What occurs when the External APU Shutoff pushbutton is pressed?

What occurs when the External APU Shutoff pushbutton is pressed?

• A. APU shutdown without horn cancellation
• B. External horn is cancelled and APU shutdown is confirmed
• C. No effect
• D. APU remains active

Answer: (B)

The device is a direct-command control for stopping the APU and silencing the external warning horn. When you press the External APU Shutoff pushbutton, the APU is commanded to shut down and the external horn signal associated with the APU is canceled. This gives you a clear, single action to both stop the APU and silence the exterior alert, with shutdown confirmation indicating the APU is no longer active. The other possibilities would either imply no action, or that the APU stays on, which isn’t how this pushbutton is designed to operate.

The device is a direct-command control for stopping the APU and silencing the external warning horn. When you press the External APU Shutoff pushbutton, the APU is commanded to shut down and the external horn signal associated with the APU is canceled. This gives you a clear, single action to both stop the APU and silence the exterior alert, with shutdown confirmation indicating the APU is no longer active. The other possibilities would either imply no action, or that the APU stays on, which isn’t how this pushbutton is designed to operate.