome Monosoupape rotary radial engine of World War I, the TsAGI 1-EA made several successful low altitude flights.

By 14 August 1932, Cheremukhin managed to get the 1-EA up to an unofficial altitude of 605 meters ( 1, 985 ft ) with what is likely to be the first successful single-lift rotor helicopter design ever tested and flown.