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Where is the merge discussion? I have started it here because it links here but the merge proposer needs to explain the arguement for it first.
This just doesn't happen on commercial jets, although maybe it's a problem for astronauts. When the pressure drops, you will exhale no matter how hard you try to keep it in. Sentence deleted.
If the reduced pressure after a decompression for hypothermia to set in, you're already dead. Sentence deleted.
Not really true: Pressurized aircraft are definitely not airtight, noise protection comes from the walls, and pressure does not protect from cold. Sentence deleted.
—Preceding unsigned comment added by 200.170.108.84 (talk) 22:10, 6 February 2008 (UTC)
What is the problem that led to the deletion (described above) of hypothermia and frostbite? Those airliners do have drop-down oxygen masks. The pressure problem is hardly any more than Everest (29,000 feet), so as long as they are breathing O-2 they are likely victims for hypothermia and frstbite unless the airline falls to a lower altitude. On another point (also above), as any SCUBA diver knows, a decrease in ambient pressure does not force you to exhale -- if you hold your breath you can be a victime of alveolar rupture and air embolism. I think both of these delitions should be reversed. The other one is correct.
Mythbusters tested this myth in their usual semi-scientific ways. Their findings are in no way proof.
"Semi-scientific" is too polite a term. "Mythbusters" uses methodologies and criteria for the public that are often outright contradictory to science (I can't watch it). Rapid decompression is a dependent on the size of the hole as well as the volume and pressure of the cabin - and the delta pressure (altitude). It can be calculated, but one can't make an absolute statement because pressure,cabin volumes, delta pressure (and window areas) are not uniform.
EditorASC (talk) 12:17, 28 August 2009 (UTC)
I decided to remove the following paragraph, along with its citation sources, for reasons to follow:
Neither source meets Wiki RS requirements. The first link goes to a source that requires you to sign up and pay, to read the entire article. The "free" teaser first part of the article provides no information that would act as a reliable source for the claim in that paragraph.
The second source amounts to a scandal sheet article, which is based on nothing more that anecdotal allegations from some cabin and flight crews. "Unnamed sources" said, or such and such reported that they got sick. Absolutely no valid scientific studies cited, in that rag article, which can verify that
I have researched this subject for many years and have read many studies from reputable sources, and none of them ever found that airliner cabin air was less than adequate for crew and passengers combined. In most cases, the cabin air in the typical airliner is fresher and totally exhausted and replaced, much faster than in the average office building. They did find that humidity tends to be low (3 to 5 % is typical), but also that CO2 has always been at less than regulatory limit levels, and that so-called "toxic" contamination from hydrualic fluid or engine oil is extremely rare, and even when that has happened, no evidence that it constituted a significant health threat. Further, that the percentage of available oxygen in the cabin atmosphere remains pretty much the same as at sea level. The modern ECS contain filters that effectively deal both with viruses and excessive ozone.
The truth is that flight attendant labor unions have used this myth allegation for years against the managements of their own airlines, as an "Industrial Action" tool, which is designed to put pressure on management, to settle union demands during contract negotiations. That is what these kinds of allegations have been, and are still about. Boeing ECS equipment and design has always met the standards of NASA, the FAA amd ICAO, among others, and there isn't one shred of valid scientific evidence that airliner cabin air is a threat to the health of anyone on board----unless, of course, a raging fire starts in the cabin, before landing.... EditorASC (talk) 03:33, 26 January 2010 (UTC)
Some people think that the Lockheed XC-35 was the first, and not the Boeing 307; However the first did not enter production.
[2] Dagoflores --189.166.14.226 (talk) 08:20, 12 January 2008 (UTC)
There seems to be disagreement between this article (stating that the XC-35 was the first pressurised aircraft) and that on the Junkers 49, which explicitly states it was the first, flying before the XC-35. Can someone who knows their stuff correct one or the other? —Preceding unsigned comment added by 78.86.228.109 (talk) 21:52, 21 January 2009 (UTC)
Does anyone know what the difference between the pressure in the cabin relative to the cargo area is? How much pressure is your luggage subjected to (if the pressure in the cabin is 0.7 bar? When does spray bottles break?
Thanks —The preceding unsigned comment was added by 63.240.133.93 (talk) 02:07, 16 March 2007 (UTC).
