What is activated when the APU FIRE PUSH button is pressed?

When the APU FIRE PUSH button is pressed, the fuel shutoff valve and the fuel line control valve (LCV) are closed to prevent the flow of fuel to the APU. This is a critical safety measure designed to minimize the risk of an explosion or fire by eliminating the fuel source.

In terms of emergency procedures, closing these valves is essential in response to an APU fire scenario. It ensures that fuel does not continue to fuel the fire, thereby increasing the chances of successfully extinguishing the fire. The action taken when the APU FIRE PUSH button is pressed is a direct response to a safety hazard, and closing these valves is a standard procedure in aircraft fire safety protocols.

The activation of this system helps to secure other components and systems on the aircraft from excessive heat or fire, maintaining overall operational integrity.