FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationHard
A pilot reports that during a rapid power reduction from cruise to idle, the turbine engine experiences a momentary flameout. The mechanic suspects an issue with the fuel control unit. Which component within the FCU is most likely responsible for preventing this condition?
- AThe primary metering valve.
- BThe power lever angle sensor.
- CThe acceleration limiting section.
- DThe deceleration limiting section.
Show answer & explanationAnswer & explanation
Correct answer: D. The deceleration limiting section.
The deceleration limiting section of a turbine engine's fuel control unit is specifically designed to prevent flameout during rapid power reductions by ensuring that the fuel flow does not decrease too quickly, which could starve the engine of fuel and extinguish the flame.
Why the other options are wrong
- A. The primary metering valve controls the main fuel flow, but its regulation during rapid deceleration is governed by other FCU sections.
- B. The power lever angle sensor provides input to the FCU about the desired power setting, but it doesn't directly prevent flameout during deceleration; the FCU's internal logic does that.
- C. The acceleration limiting section prevents compressor stall and turbine overtemperature during rapid power increases, not flameout during power reductions.
Turbine FCU Deceleration Limiting
The deceleration limiting section of a turbine engine's Fuel Control Unit (FCU) prevents flameout during rapid power reductions by controlling the rate at which fuel flow is decreased.
- Ensures adequate fuel for combustion stability during decreasing RPM.
- Prevents an overly lean mixture that could extinguish the flame.
- Works in conjunction with other FCU sections to maintain engine control.
Memory trick: FCU: Fuel Control Unit, Finds Critical Ups and Downs