FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationMedium
A fuel supplier adds ethylene glycol monomethyl ether (EGME) to aviation turbine fuel before delivery. What is the purpose of this additive?
- ATo increase the fuel's octane rating for better detonation resistance
- BTo reduce the fuel's tendency to vaporize at high altitude
- CTo lubricate fuel pump components and reduce wear
- DTo prevent the formation of ice crystals from dissolved water in the fuel system
Show answer & explanationAnswer & explanation
Correct answer: D. To prevent the formation of ice crystals from dissolved water in the fuel system
EGME (also known as Prist or FSII) is a fuel system icing inhibitor. It prevents dissolved water in turbine fuel from freezing into ice crystals that could clog fuel filters at low temperatures encountered at altitude.
Why the other options are wrong
- A. Octane rating applies to gasoline, not turbine fuel, which uses a different combustion process.
- B. Vapor lock reduction is addressed by fuel volatility control, not FSII additives.
- C. Lubricity additives are a separate additive type used to protect fuel pump components.
Fuel System Icing Inhibitor (FSII)
An additive (EGME, trade name Prist) added to turbine fuel to prevent ice crystal formation from entrained water at low temperatures.
- Prevents water from freezing and clogging fuel filters
- Common in turbine fuel operations, especially at altitude
- Also has some biocidal properties against microbial growth
Memory trick: FSII freezes out the freeze (prevents ice)