What is helicopter two propellers?

A helicopter with two propellers is typically referred to as a twin-engine helicopter. These propellers are mounted on top of the main rotor hub and are driven by separate engines. This configuration provides redundancy, improved power, and reliability, making twin-engine helicopters more capable in a wider range of flight conditions. The two propellers are usually counter-rotating, meaning they rotate in opposite directions, which helps to cancel out the torque effect of the main rotor and improve stability. Twin-engine helicopters are commonly used in commercial, military, and emergency services applications where safety and performance are essential.