On 22 October 2006 a blue haze was observed in the passenger cabin of a Boeing 757-200 being operated by Thomsonfly shortly after it reached cruise altitude on a scheduled passenger flight from Newcastle to Larnaca. A precautionary diversion was made to London Stansted, where an emergency evacuation was carried out successfully.
The following is an extract from the UK AAIB report on the Serious Incident:
[…] "Approximately five minutes after reaching its cruising level of FL 370 over the North Sea, the cabin manager (CM) contacted the flight crew via interphone to report a “haze” and an unusual smell in the cabin. She commented that the haze seemed worse in the rear of the cabin, but could not smell anything from her position at the front galley. On inspecting the cabin the commander saw a fine blue-grey haze, but could not detect any unusual smells. He returned to the flight deck, having requested that the CM report any change. She contacted him again shortly afterwards to advise that the smoke was getting worse.
The commander instructed the co-pilot to declare a ‘PAN’ to Maastricht ATC, with whom they were already in contact, to request a descent and direct routing to Stansted, approximately 100 nm distant. The CM then entered the flight deck to be briefed.
Having established the aircraft in a descent, the pilots commenced the Quick Reference Handbook (QRH) ‘SMOKE OR FUMES - AIR CONDITIONING’ checklist. The first item on the checklist related to the use of oxygen masks and smoke goggles; these were not used initially, as no fumes could be detected on the flight deck at this time. In accordance with the operator’s training, but not specified in the QRH procedure, the pilots paused for a few minutes between specific checklist items, to determine if the actions taken had been effective. When this checklist was complete the flight crew actioned the ‘SMOKE OR FUMES REMOVAL’ QRH procedure.
Whilst descending through FL200 the aircraft was handed over to the London Terminal Control Centre (LTCC). The CM advised the flight crew that the haze appeared to be worsening and that some passengers were starting to feel unwell. Fumes were then detected on the flight deck, which prompted the pilots to don oxygen masks and declare a ‘MAYDAY’. LTCC gave immediate clearance for a further descent and provided radar vectors to position the aircraft for an 8 nm final for Runway 23 at Stansted."[…]
The aircraft was evacuated on the taxiway without further incident. One cabin crew member initially had difficulty in opening the rear cabin doors, due to insufficient force being used.
"The blue haze could not be reproduced on initial investigation, which included engine ground runs. A planned post-maintenance proving flight was aborted during the takeoff roll when smoke entered the flight deck and cabin. Further investigation, which included ground runs at higher engine power settings, identified the source of the smoke to be the No 2 (right) engine.
- The cause was determined to be a fractured No 1 bearing floating seal ring, which had allowed engine oil to leak into the compressor airflow path and to be ingested into the bleed air system, which provides air to the cabin air conditioning system."
Two Safety Recommendations are made.
- "It is recommended that the Boeing Commercial Airplane Company consider revising the procedures in the Boeing 757 Fault Isolation Manual to introduce a requirement for ground running at higher engine power settings, if initial testing fails to identify the source of smoke or fumes in conditioned air.
- It is recommended that the European Aviation Safety Agency ensure that effective measures are in place for cabin crews to become, and remain familiar with, the different opening procedures and characteristics of aircraft exits in both normal and emergency modes of operation."