Just a small suggestion: The Mil Mi-4 (USAF/DoD reporting name "Type 36", NATO reporting name "Hound") is a Soviet transport helicopter that served in both military and civilian roles.
The Mi-4 was designed in response to the American H-19 Chickasaw and the deployment of U.S. helicopters during the Korean War. While the Mi-4 strongly resembles the H-19 Chickasaw in general layout, including the innovative engine position in front of the cockpit, it is a larger helicopter, able to lift more weight and built in larger numbers. The first model entered service in 1953. The helicopter was first displayed to the outside world in 1952 at the Soviet Aviation Day in Tushino Airfield.
One Mi-4 was built with a jettisonable rotor. It served as an experimental vehicle for future pilots' means of safety and ejection designs.