Incident Overview
On approach to Portland International Airport in Oregon, Horizon Air flight 2325, a de Havilland DHC-8-102, experienced an engine fire in a Pratt & Whitney PW120A engine. The aircraft was operating a scheduled flight under 14 CFR Part 121.
Examination Findings
An examination and teardown of the affected engine revealed that the #5 bearing assembly had failed. Further inspection identified that the P2.5/P3 switching valve to rear inlet case sealing air tube had become disconnected. Additionally, the NL probe port sealing tube had melted. These failures allowed an oil-fed fire to propagate outside the engine casing and into the engine compartment.
Maintenance and Service Bulletin Compliance
The investigation determined that the engine had not been placed on oil consumption and daily chip detector examination by company maintenance, as required by the engine maintenance manual. This oversight followed a loss of oil event that occurred approximately 180 flight hours before the fire.
Furthermore, the mandatory implementation of Pratt & Whitney service bulletin 20914, which addressed the sealing air tube and NL probe port sealing tube, was not carried out by the company. However, it was also not required under FAA regulations, as the airworthiness directive that made the service bulletin mandatory did not include the PW120A engine.
Additionally, the investigation revealed that another service bulletin, Pratt & Whitney 21446R3, whose implementation was mandated by the company, was not carried out during an earlier hot section inspection and immediately preceding the earlier oil loss event.
Conclusion
The engine fire on Horizon Air flight 2325 was the result of a bearing failure and the failure of sealing tubes, combined with the lack of required maintenance actions and non-implementation of relevant service bulletins.