What occurs when the L or R ENG FIRE switch is activated?

When the L or R ENG FIRE switch is activated, all fuel, hydraulic, and bleed-air shutoff valves (SOVs) close. This is a critical safety procedure designed to mitigate the risk of fire by cutting off the flow of potentially flammable materials to the affected engine. The activation of this switch is typically part of an emergency response to an engine fire, and by closing these valves, the system helps to prevent the engine from continuing to operate, which could exacerbate the situation.

Closing the fuel SOV stops the fuel supply to the engine, while the closure of hydraulic SOVs limits any hydraulic fluid that could fuel a fire. Similarly, the bleed-air SOVs are closed to avoid further air supply, which could also contribute to an ongoing fire. This coordinated action is essential for ensuring the effectiveness of fire suppression measures and maintaining the safety of the aircraft and its occupants.

The other options do not align with the function of the ENG FIRE switch:

• Powering down the APU is not an automatic action associated with the engine fire switch activation.
• The engine does not continue to operate normally following the activation of this switch as the intent is to shut down the engine.
• There is no automatic switching on of the generator