Definition
A fuel system icing inhibitor additive blended into aviation turbine fuel (jet fuel) to prevent water dissolved or suspended in the fuel from freezing into ice crystals at the low temperatures encountered at altitude. EGME bonds with water in the fuel and lowers its freezing point, keeping fuel filters and lines from becoming blocked by ice. It is added in small, regulated concentrations (typically around 0.10–0.15% by volume) and must be mixed in at the correct ratio during refueling.
Plain English
A chemical added to jet fuel in tiny amounts to stop water in the fuel from turning into ice when the airplane is high up where it's very cold. Without it, ice crystals could clog fuel filters and starve the engine.
Context Anchor
Seen in fuel-system and cold-weather operations discussions, especially when the handbook explains fuel contamination, water in fuel, and fuel-system icing.
Derivation
The chemical name describes its molecular structure: 'ethylene glycol' is the base alcohol (the same family as automotive antifreeze), and 'monomethyl ether' indicates one methyl group attached as an ether. The 'monomethyl' part — sometimes misspelled 'mononethyl' — distinguishes it from related compounds with different chemical groups attached. Knowing the antifreeze connection helps: it's literally an antifreeze for the water that ends up dissolved in fuel.
Why Pilots Care
Fuel system ice can interrupt fuel flow and cause engine power loss or failure.
Grounding Statement
In cold conditions, EGME helps keep small amounts of water in the fuel from turning into ice where fuel needs to keep flowing.
Intuition Check
Do not read EGME as a general de-icer for the whole airplane. In this context, it is a fuel additive used for water-related icing inside the fuel system.
Example Sentence 1
Before the cross-country flight, the line crew added EGME to the fuel at the correct ratio to prevent fuel system icing at altitude.
Example Sentence 2
The pilot verified that the fuel met specifications including EGME before departing into known icing conditions.