What is the combined effect when the External APU Shutoff pushbutton is pressed?

What is the combined effect when the External APU Shutoff pushbutton is pressed?

• A. APU shutdown is confirmed and the external horn is cancelled
• B. External horn is activated and APU continues
• C. Nothing happens
• D. APU shuts off but horn remains

Answer: (A)

The External APU Shutoff pushbutton is a dual action control. When you press it, the APU is commanded to shut down, and at the same time the external horn warning is canceled. The design ensures you get a clean state: the APU stops and any audible warning related to the external power/APU condition is cleared. This is why this pushbutton results in both an APU shutdown confirmation and the cancellation of the external horn.

The External APU Shutoff pushbutton is a dual action control. When you press it, the APU is commanded to shut down, and at the same time the external horn warning is canceled. The design ensures you get a clean state: the APU stops and any audible warning related to the external power/APU condition is cleared. This is why this pushbutton results in both an APU shutdown confirmation and the cancellation of the external horn.