 | The examples and perspective in this article may not represent a worldwide view of the subject.(July 2023) |
A fume event occurs when bleed air used for cabin pressurisation and air conditioning in a pressurised aircraft is contaminated by fluids such as engine oil, hydraulic fluid, anti-icing fluid, and other potentially hazardous chemicals. [1]
Because airliners fly at very high altitudes, the cabin must be pressurised to provide a safe quantity of breathable oxygen to passengers and crew. The cabin is pressurised with bleed air tapped from the jet engine's compressor sections, which are prior to the combustion sections. Bleed air is very hot and must be cooled by heat exchangers before it is directed into the air conditioning units, which cool it even further. [2]
To prevent fume events, the Boeing 787 pressurises its air with electrical compressors rather than the engines. [3]
In the event of fumes or smoke in an aircraft, flight deck crew will wear pressurised oxygen masks in order to avoid breathing in irritating fumes. Goggles are also available if necessary. Cabin crew may be able to use portable oxygen masks if they identify the fume event in time. If the fumes do not subside after an attempt is made to diagnose and fix the problem, the flight is diverted to a nearby airport. In a severe fume or smoke event, the aircraft might descend to an altitude of 10,000 feet (3,000 m) or lower where it can safely be depressurised. [4]
An FAA-funded study found that fume events occur on 1 in 5,000 flights; some planes may have multiple consecutive events if the leak is not fixed. [3] Sensors that can detect air quality issues are available and the airline Lufthansa has requested their installation, but Boeing declined due to fear of litigation from crew or passengers sickened by detectable fume events. [3]
The human physiological effects of fume events are yet to be fully understood by the medical community. Signs and symptoms of exposure can be misdiagnosed as other common ailments, due particularly to the delay between exposure to fumes and the onset of associated symptoms. While most aeromedical professionals believe no long-term health effects exist from fume events, some consumer and aircrew advocacy groups claim that it can cause a medically-unrecognised condition called aerotoxic syndrome. [5] [6]
Turbine engine oil is an irritant and contains neurotoxic chemicals such as tricresyl phosphate. The aviation industry claims that engine oil does not contain sufficient quantities of such chemicals to cause long-term damage. [5] However, there is some historical evidence that would seem to contradict this statement; in 1959, over 10,000 people in Morocco were paralyzed or otherwise adversely affected after ingesting small quantities of tricresyl phosphate in their cooking oil. [7]
Hydraulic fluid, although non-toxic in small quantities, is extremely irritating to the eyes and skin, which creates a hazard to pilots during a fume event but causes no lasting damage. [8]
Deicing fluid has a strong smell but is not very irritating or toxic if inhaled (though it has significant toxicity when ingested).[ citation needed ]
It is not mandatory for fume events to be reported in the U.S. [3]
Many lobbying groups have been set up to advocate for research into this hazard, including the Aviation Organophosphate Information Site (AOPIS) (2001), the Global Cabin Air Quality Executive (2006), and the UK-based Aerotoxic Association (2007). Cabin Environment Research is one of many functions of the ACER Group, [9] but their researchers have not yet established any causal relationship. [10] [11]
Although a study made for the EU in 2014 confirmed that contamination of cabin air could be a problem, the study also stated:
While no scientific evidence to date has found that airliner cabin air has been contaminated to toxic levels (exceeding known safe levels, in ppm, of any dangerous chemical), in March 2010 a court in Australia in ruled in favor of a former airline flight attendant who claimed she suffered chronic respiratory problems after being exposed to oil fumes on a flight in March 1992. [13] Such testing is infrequent due to Boeing's refusal to install air quality sensors in its planes, fearing litigation from passengers or crew over fume events. In the U.S., airlines refused to allow flight attendants to carry air samplers after Congress mandated chemical measurements. [14]
The FAA has revoked the medical certificates of several pilots who developed neurological issues after fume events. [15]
A Los Angeles Times analysis [3] of NASA safety reports from January 2018 to December 2019 identified 362 voluntarily-reported fume events, in which almost 400 pilots, flight attendants and passengers received medical attention. On 73 or more of those flights, pilots used emergency oxygen. Four dozen pilots were impaired so far as to be unable to perform their duties. Boeing told the Times that they believe no credible data shows that oil leaks into the bleed air stream can cause serious injuries. By contrast, a judge who awarded workers' compensation to a pilot who had suffered toxic encephalopathy (brain damage) from a fume event condemned the airline industry's obstructionism around fume events. [3]
An airliner is a type of airplane for transporting passengers and air cargo. Such aircraft are most often operated by airlines. The modern and most common variant of the airliner is a long, tube shaped, and jet powered aircraft. The largest of them are wide-body jets which are also called twin-aisle because they generally have two separate aisles running from the front to the back of the passenger cabin. These are usually used for long-haul flights between airline hubs and major cities. A smaller, more common class of airliners is the narrow-body or single-aisle. These are generally used for short to medium-distance flights with fewer passengers than their wide-body counterparts.
