Plain English Meaning
The pocket in the wing where the flap tucks away when it's pulled up, so the bottom of the wing stays smooth.
Full Definition
A recessed cavity or housing built into the underside of the wing into which the flap retracts and sits flush when fully raised, leaving a clean aerodynamic surface.
Context Anchor
Seen in flap system descriptions, aircraft inspections, and discussions of how flaps fit into the wing.
Derivation
‘Well’ here uses an older mechanical sense — a recessed space or cavity that something fits into (like a wheel well). It signals a built-in pocket, not a hole or shaft.
Why Pilots Care
A clean, unobstructed flap well allows the flap to retract fully, preserving the wing’s smooth upper surface and intended cruise performance.
Intuition Check
Do not read “well” as a water well. In this term, a well is a recessed space built into the aircraft structure.
Example Sentence 1
After landing in heavy rain, the pilot checked the flap wells for trapped water and debris before the next flight.
Example Sentence 2
With the flaps fully retracted, the trailing edge of the wing appeared smooth because the flaps sat flush inside the flap wells.