Page 495 - PPL-engelsk 2025

Principles of flight

5.7.6.5 Adjustable trim tab

The most important tab at the end. It is the adjustable trim tab, which the pilot

can operate from inside the cockpit via a trim wheel.

In principle, it can be mounted on all control but is often limited to the elevator.
It is also often seen on the rudder.

Here the elevator is seen on the
right side of a Cessna.

In this case, there is only a trim

tab on the right elevator.

Once the aircraft is established in the desired flight attitude, the trim wheel is

turned so that the aircraft is trimmed, and the pilot only needs to use a couple

of fingers to hold the aircraft in the desired attitude.

Also note the aerodynamic balancing of the elevator.

5.7.6.6 Static balancing of controls

The purpose of static balancing of controls is to prevent harmful oscillations in

the controls.

These oscillations are called “flutter”, and they can cause the controls to be torn

off the aircraft! These can occur if the center of gravity of the control is behind

the hinge line.

Often the area of the control behind the hinge line is significantly larger than the

area in front of this line.

This picture of the underside of an aileron shows how

to place a lead weight so that the rudder is balanced.

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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 495