Which statement is true about FADEC power?

Which statement is true about FADEC power?

• A. Below 50% N2, FADEC is powered by the Main Battery Direct Bus
• B. Above 50% N2, FADEC is powered by the APU Battery Direct Bus
• C. Above 50% N2, FADEC is powered by the FADEC Alternator
• D. FADEC is powered by the DC Emergency Bus at all times

Answer: (C)

The idea being tested is how FADEC gets its electrical power and how that source switches as the engine starts and runs. When the engine reaches about half its speed (N2 above 50%), the FADEC is powered by the engine’s own FADEC Alternator. This engine-driven source provides a solid, regulated 28V DC supply directly from the engine, which is important for reliable engine control as power comes up and during operation. Before the engine is turning enough to generate power, FADEC needs power from another source, typically the Main Battery Direct Bus, to enable starting and to supply essential FADEC functions. The DC Emergency Bus is reserved for critical systems in a fault condition and isn’t the normal FADEC power source, and the APU Battery Direct Bus would only come into play if the APU is supplying power rather than the engine. So, the statement is true because, once N2 is above 50%, the FADEC draws power from the FADEC Alternator—the engine’s own generator—rather than relying on other sources.

The idea being tested is how FADEC gets its electrical power and how that source switches as the engine starts and runs. When the engine reaches about half its speed (N2 above 50%), the FADEC is powered by the engine’s own FADEC Alternator. This engine-driven source provides a solid, regulated 28V DC supply directly from the engine, which is important for reliable engine control as power comes up and during operation.

Before the engine is turning enough to generate power, FADEC needs power from another source, typically the Main Battery Direct Bus, to enable starting and to supply essential FADEC functions. The DC Emergency Bus is reserved for critical systems in a fault condition and isn’t the normal FADEC power source, and the APU Battery Direct Bus would only come into play if the APU is supplying power rather than the engine.

So, the statement is true because, once N2 is above 50%, the FADEC draws power from the FADEC Alternator—the engine’s own generator—rather than relying on other sources.