What happened
While on approach to Portland International Airport in Portland, Oregon, Horizon Air flight 2325, a de Havilland DHC-8-102, experienced an engine fire. The fire occurred in one of the aircraft's Pratt & Whitney (P&W) PW120A engines during the scheduled 14CFR121 flight.
The investigation
A teardown and examination of the engine revealed that the #5 bearing assembly had failed. Further inspection determined that a P2.5/P3 switching valve to the 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 spread outside of the engine casing and into the engine compartment.
Findings
The investigation identified several maintenance-related contributing factors:
- Following an oil loss event approximately 180 hours prior to the fire, company maintenance failed to place the engine on the required oil consumption and daily chip detector examination schedule as mandated by the engine maintenance manual.
- The airline did not implement P&W service bulletin 20914, which addressed the disconnected switching valve and the melted sealing tube. This implementation was not required by an FAA airworthiness directive because that specific directive did not include the PW120A engine model.
- During a previous hot section inspection occurring just before the earlier oil loss event, the company failed to carry out the mandatory implementation of P&W service bulletin 21446R3.