Definition
The difference between the airplane's current angle of attack and the critical angle of attack at which the wing will stall. A larger stall margin means the wing is operating further away from the stall; a smaller stall margin means it is closer to stalling.
Plain English
How much room the wing has left before it stalls. The bigger the margin, the safer you are from a stall at that moment.
Context Anchor
You will see this term in stall training, slow flight, maneuvering, approach work, and any discussion of recognizing and avoiding stalls.
Derivation
‘Margin’ comes from the Latin ‘margo,’ meaning edge or border. In aviation it is used the same way it is in everyday life — the room you have before reaching a limit. Here, the limit is the critical angle of attack.
Why Pilots Care
It tells the pilot how close the wing is to stalling during maneuvers, helping prevent unintentional stalls.
Analogy
Think of stall margin like the space between your car and the edge of the road. More space gives you time to correct; very little space means a small mistake can put you over the edge.
Intuition Check
Stall margin is not just “extra speed.” An airplane can have a small stall margin at a higher speed if the wing is heavily loaded, such as in a steep turn.
Example Sentence 1
In a steep turn, the increased load factor reduces the stall margin, which is why the airplane buffets sooner than in level flight.
Example Sentence 2
Lowering the nose and adding power quickly restored the stall margin after the stall warning activated.