Abstract

There are certification and airworthiness requirements relevant to the provision of clean breathing air in the crew and passenger compartments. 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 rare seal bearing failures, to low level leakage in normal flight. A Masters of Science (MSc) research degree was undertaken 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, documented and theoretical understanding of oil leakage. Two types of interviews were conducted to address the research questions. Key aviation regulators were questioned about 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 outcome of the research 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. Low level oil leakage into the aircraft cabin in normal flight operations is a function of the design of the engine lubricating system and bleed air systems, both utilising pressurised air. The use of the bleed air system to supply the regulatory required air quality standards is not being met or being enforced as required.

Highlights

  • The first reports of concerns of exposure to jet engine oils leaking from aircraft engines into cabin air supplies date back to the early 1950s [1] [2] [3]

  • This research consisted of 3 elements: 1) A review of the certification standards and guidelines applicable to the ventilation air provided to the aircraft cabin; 2) A review of the theoretical and documented understanding of how oil may contaminate the aircraft air supply when using the bleed air system; 3) Research addressing the real world implementation of the certification requirements requiring clean bleed air

  • The key relevant European Certification Specifications (CS) and Federal Aviation Regulations (FAR) and suggested non-mandatory acceptable means of compliance (AMC) or guidance material related to the clean air requirements are outlined below

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Summary

Introduction

The first reports of concerns of exposure to jet engine oils leaking from aircraft engines into cabin air supplies date back to the early 1950s [1] [2] [3]. This coincided with the introduction of synthetic jet oils that replaced mineral oils and the introduction of higher performing, higher temperature and pressure turbine engines [4]. Varying types of reports have continued to the present day including military, airline, manufacturer and crew reports. Despite recognised under-reporting, crew impairment has been recorded in around 30% of fume event reports [8] [10] [11]

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