British Midland Airways Flight 092, a Boeing 737-400, crashed onto the motorway embankment between the M1 motorway and A453 road near Kegworth, Leicestershire, England, while attempting to make an emergency landing at East Midlands Airport on 8 January 1989.
An inerting system decreases the probability of combustion of flammable materials stored in a confined space. The most common such system is a fuel tank containing a combustible liquid, such as gasoline, diesel fuel, aviation fuel, jet fuel, or rocket propellant. After being fully filled, and during use, there is a space above the fuel, called the ullage, that contains evaporated fuel mixed with air, which contains the oxygen necessary for combustion. Under the right conditions this mixture can ignite. An inerting system replaces the air with a gas that cannot support combustion, such as nitrogen.
Bleed air in aerospace engineering is compressed air taken from the compressor stage of a gas turbine, upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPC) valves bleed air from low or high stage engine compressor sections; low stage air is used during high power setting operation, and high stage air is used during descent and other low power setting operations. Bleed air from that system can be utilized for internal cooling of the engine, cross-starting another engine, engine and airframe anti-icing, cabin pressurization, pneumatic actuators, air-driven motors, pressurizing the hydraulic reservoir, and waste and water storage tanks. Some engine maintenance manuals refer to such systems as "customer bleed air".
British Airtours was a charter airline in the United Kingdom with flight operations out of London Gatwick and Manchester Airports.
An uncontrolled decompression is an undesired drop in the pressure of a sealed system, such as a pressurised aircraft cabin or hyperbaric chamber, that typically results from human error, structural failure, or impact, causing the pressurised vessel to vent into its surroundings or fail to pressurize at all.
In aeronautics, an environmental control system (ECS) of an aircraft is an essential component which provides air supply, thermal control and cabin pressurization for the crew and passengers. Additional functions include the cooling of avionics, smoke detection, and fire suppression.
Cabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for humans flying at high altitudes. For aircraft, this air is usually bled off from the gas turbine engines at the compressor stage, and for spacecraft, it is carried in high-pressure, often cryogenic, tanks. The air is cooled, humidified, and mixed with recirculated air by one or more environmental control systems before it is distributed to the cabin.
An emergency landing is a premature landing made by an aircraft in response to an emergency involving an imminent or ongoing threat to the safety and operation of the aircraft, or involving a sudden need for a passenger or crew on board to terminate the flight. It typically involves a forced diversion to the nearest or most suitable airport or airbase, or an off airport landing or ditching if the flight cannot reach an airfield. Flights under air traffic control will be given priority over all other aircraft operations upon the declaration of the emergency.
