If a generator fails in flight, what should happen to maintain AC power?

• A. The affected generator automatically reconnects to DC bus
• B. The airplane automatically uses battery power only
• C. The APU starts to supply power to AC buses
• D. Auto Xfer relays should close to allow the remaining generator to power both AC systems

Answer: (D)

When a generator fails in flight, the aircraft’s electrical system is designed to keep AC power by reconfiguring how power is distributed. The remaining generator must be able to supply both AC buses, so the automatic transfer relays close to connect that single generator to both buses. This creates a shared power path that maintains AC power for the system loads rather than leaving power on a single bus or relying solely on the battery. In practice, the auto transfer relays doing this ensures the remaining generator can carry the load and keep essential systems powered without waiting for the APU or depleting the batteries.