Definition
The curved, graduated arc at the top of the attitude indicator marked with reference points — typically at 0°, 10°, 20°, 30°, 60°, and 90° — used to read the airplane's angle of bank by comparing it against the bank index pointer.
Plain English
The curved row of marks at the top of the attitude indicator that shows how steeply the airplane is banked left or right.
Context Anchor
Seen at the top of an analog attitude indicator during instrument flying, especially when setting or correcting a turn.
Derivation
"Scale" comes from the Latin scala, meaning "ladder" or "steps," and refers to a series of graduated marks for measuring something. A bank scale is simply the row of marks used to measure bank angle.
Why Pilots Care
Enables precise bank control to maintain standard-rate turns and coordinated flight without outside visual references.
Intuition Check
Do not read the bank scale as turn rate or heading. It shows wing tilt, not how fast the airplane is turning or where the nose is pointed.
Example Sentence 1
Rolling into the turn, she watched the bank scale until the pointer settled on the 20° mark.
Example Sentence 2
During the turn, cross-checking the bank scale confirmed the wings were not overbanked.