Cabin pressurization

“Cabin pressure” redirects here. For other uses, seeCabin Pressure (disambiguation).Cabin pressurization is a process in which conditioned

The pressurization controls on a Boeing 737-800

air is pumped into the cabin of an aircraft or spacecraft,in order to create a safe and comfortable environmentfor passengers and crew flying at high altitudes. For air-craft, this air is usually bled off from the gas turbine en-gines at the compressor stage, and for spacecraft, it iscarried in high-pressure, often cryogenic tanks. The airis cooled, humidified, and mixed with recirculated air ifnecessary, before it is distributed to the cabin by one ormore environmental control systems.[1] The cabin pres-sure is regulated by the outflow valve.

1 Need for cabin pressurization

Pressurization becomes necessary at altitudes above12,500 feet (3,800 m) to 14,000 feet (4,300 m) abovesea level to protect crew and passengers from the risk ofa number of physiological problems caused by the lowoutside air pressure above that altitude. It also serves togenerally increase passenger comfort and is a regulatory

requirement above 8,000 feet (2,400 m). The principalphysiological problems are listed below. Pressurizationof the cargo hold is also required to prevent damage topressure-sensitive goods that might leak, expand, burst orbe crushed on re-pressurization.

Hypoxia The lower partial pressure of oxygen at altitudereduces the alveolar oxygen tension in the lungs andsubsequently in the brain, leading to sluggish think-ing, dimmed vision, loss of consciousness, and ulti-mately death. In some individuals, particularly thosewith heart or lung disease, symptoms may begin aslow as 5,000 feet (1,500 m), although most passen-gers can tolerate altitudes of 8,000 feet (2,400 m)without ill effect. At this altitude, there is about 25%less oxygen than there is at sea level.[2]

Hypoxia may be addressed by the administration of sup-plemental oxygen, either through an oxygen maskor through a nasal cannula. Without pressurization,sufficient oxygen can be delivered up to an altitudeof about 40,000 feet (12,000 m). This is becausea person who is used to living at sea level needsabout 0.20 bar partial oxygen pressure to functionnormally and that pressure can be maintained up toabout 40,000 feet (12,000m) by increasing the molefraction of oxygen in the air that is being breathed.At 40,000 feet (12,000 m), the ambient air pressurefalls to about 0.2 bar, at which maintaining a mini-mum partial pressure of oxygen of 0.2 bar requiresbreathing 100% oxygen using an oxygen mask.

Emergency oxygen supply masks in the passenger com-partment of airliners do not need to be pressure-demand masks because most flights stay below40,000 feet (12,000 m). Above that altitude the par-tial pressure of oxygen will fall below 0.2 bar evenat 100% oxygen and some degree of cabin pressur-ization or rapid descent will be essential to avoid therisk of hypoxia.

Altitude sickness Hyperventilation, the body’s mostcommon response to hypoxia, does help to par-tially restore the partial pressure of oxygen in theblood, but it also causes carbon dioxide (CO2)to out-gas, raising the blood pH and inducingalkalosis. Passengers may experience fatigue,nausea, headaches, sleeplessness, and (on extendedflights) even pulmonary oedema. These are the samesymptoms that mountain climbers experience, butthe limited duration of powered flight makes the

1

2 2 CABIN ALTITUDE

development of pulmonary oedema unlikely. Alti-tude sickness may be controlled by a full pressuresuit with helmet and faceplate, which completely en-velops the body in a pressurized environment; how-ever, this is impractical for commercial passengers.

Decompression sickness The low partial pressure ofgases, principally nitrogen (N2) but including allother gases, may cause dissolved gases in the blood-stream to precipitate out, resulting in gas embolism,or bubbles in the bloodstream. The mechanismis the same as that of compressed-air divers onascent from depth. Symptoms may include theearly symptoms of “the bends”—tiredness, forget-fulness, headache, stroke, thrombosis, and subcuta-neous itching—but rarely the full symptoms thereof.Decompression sickness may also be controlled bya full-pressure suit as for altitude sickness.

