Shortly after take-off, and in accordance with standard procedure, the flight crew selected engine bleed air as the source of air for the aircraft's two air conditioning packs. Subsequently, the cabin staff reported a strong smell of fumes in the cabin. As there was also a smell of fumes entering the flight deck, the flight crew donned their oxygen masks in accordance with the non-normal procedure for suspected cabin air contamination.
The flight crew then proceeded to identify the source of the fumes using a contamination source location schedule. That procedure involved selecting different combinations of engine air and air conditioning packs. During normal operation, bleed air from engines one and two was fed to pack one, which in turn supplied conditioned air to the flight deck and cabin. Bleed air from engines three and four was fed to pack two, which normally only supplied air to the cabin. Additionally, bleed air from the Auxiliary Power Unit (APU) was used by either pack during the take-off and landing phases or when air conditioning was required during ground operations. It was determined that with pack two selected off, the fumes dissipated. The flight was continued with only pack one supplying conditioned air to the cabin and flight deck. The two cabin staff and several passengers were affected by the fumes with symptoms of sore eyes, sore throat and headache.
On arrival of the aircraft in Brisbane, a Licensed Aircraft Maintenance Engineer (LAME) addressed the reported defect in accordance with the Civil Aviation Safety Authority airworthiness directive AD/BAe146/086 and the British Aerospace Systems Information Service Bulletin (ISB) 21-150. The ISB required certain actions to be performed whenever a cabin air quality problem was identified which was suspected of being associated with oil contamination of the air supply from the air conditioning packs. The engineer's inspection of the air conditioning system, engines and APU revealed no signs of oil contamination or oil leaks. The defect was therefore cleared and the aircraft resumed service.
The following day, the same aircraft but with a different crew was involved in a similar occurrence. A strong smell of fumes was noticed, mainly in the cabin, during the cruise. The flight crew donned oxygen masks as a precautionary measure. Symptoms of sore eyes, sore throat and headache were reported by both the crew and passengers. The pilot in command, who had been affected by fumes on previous occasions, received medical attention after landing.
Engineering inspection revealed oil contamination in the number 3 engine bleed band. The defect was deferred in accordance with the aircraft's approved Minimum Equipment List that allowed the aircraft to be flown with only the number one air conditioning pack in use. No further fumes were evident during following flights. Subsequent engineering investigation of the number 3 engine revealed that the oil leak was a result of a worn number one bearing seal. The number 3 engine was replaced, and the defect was cleared.
Evidence from previous incidents of air system contamination on this type of aircraft had indicated that the fumes were associated with engine or APU oil contamination of the air conditioning system. As a result, operators have incorporated various modifications to the cabin air system, APU, and engines. They have also introduced improved maintenance practices to further address the issue. However, that action has not completely solved the problem. The air supplied to the air conditioning packs was protected from contamination by oil seals in the engines and APU. A technical defect arising in one of the seals can result in oil entering the cabin air conditioning system, with the first signal of the defect being an awareness of fumes by the members of the crew. The difficulty of identifying the origin of the contamination is exacerbated by the often-intermittent nature of the fumes events.