Definition
Microscopic living organisms — primarily bacteria and fungi — that can grow inside aircraft fuel tanks where water has collected, feeding on the fuel and producing sludge that can clog filters, corrode tank structure, and disrupt fuel flow.
Plain English
Tiny living things, too small to see, that grow in the water that settles at the bottom of fuel tanks. They eat the fuel and leave behind a slime that can block filters and eat away at the metal.
Context Anchor
Seen in aircraft maintenance, fuel contamination, fuel storage, and fuel system inspection discussions.
Derivation
From the Greek 'mikros' (small) and 'bios' (life) — literally 'small life.' The term reminds the pilot that this is a biological problem, not a chemical or mechanical one, and that it requires biological control measures (biocides) rather than just filtration.
Why Pilots Care
Unchecked growth can clog filters, corrode tank surfaces, and lead to fuel flow interruptions or engine failure.
Intuition Check
Microbes are not just “germs that make people sick.” In aviation, the concern is that tiny living organisms can grow in wet fuel or fluid areas and cause contamination or damage.
Example Sentence 1
After the aircraft sat outside through a wet season, the mechanic found microbes growing at the fuel-water interface in the wing tanks.
Example Sentence 2
Adding a fuel biocide prevents microbes from forming slime that blocks the lines.