FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesMedium
A technician inspects a turbine engine fuel system component that uses hot engine oil or compressor bleed air to raise the temperature of the fuel before it reaches the fuel control unit and filters. What is the primary purpose of this fuel heater?
- ATo preheat fuel so igniter plugs fire more reliably during engine start
- BTo prevent ice crystals, formed from dissolved water in the fuel, from clogging fuel filters
- CTo increase fuel volatility, improving combustion efficiency at high altitude
- DTo reduce fuel viscosity so the boost pump can operate at reduced RPM
Show answer & explanationAnswer & explanation
Correct answer: B. To prevent ice crystals, formed from dissolved water in the fuel, from clogging fuel filters
Jet fuel contains dissolved and entrained water that can form ice crystals at the low temperatures encountered at altitude. A fuel heater, typically an oil-to-fuel heat exchanger, warms the fuel to prevent ice from accumulating on and clogging fuel filters, which could restrict fuel flow to the engine.
Why the other options are wrong
- A. Igniter plug operation is unrelated to fuel temperature.
- C. Fuel heaters address ice prevention, not combustion volatility.
- D. Fuel heaters are not primarily for reducing pump load; icing prevention is the main function.
Turbine Fuel Heater
A heat exchanger (fuel-oil or bleed air) that warms turbine engine fuel to prevent ice crystal formation from clogging fuel filters at low temperatures.
- Also serves as an oil cooler by transferring heat from oil to fuel
- Prevents fuel filter icing at high altitude/low temperature
- Often has a bypass valve if the filter becomes blocked
Memory trick: Fuel heater = a tiny sunbath that melts ice before it clogs the filter