Helios Airways Flight 522 was a scheduled passenger flight from Larnaca, Cyprus, to Prague, Czech Republic, with a stopover in Athens, Greece. Shortly after take-off on 14 August 2005, air traffic control (ATC) lost contact with the aircraft operating the flight, named Olympia; it eventually crashed near Grammatiko, Greece, killing all 121 passengers and crew on board. It is the deadliest aviation accident in Greek history.
Tricresyl phosphate (TCP), is a mixture of three isomeric organophosphate compounds most notably used as a flame retardant. Other uses include as a plasticizer in manufacturing for lacquers and varnishes and vinyl plastics and as an antiwear additive in lubricants. Pure tricresyl phosphate is a colourless, viscous liquid, although commercial samples are typically yellow. It is virtually insoluble in water, but easily soluble in organic solvents like toluene, hexane, and diethylether among others. It was synthesized by Alexander Williamson in 1854 upon reacting phosphorus pentachloride with cresol, though today's manufacturers can prepare TCP by mixing cresol with phosphorus oxychloride or phosphoric acid as well. TCP, especially the all-ortho isomer, is the causative agent in a number of acute poisonings. Its chronic toxicity is also of concern. The ortho-isomer is rarely used on its own outside of laboratory studies that require isomeric purity, due to its extremely toxic nature, and is generally excluded from commercial products where TCP is involved.
Aircraft emergency oxygen systems or air masks are emergency equipment fitted to pressurized commercial aircraft, intended for use when the cabin pressurisation system has failed and the cabin altitude has climbed above a safe level. It consists of a number of individual yellow oxygen masks stored in compartments near passenger seats and near areas like lavatories and galleys, and an oxygen source, like a centralized gaseous cylinder or decentralized chemical oxygen generator.
A turbine engine failure occurs when a turbine engine unexpectedly stops producing power due to a malfunction other than fuel exhaustion. It often applies for aircraft, but other turbine engines can fail, like ground-based turbines used in power plants or combined diesel and gas vessels and vehicles.
Skydrol is a brand name of fire-resistant hydraulic fluid used in aviation and aerospace applications. It is a phosphate ester-based fluid that is known for its excellent fire resistance and ability to withstand extreme temperature and pressure conditions. It is manufactured by Solutia, and formerly manufactured by Monsanto. There are various lines of Skydrol including Skydrol 500B-4, Skydrol LD-4, and Skydrol 5.
Welcome Aboard Toxic Airlines is a 2007 British documentary film about aerotoxic syndrome directed and produced by former airline captain Tristan Loraine.
Aircraft systems are those required to operate an aircraft efficiently and safely. Their complexity varies with the type of aircraft.
The Aerotoxic Association was founded on 18 June 2007, at the British Houses of Parliament by former BAe 146 Training Captain John Hoyte, to raise public awareness about the ill health allegedly caused after exposure to airliner cabin air that he claimed been contaminated to toxic levels, by engine oil leaking into the bleed air system, which pressurizes all jet aircraft, with the exception of the Boeing 787.
Aerotoxic syndrome relates to ill-health effects associated with breathing contaminated air in an airliner cabin. Researchers have associated aerotoxic syndrome with exposure to substances such as engine oil and hydraulic fluid. Although researchers have identified correlations between the aircraft occupational environment and symptoms of aerotoxic syndrome, this condition is not an established medical diagnosis because the incidence and aetiology of the condition are still under debate.
A Dark Reflection is a 2015 British independent investigative thriller film directed and produced by former British Airways airline captain Tristan Loraine. Billed as Erin Brockovich meets All the President's Men and as a fact-based investigative thriller, the film is based on the director's own experience as a commercial pilot.
Susan Michaelis is a former Australian flight instructor and airline transport pilot. She is also a researcher working on the issue of contaminated air on aircraft and the health effects of exposure to heated jet engine oils and hydraulic fluids known to contaminate the breathing air supply on aircraft, often called aerotoxic syndrome. She is a part of the University of Stirling's Occupational and Environmental Health Research group, where she is an Honorary Sensor Research Fellow.
