Which power sources supply the DC Emergency Bus?

• A. APU Direct Battery Bus and DC Battery Bus
• B. DC Essential Bus
• C. Main Battery Bus
• D. APU Fire Extinguisher

Answer: (A)

The DC Emergency Bus is designed to stay powered during electrical failures by having two independent feeds. It can be energized from the APU Direct Battery Bus, which draws from the APU’s battery, and from the DC Battery Bus, which is tied to the aircraft’s main batteries. This setup provides redundancy: if one source isn’t available, the other can still keep the DC Emergency Bus energized so essential systems remain operating. The DC Essential Bus, main Battery Bus, and other items have their own roles and aren’t the sources that feed the DC Emergency Bus in this configuration. An APU Fire Extinguisher, of course, provides a fire-suppression capability, not electrical power.