Definition
The preflight act of draining a small sample of fuel from each fuel tank and fuel system drain point into a clear container, then visually checking the sample for water, sediment, or the wrong grade of fuel before flight.
Plain English
Pulling a small amount of fuel out of the lowest part of each tank and the fuel lines to check that it is clean, free of water, and the correct fuel.
Context Anchor
You encounter sumping during the preflight inspection, usually when checking each fuel tank drain and fuel system drain before engine start.
Derivation
From 'sump,' a low point or pit where liquid collects. In aviation, the sump is the lowest point of a fuel tank where water and sediment naturally settle, so 'sumping' literally means drawing fuel from that low point to inspect it.
Why Pilots Care
Confirms fuel is free of water and debris that could cause engine failure.
Analogy
It is like checking the bottom of a glass for sand or water before drinking from it. The bottom is where unwanted material is most likely to settle.
Intuition Check
Sumping does not mean pumping fuel into the airplane. It means draining a small sample out of the lowest part of the fuel system to inspect it.
Example Sentence 1
After parking outside overnight in the rain, the pilot was careful to spend extra time sumping each tank before the morning flight.
Example Sentence 2
After refueling, the student performed sumping on all four drains to verify the new fuel was clean.