Definition
A pointer on the turn-and-slip indicator or turn coordinator that shows the angle at which the aircraft is rolled left or right relative to its longitudinal axis. It works alongside the inclinometer (the ball) to give the pilot a continuous reference for how steeply the wings are tilted during a turn.
Plain English
An instrument display that tells the pilot how far the aircraft is leaning to the left or right.
Context Anchor
Seen on cockpit flight instruments, especially when checking whether the wings are level or when holding a steady turn.
Derivation
‘Bank’ comes from an old Norse word for a ridge or sloped surface, later applied to the tilted attitude of an aircraft in a turn — the wings forming a sloped surface against the horizon. ‘Indicator’ simply means something that points to or shows a value.
Why Pilots Care
Ensures coordinated turns for safety, comfort, and efficient flight without unnecessary side loads.
Intuition Check
Bank does not mean a financial bank or a river bank here. In aviation, bank means the sideways tilt of the aircraft’s wings.
Example Sentence 1
Entering the clouds, the pilot scanned the bank indicator to confirm the wings were level.
Example Sentence 2
When the ball slid to the outside of the turn, the bank indicator showed a skidding condition that needed rudder correction.