Definition
A gyroscopic flight instrument that shows the rate at which the aircraft is rolling into or out of a turn, and the rate at which it is turning once established. Its gyro is canted about 30 degrees from horizontal, so it senses both roll and yaw. A separate ball in a curved liquid-filled tube, mounted below the miniature aircraft display, indicates whether the turn is coordinated (ball centered), slipping (ball toward the inside of the turn), or skidding (ball toward the outside).
Plain English
An instrument with a small airplane symbol that tilts left or right to show how quickly you are rolling into a turn and how fast you are turning. A ball underneath shows whether your feet and hands are working together properly through the turn.
Context Anchor
Seen on the instrument panel, especially during instrument flying and when practicing controlled turns by reference to instruments.
Derivation
Called a 'turn coordinator' because, unlike the older turn-and-slip indicator that only showed yaw rate, its canted gyro also senses roll. It coordinates information about both rolling into and turning through a maneuver in one display.
Why Pilots Care
It lets the pilot keep turns balanced so the airplane maintains altitude, airspeed, and control without unnecessary stress on the airframe or passengers.
Intuition Check
Do not treat the turn coordinator as a bank-angle instrument. It shows turn direction and turn rate, and its ball shows balance; it does not directly tell you the airplane’s exact bank angle.
Example Sentence 1
Entering the turn, the pilot rolled until the wing of the turn coordinator's miniature aircraft aligned with the standard-rate index.
Example Sentence 2
During the steep turn, the turn coordinator showed the rate increasing while the ball remained in the center.