Definition
A flight condition in which the airplane is rolled about its longitudinal axis to an angle exceeding 45 degrees from wings-level, measured between the airplane's lateral axis and the horizon. In the context of an airplane upset, this is one of the defined parameters indicating the aircraft has departed from intended flight attitudes during normal operations.
Plain English
The airplane is tilted sideways more than 45 degrees — meaning one wing is pointed noticeably more downward than the other, past the halfway point between level flight and a wing pointing straight at the ground.
Context Anchor
Seen in upset prevention and recovery training, especially when identifying whether the airplane has moved outside normal flight attitudes.
Derivation
In aviation, “bank” comes from the idea of an aircraft tilting or sloping to one side during a turn, like a road or track that is banked. “Angle” is the measured difference between two lines or positions. Together, “bank angle” means how far the wings are tilted compared with level.
Why Pilots Care
Unintentional bank angles beyond this limit reduce lift, increase stall risk, and demand immediate, specific recovery actions to restore controlled flight.
Grounding Statement
Picture the horizon cutting across the windshield at a steep slant instead of staying nearly level.
Intuition Check
“Bank” here does not mean a financial bank or the side of a river. It means the airplane is tilted left or right around its lengthwise axis.
Example Sentence 1
The instructor explained that any bank angle greater than 45° during normal cruise flight should be treated as an upset and recovered immediately.
Example Sentence 2
During the briefing the instructor explained that any bank angle greater than 45° combined with an unusual attitude counts as an upset.