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Pressurization  
User currently offlineAlitaliaORD From United States of America, joined Aug 2003, 242 posts, RR: 0
Posted (10 years 11 months 1 day 5 hours ago) and read 4857 times:

What does it actually mean to lose cabin pressure. I always used to think it meant there was a hole in the plane while it was in flight. What happens as a result of losing cabin pressure? For anyone who has ever been on a flight when this sorta of thing has happened is it noticible? Can it be restored after it has been lost?


Joy To The World, All The Boys and Girls, Joy to the Fishes in the Deep Blue Sea, Joy to You and Me
28 replies: All unread, showing first 25:
 
User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 1, posted (10 years 11 months 1 day 5 hours ago) and read 4808 times:

When the Oxygen Masks come down, you tend to notice it then.

DLKAPA


User currently offlineFritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2
Reply 2, posted (10 years 11 months 1 day 5 hours ago) and read 4793 times:

"What happens as a result of losing cabin pressure?"

The air pressure inside the cabin will decrease, as the air pressure outside the aircraft is lower than inside, during flight of course.
The pilots will decent to around 14,000 feet immedietly so that you wont pass out from hypoxia.


User currently offlineAlitaliaORD From United States of America, joined Aug 2003, 242 posts, RR: 0
Reply 3, posted (10 years 11 months 1 day 5 hours ago) and read 4781 times:

DLKAPA,
hahaha, i meant can you feel changes (besides difficulty of breathing)



Joy To The World, All The Boys and Girls, Joy to the Fishes in the Deep Blue Sea, Joy to You and Me
User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 4, posted (10 years 11 months 1 day 5 hours ago) and read 4738 times:

14,000, hell I could breathe without the Oxygen mask at that altitude, and I have before, climbing Mt Elbert, at 14,334 ft.

DLKAPA


User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 5, posted (10 years 11 months 1 day 3 hours ago) and read 4702 times:

I was on a jumbo frieghter in 90 when an R5 window blew out while climbing through 21000. I felt the pressure change in my ears. The aircraft pressurization system "caught up" to the pressure loss and tried to maintain the pressurization schedule. Of, course we turned around and went right back into JFK to get it looked at.

It really wasn't un-comfortable at all. We never went on O2 because the aircraft was able to stabilize the pressure.


User currently offlineFritzi From United Arab Emirates, joined Jun 2001, 2762 posts, RR: 2
Reply 6, posted (10 years 11 months 1 day 1 hour ago) and read 4605 times:

DLKAPA,

Thats why they decend to that altitude!

The use of O2 masks will not be necessary then.


User currently offlineLiamksa From Australia, joined Oct 2001, 308 posts, RR: 0
Reply 7, posted (10 years 11 months 23 hours ago) and read 4583 times:

For anyone who has ever been on a flight when this sorta of thing has happened is it noticible?

An explosive decompression in the cruise definitely won't go unnoticed. The air will be forced out of your lungs, the partial pressure of oxygen won't be high enough to get any oxygen into the bloodstream (hypoxia) and you'll have a time of useful consciousness of around 15 seconds (FL400).

The less severe case is the slow loss of cabin pressure which would probably go unnoticed by passengers initially. Indications to the flight crew would be a positive rate of climb on the cabin VSI accompanied by (obviously) an increasing cabin altitude indication. Modern aircraft have a built in warning system which alerts the crew when the cabin altitude exceeds a preset value.

On the photo below you can see the cabin altimeter and VSI:

View Large View Medium
Click here for bigger photo!

Photo © John Miller



Rob.


User currently offlineInbound From Trinidad and Tobago, joined Sep 2001, 851 posts, RR: 2
Reply 8, posted (10 years 11 months 20 hours ago) and read 4546 times:

I thought O2 supply followed this rule...??

human body can survive for 30 minutes at 10,000 feet.
and nothing past 13,000 feet.

or is that just for Canadian standards?



Maintain own separation with terrain!
User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 9, posted (10 years 11 months 17 hours ago) and read 4532 times:

When climbing Mt Elbert I was above 13,000 for almost Four hours.

