Which of the following statements about the FADEC power supply is true?

• A. The FADEC can be powered by the engine-driven alternator when N2 exceeds 50%
• B. The FADEC is always powered by the battery
• C. The FADEC is powered only during takeoff
• D. The FADEC is never powered from the alternator

Answer: (A)

FADEC power is drawn from more than one source, with the engine-driven alternator serving as the normal power source once the engine is turning fast enough. When N2 climbs past about 50%, the alternator begins generating power and can take over supplying the FADEC. This keeps the battery from being drained during steady operation and provides a stable power source tied to the engine's speed. The battery acts as a backup during start or if the alternator isn’t available.

So the statement is true because it describes the typical transfer of FADEC power to the engine-driven alternator once the engine reaches sufficient speed. The other options aren’t correct because FADEC is not limited to battery power only, it isn’t powered only during takeoff, and it is indeed designed to be powered from the alternator when available.