In the context of APU operation, which component monitors load and regulates fuel to prevent exceeding safe limits?

• A. The bleed air valve.
• B. The exhaust temperature gauge.
• C. The engine fuel pump.
• D. The FADEC.

Answer: (D)

The thing being tested is automatic fuel control to keep the APU within safe limits. The FADEC is the device that continuously watches how hard the engine is working (the load) and what the engine parts are doing, using sensors for speeds, temperatures, and fuel flow. Based on that information, it commands the right amount of fuel to meet the requested power while staying under maximums. If putting more fuel would push parameters like turbine temperature or RPM past safe values, the FADEC trims back fuel to prevent damage. It can also take protective actions if a limit is approached or exceeded.

Bleed air valves regulate compressed air, not fuel. An exhaust temperature gauge shows the temperature but does not control fuel itself. The engine fuel pump supplies fuel, but it does not autonomously regulate fuel to stay within limits—the FADEC does that.