Which electrical buses are shed when the APU is the sole power source in flight?

Which electrical buses are shed when the APU is the sole power source in flight?

• A. Essential bus only
• B. All galley and main buses
• C. Avionics bus only
• D. Battery and essential bus

Answer: (B)

When the APU is the only power source, the electrical system prioritizes essential needs and trims away nonessential loads to stay within the APU’s capacity. The galley and main buses feed nonessential equipment and general distribution across the aircraft, so disconnecting them reduces the overall electrical load without compromising critical systems. Thus, the buses that are shed are the galley and main buses. The essential and avionics buses (often supported by the battery for standby power if needed) stay powered to maintain flight safety and critical operations. Other options would either keep noncritical loads active or remove more power than necessary, risking essential systems.

When the APU is the only power source, the electrical system prioritizes essential needs and trims away nonessential loads to stay within the APU’s capacity. The galley and main buses feed nonessential equipment and general distribution across the aircraft, so disconnecting them reduces the overall electrical load without compromising critical systems.

Thus, the buses that are shed are the galley and main buses. The essential and avionics buses (often supported by the battery for standby power if needed) stay powered to maintain flight safety and critical operations. Other options would either keep noncritical loads active or remove more power than necessary, risking essential systems.