Definition
An opening or channel built into an aircraft structure that allows trapped fluids — typically fuel, water, or other liquids — to drain overboard rather than pool inside the airframe. Scuppers are commonly found around fuel filler caps, where they catch spilled fuel during refueling and route it safely outside the aircraft skin.
Plain English
A small built-in drain that lets liquid escape to the outside of the aircraft instead of collecting inside it. The classic example is the little recessed area around a fuel filler cap that channels any spilled fuel out through a drain hole.
Context Anchor
Seen during aircraft maintenance, preflight inspection, fueling, and discussions of fuel tank filler areas or drainage paths.
Derivation
The word comes from a much older shipbuilding term for a drain hole cut in a ship's deck or side to let water run off. Aircraft borrowed both the word and the idea — a small opening whose only job is to let unwanted liquid escape.
Why Pilots Care
Prevents water buildup that can lead to corrosion, added weight, or icing problems affecting flight safety and airframe longevity.
Intuition Check
Do not think of a scupper as a cap or cover. It is a drain path that lets liquid leave an area.
Example Sentence 1
After topping off the tanks, the technician wiped the filler area and confirmed the scupper drain was clear so any future spill would run overboard.
Example Sentence 2
The maintenance technician flushed the fuselage scupper to clear trapped moisture after heavy rain.