What happened
On January 16, 2019, a Bombardier DHC-8-402 (Q400) was descending toward Poznań Airport (EPPO) when the crew received multiple fire warnings on the CWP MASTER WARNING panel, including "CHECK FIRE DETECT" and "ENGINE FIRE." The indicator for the engine number 1 fuel/hydraulic shut-off handle also illuminated.
In accordance with established procedures, the crew immediately executed the in-flight engine failure/fire/shutdown checklist. They shut down the engine and discharged two fire extinguishers. Following the completion of memory items, the fire warnings ceased. The crew declared a MAYDAY, notified Poznań Tower of the engine fire, and continued the approach. The cabin crew was notified to prepare the cabin for an emergency landing, and airport rescue and firefighting services were dispatched to the taxiways.
The aircraft landed on a single engine at 08:28 LMT without incident. However, during the subsequent taxi, the red engine fire warning for engine number 1 re-activated. The pilot and fire services performed a visual inspection of the engine, which revealed no signs of fire. The crew concluded the indication was false.
The investigation
The investigation focused on identifying the source of the erroneous fire signal. While a maintenance inspection found no physical evidence of fire, technicians discovered a fault in connector 2600-J24. Measurements revealed that the insulation resistance at this connector was lower than the required specification.
An analysis provided by the manufacturer, Bombardier, indicated that the fault was likely caused by an internal short circuit. This short was attributed to moisture entering the connector. The investigation noted that because the connector is mounted vertically and lacks adequate sealing, it is susceptible to moisture ingress. The manufacturer further noted that seven similar incidents involving this specific connector fault had been recorded within the global Q400 fleet.
Findings
- The primary cause of the event was an internal short circuit within connector 2600-J24, triggered by moisture ingress.
- The vertical mounting and insufficient sealing of the connector allowed moisture to penetrate the component.
- The fire indication was a false alarm with no actual fire present on the aircraft.