In the case of an APU fire detection, what is the initial response?

In the event of an APU (Auxiliary Power Unit) fire detection, the initial response is to shut down the APU immediately. This action is critical because it helps to stop the source of any possible fire and prevents further escalation of the situation. Shutting down the APU cuts off fuel supply and electrical power, reducing the risk of a fire growing out of control and potentially threatening the aircraft's safety.

Taking immediate action by shutting down the APU is consistent with best safety practices, as the APU is located in a compartment that can be hazardous if a fire occurs. The urgency of this response emphasizes the importance of addressing any fire condition swiftly to safeguard both the aircraft and its occupants.

The other actions, while important, are not the initial response. Notifying the cabin crew or deploying fire extinguishing agents are subsequent steps that occur once the first safety measures, such as the APU shut down, have been implemented or if conditions require further action. Checking for faults before responding is less crucial in an emergency scenario, as the priority is to act quickly to minimize risk.