What happens when the Master switch is set to OFF?

What happens when the Master switch is set to OFF?

• A. It disables electrical systems entering service
• B. It disconnects the battery from the bus only
• C. It halves the main generator output
• D. It triggers automatic reconfiguration of buses

Answer: (A)

The Master switch controls power to the aircraft’s electrical buses. When it’s set to OFF, the entire electrical system is isolated from its power sources, so no power is supplied to the buses and no systems can enter service. This is why OFF disables electrical systems entering service. It doesn’t just disconnect the battery from the bus, and it doesn’t halve the generator output or trigger automatic bus reconfiguration. Those behaviors would imply partial or dynamic changes to power delivery, which do not occur when the Master switch is OFF.

The Master switch controls power to the aircraft’s electrical buses. When it’s set to OFF, the entire electrical system is isolated from its power sources, so no power is supplied to the buses and no systems can enter service. This is why OFF disables electrical systems entering service.

It doesn’t just disconnect the battery from the bus, and it doesn’t halve the generator output or trigger automatic bus reconfiguration. Those behaviors would imply partial or dynamic changes to power delivery, which do not occur when the Master switch is OFF.