Definition
Mistakes in the use of the trim controls that result in the pilot holding control pressures to keep the aircraft in the desired attitude, or in over-trimming so the aircraft drifts off the desired attitude on its own. Common trim errors include using trim as a primary control to change attitude, trimming before the attitude is established and stable, and chasing the airplane with continuous trim adjustments instead of setting attitude first and then relieving the held pressure.
Plain English
Trim errors are the wrong ways pilots use the trim wheel — like trying to fly the airplane with trim instead of with the controls, or adjusting trim too soon, too often, or too much. The result is that the pilot ends up fighting the airplane instead of flying it smoothly hands-light.
Context Anchor
Seen during instrument flying practice, especially when correcting common straight-and-level flight problems.
Derivation
Trim comes from older nautical use, where it meant arranging a ship so it sat and moved properly in the water. In aviation, the idea carried over: trim helps arrange the aircraft’s control forces so it flies steadily without the pilot having to hold constant pressure.
Why Pilots Care
Unresolved trim errors raise workload and make it harder to hold altitude and heading, especially during instrument flight.
Grounding Statement
If the airplane keeps trying to climb, descend, speed up, or slow down after you have set the desired flight condition, trim may not be set correctly.
Intuition Check
Do not think of trim as the main way to steer or pitch the airplane. First set the airplane with the flight controls, then use trim to remove the pressure needed to hold that setting.
Example Sentence 1
The instructor pointed out a classic trim error: the student was rolling the trim wheel to climb instead of pitching up first and then trimming.
Example Sentence 2
A speed change without resetting trim produced a trim error that caused gradual altitude loss until corrected.