Definition
A precisely tensioned spring inside a turn-and-slip indicator that opposes the gyro's tendency to tilt when the aircraft turns. The spring is set so that a specific rate of turn produces a specific needle deflection, allowing the instrument to display turn rate accurately.
Plain English
A small spring inside the turn indicator that pushes back against the gyro just enough so the needle moves the right amount for the rate you are turning.
Context Anchor
Seen when learning how a turn-and-slip indicator senses and displays aircraft turns.
Derivation
Calibration comes from the Latin calibrare, meaning to set to a correct measure. The spring is calibrated, meaning its tension is precisely set, so the needle reads the turn rate correctly.
Why Pilots Care
It makes the turn needle reliable for maintaining a precise standard-rate turn when flying by instruments alone.
Analogy
It is like the spring in a bathroom scale: the spring’s resistance helps the pointer move the right amount for the force applied.
Intuition Check
Do not think of this as a spring that powers the instrument. Here, the spring is used to restrain and adjust the needle’s response so the indication is accurate.
Example Sentence 1
The calibration spring inside the turn-and-slip indicator resists the gyro's tilt so the needle deflects in proportion to the rate of turn.
Example Sentence 2
During the instrument scan, any hesitation in the needle returning to center would indicate a problem with the calibration spring.