Definition
A stall in which one wing stalls before the other, producing unequal lift between the two wings. The wing that stalls first loses lift and drops, while the still-flying wing continues to produce lift, generating a strong rolling and yawing motion toward the stalled side. In the split-flap context, an asymmetric stall can occur when the wing without flap reaches its critical angle of attack before the wing with flap extended.
Plain English
A stall where one wing quits flying before the other, so the airplane rolls sharply toward the wing that stalled.
Context Anchor
Encountered in discussions of split or uneven flap conditions, stall recognition, and recovery from slow flight near the ground.
Derivation
Asymmetric comes from the Greek 'a-' meaning 'not' and 'symmetria' meaning 'agreement in proportion.' So asymmetric simply means 'not the same on both sides' -- which is exactly what is happening: one wing is stalled, the other is not.
Why Pilots Care
An asymmetric stall can produce an abrupt roll at the stall speed that may progress into a spin if not promptly corrected.
Grounding Statement
Picture one wing still lifting while the other starts to quit; the airplane naturally wants to drop toward the wing that is quitting first.
Intuition Check
Do not read “stall” here as the engine stopping. In this term, a stall is a loss of smooth lift from the wing; “asymmetric” means that loss is unequal from one wing to the other.
Example Sentence 1
With the right flap stuck up and the left flap extended, the pilot kept extra airspeed on final to avoid an asymmetric stall during the flare.
Example Sentence 2
The pilot applied rudder to keep the wings level and recovered from the asymmetric stall before it developed further.