Most cabin cargo bins are pressurized, although there are exceptions. As for heating, some bins have their own heaters, and some receive residual heat from the passenger cabins. In the second case (residual heat), the bins can get chilly. Mikepurves (talk) 09:06, 26 July 2008 (UTC)
"An otherwise-harmless pinhole under these pressure differences will generate a high-pitched squeal as the air leaks out at supersonic speeds[citation needed]." --This does not seem right, because even assuming a complete vaccum (due to aerodynamic effects, if any) just outside the skin of the aircraft, the pressure differential is less than 10 PSI, and a pinhole in a car tire (30 psi) does not generate such a loud noise. —Preceding unsigned comment added by 200.170.108.84 (talk) 21:42, 6 February 2008 (UTC)
I join in the comment. The claim of air escaping at "supersonic speeds" seems implausible on its face. Sound is caused by the movement of molecules. The speed of sound is the upper limit. It appears that by definition, the upper speed limit of fluid escaping a pressure vessel would be the speed of sound, and that escaping air is not likely to hit that upper limit for the reasons stated above.
The only way to move a fluid above the speed of sound is to have a solid object strike it, physically pushing it out of the way.
I am not a physicist, but this appears to be basic fluid dynamics.
Mikepurves (talk) 08:56, 26 July 2008 (UTC)
This may have been sorted out in the article, but sonic flow through an orifice is a common occurrence. Supersonic flow is less likely and depends on specific geometry of the flow passage. See Choked flow. Cheers, • • • Peter (Southwood) (talk): 09:49, 21 July 2013 (UTC)
I don't have the data, but this blanket assertion is highly dubious. There are many variables which go into the rate of decompression.
First, all airliners are continously pumping in fresh air, and dumping pressurized air overboard. On virtually all jet transports, the engines pump pressurized air into the plane (the 787 will have a separate compressor system). "Outflow valves" leak the cabin air overboard, and the pressurization controller controls the rate in which the outflow valves leak the air overboard. All airliners have unintended leaks (some more, some less), and the pressurization controller closes the outflow valves more to compensate.
If the airplane suffers a large-enough hole, the outflow valves will close altogether while fresh air continues to be pumped into the plane. If the hole is too large, the airplane will begin to lose pressure (failure of all engines would have a similar effect as all incoming air would be shut off). Legend says (I cannot confirm this) that the Boeing 777 can maintain pressure with three windows out.
The total pressure vessel volume, the inside/outside pressure differential, the rate of air inflow and the rate of air outflow will determine how quickly an airplane will depressurize. A blanket statement that a 5' diameter hole causes instant decompression is far too oversimplified and almost certainly at odds with the facts. It fails to take into account different airplanes' cabin volumes (an Airbus 380 or a Boeing 747 has a bit more volume than, say a DC-9 or F-28), different engine, and the different cabin inflow and outflow configurations.
Finally, remember that a cabin which is not maintaining pressure ("leaking up") is not the same thing as an instant equalization with the ambient (outside) air pressure. To instantly equalize the pressure of a large volume of cabin air with the outside, the hole has to be massive, e.g., the airplane blown in half. A slower decompression allows plenty of time to address the problem while oxygen masks are deployed and a descent is started.
Mikepurves (talk) 06:13, 26 July 2008 (UTC)
Minor edit 7/31/08 Mikepurves (talk) 19:17, 31 July 2008 (UTC)
I've heard several reports, none independently verifiable as yet, that airlines routinely increase the cabin altitude during longhaul flights (e.g. after meals) in order to save fuel and to the settle the passengers down quicker by decreasing the amount of oxygen in the cabin (within allowable tolerances). Has anyone else come across this before? If so, do you have a reference please? Socrates2008 (Talk) 15:02, 5 September 2008 (UTC)
---
I am a former airline pilot for a US domestic airline. I have serious doubts that any US-based airline would do this, for the following reasons:
1. Pursuant to Federal Aviation Regulations, the airplane's cabin altitude must be kept below 8,000 feet. Because each flight's pressurization and depressurization puts stress on the pressure vessel (remember the Aloha airlines burst fuselage), and the greater the inside/outside pressure differential, the greater the stress, most airliners flying at their service ceilings will not be capable of a cabin altitude much lower than 8,000 feet. In other words, if the airplane is flying at its ceiling, the pilots don't have the discretion to raise the cabin, and the airplane doesn't have the physical capability of lowering it.
