included a news item on the request for an inquiry into aircraft cabin air quality.
I have now had a chance to look at some of the supporting information from the Global Cabin Air Quality Executive (GCAQE) and it makes quite interesting reading. Most of the information and reports cover the health effects of turbine oil additives and a lot of statistics and reports of cabin fume incidents. It seems that in the UK there are typically four or five such incidents reported each week, and to be reported it means that it was bad enough for the crew to think it unusual or be physically affected. There are two aspects of the reports from which we can draw some seal related information. The first is aircraft types. Just about every aircraft type appears in the reports but three stand out; BAe 146, Boeing 757 and MD80. Presumably there is some potential to look at the seals on these relative to other aircraft. The second is that a considerable proportion of incidents are reported as occurring, at engine start, during take off and climb, or during descent. When would we expect such seals to be most likely to exhibit increased leakage, dare I suggest during transient operation?
While I do not have specialist knowledge of aircraft gas turbines it still appears to me that there is at least one, or perhaps more, high speed seals where there is a single seal between the hot oil and passenger air. Assuming a good quality mechanical seal, operating at a relatively high speed, how much would we expect it to leak, maybe 1-10ml/hr? This would mean that on an eight hour flight with four engines and two seals per engine that up to perhaps half a litre of oil mist could be leaked into the enclosed cabin space.
Seal leakage has been addressed vigorously for process pumps. Industrial compressed air systems have been converted to dry air to avoid lubricant aerosol in the exhaust. However, it appears that similar health standards are not being applied to the confines of an aircraft cabin.
It is unrealistic to expect large scale changes can be made to thousands of aircraft engines, but there does appear to be plenty of scope for some imaginative seal development.