During a hover, one effect of the tail rotor is that it can cause the helicopter to drift sideways (if no corrective actions are taken). This kind of drift is:
Refer to Figure.
Translating Tendency also known as Tail Rotor Drift is the tendency of the helicopter to drift in the direction of the tail rotor thrust. For this example, consider a counter-clockwise rotor system.
Since torque works both to right (rotor torque) and left (fuselage torque) as the main rotor rotates and the tail rotor only produces thrust to the right, the fuselage torque and the tail rotor thrust will couple and create a greater force to the right causing drifting tendency.
The tail rotor drift is corrected by tilting the main rotor disc in the opposite direction of the drift, this can be achieved by the following methods:
- Rotor mast rigged slightly to the left, creating a horizontal lift component to oppose the tail rotor drift.
- Flight controls are rigged so that when the stick is in centre, the disc is actually tilted by the correct amount.
- Manual cyclic stick inputs by the pilot.
Biasing the cyclic pitch control of the main rotor in a helicopter means setting a preferred or initial position for the cyclic control system. In the context of helicopter flight control, the cyclic pitch control is responsible for tilting the rotor blades during rotation to control the helicopter's attitude and direction of movement. In terms of tail rotor drift it means tilting the rotor disc slightly to counter act the drift.
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