FAA Aviation Mechanic Airframe (AMA)Fuel, Cabin and Ice Control SystemsEasy
A technician is troubleshooting a turbine engine fuel system on an aircraft that experiences fuel filter icing during high-altitude cruise in cold weather, even though the fuel meets FSII specifications. Which additional component is installed in the fuel supply line to prevent ice crystal buildup by transferring heat from engine oil to the fuel?
- AFuel selector valve
- BGascolator
- CFuel heater (fuel/oil heat exchanger)
- DFuel boost pump
Show answer & explanationAnswer & explanation
Correct answer: C. Fuel heater (fuel/oil heat exchanger)
A fuel heater is a heat exchanger that uses hot engine oil (or bleed air) to warm the fuel before it reaches the filter, melting any ice crystals that may have formed from dissolved water. FSII lowers the freezing point of water in fuel but does not add heat, so a separate heater is still used on many turbine installations.
Why the other options are wrong
- A. A selector valve routes fuel flow and has no heating function.
- B. A gascolator is a sediment/water trap, not a heat exchanger.
- D. A boost pump moves fuel but provides no heating.
Fuel Heater
A heat exchanger in the turbine engine fuel system that warms fuel using hot engine oil (or bleed air) to prevent ice crystal accumulation on fuel filters.
- Uses hot oil or bleed air as the heat source
- Prevents fuel filter icing at altitude
- Works alongside, not instead of, FSII additive
Memory trick: 'Heater Hugs the Filter to keep it warm.'