2025-04 · NASA ASRS report 2236045
CRJ-200 flight crew reported an APU Fire Warning caution message during cruise that extinguished after executing the QRC. The flight diverted to an alternate airport.
While cruising at FL340; we received an APU FAULT caution message; immediately followed by an APU FIRE warning message and associated fire bell; which lasted approximately 5-10 seconds. This was followed by an APU PUMP caution message and the automatic shutdown of the APU.At this time; the captain assumed control of the aircraft and radios. I ran the QRC for an in-flight APU Fire. We executed the appropriate checklist steps in the order outlined on the QRC; followed by applicable items in the QRH. As per the QRC:The APU automatically shut down.I confirmed and selected the APU FIRE PUSH button.The APU FIRE warning extinguished within a few seconds; so there was no need to discharge the fire bottle.Following checklist completion; the captain [notified] ATC and requested a diversion to the nearest suitable airport; which was ZZZ. The captain briefed the flight attendants and advised that we would not be evacuating unless a fire was confirmed upon landing. The captain also informed them that we would be stopping on the runway for the fire department to assess the aircraft. If a fire was confirmed; we would initiate an evacuation at that point.The captain then made a PA to the passengers; advising them that we were making a precautionary landing at ZZZ; instructing them to remain calm and informing them that an evacuation was not anticipated at that time.The descent and approach were uneventful; with no need for an emergency descent. We complied with all speed and procedural requirements.Upon landing at ZZZ; we came to a full stop on the runway. The airport fire department conducted an external inspection and confirmed there were no signs of active fire. When asked about our plan; the captain advised we would taxi to the gate and requested the fire department to follow us as a precaution. They accompanied us to the ramp area.Once on the ramp; the fire crew performed a thermal scan to confirm no residual heat or fire. After they cleared us; we proceeded to the gate; connected to ground power; and deplaned passengers normally.The in-flight event originated from a fault within the Auxiliary Power Unit (APU) system. The sequence began with an APU FAULT caution message; followed within seconds by an APU FIRE warning and activation of the fire bell; indicating a detected fire condition in the APU compartment. This was followed by an APU PUMP caution and automatic shutdown of the APU; as per design.The rapid extinguishing of the fire indication and absence of physical fire evidence suggest that the fire detection system may have responded to a transient overheat or false positive; rather than an actual sustained fire. However; in accordance with procedures; the crew treated the indication as a confirmed fire and executed the QRC and QRH checklists without delay. No fire suppression discharge was required; as the fire warning cleared within the wait period after pressing the APU FIRE PUSH switch. Upon landing a thermal scan and visual inspection confirmed no residual heat or active fire.Suggestion: While the crew executed the QRC/QRH procedures effectively; this event highlights the importance of ongoing familiarity with abnormal procedures; especially for fire-related scenarios where rapid; confident execution is critical. Recurrent training with emphasis on high-stress checklist management could further enhance crew performance. not already standard; recommend a review of recent APU health monitoring data and maintenance history to identify any early warning indicators or trends that could help prevent similar in-flight issues.
While cruising at FL340; we received an APU FAULT caution message; immediately followed by an APU FIRE warning message and associated fire bell; which lasted approximately 5-10 seconds. This was followed by an APU PUMP caution message and the automatic shutdown of the APU.At this time; I assumed control of the aircraft and radios. I instructed FO Ayush to run the QRC for an in-flight APU Fire. We executed the appropriate checklist steps in the order outlined on the QRC; followed by applicable items in the QRH. As per the QRC:The APU automatically shut down.I confirmed and selected the APU FIRE PUSH button.The APU FIRE warning extinguished within a few seconds; so there was no need to discharge the fire bottle.Following checklist completion; I [notified] ATC and requested a diversion to the nearest suitable airport; which was ZZZ. I briefed the flight attendants and advised that we would not be evacuating unless a fire was confirmed upon landing. I also informed them that we would be stopping on the runway for the fire department to assess the aircraft. If a fire was confirmed; we would initiate an evacuation at that point.I then made a PA to the passengers; advising them that we were making a precautionary landing at ZZZ; instructing them to remain calm and informing them that an evacuation was not anticipated at that time.The descent and approach were uneventful; with no need for an emergency descent. We complied with all speed and procedural requirements.Upon landing at ZZZ; we came to a full stop on the runway. The airport fire department conducted an external inspection and confirmed there were no signs of active fire. When asked about our plan; I advised we would taxi to the gate and requested the fire department to follow us as a precaution. They accompanied us to the ramp area.Once on the ramp; the fire crew performed a thermal scan to confirm no residual heat or fire. After they cleared us; we proceeded to the gate; connected to ground power; and deplaned passengers normally.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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