Barotrauma As the aircraft climbs or descends, pas-sengers may experience discomfort or acute pain asgases trappedwithin their bodies expand or contract.The most common problems occur with air trappedin the middle ear (aerotitus) or paranasal sinuses bya blocked Eustachian tube or sinuses. Pain may alsobe experienced in the gastrointestinal tract or eventhe teeth (barodontalgia). Usually these are not se-vere enough to cause actual trauma but can result insoreness in the ear that persists after the flight andcan exacerbate or precipitate pre-existing medicalconditions, such as pneumothorax.

2 Cabin altitude

The pressure inside the cabin is technically referred to asthe equivalent effective cabin altitude or more commonlyas the cabin altitude. This is defined as the equivalent al-titude above mean sea level having the same atmosphericpressure according to a standard atmospheric model suchas the International Standard Atmosphere. Thus a cabinaltitude of zero would have the pressure found at meansea level, which is taken to be 101,325 pascals (14.696psi).[3]

2.1 Aircraft

In practice, cabin altitude is almost never kept at zero dueto design limits of the fuselage and practical considera-tions for landing at airports located above sea level. Ina typical pressurization approach for a commercial pas-senger plane, the cabin altitude of an aircraft planningto cruise at 40,000 ft (12,000 m) is programmed to risegradually from the altitude of the airport of origin toaround a maximum of 8,000 ft (2,400 m) (approximately10.9 psi, or 0.75 atm), and to then reduce gently during

An empty bottle, closed during a commercial flight with a cabinaltitude of around 8,000 ft, is crushed by the pressure at groundlevel after descent.

descent until the interior cabin pressure matches the am-bient air pressure of the destination.A typical cabin altitude for an aircraft such as the Boeing767 is 6,900 feet (2,100 m), when cruising at 39,000 feet(12,000 m).[4] A design goal for many, but not all, neweraircraft is to lower the cabin altitude, which can be ben-eficial for passenger comfort.[5] For example, the highestinternal cabin altitude of the Boeing 787 Dreamliner is6,000 feet (1,800 m). The Bombardier Global Expressbusiness jet has one of the lowest cabin altitudes of cur-rently flying aircraft; 4,500 ft (1,400 m) when cruisingat 41,000 feet (12,000 m).[6][7][8] The Airbus A380 hasa cabin altitude of 4,990 feet (1,520 m), which is lowerthan that of the Boeing 747-400 (9,010 feet (2,750m)).[9]The absolute lowest cabin altitude available on an aircraftis found on the Emivest SJ30 business jet which featuresa sea level cabin altitude when cruising at 41,000 feet(12,000 m).[10][11]

Keeping the cabin altitude below 8,000 ft (2,400 m)generally prevents significant hypoxia, altitude sickness,decompression sickness, and barotrauma. Federal Avia-tion Administration (FAA) regulations in the U.S. man-date that under normal operating conditions, the cabin al-titude may not exceed this threshold at the maximum op-erating altitude of the aircraft. This mandatorymaximumcabin altitude does not eliminate all physiological prob-

3

lems; passengers with conditions such as pneumothoraxare advised not to fly until fully healed, and people suf-fering from a cold or other infection may still experiencepain in the ears and sinuses. Scuba divers flying withinthe “no fly” period after a dive are at risk for decompres-sion sickness because the accumulated nitrogen in theirbodies can form bubbles when exposed to reduced cabinpressure.Before 1996, approximately 6,000 large commercialtransport airplanes were type-certificated to fly up to45,000 ft (14,000m)without having tomeet high-altitudespecial conditions.[12] In 1996, the FAA adopted Amend-ment 25-87, which imposed additional high-altitudecabin pressure specifications for new-type aircraft de-signs. Aircraft certified to operate above 25,000 ft (7,600m) “must be designed so that occupants will not be ex-posed to cabin pressure altitudes in excess of 15,000 ft(4,600 m) after any probable failure condition in the pres-surization system”.[13] In the event of a decompressionwhich results from “any failure condition not shown tobe extremely improbable”, the plane must be designedsuch that occupants will not be exposed to a cabin al-titude exceeding 25,000 ft (7,600 m) for more than 2minutes, nor to an altitude exceeding 40,000 ft (12,000m) at any time.[13] In practice, that new Federal AviationRegulations amendment imposes an operational ceilingof 40,000 ft (12,000 m) on the majority of newly de-signed commercial aircraft.[14][15] Aircraft manufacturerscan apply for a relaxation of this rule if the circumstanceswarrant it. In 2004, Airbus acquired an FAA exemptionto allow the cabin altitude of the A380 to reach 43,000ft (13,000 m) in the event of a decompression incidentand to exceed 40,000 ft (12,000 m) for one minute. Thisallows the A380 to operate at a higher altitude than othernewly designed civilian aircraft.[14]

