What is a 'nonessential bus' used for?

• A. To power cabin lighting and entertainment, which can be shed when power is limited
• B. To power essential flight controls
• C. To power aircraft navigation sensors
• D. To regulate engine starting

Answer: (A)

A nonessential bus is a power distribution path for systems that aren’t required for safe flight. It powers cabin lighting and passenger amenities that can be shed when power is limited. In normal operation, all of these loads are supported, but if generation is limited or a fault occurs, nonessential loads can be disconnected to preserve power for essential systems. That’s why this bus is used for cabin lights and entertainment, rather than for essential flight controls, navigation sensors, or engine starting, which stay on power paths that must be kept energized.