Works on Electric Helicopter in the USSR (1935-1941)

The article summarizes the unusual idea of building a tethered helicopter with electric motor for observational purposes. The motors powering the rotors were to be connected to a source of electricity on ground via cable. The author of this scheme was an engineer of the All-Union Electrotechnical Institute, A.G. Iosifjan. Experiments with the apparatus started in the mid-1930s. The work was carried out in three stages. At first, Iosifjan constructed a model with an electric motor powering a coaxially rotors. As a next step, he built a manned vehicle with electric motors placed at the ends of the rotor blades. Finally, in 1940-41, conventional petrol engines installed on a helicopter that had flown before were replaced by electric motors. In terms of the weight-power ratio, these new motors were 10 times lighter compared to traditional ones. The electric helicopter was subjected to real-life tests - it was able to take-off and perform simple flight maneuvers. Due to the war, though, further work was cancelled; development was not resumed after the war.