Definition
A low point built into a fuel tank where water and sediment collect by gravity, and which is fitted with a drain valve so the contaminants can be removed during preflight or maintenance.
Plain English
The lowest spot in a fuel tank where water and dirt settle so they can be drained out before flight.
Context Anchor
Seen during preflight fuel sampling, fuel tank inspection, and maintenance discussions about fuel drains.
Derivation
From the Middle English 'sompe' meaning a marsh or low pit. The idea carried into engineering: a sump is the low point where unwanted liquid or debris collects so it can be removed.
Why Pilots Care
Undrained water in the sump can reach the engine and cause power loss or failure.
Analogy
Like the U-shaped trap under a kitchen sink that catches debris before it goes down the drain.
Intuition Check
A sump is not the whole fuel tank and it is not a fuel pump. In this context, it is the low collecting point in the tank where water and dirt settle.
Example Sentence 1
During preflight, the pilot drained a small sample from each fuel tank sump and checked it for water and sediment.
Example Sentence 2
During the preflight inspection, sediment was found in the left wing sump and removed.