2.2 Spacecraft

Russian engineers have chosen to use an air-like nitro-gen/oxygen mixture, kept at a cabin altitude near zero atall times, in their 1961 Vostok, 1964 Voskhod, and 1967to present Soyuz spacecraft.[16] This requires a heavierspace vehicle design, because the spacecraft cabin struc-ture must withstand the stress of 14.7 pounds per squareinch (1.01 bar) against the vacuum of space, and also be-cause an inert nitrogen mass must be carried. Care mustalso be taken to avoid decompression sickness when cos-monauts perform extravehicular activity, as current softspace suits are pressurized with pure oxygen at relativelylow pressure in order to provide reasonable flexibility.[17]

By contrast, the United States chose to use a pure oxy-gen atmosphere for its 1961 Mercury, 1965 Gemini, and1967 Apollo spacecraft, mainly in order to avoid decom-pression sickness.[18][19] Mercury used a cabin altitude of24,800 feet (7,600 m) (5.5 pounds per square inch (0.38bar));[20] Gemini used an altitude of 25,700 feet (7,800m) (5.3 pounds per square inch (0.37 bar));[21] andApollo

used 27,000 feet (8,200 m) (5.0 pounds per square inch(0.34 bar))[22] in space. This allowed for a lighter spacevehicle design. Before launch, the pressure was kept atslightly higher than sea level (a constant 5.3 pounds persquare inch (0.37 bar) above ambient for Gemini, and2 pounds per square inch (0.14 bar) above sea level atlaunch for Apollo), and transitioned to the space cabinaltitude during ascent. However, the high pressure pureoxygen atmosphere proved to be a fatal fire hazard inApollo, contributing to the deaths of the entire crew ofApollo 1 during a 1967 ground test. After this, NASArevised its procedure to use a 40% nitrogen/60% oxygenmix at zero cabin altitude at launch, but kept the low-pressure pure oxygen in space.After Apollo, the United States chose to use air-likecabin atmospheres for its Skylab, Space Shuttle, and theInternational Space Station.

3 Mechanics

Pressurization is achieved by the design of an airtightfuselage engineered to be pressurized with a source ofcompressed air and controlled by an environmental con-trol system (ECS). The most common source of com-pressed air for pressurization is bleed air extracted fromthe compressor stage of a gas turbine engine, from a lowor intermediate stage and also from an additional highstage; the exact stage can vary depending on engine type.By the time the cold outside air has reached the bleed airvalves, it is at a very high pressure and has been heated toaround 200 °C (392 °F). The control and selection of highor low bleed sources is fully automatic and is governed bythe needs of various pneumatic systems at various stagesof flight.[23]

The part of the bleed air that is directed to the ECS is thenexpanded and cooled to a suitable temperature by passingit through a heat exchanger and air cycle machine knownas the packs system. In some larger airliners, hot trim aircan be added downstream of air conditioned air comingfrom the packs if it is needed to warm a section of thecabin that is colder than others.At least two engines provide compressed bleed airfor all the plane’s pneumatic systems, to provide fullredundancy. Compressed air is also obtained from theauxiliary power unit (APU), if fitted, in the event of anemergency and for cabin air supply on the ground beforethe main engines are started. Most modern commercialaircraft today have fully redundant, duplicated electroniccontrollers for maintaining pressurization along with amanual back-up control system.All exhaust air is dumped to atmosphere via an outflowvalve, usually at the rear of the fuselage. This valve con-trols the cabin pressure and also acts as a safety reliefvalve, in addition to other safety relief valves. If the au-tomatic pressure controllers fail, the pilot can manually

