FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationHard
A turbine engine is experiencing intermittent compressor stalls, particularly during rapid throttle movements. A mechanic suspects an issue with the fuel control unit. Which aspect of the fuel control unit's operation is most critical in preventing compressor stalls?
- APreventing over-fueling during engine acceleration.
- BEnsuring proper fuel-oil heat exchange for viscosity control.
- CProviding accurate fuel flow measurement for the cockpit gauges.
- DMaintaining a constant fuel pressure to the nozzles.
Show answer & explanationAnswer & explanation
Correct answer: A. Preventing over-fueling during engine acceleration.
Compressor stalls in a turbine engine are often caused by an excessively rich mixture during rapid acceleration, leading to combustion instability and airflow disruption. The fuel control unit's acceleration limiting function is critical in preventing over-fueling (too much fuel for the current airflow) during these transients, thereby preventing stalls.
Why the other options are wrong
- B. Fuel-oil heat exchange is for fuel heating and oil cooling, not directly related to preventing compressor stalls.
- C. Accurate fuel flow measurement is for pilot information, not a direct control function for stall prevention.
- D. While important, constant fuel pressure alone doesn't directly prevent stalls caused by transient over-fueling.
Turbine FCU Acceleration Schedule
A function within the turbine engine fuel control unit that limits fuel flow during rapid throttle movements to prevent compressor stalls and turbine over-temperature.
- Prevents over-fueling, which causes stalls.
- Balances fuel flow with available airflow.
- Ensures smooth, controlled engine acceleration.
Memory trick: FCU's a 'throttle cop', stops over-fueling to keep air flowing fine.