Aircraft Clean Air Requirements Using Bleed Air Systems

Michaelis, Susan

doi:10.4236/eng.2018.104011

Cited by 11 publications

(14 citation statements)

References 19 publications

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“…High doses of organophosphates are known to cause organophosphate induced peripheral neuropathy (OPIDN) [56], however the doses encountered here are much lower, suggesting other chronic mechanisms [57]. The toxicity evidence indicates the need for clean air requirements for aircraft using bleed air for cabin pressurization [58].…”

Section: Consequences Of Lubricant Degradationmentioning

confidence: 81%

Turbine Engine Lubricant and Additive Degradation Mechanisms

Johnson¹

2019

Aerospace Engineering

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Modern ester based synthetic lubricants have been used in various formulations with anti-oxidants, phosphorus based anti-wear additives and other additives for many years. The physical and chemical properties of both the basestock and additives are known to change through use. Basestocks are normally thought to degrade through various mechanisms, while additive can either degrade or are used as they react when they complete the function that they are added for. In this chapter, the composition of modern turbine engine lubricants and the mechanisms by which the lubricants degrade over time will be examined. Potential changes in bearing materials being evaluated for future engines and the effects of possible new ionic liquids based additives will be will be discussed as they relate to currently used additives. Also included will be a discussion of effects of degradation on the lubricant properties, how the changes affect turbine engines and how the changes can impact human health. These new materials introduce a number of new possible degradation schemes that must be evaluated before the materials enter widespread use.

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Section: Consequences Of Lubricant Degradationmentioning

confidence: 81%

Turbine Engine Lubricant and Additive Degradation Mechanisms

Johnson¹

2019

Aerospace Engineering

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“…Low levels of oil leakage past seals in normal operations are increasingly recognised to occur. Michaelis (2016) identified that jet engine seals reliant upon compressor generated pressurised air for sealing the engine oil bearing chambers allows low levels of oil to leak past the seals, back into the compressor airstream as a function of design [ 22 , 23 ]. These findings were supported by Howard et al (2018) [ 25 ].…”

Section: Discussionmentioning

confidence: 99%

“…These findings were supported by Howard et al (2018) [ 25 ]. Oil leakage occurs at very low levels during normal engine operation as dynamic oil seals are not an absolute design and are designed to leak, or limit leakage, rather than prevent it [ 23 , 25 , 39 ]. While seals are used to limit oil escape, they are not completely leakproof and other design factors are also used to limit leakage [ 40 ].…”

Section: Discussionmentioning

confidence: 99%

Ultrafine particle levels measured on board short-haul commercial passenger jet aircraft

Michaelis

Loraine²,

Howard

2021

Environ Health

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Background Airline crew members report adverse health effects during and after inhalation exposure to engine oil fumes sourced to the air supply system onboard commercial and military aircraft. Most investigations into the causal factors of their reported symptoms focus on specific chemical contaminants in the fumes. The adverse health effects reported in aircrew exposed to the aircraft air supply, bled unfiltered off the engine or Auxiliary Power Unit (APU) may be related to particulate exposures, which are widely known to effect health. While oil contaminates the aircraft air supply, some suggest that this will only occur when there is a bearing seal failure, others document that there is low level oil contamination of the air supply during normal engine operation. This brief pilot study explores whether particulate exposure may be associated with the normal engine/APU and air supply operation and to therefore increase the understanding that UFP exposures may have on crew and passengers. Methods An ultrafine particle counter was utilised by an experienced airline captain in the passenger cabin of four short-haul commercial passenger aircraft. All flights were under 90 min on aircraft from two different carriers ranging from 7 months to 14 years old. Results UFP concentrations showed maximum concentrations ranging from 31,300 to 97,800 particles/cm3 when APU was selected on as a source of air on the ground and with engine bleed air and the air conditioning packs selected on during the climb. In 2 of the 4 flights the peaks were associated with an engine oil smell. Increases in UFP particle concentrations occurred with changes in engine/APU power and air supply configuration changes. Conclusions This study identified increases in UFP concentrations associated with engine and APU power changes and changes in air supply configuration. These results correlated with times when engine and APU oil seals are known to be less effective, enabling oil leakage to occur. The concentrations reached in the passenger cabins exceeded those taken in other ground-based environments. UFP exposures in aircraft cabins during normal flight indicates there will be health consequences for long serving aircrew and some passengers.

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“…All current pressurised commercial aircraft, with the exception of the Boing 787, use engine bleed air to ventilate and pressurise the cockpit and the cabin. Because the engine bleed air take-off port is aft of the front engine bearings, fugitive emissions from the engine bearing chambers escape into the cabin breathing air via the oil seals [11,12]. Lower levels of oil can migrate past the seals during transient engine power changes, at low power settings and with changes in air supply configurations as part of normal engine operation.…”

Section: Introductionmentioning

confidence: 99%

Inappropriate Use of Risk Assessment in Addressing Health Hazards Posed by Civil Aircraft Cabin Air

Howard¹

2020

oajt

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Over decades, the airline industry has published considerable documentation on the potential for inhalation exposure to organophosphates and other toxins sourced to engine oil fumes supplied by “bleed air” systems, which are used on most commercial and military aircraft. Case studies on the subsequent development of neurological and other symptoms reported by crewmembers have also been widely documented. However, airline industry reviews tend to define toxicity of engine oil fumes according to a single toxicological endpoint - Organo Phosphate Induced Delayed Neuropathy (OPIDN) – which is acknowledged to be the result of a very high dose of exposure to a specific chemical, Tri-Ortho Cresyl Phosphate (TOCP). Industry reviews typically argue that the low levels of TOCP in aviation engine oils justifies the safety of continuing to use unfiltered engine bleed air to ventilate civil and military aircraft cabins. In fact, this approach ignores the routine presence and toxicity of a complex mixture of OPs in oil fumes supplied by engine bleed air systems and ignores the type of neurological symptoms that crews report (i.e., not OPIDN). The industry approach also ignores the scientific literature on repeated low-dose exposure to OPs over extended periods (particularly relevant for airline crewmembers) and the variable susceptibility of individuals to toxicological damage. This paper reviews the above-mentioned studies and presents the scientific literature that should be considered to make a realistic risk assessment of the hazards of aircraft engine bleed air.

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Aircraft Clean Air Requirements Using Bleed Air Systems

Cited by 11 publications

References 19 publications

Turbine Engine Lubricant and Additive Degradation Mechanisms

Turbine Engine Lubricant and Additive Degradation Mechanisms

Ultrafine particle levels measured on board short-haul commercial passenger jet aircraft

Inappropriate Use of Risk Assessment in Addressing Health Hazards Posed by Civil Aircraft Cabin Air

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