4 5 HISTORY

Outflow and pressure relief valve on a Boeing 737-800

control the cabin pressure valve, according to the backupemergency procedure checklist. The automatic controllernormally maintains the proper cabin pressure altitude byconstantly adjusting the outflow valve position so that thecabin altitude is as low as practical without exceedingthe maximum pressure differential limit on the fuselage.The pressure differential varies between aircraft types,typical values are between 7.8 psi (54 kPa) and 9.4 psi(65 kPa).[24] At 39,000 feet (12,000 m), the cabin pres-sure would be automatically maintained at about 6,900feet (2,100 m) (450 feet (140 m) lower than MexicoCity), which is about 11.5 psi (79 kPa) of atmospherepressure.[23]

Some aircraft, such as the Boeing 787 Dreamliner, havere-introduced electric compressors previously used onpiston-engined airliners to provide pressurization.[25] Theuse of electric compressors increases the electrical gen-eration load on the engines and introduces a number ofstages of energy transfer, therefore it is unclear whetherthis increases the overall efficiency of the aircraft air han-dling system. It does, however, remove the danger ofchemical contamination of the cabin, simplify engine de-sign, avert the need to run high pressure pipework aroundthe aircraft, and provide greater design flexibility.

4 Unplanned decompression

Main article: Uncontrolled decompressionUnplanned loss of cabin pressure at altitude is rare buthas resulted in a number of fatal accidents. Failures rangefrom sudden, catastrophic loss of airframe integrity (ex-plosive decompression) to slow leaks or equipment mal-functions that allow cabin pressure to drop undetected tolevels that can lead to unconsciousness or severe perfor-mance degradation of the aircrew.Any failure of cabin pressurization above 10,000 feet(3,000 m) requires an emergency descent to 8,000 feet(2,400 m) or the closest to that while maintaining terrainclearance (MSA), and the deployment of an oxygen mask

Passenger oxygen mask deployment

for each seat. The oxygen systems have sufficient oxygenfor all on board and give the pilots adequate time to de-scend to below 8,000 ft (2,400 m). Without emergencyoxygen, hypoxia may lead to loss of consciousness anda subsequent loss of control of the aircraft. The time ofuseful consciousness varies according to altitude. As thepressure falls the cabin air temperature may also plum-met to the ambient outside temperature with a danger ofhypothermia or frostbite.In jet fighter aircraft, the small size of the cockpit meansthat any decompression will be very rapid and would notallow the pilot time to put on an oxygen mask. Therefore,fighter jet pilots and aircrew are required to wear oxygenmasks at all times.[26]

On June 30, 1971, the crew of Soyuz 11, Soviet cosmo-nauts Georgy Dobrovolsky, Vladislav Volkov, and ViktorPatsayev were killed after the cabin vent valve acciden-tally opened before atmospheric re-entry. There had beenno indication of trouble until the recovery team openedthe capsule and found the dead crew.[27][28]

5 History

The aircraft that pioneered pressurized cabin systems in-clude:

5

• Packard-Le Père LUSAC-11, (1920, a modifiedFrench design, not actually pressurized but with anenclosed, oxygen enriched cockpit)

• Engineering Division USD-9A, a modified AircoDH.9A (1921 - the first aircraft to fly with the addi-tion of a pressurized cockpit module)

• Junkers Ju 49 (1931 - a German experimental air-craft purpose-built to test the concept of cabin pres-surization)

• Farman F.1000 (1932 - a French record breakingpressurised cockpit, experimental aircraft)

• Chizhevski BOK-1 (1936 - a Russian experimentalaircraft)

• Lockheed XC-35 (1937 - an American pressurizedaircraft. Rather than a pressure capsule enclosingthe cockpit, the monocoque fuselage skin was thepressure vessel.)

