If you have ever closely watched a hovering helicopter, you might have noticed that most times the skids are not level with the ground. In other words, one of the helicopter’s skids is lower than the other. Although wind and loading can cause this, the tail rotor thrust determines the base line for either right skid low or left skid low. Tail rotor thrust tends to make the helicopter drift in the same direction and is called translating tendency.
The tail rotor is designed to produce thrust to oppose the torque that tries to spin the helicopter in the opposite direction of the main rotor. Some of this thrust applies a force to the fuselage that causes the helicopter to drift laterally in the same direction. A tilt in the main rotor causes a small sideward thrust opposite the tail rotor to counteract the drift. The tilt can be accomplished by mounting the transmission at a slight angle or designing the flight control system to tilt the rotor disc when the cyclic control is centered.
The direction the rotor spins makes a difference. In a system the turns clockwise when viewed from above, the tail rotor thrust causes the helicopter to drift to the left. Tilting the main rotor disc to the right to counter this causes the right skid to hang low. A counterclockwise turning system will cause a right drift and a left tilt making the helicopter hover left skid low.