On the ground, when are all the DC buses energized?

On the ground, when are all the DC buses energized?

• A. At least three generators are on, the GPU is on and connected, or at least one generator is on and the SHED BUSES Selector Knob is set to OVRD
• B. Only when the APU is running
• C. When the backup battery is charging
• D. When Battery 1 is connected

Answer: (A)

On the ground, all DC buses come up when there’s enough power available and the shedding logic allows energizing every bus. If at least three generators are online, there’s sufficient total power to feed every DC bus, so they all energize. If a Ground Power Unit is connected and providing power, that external source can supply the entire DC bus system, bringing all buses online. If only one generator is online, the SHED BUSES selector can be set to OVERRIDE to force all DC buses to energize, bypassing the normal shedding. Others conditions like only the APU running or the backup battery charging don’t guarantee all DC buses are energized because the power sources or shedding limits may not support full bus energization in those cases.

On the ground, all DC buses come up when there’s enough power available and the shedding logic allows energizing every bus. If at least three generators are online, there’s sufficient total power to feed every DC bus, so they all energize. If a Ground Power Unit is connected and providing power, that external source can supply the entire DC bus system, bringing all buses online. If only one generator is online, the SHED BUSES selector can be set to OVERRIDE to force all DC buses to energize, bypassing the normal shedding. Others conditions like only the APU running or the backup battery charging don’t guarantee all DC buses are energized because the power sources or shedding limits may not support full bus energization in those cases.