• Renard R.35 (1938 - the first pressurized piston air-liner, which crashed on first flight)

• Boeing 307 (1938 - the first pressurized airliner toenter commercial service)

• Lockheed Constellation (1943 - the first pressurizedairliner in wide service)

• Avro Tudor (1946 - first British pressurized airliner)

• de Havilland Comet (British, Comet 1 1949 - thefirst jetliner, Comet 4 1958 - resolving the Comet 1problems)

• Tupolev Tu-144 and Concorde (1968 USSR and1969 Anglo-French respectively - first to operate atvery high altitude)

• SyberJet SJ30 (2005) First civilian business jet tocertify 12.0 psi pressurization system allowing for asea level cabin at 41,000 feet.

In the late 1910s, attempts were being made to achievehigher and higher altitudes. In 1920, flights well over37,000 ft were first achieved by test pilot Lt. John A.Macready in a Packard-Le Père LUSAC-11 biplane atMcCook Field in Dayton, Ohio.[29] The flight was possi-ble by releasing stored oxygen into the cockpit, which wasreleased directly into an enclosed cabin and not to an oxy-genmask, which was developed later.[29]With this systemflights nearing 40,000 ft (12,000m)were possible, but thelack of atmospheric pressure at that altitude caused thepilot’s heart to enlarge visibly, and many pilots reportedhealth problems from such high altitude flights.[29] Someearly airliners had oxygen masks for the passengers forroutine flights.In 1921, a Wright-Dayton USD-9A reconnaissance bi-plane was modified with the addition of a completely en-closed air-tight chamber that could be pressurized with air

forced into it by small external turbines.[29] The chamberhad a hatch only 22 in (0.56 m) in diameter that wouldbe sealed by the pilot at 3,000 ft.[29] The chamber con-tained only one instrument, an altimeter, while the con-ventional cockpit instruments were all mounted outsidethe chamber, visible through five small portholes.[29] Thefirst attempt to operate the aircraft was again made byLt. John A. McCready, who discovered that the turbinewas forcing air into the chamber faster than the smallrelease valve provided could release it.[29] As a result,the chamber quickly over pressurized, and the flight wasabandoned.[29] A second attempt had to be abandonedwhen the pilot discovered at 3,000 ft that he was too shortto close the chamber hatch.[29] The first successful flightwas finally made by test pilot Lt. Harrold Harris, makingit the world’s first flight by a pressurized aircraft.[29]

The first airliner with a pressurized cabin was the Boeing307 Stratoliner, built in 1938, prior to World War II,though only ten were produced. The 307’s “pressure com-partment was from the nose of the aircraft to a pres-sure bulkhead in the aft just forward of the horizontalstabilizer.”[30]

World War II era flying helmet and oxygen mask

WorldWar II was a catalyst for aircraft development. Ini-tially, the piston aircraft of World War II, though theyoften flew at very high altitudes, were not pressurizedand relied on oxygen masks.[31] This became impracti-cal with the development of larger bombers where crewwere required to move about the cabin and this led to thefirst bomber with cabin pressurization (though restrictedto crew areas), the Boeing B-29 Superfortress. The con-trol system for this was designed by Garrett AiResearchManufacturing Company, drawing in part on licensing ofpatents held by Boeing for the Stratoliner.[32]

Post-war piston airliners such as the Lockheed Constel-lation (1943) extended the technology to civilian service.The piston engined airliners generally relied on electrical