DLKAPA


User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 10, posted (10 years 11 months 12 hours ago) and read 4511 times:

And the pressure in your bowels will be way higher than ambient... that you'll notice as well, but chances are you will be too preoccupied to care much.

Ah, the glamour!

Cheers,
Fred



I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlinePilotpip From United States of America, joined Sep 2003, 3152 posts, RR: 10
Reply 11, posted (10 years 11 months 8 hours ago) and read 4489 times:

Your ears and bowels can tell you the difference in as few as a thousand or less feet. Flying light aircraft that aren't pressurized will make you an expert at popping your ears and letting out a timely burp, or worse  Big thumbs up

DLKAPA, Many people don't have the luxury of having that sort of ability. People with health problems, smokers, and people like me, who live at a low altitude often can't handle high alitude environments like that. I've seen a guy start getting hypoxic at 6,000 feet. I consider myself to be in decent shape. I work out at least 3 times per week and durning the summer I ride my bicycles as much as 200 miles per week. I have no trouble doing this around St. Louis, about 500ft MSL. However, when I took a trip to Utah a couple years ago and was riding regularly at over 7,000 feet I found myself much more fatigued after a ride than I do at home.



DMI
User currently offlineBMAbound From Sweden, joined Nov 2003, 660 posts, RR: 4
Reply 12, posted (10 years 10 months 3 weeks 5 days 1 hour ago) and read 4376 times:

I spent 3.5 hrs flying unpressurized at 12000 ft.

I think I was alive most of the time.

johan



Altitude is Insurance - Get Insured
User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6536 posts, RR: 54
Reply 13, posted (10 years 10 months 3 weeks 5 days ago) and read 4384 times:

Rules of thomb for playing safe with complete pressure loss:

Below 15,000 ft: No problem.

15,000 to 25,000 ft: You are on O2 and descend to 15,000 before O2 supply runs out.

25,000 to 50,000 ft: You are on O2 and descend below 25,000 ft. ASAP.

Above 50,000 ft: Better wear at least a partial pressure suit, or you are in danger.

And finally above some 65,000 ft: You wear full pressure suit (space suit), or your blood boils and kills you instantly.

Happy landing, Preben Norholm



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineSovietjet From Bulgaria, joined Mar 2003, 2648 posts, RR: 17
Reply 14, posted (10 years 10 months 3 weeks 4 days 7 hours ago) and read 4257 times:

Why does blood biol over 65000 feet? At 40000 the temperature is like -55 degrees celsius does it rise to boiling in 25000 feet?

User currently offlineBen From Switzerland, joined Aug 1999, 1391 posts, RR: 50
Reply 15, posted (10 years 10 months 3 weeks 4 days 4 hours ago) and read 4233 times:

Sovietjet,

The boiling point is related to atmospheric pressure.

As the pressure decreases, the boiling point also decreases.

For instance, at an altitude of 10,000 feet (lower pressure), the boiling point of water is about 10 degrees celsius colder than at sea level (higher pressure). There are anecdotes about not being able to make a good cup of coffee or boil an egg when camping on high mountains.. basically, the water will be boiling at a lower temperature and wont cook the egg as fast (I don't understand the relevance to coffee tho)

If you take that analogy to it's logical end and take the water up to 60,000 feet or beyond, it will boil at lower and lower temperatures until it boils at only a few degrees. Same with blood, which if you aren't asphyxiated already, will be at about +37 degrees C, not -55.

There is a calculator on this page that shows boiling points of water, but it only does imperial measures sorry. http://www.biggreenegg.com/boilingPoint.htm


User currently offlineL-188 From United States of America, joined Jul 1999, 29832 posts, RR: 58
Reply 16, posted (10 years 10 months 3 weeks 3 days 18 hours ago) and read 4174 times:

Same with blood, which if you aren't asphyxiated already, will be at about +37 degrees C, not -55.

You are thinking of the Armstrong line, can't recall what altitude that actually occurs at.