2. There are already health considerations associated with the reduced cabin pressure at altitude. Elderly people with pulmonary problems or circulation problems can develop health issues even under the normally lower air pressure at altitude, and flight diversions for these are more common than you might expect. Pregnant women may have problems with their fetuses. Any scuba divers on board are at an elevated risk of decompression sickness. People who have consumed too much alcohol have the effects magnified, and are more likely to cause the cabin crew or other passengers trouble. On any given flight, the pilots don't know whether anyone, or who, could be affected by one or more of these. Deliberately raising the cabin increases the risks to all of them. Doing so as an act of discretion would expose the pilots and the airline to lawsuits.
My guess is that it is an urban legend. It is extremely unlikely that any airline would authorize the practice. It is possible that some pilots, somewhere, have done this. If they had, it would have constituted extremely poor judgment on the pilots' part.
Mikepurves (talk) 17:23, 6 September 2008 (UTC)
As for "saving fuel" by reducing the volume of air in the cabin, I am unsure how that would work. The bleed air tapped off the engines to pressurize and heat or cool the cabin is a continuous process. Outflow valves at the back of the plane dump the air off, and the outflow valves (not the bleed air) directly regulate the pressure. The air is coming in anyway.
The only potential fuel savings would be by reducing the weight of the air in the cabin. How much weight difference there is between, say an 8,000' cabin and a 10,000' cabin I don't know (it would vary from plane to plane). I do know that the airlines are considering every available option to save fuel, and the idea might even have been batted around in an airline office somewhere. But since you would be breaking regulations and exposing your passengers and cabin crew to potential health problems, I just don't see it happening.
Airline managements and employees really do put their passengers' safety first: aviation gets dangerous very quickly if you do not.
The FAA's oversight of airlines is extremely close; every airline manager, every mechanic and every pilot and flight attendant gets to know the local "Feds" over time: they are regularly be observed in the process of doing their jobs. Flight records are pored over, and computer systems such as ACARS record flight parameters which are reviewed on a spot-check basis, and occasionally as part of a comprehensive investigation. When pilots fly their airplanes, two questions are continually running through their minds: Is what I am doing safe? And how do I explain it to management and to the FAA if they ask later -- am I adhering to company standards and FAA regulations, and showing the good judgment they expect of someone carrying 200 passengers with a $100 million piece of equipment? That internal dialog puts a stop to 98% of the "cowboy" actions that people might otherwise consider.
Finally, airlines are extremely sensitive to the public trust in their safety -- fear of news stories saying "airline risks passengers' health to save money" is a powerful motivator in this business. Because of aviation's high profile and a natural public fear of being high in the air but not in control, airlines know that aviation makes good press copy and raises circulation -- the press will report FAST on aviation matters, and the airlines don't want that kind of press. Every airline manager considers this all the time, and many employees do, too.
Mikepurves (talk) 17:50, 6 September 2008 (UTC)
I believe that this article has improved very considerably since rated start class and I have listed it for re-assessment at Wikipedia:WikiProject Aviation/Assessment. Ex nihil (talk) 00:27, 2 October 2008 (UTC)
Can I suggest using only fractions of atmospheres for the pressure units in this article? Bar/KPa are essentially this already but is there any reason that someone would need to know that the pressure is 12 psi? Wouldn't they then compare that to atmospheric pressure of 14.5psi? —Preceding unsigned comment added by Shniken (talk • contribs) 05:44, 4 June 2009 (UTC)
Re: "The low local partial pressure of carbon dioxide (CO2) causes CO2 to out-gas from the blood raising the blood pH and inducing alkalosis." The partial pressure of carbon dioxide at sea level is approximately 0.2 mm Hg (pressure at sea level = 760 mm Hg x percentage CO2 = 0.03%). The partial pressure of carbon dioxide in the alveoli of the lungs (and in arterial blood) is 40 mm Hg. Thus even at sea level the CO2 in the body is at almost 200 times that in the ambient atmosphere. The fall in carbon dioxide is mainly due to hyperventilation (increased rate and depth of breathing), caused by the low oxygen concentration at altitude. At very high altitudes it is irrelevant, as you will lose consciousness in seconds due hypoxia. —Preceding unsigned comment added by Mjwciw (talk • contribs) 10:04, 18 July 2009 (UTC)
"Pressurization is essential over 3,000 metres (9,800 ft) to prevent crew and passengers from becoming unconscious through the lack of oxygen (hypoxia) in the thin air above that altitude." This statement as it stands is nonsense. People do not become unconscious at 3000 meters. How do you think people live in Bolivia ? Eregli bob (talk) 12:08, 28 August 2009 (UTC)
