Definition
A feature of an autopilot or flight control system in which the control yoke or stick is held in a centered, neutral position by spring pressure, and any pilot input must be made against that spring force. Releasing the controls returns them to the trimmed reference position, which the autopilot then uses as the commanded attitude.
Plain English
A spring-loaded system that holds the control stick in a set position. You can move it, but you have to push against the spring, and when you let go it springs back to where the autopilot wants it.
Context Anchor
Seen in rotorcraft instrument flying and automatic flight control system discussions, especially when describing how the controls are stabilized and how the pilot sets a comfortable control position.
Derivation
The name describes the function: the system applies a force to keep the controls in trim (in a balanced, neutral reference position). Trim in aviation has long meant adjusting controls so the aircraft holds a desired attitude with no pilot effort.
Why Pilots Care
It reduces pilot workload by maintaining a steady control position without constant physical effort.
Intuition Check
Force trim does not mean trimming engine power or adding more force to the aircraft. It means setting the control position that the helicopter’s controls will try to hold.
Example Sentence 1
The pilot pressed the force trim release button, repositioned the cyclic, and let go so the new position became the trimmed reference.
Example Sentence 2
After establishing cruise, force trim was engaged to maintain level flight with relaxed control inputs.