Definition
The presence of solid particles such as dust, dirt, rust, or debris suspended in or settled within an aircraft's fuel supply. Sediment can accumulate in fuel tanks, lines, filters, or sumps, and may restrict fuel flow or cause engine roughness or stoppage if it reaches the engine.
Plain English
Tiny bits of solid material — like dirt, rust flakes, or grit — that have ended up in the fuel. Even small amounts can clog fuel system parts and starve the engine.
Context Anchor
A pilot most often checks for sediment contamination during the preflight inspection by draining a fuel sample into a clear container and looking for particles or debris.
Derivation
Sediment' comes from the Latin sedimentum, meaning 'a settling' — material that sinks and settles at the bottom. In a fuel tank, solid particles heavier than fuel settle to the lowest point, which is exactly where the sump drain is located so the pilot can check for them.
Why Pilots Care
Can clog fuel filters, strainers, and lines, restricting fuel flow and causing engine stoppage.
Analogy
Like finding sand settled at the bottom of a bottle of old gasoline left sitting.
Grounding Statement
If a clear fuel sample shows grit, flakes, or particles at the bottom, the fuel is not clean enough to ignore.
Intuition Check
Do not assume sediment contamination means only a large amount of dirt. Even small particles can matter in an aircraft fuel or oil system.
Example Sentence 1
During preflight, she drained fuel from each sump and checked the sample for water and sediment contamination before flying.
Example Sentence 2
After the airplane had sat unused for weeks, the mechanic checked all sumps for sediment contamination before the next flight.