Dr Susan Michaelis, a guest speaker at the ESA Annual General Meeting 2016, has kindly shared with us her MSc research work that covers how oil may leak past compressor oil bearing seals in aero engine and contaminate the air system utilized by cabin crew and passengers. We found her presentation fascinating in 2016 at the AGM and thought you may want to read her completed MSC. Susan sends her regards and appreciates the help given by the ESA and FSA members in her research.

Michaelis, S. (2016) MSc Thesis, full text

Abstract

There are certification and airworthiness requirements related to the provision of clean crew and passenger compartment breathing air utilising the aircraft bleed air system. There have been continuing reports and studies over the years regarding oil fumes in aircraft including impaired crew performance. Oil fumes are viewed in varying ways ranging from low occasional seal bearing failures, to low-level leakage in normal or failure conditions.

The aim of this research is to assess whether there is any gap between the certification requirements for the provision of clean air in crew and passenger compartments and the theoretical and practical implementation of the requirements using the bleed air system.

A comprehensive literature search reviewed applicable certification standards and the documented and theoretical understanding of oil leakage. Interviews were undertaken to address the research questions. These involved the key aviation regulators and the process by which they certify and ensure compliance with the clean air requirements. Aerospace engineers and sealing professionals were interviewed about their understanding of how oil may leak past compressor oil bearing seals, and into the air supply under various flight conditions.

The overall objective of this thesis is intended to contribute to flight safety by analysing the theoretical and practical implementation of the use of the compressor bleed air system to supply the required air quality under the regulatory requirements. The final outcome of the evaluation showed that there is a gap between the clean air certification requirements and the theoretical and practical implementation of the requirements using the bleed air system. Lowlevel oil leakage in normal flight operations is a function of the design of the pressurised oil and bleed air systems. The use of the bleed air system to supply the regulatory required air quality standards is not being met or being enforced as required.

Other sources

There are also various documentaries made on this issue available at no charge.

Videos on Vimeo:

The 2015 movie is available for download or DVD:

UK A Dark Reflection available at