Refer to figure.
The purpose of the trim system is to relieve the pilot of forces on the aircraft controls while maintaining aircraft attitude. In manual control, trim on light aircraft is provided in all three axes through mechanical linkages to trim tabs on the control surfaces. On larger aircraft this is usually achieved by electrical actuators that bypass the Powered Flying Control Unit (PFCU), particularly for pitch trim.

The main purpose of the pitch trim setting for take-off is to provide consistent rotation characteristics. Take-off pitch trim is set manually via the pitch trim wheel.

The limits of the THS normal setting range for take-off are indicated by a green band on the pitch trim wheel, therefore, the aircraft performs a safe take-off, provided the pitch trim setting is within the green band on the pitch trim wheel.