Definition
A living organism too small to be seen with the naked eye, such as bacteria, fungi, mold, or yeast. In aviation maintenance, micro-organisms of concern are those that grow at the fuel-water interface inside fuel tanks, where they form sludge and slime that can clog fuel filters, corrode tank structure, and contaminate fuel.
Plain English
Tiny living things — like bacteria and mold — that are too small to see without a microscope. In aircraft, they grow inside fuel tanks where water collects, creating slime that damages the tank and blocks fuel flow.
Context Anchor
Seen in aircraft fuel system maintenance, fuel contamination checks, and discussions of corrosion or biological growth in tanks.
Derivation
From the Greek 'mikros' meaning small, and 'organismos' meaning a living thing. Together it simply means 'a tiny living thing' — which is exactly what it refers to in fuel tanks.
Why Pilots Care
Unchecked growth can clog filters and contribute to engine malfunctions.
Grounding Statement
If water sits in a fuel tank, tiny living things can grow at the water-fuel boundary and leave behind slime or corrosive material.
Intuition Check
Do not think of micro-organisms only as “germs” that affect people. In this aviation context, the concern is tiny living growth that can contaminate fuel or damage aircraft systems.
Example Sentence 1
During the fuel tank inspection, the technician found micro-organism growth at the bottom of the tank where water had collected.
Example Sentence 2
Regular treatment prevents micro-organisms from forming sludge that blocks fuel lines.