Definition
A group of simple living organisms — including molds, mildews, and yeasts — that grow in damp, dark conditions and feed on organic material. In aircraft, fungi can colonize fuel tanks (especially in jet fuel where water has settled), and can also grow on seals, wiring insulation, and inside hidden structural cavities, producing acidic byproducts that contribute to corrosion and contamination.
Plain English
A type of living growth, similar to mold, that can take hold inside an aircraft where moisture is trapped — particularly in fuel tanks. As it grows, it produces waste that eats away at metal and clogs filters and fuel lines.
Context Anchor
Seen in aircraft cleaning, inspection, storage, fabric covering, cabin interior, and corrosion-control discussions.
Derivation
From the Latin fungus, meaning 'mushroom' or 'spongy growth.' The word has carried the same general meaning since Roman times — any soft, spreading growth that thrives in moist conditions — which is exactly what forms inside a wet fuel tank.
Why Pilots Care
Unchecked fungus growth can restrict fuel flow, damage components, and lead to engine power loss or failure.
Intuition Check
Do not think of fungus only as a mushroom. In aircraft maintenance, fungus usually means mold or mildew-type growth on or in materials, often caused by damp conditions.
Example Sentence 1
During the inspection, the technician found fungus growth at the bottom of the fuel tank where water had collected over time.
Example Sentence 2
Adding the approved biocide to the fuel prevents fungus from forming in the aircraft system.