Turn and Slip Indicator/Turn Co-ordinator

The turn and slip indicator (or turn coordinator) is a gyroscopic flight instrument that displays the aircraft’s rate of turn and whether the aircraft is in coordinated flight (ball in centre = coordinated; ball displaced = skid or slip). It is one of the six basic flight instruments and provides attitude information on partial panel if the attitude indicator fails.

Components

• Turn indicator: A gyroscope driven by vacuum or electricity; shows rate of turn — one bar = rate one (3°/sec); two bars = rate two (6°/sec)
• Inclinometer (ball): A fluid-damped ball in a curved tube; indicates yaw balance — “step on the ball” to centre it using rudder

Coordinated vs. Uncoordinated Flight

• Skid: Ball displaced toward the outside of the turn — too much bank, not enough rudder; slip on the base-to-final turn can lead to a skidded turn stall
• Slip: Ball displaced toward the inside of the turn — too much rudder, not enough bank; slipping toward the ground

Partial Panel Flying

If the attitude indicator fails, the turn coordinator becomes the primary bank reference. Fly rate-one turns using the turn indicator; use the altimeter and VSI for pitch reference; cross-check with the heading indicator. This is partial panel flying — a required skill for the instrument rating.

Related Terms

See also: Attitude Indicator, Rate-One Turn, IFR.