A separate power module provides 24 VDC as emergency power for the emergency lighting system and the _________.

• A. Standby horizon
• B. Primary bus
• C. Avionics bay
• D. Fuel pump

Answer: (B)

In aviation electrical systems, emergency power is used to keep critical functions alive when normal power is lost. The emergency lighting must work to illuminate exits and paths to safety, so it relies on this dedicated 24 VDC emergency source. The same emergency source also feeds the primary bus, which is the main distribution path for essential electrical loads. Keeping the primary bus energized ensures that flight-critical systems and instruments remain powered during an electrical failure. The other options aren’t the standard loads tied to the emergency power module: a standby horizon typically has its own backup power, avionics bays aren’t a single emergency-linked load, and the fuel pump is not a primary emergency electrical load.