Definition
A flap malfunction in which the flap on one wing extends or retracts while the flap on the opposite wing fails to move with it, leaving the two flaps at different positions. The unequal lift and drag produced by the mismatched flaps creates a rolling and yawing tendency toward the wing with the lesser flap deflection.
Plain English
One wing's flap moves and the other wing's flap doesn't, so the two wings are no longer matched. The airplane wants to roll and turn toward the side with less flap out.
Context Anchor
Encountered during flap extension or retraction, especially in approach, landing, go-around, or any phase where the pilot selects a new flap setting.
Derivation
Asymmetric' comes from Greek, meaning 'not matching on both sides.' 'Split' is used here in its everyday sense — the two flaps are no longer together, they have split apart in position. The name describes exactly what has happened: the left and right flaps are no longer in agreement.
Why Pilots Care
The airplane immediately rolls toward the side with the more retracted flap and requires prompt aileron and rudder correction plus possible flap retraction or landing with asymmetric drag.
Grounding Statement
Picture one flap down and the other not as far down; one wing now behaves differently from the other.
Intuition Check
Do not read “split flap” here as only a flap design. In this malfunction context, it means the left and right flaps are split from each other in position.
Example Sentence 1
When the pilot selected flaps 30 on final, the airplane rolled sharply left, indicating a possible asymmetric flap condition.
Example Sentence 2
The pilot maintained coordinated flight with opposite aileron while completing the asymmetric flap checklist and returned for a flaps-up landing.