Definition
An abnormal flap condition in which the flaps on one wing extend or retract while the flaps on the other wing remain in a different position, producing unequal lift between the two wings and a strong rolling tendency toward the wing with the lower flap setting.
Plain English
One wing's flap moves and the other wing's flap doesn't, so the two wings produce different amounts of lift and the airplane wants to roll toward the wing whose flap stayed up.
Context Anchor
Encountered during abnormal or emergency discussions about flap problems, especially during approach, landing, or flap retraction after takeoff.
Derivation
Asymmetric comes from the Greek 'a-' (not) and 'symmetria' (same measure) — literally 'not the same on both sides.' Here it describes flaps that are no longer matched left and right.
Why Pilots Care
The resulting roll can become uncontrollable near the ground and has caused accidents during both takeoff and landing.
Grounding Statement
Picture one wing making more lift and drag than the other because its flap is down farther; the airplane will not feel balanced.
Intuition Check
Asymmetric does not just mean “slightly uneven” here. In this context, it means the left and right flaps are not matched, which can make the airplane roll.
Example Sentence 1
When the right flap failed to extend on final approach, the pilot recognized the asymmetric flap condition by the sudden roll toward the right wing.
Example Sentence 2
On final approach the crew used differential aileron and reduced flap setting to manage the asymmetric flap until landing.