Which statement describes the power source for FADEC when engine N2 is above 10%?

Which statement describes the power source for FADEC when engine N2 is above 10%?

• A. It is powered by the external power supply
• B. It is powered by the aircraft's main electrical bus
• C. It is powered by a magnetic alternator
• D. It is powered by the hydraulic generator

Answer: (C)

The line of reasoning here centers on how FADEC stays powered once the engine starts turning. When N2 reaches about 10%, the engine-driven magnetic alternator (an on-engine generator connected to the accessory gearbox) takes over as the power source for the FADEC. This provides a stable, engine-synchronous supply (typical 28 V DC) directly to the FADEC without relying on the aircraft’s main electrical bus. This arrangement keeps FADEC powered during start and low-speed conditions, even if the external power or main bus isn’t yet fully available. External power is used only when connected from outside, and a hydraulic generator isn’t used to power FADEC in normal operation. So, the engine-mounted magnetic alternator is the appropriate source once N2 is above 10%.

The line of reasoning here centers on how FADEC stays powered once the engine starts turning. When N2 reaches about 10%, the engine-driven magnetic alternator (an on-engine generator connected to the accessory gearbox) takes over as the power source for the FADEC. This provides a stable, engine-synchronous supply (typical 28 V DC) directly to the FADEC without relying on the aircraft’s main electrical bus. This arrangement keeps FADEC powered during start and low-speed conditions, even if the external power or main bus isn’t yet fully available. External power is used only when connected from outside, and a hydraulic generator isn’t used to power FADEC in normal operation. So, the engine-mounted magnetic alternator is the appropriate source once N2 is above 10%.