Which power sources supply hydraulic pump 3B?

• A. AC Bus 1 or the ADG Bus
• B. DC Bus 1
• C. Essential Bus
• D. Battery Bus

Answer: (A)

Hydraulic pump 3B is driven by an AC electric motor, so it needs an AC power source. Under normal conditions it draws power from AC Bus 1. If AC power is lost, the aircraft can bring in the Air Driven Generator, which powers the ADG bus and allows that same pump to keep running. DC sources, the Essential Bus, or the Battery Bus don’t provide the required AC supply for this motor-driven pump, so they aren’t used to power 3B. This arrangement ensures hydraulic capability remains available even when normal generators aren’t operating.