Definition
To readjust the airplane's trim controls so that the aircraft maintains a desired attitude or airspeed without the pilot holding continuous pressure on the flight controls, typically required after a configuration or power change alters the existing control forces.
Plain English
To adjust the trim again so the airplane flies hands-off at the new speed or attitude after something has changed, like extending flaps or changing power.
Context Anchor
Commonly encountered after extending or retracting flaps, when the airplane may need a new trim setting to stay stable and comfortable to control.
Derivation
The prefix 're-' means 'again,' and 'trim' here refers to the trim system on the aircraft -- small adjustable surfaces (or systems) that relieve control pressures. So 're-trim' simply means 'trim again' after conditions have changed.
Why Pilots Care
Failing to re-trim after flap changes produces unexpected pitch forces, increases workload, and can lead to airspeed or altitude deviations.
Grounding Statement
When flaps move, the airplane may start wanting to raise or lower its nose, and re-trimming removes that steady push or pull from the pilot’s hands.
Intuition Check
Re-trim does not mean starting over or correcting a mistake. It means adjusting the trim again because the airplane now needs a different balance setting.
Example Sentence 1
After lowering the flaps to 20 degrees on final approach, the pilot needed to re-trim to relieve the nose-down control pressure.
Example Sentence 2
During the go-around, the instructor reminded the student to re-trim as the flaps were retracted in stages.