Helicopters

A helicopter’s tail has no rudder or elevators. Its main rotor controls alti­tude, so elevators are not needed. Its tail rotor controls yaw, so a rudder is not needed either. The sideways thrust of the tail rotor stops the helicopter from spin­ning in the opposite direction to the main rotor. Increasing or decreasing the tail rotor thrust makes the helicopter turn, or yaw.

Not all helicopters have a tail rotor. A NOTAR (short for NO TAil Rotor) heli­copter has a jet thruster at the end of its
tail boom. It blows air out of a slot in the side of the boom. Some helicopters do not have a tail at all. These helicopters have two main rotors instead of one, and the two rotors spin in opposite directions. The turning forces they apply to the helicopter are equal and opposite. No overall turning force, or torque, is applied to the helicopter, and so no tail rotor or thruster is needed.