6 7 FOOTNOTES

compressors to provide pressurized cabin air. Engine su-percharging and cabin pressurization enabled planes likethe Douglas DC-6, the Douglas DC-7, and the Constel-lation to have certified service ceilings from 24,000 ft to28,000 ft. Designing a pressurized fuselage to cope withthat altitude range was within the engineering and met-allurgical knowledge of that time. The introduction ofjet airliners required a significant increase in cruise alti-tudes to the 30,000–41,000 feet (9,100–12,500m) range,where jet engines are more fuel efficient. That increase incruise altitudes required far more rigorous engineering ofthe fuselage, and in the beginning not all the engineeringproblems were fully understood.The world’s first commercial jet airliner was the Britishde Havilland Comet (1949) designed with a service ceil-ing of 36,000 ft (11,000 m). It was the first time thata large diameter, pressurized fuselage with windows hadbeen built and flown at this altitude. Initially, the designwas very successful but two catastrophic airframe failuresin 1954 resulting in the total loss of the aircraft, passen-gers and crew grounded what was then the entire world jetairliner fleet. Extensive investigation and groundbreak-ing engineering analysis of the wreckage led to a num-ber of very significant engineering advances that solvedthe basic problems of pressurized fuselage design at alti-tude. The critical problem proved to be a combination ofan inadequate understanding of the effect of progressivemetal fatigue as the fuselage undergoes repeated stress cy-cles coupled with a misunderstanding of how aircraft skinstresses are redistributed around openings in the fuselagesuch as windows and rivet holes.The critical engineering principles concerning metal fa-tigue learned from the Comet 1 program[33] were ap-plied directly to the design of the Boeing 707 (1957) andall subsequent jet airliners. One immediately noticeablelegacy of the Comet disasters is the oval windows on ev-ery jet airliner; the metal fatigue cracks that destroyedthe Comets were initiated by the small radius corners onthe Comet 1’s almost square windows. The Comet fuse-lage was redesigned and the Comet 4 (1958) went on tobecome a successful airliner, pioneering the first transat-lantic jet service, but the program never really recoveredfrom these disasters and was overtaken by the Boeing707.Concorde had to deal with unusually high pressure dif-ferentials because it flew at unusually high altitude (up to60,000 feet (18,000 m)) and maintained a cabin altitudeof 6,000 ft (1,800 m).[34] This made the aircraft signifi-cantly heavier and contributed to the high cost of a flight.The Concorde also had smaller cabin windows than mostother commercial passenger aircraft in order to slow therate of decompression if a window failed.[35] The highcruising altitude also required the use of high pressureoxygen and demand valves at the emergencymasks unlikethe continuous-flow masks used in conventional airliners.

The designed operating cabin altitude for new aircraft isfalling and this is expected to reduce any remaining phys-iological problems.

6 See also• Aerotoxic syndrome

• Air cycle machine

• Atmosphere (unit)

• Compressed air

• Fume event

• Rarefaction

• Space suit

• Time of useful consciousness

7 Footnotes[1] Brain, Marshall (April 12, 2011). “How Airplane Cabin

Pressurization Works”. How Stuff Works. Retrieved De-cember 31, 2012.

[2] K. Baillie and A. Simpson. “Altitude oxygen calculator”.Retrieved 2006-08-13. - Online interactive altitude oxy-gen calculator

[3] Auld, D.J.; Srinivas, K. (2008). “Properties of the Atmo-sphere”. Retrieved 2008-03-13.

[4] “Commercial Airliner Environmental Control System:Engineering Aspects of Cabin Air Quality” (PDF).

[5] “Manufacturers aim for more comfortable cabin climate”.Flightglobal. 19 Mar 2012.

[6] “Bombardier’s Stretching Range on Global ExpressGlobal Express XRS”. Aero-News Network. October 7,2003.

[7] “Bombardier Global Express XRS Factsheet” (PDF).Bombardier. 2011.

[8] “Aircraft Environmental Control Systems” (PDF). Car-leton University. 2003.

[9] “Airlines are cutting costs – Are patients with respiratorydiseases paying the price?". European Respiratory Society.2010.

[10] FLIGHT TEST: Emivest SJ30 - Long-range rocket Re-trieved 27 September 2012.

[11] SJ30-2, United States of America Retrieved 27 Septem-ber 2012.

[12] “Final Policy FAR Part 25 Sec. 25.841 07/05/1996|At-tachment 4”.

[13] “FARs, 14 CFR, Part 25, Section 841”.

7

[14] “Exemption No. 8695”. Renton, Washington: FederalAviation Authority. 2006-03-24. Retrieved 2008-10-02.

[15] Steve Happenny (2006-03-24). “PS-ANM-03-112-16”.Federal Aviation Authority. Retrieved 2009-09-23.

