Contaminated Air Service Bulletins

Source: Aviation Contaminated Air Reference Manual

Service Bulletin ISB 21-150 © 10th April 2008
by Susan Michaelis

The two British Aerospace AOMs for the BAe 146 were followed in March 2001 by a British Aerospace Service Bulletin, or in this particular case an Inspection Service Bulletin (ISB). Service Bulletins (SB) are bulletins issued by the manufacturer identifying inspections or modifications that it has issued. It will list the title of the modification, effectivity, reason and in some cases background for its release, description, compliance, man-hours, costs etc. This particular SB was called ISB 21-150 and dated 20 March 2001. The main extracts are shown below:

British Aerospace BAe 146
Service Bulletin ISB 21-150
Date: 20 March 2001


Title: AIR CONDITIONING - TO INSPECT ENGINE OIL SEALS, APU AND ECS JET PUMP AND AIR CONDITIONING PACK FOR SIGNS OF OIL CONTAMINATION

Reason:

Incidents have been reported involving impaired performance of the flight crew. Investigations have been conducted to determine whether the events could have been caused by inhalation of an agent(s) resulting from oil and/or oil breakdown products leaking from the engine(s) or APU and contaminating the environmental control system. At this time, there is no substantiated evidence indicating that oil breakdown products can impair crew performance. In the past, oil leaks and cabin / flight deck odours and fumes may have come to be regarded as a nuisance rather than a potential flight safety issue.

However, whilst investigations are being carried out to determine the nature of any agents that may be released into the cabin environment and to define any necessary corrective actions, oil leaks and cabin / flight deck odours must be regarded as a potential threat to flight safety, they should not be dismissed as a mere nuisance and should be addressed as soon as possible.

While service bulletins are generally made as for information, optional or recommended at a particular time, the aviation regulator has the power to make any SB mandatory, which is what happened in this case as will be discussed shortly.

While the documents are very revealing, they appear to be heavily biased towards the manufacturer with much of the extensive history of contaminated air events and industry recognition of this ignored. It is interesting that both AOMs and the SB fail to mention the paper written by Dr Weir in 1977, the then Head Doctor at the US Air National Guard reporting on a pilot exposed to synthetic jet oils. Additionally, the BAe comments such as, ‘At this time, there is no substantiated evidence indicating that oil breakdown products can impair crew performance’, or the comment, ‘Incident reports from other aircraft manufacturers continue to identify flight crews' sensitivity to the issue of smoke and fumes,’ fail to point out that the significant information showing contaminated air was already well known, as were the documented effects on crew performance and health. They also failed to highlight that the BAe 146 statistics of contaminated air events and documented evidence of such events were far higher than all other aircraft types. The comment, ‘Improvements in seal design continue to increase efficiency, and when available, modifications are provided for the engines and APU’ fails to mention that the engine manufacturers had been attempting to sort the engine oil seal and related problems out for almost 20 years.

Appendix 5 lists many of the BAe 146 service bulletins and industry related data that goes back to 1984 recognizing the problem of contaminated air and oil leaks. As an example there are service bulletins for the BAe 146 engine listed in early 1995 addressing problems specifically connected with the number 1 engine oil seal bearing. Service bulletins from 2003, 8 years later address the, ‘Field evaluation for the incorporation of a new No 1 seal,’ believed to be around version number 10 of the seal. [65] Furthermore, there was a failure in many people’s eyes to highlight the fact that service information leaflets and service bulletins from the aircraft manufacturer appear to go back to late 1984 regarding this issue. [66] Information contained throughout this reference manual shows that there was extensive ongoing information going right back to 1984, the first year of commercial operation of the BAe 146 showing that the quality of conditioned air, oil leakage and contamination of the bleed air supply was an issue. However, both the manufacturer and Civil Aviation Authority continued as late as 2001 to deliver statements such as, ‘there is some circumstantial evidence’ or ‘there is no substantiated evidence that fumes could be a problem’ and similar. By reading this manual it can be seen that vast amounts of information were already well known before 2001.

British Aerospace advised the Australian Senate Inquiry in 1999 that:

  • A testament to our aircraft safety record is seen in this chart which shows the number of federal aviation airworthiness directives issued throughout 1998 and 1999. An airworthiness directive is issued by the regulators when they feel sufficiently concerned that a real or potential risk exists to the safe operation of the aircraft… I can also say that none of the nine airworthiness directives which were on the BAe146 aircraft are in any way related to cabin fumes or smoke-in-cabin incidents. [17]


    • Flight Safety Aspects of Contaminated Air


    References

    17. British Aerospace (2000) Hansard Evidence by British Aerospace to the Australian Senate inquiry into air safety (1999–2000) BAe 146 cabin air quality. Parliament of Australia, Canberra.

    65. Allied Signal Service bulletins: SB ALF 502R-72-309, March 1995 ; SB ALF/ LF 72-1082FE, August 2003.

    66. British Aerospace service information leaflet SIL 21/7, December 1984 ; Service Information Bulletin 49-5- 35040G, October 1984.


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