From, Техника - молодежи 1946/8-9,I think the translation is wrong or what ?,
Reader Grebnev L.
(Tetievskiy district, Knevsky region) asks: Do jet helicopters exist?
There are a number of jet helicopter projects. These projects are based on one general principle. Combustion products flow out of the hollow rotor blades through nozzles, and the rotor is set in rotation by the reaction force. However, the efficiency of a jet helicopter is very low. Therefore, jet helicopters are not used in practice yet. You can read about the rocket helicopter project in the Express Information of VNT TsAGI, 1944, No. 92/203, pp. 7-8, and in the book by N. V. Inozemtsev, Jet Engines in Aviation, NKAP, Oborongiz, Moscow, 1946.