What does the term 'main bus' refer to?

• A. The primary DC bus that distributes power from the main generator/alternator to most nonessential and essential circuits
• B. A separate bus for engine instruments only
• C. The bus that carries power from the battery only
• D. The backup power distribution network

Answer: (A)

The main bus is the primary DC power distribution path fed by the main generator or alternator, and it supplies power to the majority of the aircraft’s circuits under normal operation. It acts as the central hub for distributing electrical power to various loads, including many essential and nonessential systems. In normal conditions, the main generator keeps the main bus energized so most loads can operate through it. Other buses exist for specific purposes: a separate bus for engine instruments would be a specialized engine-instrument or avionics-related bus, the battery-only path describes the battery bus, and the backup power distribution network handles emergency or standby power. So the main bus is the main distribution path from the generator to most of the aircraft’s circuits.