First time students often wonder why helicopters have tail rotors. The tail rotor system seems an unusual feature especially for fixed-wing pilots, but it serves a critically important function. The tail rotor creates a thrust to counter the torque which is created by the main rotor system, or blades, of the craft. This helps to stabilize the fuselage/cabin of the helicopter which would otherwise spin out of control.
The tail rotor is not the only type of antitorque system available. The fenstron (popularly known as “fan-in-tail”) is popular on Eurocopters and works in a similar way through the use of a fan rather than blades. Another option is the NOTAR system which eliminates the need for fans or blades on the tail through a jet engine which expels low pressure high volume air through slots in the tail.
Most pilots pay little or no attention to the antitorque system until it fails. Failure of this system is a leading cause of accidents in helicopters. This is why it is so important to not only understand how the system works, but what to do when it stops working.