How does the power distribution system protect critical systems if a generator fails?

• A. It isolates nonessential loads to preserve stability
• B. Essential bus and standby power sources keep critical equipment running
• C. The system automatically disconnects all circuits
• D. It uses only the main battery to supply critical loads

Answer: (B)

When a generator fails, the system is designed to keep the most critical equipment powered by routing energy through the essential electrical pathways and using standby sources as needed. The essential bus is the power path that feeds critical systems such as flight controls, avionics, navigation, and safety-related equipment. If a primary generator drops offline, the remaining power sources (other generators or the APU) continue energizing this essential bus, and nonessential loads can be shed to reduce demand so voltage and frequency stay stable for those critical systems. If the remaining sources can’t meet even that reduced load, standby power sources—such as a standby generator, a battery, or a ram air turbine—step in to keep the essential bus powered, ensuring critical equipment keeps running until normal power is restored or the aircraft can safely land.