Which statement best describes the role of the essential AC bus?

Which statement best describes the role of the essential AC bus?

• A. To power critical avionics and flight instruments and remain energized during certain faults.
• B. To power main cabin lighting.
• C. To supply hydraulic pumps.
• D. To power the standby instruments only.

Answer: (A)

The essential AC bus is dedicated to keeping the most critical flight equipment powered and available even when electrical faults occur. It is sized and isolated so that, if other parts of the electrical system fade or fail, the crew still has power for the essential avionics and flight instruments that provide attitude, guidance, and critical information needed to fly safely. That’s why this bus is described as powering critical avionics and flight instruments and remaining energized during certain faults. Main cabin lighting and other nonessential systems are not the focus of this bus, and hydraulic pumps are not served by this essential AC bus. Standby instruments may be powered by related essential or standby power paths, but the essential AC bus covers more than just standby instruments.

The essential AC bus is dedicated to keeping the most critical flight equipment powered and available even when electrical faults occur. It is sized and isolated so that, if other parts of the electrical system fade or fail, the crew still has power for the essential avionics and flight instruments that provide attitude, guidance, and critical information needed to fly safely. That’s why this bus is described as powering critical avionics and flight instruments and remaining energized during certain faults.

Main cabin lighting and other nonessential systems are not the focus of this bus, and hydraulic pumps are not served by this essential AC bus. Standby instruments may be powered by related essential or standby power paths, but the essential AC bus covers more than just standby instruments.