hännäroottorin

Hännäroottori is a Finnish term that translates to "tail rotor" in English. It is a small rotor, typically located on the tail of a helicopter, that is driven by the main rotor system. Its primary function is to counteract the torque produced by the main rotor, which would otherwise cause the helicopter's fuselage to spin in the opposite direction. The tail rotor generates thrust in a direction perpendicular to the fuselage, thereby stabilizing the aircraft.

Without a tail rotor, or a similar anti-torque system like a NOTAR (No Tail Rotor) system, a conventional single-rotor helicopter would be uncontrollable. The pilot manipulates the pitch of the tail rotor blades to control yaw, which is the rotation of the helicopter around its vertical axis. Increasing the pitch of the tail rotor blades increases their angle of attack, generating more thrust and causing the tail to move in a specific direction, thereby turning the nose of the helicopter. Conversely, decreasing the pitch reduces thrust and allows the tail to move in the opposite direction.

The size, number of blades, and rotational speed of the tail rotor are critical design parameters that depend on the size and power of the main rotor. In some cases, two counter-rotating tail rotors may be used to provide enhanced control and stability. The tail rotor is a vital component for the safe and effective operation of most helicopters.