Pack burns
3.24 A pack burn is a process under which, before the first flight by an aircraft on a given day, the first officer manually adjusted the aircraft air conditioning outlet temperature to a very high setting in order to vaporise residual oil traces in the air conditioning ducts of the BAe 146. As the procedure was normally carried out in the morning before aircraft operations commenced, cabin crew were often exposed to large amounts of smoky residue flushed from the ducting.22
3.25 The Flight Attendants’ Association of Australia gave this additional information concerning pack burns:
Pack burn offs were introduced in March 1997 as a BAe 146 Odour Inquiry Committee initiative. The intention was to remove the engine oil gathered in the sump, near the cabin air inlet, during overnight stops. It was demonstrated that pack burn-offs were counter-productive because they loaded the filters with carbon and bi-products from the burnt oil and the loaded filters were then unable to remove the contaminants from the air destined to air condition the cabin and flight deck. Pack burn offs were discontinued as a routine procedure in mid 1998.
The process of pack-burn offs was used regularly on BAe 146 aircraft as it was believed that it cleansed the air conditioning systems, and thus reduced odour occurrences.
After crew reported odours a pack burn would routinely be ordered during the turn-around or before start up for the next day’s duty.23
and,
Allied Signal, the APU manufacturers, warned of the danger of pack burns in their Richard Fox Report of November 1997.
“Total contaminant levels, in the supply air to the cabin exceed 50% of the current Safety Standard Limit (NIOSH, ACCIH) during pack burn outs.
Compounds present include formaldehyde, tetro-hydrofuran, and cumene. These compounds are recognised as causing skin, respiratory and eye irritation, as well as nausea and narcosis, if present in excessive levels. The majority of currently detected compounds do not have established exposure limits.”
Fox also states that “ this exposure can continue for some time after the completion of this procedure”. 24
22 Confidential submission C6
23 Submission 24, FAAA, pp 7-8
24 Submission 24, FAAA, p 8
3.26 The FAAA drew attention to a 1997 Ansett notice to cabin crew on BAe 146 aircraft directing them not to remain on board during pack burns. Ansett also issued a notice to its engineering section to discontinue pack burn procedures, “… in line with the recommendations of the Fox Report”.25
Difficulty in finding the source of fumes
3.27 A confidential submission to the inquiry set out the difficulties involved in precisely locating the source of fumes on board the BAe 146:
The result of this air condition design, the output temperature and pack contamination problems is that it is almost impossible to accurately locate the original source of an oil leak. In the event of more than one engine/APU leak combination, identification becomes almost impossible.26
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