What are the FADECs powered by?

• A. The DC electric system below 60% N2 and a dedicated FADEC PMA above 60% N2
• B. The AC electrical system only
• C. The DC electric system below 50% N2 and a dedicated FADEC PMA alternator above 60% N2
• D. The DC electric system below 50% N2 and by a dedicated FADEC PMA alternator above 50% N2

Answer: (A)

FADEC power is arranged to stay reliable through all phases of engine operation. In normal low to mid spool speeds, the FADEC draws from the aircraft’s DC electrical system. Once the engine crosses a defined threshold (60% N2), a dedicated FADEC PMA takes over to supply power directly, driven by the engine, providing a stable and independent power source for the FADEC. This setup protects FADEC operation from faults or transient conditions in the main DC bus during high-speed or high-demand operation. The AC system isn’t used to power FADEC in this arrangement, and the 60% N2 breakpoint for switching to the dedicated PMA reflects the intended balance between normal bus usage and redundant, engine-driven power.