Definition
An older gyroscopic flight instrument that displays the rate at which the aircraft is turning (yawing) about its vertical axis, along with a separate inclinometer ball that shows whether the turn is coordinated. The turn portion uses a rate gyro to drive a needle that deflects left or right in proportion to turn rate, while the ball indicates slip or skid based on the balance of gravity and centrifugal force.
Plain English
A cockpit instrument with a needle that shows how fast the aircraft is turning left or right, and a small ball that shows whether the turn is being flown smoothly. It is an older version of the turn coordinator.
Context Anchor
Seen in instrument flying discussions, especially when comparing older turn-and-bank indicators with turn-and-slip indicators and turn coordinators.
Derivation
The name describes exactly what the instrument shows: the rate of turn and the bank quality of that turn. 'Bank' here originally referred to the angle of the wings, but on this instrument the ball is actually showing coordination, not bank angle. This historical naming is why the instrument was later redesigned and renamed the 'turn coordinator.'
Why Pilots Care
Proper use prevents slips and skids that can cause heading errors, increased stall risk, or disorientation in instrument conditions.
Analogy
The ball part works a little like a level: if the ball is centered, the turn is balanced; if it moves to one side, the airplane is not moving cleanly through the turn.
Intuition Check
Do not assume “bank indicator” means it shows the exact tilt of the wings. Here, the instrument shows turn rate and coordination; bank angle must be understood from other cues or instruments.
Example Sentence 1
After losing the attitude indicator, the pilot used the turn-and-bank indicator to hold a standard-rate turn while descending through the clouds.
Example Sentence 2
During the instrument approach, a slipping indication on the turn-and-bank indicator prompted immediate rudder correction.