Definition
The airspeed at which an aircraft, once trimmed, will tend to maintain in stable, hands-off flight. If disturbed from this airspeed, the aircraft will naturally try to return to it through its inherent longitudinal stability.
Plain English
The speed the aircraft is set up to fly on its own, without you holding pressure on the controls. Push it faster or slower and it will try to return to that speed by itself.
Context Anchor
Seen in instrument flying when learning how trim affects aircraft control, workload, and the airplane’s tendency to hold a selected speed.
Derivation
The word 'trim' originally meant to put something in proper order or balance — as in trimming the sails of a boat so it sails steadily without constant correction. In aviation, trimming the aircraft balances the control forces so it flies steadily at a chosen speed without the pilot holding pressure on the yoke.
Why Pilots Care
Knowing the trim speed lets the pilot reduce workload and maintain precise altitude and heading with minimal effort during instrument flight.
Analogy
Like setting the cruise control on a car so it holds a chosen speed without continuous pressure on the accelerator.
Intuition Check
Trim speed does not mean the fastest, safest, or recommended speed. It means the speed the airplane is balanced to hold with the current trim setting.
Example Sentence 1
After leveling off in cruise, she adjusted the trim wheel until the aircraft held altitude hands-off, settling into its trim speed.
Example Sentence 2
A power change without retrimming caused the aircraft to drift away from its trim speed until back pressure was applied.