Definition
Solid material that has settled out of a liquid and collected at the bottom of a container, tank, or sump. In aircraft systems, sediment typically refers to dirt, rust, water, or other contaminants that separate from fuel or oil and accumulate at low points where they can be drained off.
Plain English
The bits of dirt, water, or grit that sink to the bottom of a tank or container after sitting still.
Context Anchor
Pilots most often encounter sediment during preflight fuel sampling, when checking drained fuel for particles or contamination before flight.
Derivation
From the Latin sedimentum, meaning 'a settling,' from sedere, 'to sit.' The word literally describes material that has 'sat down' to the bottom — which is exactly what pilots are checking for when they sump a fuel tank.
Why Pilots Care
Sediment can clog fuel filters, lines, and injectors, leading to engine power loss or failure.
Intuition Check
Sediment is not harmless just because it is sitting at the bottom. In an aircraft system, it can be stirred up, block flow, or point to a bigger contamination problem.
Example Sentence 1
During preflight, the pilot drained a small sample from each fuel sump to check for water or sediment.
Example Sentence 2
Sediment in the carburetor bowl showed that the fuel tank had been contaminated.