FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsEasy
A mechanic is servicing a turbine-powered aircraft with fuel containing fuel system icing inhibitor (FSII). What hazard does FSII primarily protect against?
- ABacterial growth in the fuel tank
- BStatic electricity buildup during refueling
- CCorrosion of aluminum fuel tank walls
- DFormation of ice crystals from dissolved water that could clog fuel filters
Show answer & explanationAnswer & explanation
Correct answer: D. Formation of ice crystals from dissolved water that could clog fuel filters
FSII lowers the freezing point of water suspended in turbine fuel, preventing ice crystals from forming and clogging fuel filters and lines at altitude.
Why the other options are wrong
- A. While FSII has some biocidal effect, its primary purpose is ice prevention.
- B. Static electricity is controlled by bonding and grounding, not FSII.
- C. FSII is not primarily a corrosion inhibitor, though some formulations have secondary benefits.
FSII (Fuel System Icing Inhibitor)
An additive blended into turbine fuel that depresses the freezing point of entrained water to prevent ice formation in the fuel system.
- Common additive: Prist
- Prevents ice crystal blockage of filters/lines
- Has secondary mild anti-microbial effect
Memory trick: FSII keeps water from freezing solid in the fuel.