What are the signs of an APU fire?

The presence of fire coming out of the APU intake is a critical sign of an APU fire. The Auxiliary Power Unit (APU) is designed for safety, but in the event of a malfunction or failure, particularly within the combustion chamber or fuel system, flames can emanate from the APU intake due to fuel igniting. Recognizing this sign is crucial for quick identification and response to a potential fire situation.

Effective response involves immediate notification of ground crews and emergency protocols activation to ensure safety and prevent escalation. Understanding this sign is vital for anyone involved in the operation and maintenance of the aircraft, as timely action can be the difference between a controlled situation and a catastrophic event.

Flames coming from the exhaust can occur under other circumstances, like normal operation, and smoke in the cockpit area can be indicative of various issues, not just an APU fire. Engine sputtering is more related to power issues rather than direct signs of an APU fire.