Trim

Chapter 4.2

The purpose of the TRIM

During practical exercises we feel the pressures of the controls when changing the attitude or performance. The attitude can only be maintained by constantly either pulling or pushing on the elevator control. This prolonged manual compensation becomes tiring.

The trim mechanism will eliminate the pressures from the flight control. After having trimmed, the flight controls can be released. The airplane will remain within its attitude due to its proper stability.

If the attitude is to be maintained for long periods of time, then the trim should be used. You have to decide whether to use the trim or not depending on the situation. Trimming is only done when the attitude or the desired speed has been achieved.

Which pressures on the controls should be compensated?

All airplanes have a trim on the elevator.

Certain types of airplane are equiped with trim mechanisms for both Yaw and Roll.

Pressure compensation on controls

The remaining pressures on the flight controls after a change of attitude or configuration are first manually
compensated during the stabilization phase. After stabilization of the new flight situation, they will be compensated.

If, after a change of attitude, a permanent exceptional effort is to be exerted on a flight control, for example
during a Go-Around, the effort on the flight control can be first reduced by placing the trim wheel to a setting
predetermined by experience. After stabilizing the trim, fine adjustments are carried out.

Never try to change an attitude by means of the trim.

Pressure compensation on controls

Trimming of the flight attitude prior to stabilization can lead to an unstable flight phase which can extend over a long period. As a consequence you will have to focus on this maneuver for a much longer time.

After each change of engine power or configuration - TRIM!

Construction of the Trim

School aircraft normally have only a pitch trim. It is operated by a wheel, a lever or an electric switch. An index next to the control gives the trim’s position. In general, the TAKE OFF position is indicated by a mark.

The direction of the trim wheel or lever movement indicates the direction to which the neutral pressure point moves on the flight control.

Direction of the Elevator Trim