Definition
A small, continuous oscillating signal deliberately applied to a mechanical or electromechanical component to keep it in constant slight motion, preventing it from sticking and ensuring it responds smoothly and immediately to control inputs.
Plain English
A tiny, fast vibration added on purpose to a part so it never sits perfectly still. Because the part is always twitching slightly, it doesn't get stuck and reacts instantly when a real command comes through.
Context Anchor
Seen in discussions of aircraft electronics, autopilot control systems, instrument systems, and troubleshooting of control circuits.
Derivation
From the Old English 'didderen,' meaning to tremble or shake. The everyday meaning of 'dither' (to be indecisive, to waver) comes from the same root. In engineering, the word kept its literal sense — a small trembling motion — rather than the figurative one.
Why Pilots Care
Maintains accuracy in attitude and heading information from laser gyros during all phases of flight.
Analogy
It is like gently wiggling a sticky drawer while pulling it open. The wiggle is not the main action, but it helps the drawer move smoothly instead of sticking.
Intuition Check
Do not assume a dither signal is unwanted electrical noise. In this context, it is added on purpose to improve how the system behaves.
Example Sentence 1
The dither signal applied to the hydraulic servo valve prevents static friction from causing a sluggish response to autopilot commands.
Example Sentence 2
Maintenance checks confirm the dither signal is present before releasing the aircraft for flight.