[16] Gatland, Kenneth (1976). Manned Spacecraft (Seconded.). New York: MacMillan. p. 256.

[17] Gatland, p. 134

[18] Catchpole, John (2001). Project Mercury - NASA’s FirstManned Space Programme. Chichester, UK: SpringerPraxis. p. 410. ISBN 1-85233-406-1.

[19] Giblin, Kelly A. (Spring 1998). "'Fire in the Cockpit!'".American Heritage of Invention & Technology (AmericanHeritage Publishing) 13 (4). Archived from the originalon November 20, 2008. Retrieved March 23, 2011.

[20] Gatland, p. 264

[21] Gatland, p. 269

[22] Gatland, p. 278,284

[23] Commercial Airliner Environmental Control System “En-gineering Aspects of Cabin Air” Check |url= scheme(help).

[24] “Differential Pressure Characteristics of Aircraft”.

[25] “Boeing 787 from the Ground Up”

[26] Jedick MD/MBA, Rocky (28 April 2013). “Hypoxia”.goflightmedicine.com. Go Flight Medicine. Retrieved 17March 2014.

[27] TimeMagazine (12 July 1971). “Triumph and Tragedy ofSoyuz 11”. Time Magazine. Retrieved 20 October 2007.

[28] Encyclopedia Astronautica (2007). “Soyuz 11”. Encyclo-pedia Astronautica. Retrieved 20 October 2007.

[29] Cornelisse, Diana G. (2002). Splended Vision, Unswerv-ing Purpose; Developing Air Power for the United StatesAir Force During the First Century of Powered Flight.Wright-Patterson Air Force Base, Ohio: U.S. Air ForcePublications. pp. 128–129. ISBN 0-16-067599-5.

[30] William A. Schoneberger and Robert R. H. Scholl, Out ofThin Air: Garrett’s First 50 Years, Phoenix: Garrett Cor-poration, 1985 (ISBN 0-9617029-0-7), p. 275.

[31] Some extremely high flying aircraft such as the WestlandWelkin used partial pressurization to reduce the effort ofusing an oxygen mask.

[32] Seymour L. Chapin (August 1966). “Garrett and Pressur-ized Flight: A Business Built on Thin Air”. Pacific His-torical Review 35: 329–43. doi:10.2307/3636792.

[33] R.J. Atkinson, W.J. Winkworth and G.M. Norris (1962).“Behaviour of Skin Fatigue Cracks at the Corners ofWin-dows in a Comet Fuselage” (PDF). Ministry of Aviation.

[34] Hepburn, A.N. “Human Factors in the Concord”. Occu-pational Medicine, 17: 1967, pp. 47–51.

[35] Nunn, John Francis (1993). Nunn’s applied respiratoryphysiology. Butterworth-Heineman. p. 341. ISBN 0-7506-1336-X.

8 General references• Seymour L. Chapin (August 1966). “Garrett andPressurized Flight: A Business Built on ThinAir”. Pacific Historical Review 35: 329–43.doi:10.2307/3636792.

• Seymour L. Chapin (July 1971). “Patent Interfer-ences and the History of Technology: A High-flyingExample”. Technology and Culture 12 (3): 414–46.doi:10.2307/3102997. JSTOR 3102997.

• Cornelisse, Diana G. Splended Vision, Unswerv-ing Purpose; Developing Air Power for the UnitedStates Air Force During the First Century of Pow-ered Flight. Wright-Patterson Air Force Base, Ohio:U.S. Air Force Publications, 2002. ISBN 0-16-067599-5. pp. 128–129.