Supplemental oxygen isn't required for crew or passengers unless above 15,000ft(cabin altitude). Obviously, there is a safety margin involved there. Most people will not actually lose consciousness until above 20,000ft(cabin altitude). — Preceding unsigned comment added by 65.36.69.148 (talk) 20:16, 14 November 2016 (UTC)
I have removed note # one, which read thus:
::"1. ^ Notable exceptions include the Airbus A380, Boeing 787 and Concorde"
For these reasons:
Here is how the subsequent paragraph currently reads:
Further exemptions of the "newly designed" planes should be added to that paragraph, with their verifying citations. EditorASC (talk) 01:38, 6 October 2009 (UTC)
Concorde had to deal with unusually high pressure differentials, as of necessity it flew at unusually high altitude (up to 60,000 ft) while the cabin altitude was maintained at 6000 ft."Human Factors in the Concord". This made the vehicle significantly heavier and contributed to the high cost of a flight. Concorde also had to have smaller than normal cabin windows to limit decompression speed in the event of window failure. [citation needed]
The pressure maintained within the cabin is referred to as the equivalent effective cabin altitude or more normally, the ‘cabin altitude’. Cabin altitude is not normally maintained at average mean sea level (MSL) pressure (1013.25 mbar, or 29.921 inches of mercury) throughout the flight, because doing so would cause the designed differential pressure limits of the fuselage to be exceeded. An aircraft planning to cruise at 40,000 ft (12,000 m) is programmed to rise gradually from take-off to around 8,000 ft (2,400 m) in cabin pressure altitude, and to then reduce gently to match the ambient air pressure of the destination. That destination may be significantly above sea level and this needs to be taken into account; for example, El Alto International Airport in La Paz, Bolivia is 4,061 metres (13,323 feet) above sea level.
This doesn't sound right. How does the controller know what the pressure is at La Paz or any other airport? Sounds like BS to me. If the altitude of an airport is above the rated altitude then the pressure controllers will try to maintain a pressure differential until the air supply is exhausted, i.e. engines shut down, when the pressure would gradually equalise. No need for BS.Petebutt (talk) 10:24, 16 March 2010 (UTC)
After doing a Google search for the FARs that limit operating altitude to FL400, this immediately came up: http://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgPolicy.nsf/0/90AA20C2F35901D98625713F0056B1B8?OpenDocument
It outlines that they have a new interim policy that allows a service ceiling of FL450. This is a 2006 document, and this page hasn't been updated with this information yet. I would do it if I were more familiar with the FAR approval process, but if this is currently in effect the information on this wiki page would be outdated. Could someone who knows who the FAA works please check this? 94.210.18.219 (talk) 10:28, 20 September 2010 (UTC)
I just had to revert a recent edit, because one editor inserted his comments in the middle of a paragraph that was written by another editor. That is improper---comments by one editor should not be altered or broken up by another editor. If one wants to comment on what another editor said, then copy it and show it as a quotation, to which you are responding. It is NEVER proper to break up or alter what another editor said, on a Wiki TALK PAGE! Only Administrators have the right to delete comments on Talk Pages, and then only for some violation of Talk Page posting rules.
Additionally, when quoting and then responding to what another editor said, it should be posted in the same section where the original quotation was posted. It makes for serious confusion to the rest of us, if you post a response in one section, to statements made by another editor, in an entirely different section.
Finally, any post should not cause the page to go way wide, i.e., your post should not force others to have to slide the page back and forth on the horizontal scale, to read it. If you see that your post did that to the page, then you should correct it yourself right away. Please do not leave messes for others to clean up. Thanks for your consideration. EditorASC (talk) 11:11, 16 March 2010 (UTC)
Bilcat removed the Notable incident tables! Having recovered from the shock of that and accepting it reluctantly as the right decision, most of the rest of this section also needs to go for the same reason, it is redundant, being dealt with in Uncontrolled decompression and prone to contradiction. Ex nihil (talk) 01:13, 21 April 2010 (UTC)
The "need for cabin pressurization" section doesn't make sense when it describes barotrama, because that section says that avoiding barotrama is one of the reasons that pressurizing flights is necessary, yet when it describes barotrama it only describes the symptoms of barotrama that people experience on pressurized flights. In contrast, the other three "illnesses" mentioned in that section appear to be described in terms of the symptoms that would be experienced on unpressurized flights above 3000 meters, which makes more sense in context.
