Definition
The angle of attack at which the airflow over the wing's upper surface separates and the wing stalls, causing a sudden loss of lift regardless of airspeed, weight, or attitude.
Plain English
It's the steepest angle the wing can meet the oncoming air before the air stops flowing smoothly over the top and the wing stops producing enough lift to fly. Go past this angle, and the wing stalls.
Context Anchor
Seen in discussions of stalls, slow flight, and flap use. In the flap chapter, it matters because extending flaps changes the wing’s shape and affects how the wing behaves near a stall.
Derivation
Critical' comes from the Greek 'krisis,' meaning a turning point or decisive moment. Here it marks the exact angle where the wing's behavior changes decisively -- from flying to stalled.
Why Pilots Care
Exceeding this angle produces an aerodynamic stall that can lead to sudden loss of altitude or control if recovery is delayed.
Analogy
Think of holding your hand out a car window. At a small angle, the air flows over it smoothly; if you tilt it too far, the air breaks away and your hand buffets instead of lifting smoothly.
Grounding Statement
In slow flight or during landing, raising the nose too much can make the wing reach its critical angle of attack even if the airplane still seems controllable a moment before.
Intuition Check
Critical does not mean “dangerous only in an emergency.” Here it means the exact turning point where the wing changes from normal lift to the start of a stall. Attack does not mean combat; it means how the wing meets the oncoming air.
Example Sentence 1
The instructor demonstrated that exceeding the critical angle of attack causes the wing to stall, even at high airspeed during a steep turn.
Example Sentence 2
Extending the flaps lowers the critical angle of attack, allowing the airplane to fly at a slower airspeed before stalling.