• Portions from the United States Naval Flight Sur-geon’s Manual

• CNN: 121 Dead in Greek Air Crash

9 External Links• Video with Cabin Pressurization Demo in Civil Air-craft on YouTube

8 10 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

10 Text and image sources, contributors, and licenses

10.1 Text• Cabin pressurization Source: https://en.wikipedia.org/wiki/Cabin_pressurization?oldid=675329469 Contributors: Robert Merkel,Patrick, Lexor, Anders Feder, Bueller 007, Jeffq, Kizor, Nurg, Rsduhamel, Dave6, Pavon, Wolfkeeper, Markus Kuhn, Mboverload, Cck-kab, Sonett72, Ericg, Gazpacho, Hydrox, Vsmith, Alistair1978, ESkog, Kilrogg, FirstPrinciples, Vystrix Nexoth, Hooperbloob, AnthonyAppleyard, BRW, Stephan Leeds, Drat, Gene Nygaard, Axeman89, Dismas, Unixxx, Woohookitty, Ben Liblit, Broquaint, GraemeLeggett,Factoid, Graham87, Rjwilmsi, Vegaswikian, Gene Wood, Komodon, Mariocki, Ysangkok, Kolbasz, Mathrick, YurikBot, Splintercellguy,RussBot, Gaius Cornelius, THB, Speculatrix, Phil Holmes, Airodyssey, Tim R, SmackBot, Unschool, Rebollo fr~enwiki, Mr john, Sax-Teacher, Commander Keane bot, Uxejn, Chris the speller, TimBentley, Agateller, RDBrown, Epastore, Gyrobo, Korte, Mikepurves, Kenkeisel, Underbar dk, Pilaftank, Wcleveland, Chingon, EditorASC, Khazar, Vgy7ujm, Jaganath, DeC, Ex nihil, Peter Horn, SmokeyJoe, In-quisitus, DabMachine, Gustavo.mori, Dkazdan, Dycedarg, Cydebot, Fnlayson, Headbomb, Rob.au, Shimada22~enwiki, Rees11, Rehnn83,Mack2, Steelpillow, CZMQFRG, Albany NY, Jetlife2, Myxoma, JNW, SHCarter, Fibrosis, BilCat, JaGa, Aeroweanie, Shawn in Montreal,Skrelk, Inwind, Petershen1984, Mark cummins, Gunnerdevil4, Seattle Skier, TXiKiBoT, Diamond20, Petebutt, Aspire3623WXCi, Nuance4, Wikiisawesome, Drutt, Willywonka12098, Ratsbew, SieBot, Strayan, Harry the Dirty Dog, YSSYguy, ClueBot, Garyzx, Bonchygeez,Socrates2008, Sun Creator, Qwfp, DumZiBoT, HIF-1A, Dthomsen8, Alansplodge, Dsimic, Addbot, M.nelson, Lightbot, Bkusmono, Rc-coms, Donfbreed, Triquetra, Elizgoiri, Starbois, AnomieBOT, Leyka~enwiki, Citation bot, .45Colt, Gammarian, This is ECS, Shadow-jams, GliderMaven, FrescoBot, Tavernsenses, Citation bot 1, Thinking of England, Full-date unlinking bot, DexDor, EmausBot, Justin-Time55, Sp33dyphil, ZéroBot, Enginesmax, Δ, , Jguy, Correctaboot, Mikhail Ryazanov, ClueBot NG, Siraustintatious, Helpful PixieBot, BG19bot, Rskurat, BattyBot, Cyberbot II, Zackoo77, Paul.levold, Reatlas, Zlelik2000, Monkbot, Laatu, Mfairchildsj30, Inkycallig,KasparBot, Exit Pursued by Bear, Mitnerf and Anonymous: 133

10.2 Images• File:B-8_winter_helmet_&_A-14_oxygen_mask_(1944).jpg Source: https://upload.wikimedia.org/wikipedia/commons/f/f7/B-8_winter_helmet_%26_A-14_oxygen_mask_%281944%29.jpg License: Public domain Contributors: http://www.nationalmuseum.af.mil/shared/media/photodb/photos/071026-F-1234S-020).jpg Original artist: USAF

• File:Empty_bottle_crushed_by_cabin_pressurization.jpg Source: https://upload.wikimedia.org/wikipedia/en/a/ae/Empty_bottle_crushed_by_cabin_pressurization.jpg License: PD Contributors: ? Original artist: ?

• File:Outflow.jpg Source: https://upload.wikimedia.org/wikipedia/commons/7/72/Outflow.jpg License: Public domainContributors: Ownwork Original artist: wsombeck

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