Which of the following statements is accurate about the DC Emergency Bus power configuration?

• A. APU Direct Battery Bus and DC Battery Bus provide the power
• B. DC Essential Bus powers DC Emergency Bus
• C. Main Battery Bus powers DC Emergency Bus
• D. APU Fire Extinguisher powers DC Emergency Bus

Answer: (A)

The DC Emergency Bus is designed to stay powered in an electrical emergency, so it receives power from sources that remain available when the normal systems fail. In this configuration, two independent sources feed the DC Emergency Bus: the APU Direct Battery Bus and the DC Battery Bus. This dual-source setup provides redundancy—if one source drops out, the other can keep essential electrical loads alive, such as critical flight instruments and controls. The DC Essential Bus is not used to power the DC Emergency Bus in this arrangement, and the Main Battery Bus is not the source for the emergency bus. An APU Fire Extinguisher is not a power source, so it cannot feed the DC Emergency Bus.