While in flight, which electrical buses are powered with only one generator online?

While in flight, which electrical buses are powered with only one generator online?

• A. ESSENTIAL only
• B. MAIN only
• C. ESSENTIAL and MAIN
• D. AUX and MAIN

Answer: (C)

With one generator online, power is routed to the essential and main buses. This keeps the critical flight instruments and primary avionics energized while the auxiliary bus—which serves nonessential cabin and comfort circuits—remains unpowered until a second generator or external power is available. In practice, the bus-tie arrangement and priority load distribution ensure the essential and main systems stay powered first, which is why the correct choice is that both the essential and main buses are energized with a single generator online.

With one generator online, power is routed to the essential and main buses. This keeps the critical flight instruments and primary avionics energized while the auxiliary bus—which serves nonessential cabin and comfort circuits—remains unpowered until a second generator or external power is available. In practice, the bus-tie arrangement and priority load distribution ensure the essential and main systems stay powered first, which is why the correct choice is that both the essential and main buses are energized with a single generator online.