The aircraft was en-route from Glasgow to Belfast, when an oil pressure failure and subsequent fire in the left engine prompted a diversion to Belfast Aldergrove Airport. The fire indications on the flight deck cleared several minutes after both fire bottles had been discharged into the engine nacelle. However, observations from the cabin suggested that the fire returned shortly before arrival at Belfast. The aircraft landed safely and stopped on the runway, following which the Airport RFFS confirmed there was still signs of fire. Consequently, the passengers and crew were evacuated from the aircraft, while the fire was rapidly extinguished.
The investigation revealed that the left engine oil pump assembly had failed. This was the result of fatigue cracking in an engine bearing key washer, which caused a section of the washer to be released and migrate to the engine’s oil pump. Consequent mechanical failure of the oil pump assembly upset the oil flow, resulting in engine lubrication failure, internal overheat and fire.
In December 2015, the engine manufacturer issued an Alert Service Bulletin requiring specialist internal inspection of engines to be carried out, in a time span dictated by the service life of the relevant key washer. In addition to this on-wing inspection, a revision to the engine manual has been made requiring replacement of the key washer upon access, and a Service Bulletin has been issued requiring replacement on engine shop visits, for any reason. A new, improved key washer has also been introduced.