What happened
On 20 September 2006, an Avro 146-RJ100, registration G-CFAA, was descending through FL120 toward Edinburgh when the crew detected fumes in the flight deck. The pilots donned oxygen masks and, after noting low oil pressure in the No 2 engine, shut the engine down. Following established procedures, the crew broadcast a ‘PAN’ call and requested an immediate return to Birmingham. The aircraft landed safely at Edinburgh, and passengers were disembarked via the terminal gate.
Following maintenance at Birmingham, which included the replacement of the No 2 engine, the aircraft returned to service on 26 September 2006. During the initial climb of this second flight, passing approximately 3,500 feet, dense smoke rapidly filled the flight deck. The crew shut down the engine and restarted the APU to clear the smoke. The cabin crew reported that the cabin was also filled with smoke, though passenger oxygen masks were not deployed. The aircraft landed safely at Birmingham, and the aircraft was subsequently removed from service for investigation.
The investigation
The AAIB examined the technical logs and the sequence of events for both flights. The investigation focused on the engine replacement process and the air conditioning system's state following the initial maintenance. The investigators reviewed the engine's internal condition and the maintenance actions taken at the Birmingham base.
Findings
- The initial event was caused by a bearing failure in the No 2 engine, which led to seal damage and the subsequent contamination of the air conditioning system with oil.
- During the first flight, residual oil remained in the air conditioning system.
- During the second flight, the smoke recurred because the residual oil in the air conditioning packs and ducting was not effectively eliminated during maintenance.
- The contamination was not detected because the ground running performed after the engine change did not involve full operation of the air conditioning system.
- The smoke entered the cabin when the air supply was switched from APU to engine air during the climb.