What does the MAX APU DOOR light indicate when the APU is shut down?

What does the MAX APU DOOR light indicate when the APU is shut down?

• A. APU door open when the APU is shut down
• B. APU door closed when the APU is shut down
• C. APU is running
• D. APU door status unknown

Answer: (A)

The MAX APU DOOR light is a status indicator for the APU intake/exhaust door when the APU is not running. If this light is on while the APU is shut down, it means the APU door is open. This matters because with the APU off, an open door can allow weather, debris, or birds into the bay and can affect aerodynamics and readiness to start the APU again. Therefore, an open-door condition is the condition the light is signaling. If the door were closed, the light would not be illuminated. The light is not used to indicate that the APU is running—the running state is shown by other indicators. It also isn’t used to indicate unknown status; the light specifically flags an open door when the APU is shut down.

The MAX APU DOOR light is a status indicator for the APU intake/exhaust door when the APU is not running. If this light is on while the APU is shut down, it means the APU door is open. This matters because with the APU off, an open door can allow weather, debris, or birds into the bay and can affect aerodynamics and readiness to start the APU again. Therefore, an open-door condition is the condition the light is signaling.

If the door were closed, the light would not be illuminated. The light is not used to indicate that the APU is running—the running state is shown by other indicators. It also isn’t used to indicate unknown status; the light specifically flags an open door when the APU is shut down.