Definition
The angle of attack at which the airflow over the wing separates to the point that lift decreases sharply and the wing stalls. Beyond this angle, increasing pitch will not produce more lift — it will reduce it. The critical angle of attack is a fixed property of the wing's shape and is the same regardless of airspeed, weight, bank angle, or load factor.
Plain English
The steepest angle the wing can meet the oncoming air before it stops flying. Push past that angle and the wing stalls — no matter how fast you're going.
Context Anchor
Seen in stall training, slow flight, approach and landing discussions, and explanations of how flaps affect stall speed and wing behavior.
Derivation
Critical' comes from the Greek 'krisis,' meaning a turning point or decisive moment. That's exactly what this angle is — the turning point past which the wing stops producing useful lift.
Why Pilots Care
Exceeding this angle produces an aerodynamic stall and sudden loss of lift, which must be recognized and recovered from to avoid loss of control.
Analogy
It is like tilting your hand out a car window. At a moderate angle the air pushes on it smoothly, but if you tilt it too far, the airflow breaks away and the smooth lifting force is lost.
Grounding Statement
A stall begins when the wing exceeds this angle, not simply because the airplane is flying slowly.
Intuition Check
Critical does not mean “dangerous speed” here. It means the wing’s limit angle to the airflow; when that angle is exceeded, the stall begins.
Example Sentence 1
The instructor explained that the wing will stall at the critical angle of attack regardless of how fast the airplane is flying.
Example Sentence 2
Lowering the flaps increased the critical angle of attack, allowing the airplane to fly at a slower speed before stalling.