When does the FADEC system receive power from the engine-driven accessory-mounted alternator?

When does the FADEC system receive power from the engine-driven accessory-mounted alternator?

• A. N2 >50%
• B. N2 <50%
• C. On startup only
• D. When engine is off

Answer: (A)

The FADEC draws power from the engine-driven accessory-mounted alternator only after the engine is turning fast enough to generate usable electrical power. Specifically, once N2 exceeds about 50%, the alternator can produce the required voltage and current to run the FADEC. Before that point (startup or at very low RPM) the alternator output is insufficient, so FADEC relies on other power sources (like the battery or ground power). This threshold ensures a stable power supply for FADEC operation while protecting the electrical system during startup.

The FADEC draws power from the engine-driven accessory-mounted alternator only after the engine is turning fast enough to generate usable electrical power. Specifically, once N2 exceeds about 50%, the alternator can produce the required voltage and current to run the FADEC. Before that point (startup or at very low RPM) the alternator output is insufficient, so FADEC relies on other power sources (like the battery or ground power). This threshold ensures a stable power supply for FADEC operation while protecting the electrical system during startup.