What emergency light activates if only AC BUS 1 fails?

When AC BUS 1 fails, the overhead emergency lights are designed to activate as part of the aircraft's emergency system. This configuration ensures that critical lighting remains available in the cabin, allowing both crew and passengers to navigate safely during an emergency situation.

The overhead emergency lights are specifically arranged to provide illumination in areas that may otherwise become dark due to a loss of power on the primary electrical bus. Their activation under this condition helps maintain safety and visibility for evacuation or other necessary actions.

In contrast, while aisle escape lights, exterior lights, and cabin emergency lights also play crucial roles in emergency scenarios, their operation may not be linked directly to the failure of AC BUS 1. Aisle escape lights typically operate on a different power system to ensure they are functional during emergencies, and cabin emergency lights may rely on other bus arrangements or backup battery systems.