While I think this information is important to present in some way and perhaps even expand on (i.e. many people experience ear pain from mild barotrama due to normal, controlled cabin pressure changes) the way it's presented in this section is strange.
69.181.161.106 (talk) 04:02, 6 January 2011 (UTC)
Interesting point: In naval aircraft and probably other types, insufficient cabin altitude can also cause tooth pain due to tiny pockets of air trapped in poorly done dental repairs.166.147.104.25 (talk) 21:14, 19 September 2013 (UTC)
At the beginning of the article is a sentence:
First, "cabin altitude" is used without any additional explanation, even if it is used as a pressure unit all over the article. Second, it used a capital "t" after a comma. Third, it tries to say too much in a single sentence. I begun to understand it only after the third reading. It needs a strong cleanup. --Xerces8 (talk) 20:43, 21 August 2011 (UTC)
I am wondering if Wikipedia has any rules or guidelines about when and how to name the crew members on accident flights? I have recently noticed that in some articles, no crew member names are given at all [here], and in other accidents, the full crew (both cockpit & cabin) are named [here], and in still others only the Captains and First Officers are named [here]. Is that disparity just the result of happenstance, as to who first writes an article, or is it by design? It would be helpful for some of us IP editors if someone can explain if there are some specific guidelines to follow, on this aspect of aviation accident articles. Thank you, 66.81.52.230 (talk) 11:02, 23 October 2011 (UTC)
I'm assuming that both the passenger cabin and the freight space on an airliner are pressurized. If so, there is an anomaly. Passenger doors open inwards to help ensure cabin pressure keeps the doors closed, but the undercarriage doors (undercarriage is often partly or completely retracted within the fuserlarge, esp nose wheel) open outwards creating a greater risk. It would also require the cabin to be depressurised before lowering undercarriage (not unreasonable). Is this right, or is the freight space not pressurised (the cabin floor looks to me to be stronger than the cabin wall)? Presumably one of you experts know the answer and can add it to the article for completeness.FreeFlow99 (talk) 19:03, 15 November 2012 (UTC)
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I changed a sentence under "Aircraft" to correctly reflect the content in the reference that was cited for it. The reference clearly says that the Boeing 747 carries a relatively high cabin pressure (CP), or equivalently a relatively low equivalent cabin pressure altitude, than the Airbus A380. The sentence said the reverse, and included a cabin altitude figure for the Boeing 747 that was simply fictitious, not based on any source at all.
This edit was reverted by Ex nihil with the explanation "Change, and the article, refers to operational decisions by airlines and not to the design CP by manufacturers" but this doesn't make any sense. If the "design CP" for the 747 was as low as was implied by the original statement that I changed, it would not be possible for airline "operational decisions" to produce the higher pressure / lower pressure altitude described in the reference.
Looking around online for more information on this topic, I found [4]. I can't really say that this website is a reliable source, but it does show that the 747 has a higher maximum pressure differential than the A380 (8.9 psi vs 8.6 psi), which is consistent with the facts as described in the existing reference.
So I think my original edit here is solid and should not be reverted again without citing a source of information that contradicts it. 71.197.166.72 (talk) 01:57, 12 December 2015 (UTC)
I don't think this article explains the reason to use a cabin pressure less than sea level. Does it really reduce stress on the airframe? Is it to save weight (several hundred kilos)? — Preceding unsigned comment added by 106.68.193.191 (talk) 03:03, 14 January 2016 (UTC)
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In the introduction, the article appears to mis-state the cause of the Aloha 243 incident. There was no pre-existing Boeing design limitation on number of cycles that the airframe was designed to endure. Boeing and Aloha both knew the cycles the aircraft had accumulated, and it was not out of specification. Rather, poor inspection and maintenance of the fuselage was the cause, which would have detected the fatigue cracks. If there is no objection, I will delete the Aloha 243 sentence from the introduction. --Westwind273 (talk) 16:39, 3 March 2022 (UTC)
The first image caption says, An airliner fuselage, such as this Boeing 737, forms a cylindrical pressure vessel
. It's certainly true that most airliners are cylinders, but not all. Counter-examples include Airbus A380 and Boeing 377 Stratocruiser. We shouldn't be introducing (unsourced) new information in image captions which doesn't appear anywhere in the main text, and we shouldn't be implying that all airliners are cylinders. This needs a WP:RS and a better discussion. -- RoySmith (talk) 17:39, 24 July 2022 (UTC)