Contra-rotating propellers are an innovative design where two propellers are connected to the same engine, one positioned directly behind the other. These propellers rotate in opposite directions around the same axis, a process known as contra-rotation. Power from the engine is transmitted through a planetary gear or spur gear reduction gearbox. This setup is beneficial as it recovers energy lost in the airflow of the first propeller’s slipstream, enabling more power without needing larger propellers. Additionally, it helps to counteract the torque generated by high-power piston engines. It’s important to note that contra-rotating propellers differ from counter-rotating propellers.
