When N2 is above 50%, the FADEC is powered by which source?

When N2 is above 50%, the FADEC is powered by which source?

• A. FADEC Alternator
• B. AC Essential Bus
• C. DC Emergency Bus
• D. APU Battery Direct Bus

Answer: (A)

During engine start and spool-up, the FADEC is powered by the engine-driven FADEC alternator. This dedicated alternator, mounted on the engine accessory gear train, comes online when N2 passes about 50% and provides stable DC power to the FADEC, allowing it to control ignition, fuel flow, and other engine parameters as the engine climbs through start. Other power sources listed exist for different situations, but they aren’t the normal FADEC source during high N2: the AC Essential Bus is an AC power path for various systems, the DC Emergency Bus is a backup for loss of normal power, and the APU Battery Direct Bus powers FADEC only when the APU is providing electrical power.

During engine start and spool-up, the FADEC is powered by the engine-driven FADEC alternator. This dedicated alternator, mounted on the engine accessory gear train, comes online when N2 passes about 50% and provides stable DC power to the FADEC, allowing it to control ignition, fuel flow, and other engine parameters as the engine climbs through start. Other power sources listed exist for different situations, but they aren’t the normal FADEC source during high N2: the AC Essential Bus is an AC power path for various systems, the DC Emergency Bus is a backup for loss of normal power, and the APU Battery Direct Bus powers FADEC only when the APU is providing electrical power.