Think if it as an extreme case of the bends, the gasses in your blood boil out because the atmospheric pressure isn't there.



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineDelta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 6
Reply 17, posted (10 years 10 months 3 weeks 2 days 17 hours ago) and read 4094 times:

Preben ... at 37C, what would be the boiling pressure of blood? Water would not boil at that temperature even at zero pressure, and I don't think blood would either. You would need a pressure suit only if you are going to be exposed to reduced or zero gravity in addition to low pressure.

Pete


User currently offlineL-188 From United States of America, joined Jul 1999, 29832 posts, RR: 58
Reply 18, posted (10 years 10 months 3 weeks 2 days 14 hours ago) and read 4082 times:

Pete and Preben.

Blood boiling has nothing to do with temperture and everything to do with altitude.

All fluids have some amount of gas in them, if you take a fluid with a pressure and suddenly lessen the pressure, those gases will come out of solution violently. Do you want to see a real time example of this? Get a can of Soda, Pop, Seltzer water and pop the top, those bubbles are carbon dioxide gas comming out of the solution because the pressure in the can has suddenly been reduced to atmospheric and the gasses are comming out of solution.


Man in pressure suit in altitude chamber in which the pressure has been lowered to 63000 feet. The beaker holds ordinary water.


For human blood the equivlent pressure altitude is known as the Armstrong Line, like I mentioned in my earlier post. I have seen did a little checking and found out that for human blood will "boil" at 63000 feet depending on the circumstances.

But keep in mind your not going to exlode like you see in some space movies, what you end up with is the aeronautical equivelent of a case of the bends that divers get.

Same idea, they go down to a depth (higher pressure) their blood gets gasses in it at that same pressuere, when they come up they have to stop at various depths to give their blood a chance to get used to the lower pressure.

That is why they say you shouldn't fly after you dive.

Here are a couple of links to help you figure it out.

http://www.sff.net/people/Geoffrey.Landis/vacuum.html

http://www.sff.net/people/Geoffrey.Landis/ebullism.html





OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 19, posted (10 years 10 months 3 weeks 2 days 14 hours ago) and read 4084 times:

Delta-flyer

…at 37C…Water would not boil...even at zero pressure...I don't think blood would either…

The pressurized aircraft we have today are a direct result of the pioneering work done by Dr Harry Armstrong at Wright Field in the late 1930’s.

It was there he discovered, amongst other things, that at 63,000 feet pressure altitude, blood will boil at body temperature, an altitude limit still know to this day as the Armstrong Line.

If you would like to know more about Dr Armstrong try this link:

http://www.nationalaviation.org/museum_enshrinee.asp?eraid=4&enshrineeid=329


Regards

Bellerophon


User currently offlineL-188 From United States of America, joined Jul 1999, 29832 posts, RR: 58
Reply 20, posted (10 years 10 months 3 weeks 2 days 14 hours ago) and read 4078 times:

Bellerphon, thanks for the historic notes.

But i can't get that link to work.

Use this one instead.

http://www.nationalaviation.org/website/index.asp?webpageid={F3401AC2-408C-42A7-AD0F-CDDC7942F110}&eID=329



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineDelta-flyer From United States of America, joined Jul 2001, 2676 posts, RR: 6
Reply 21, posted (10 years 10 months 3 weeks 2 days 7 hours ago) and read 4048 times:

L-188 .... I can buy the dissolved gas theory -- I didn't think of that, although I should have, as I suffer with it regularly in the context of dissolved air in hydraulic fluid coming out of solution when the inlet pressure to a pump is reduced.

Bellerphon, thanks for the info ... I couldn't open the link, either. In any event, as I said, I overlooked the dissolved gas content of blood. I don't disagree with Preben's comments in that case.

Pete


User currently offlineBellerophon From United Kingdom, joined May 2002, 585 posts, RR: 59
Reply 22, posted (10 years 10 months 3 weeks 1 day 22 hours ago) and read 4013 times:

L-188

Thanks for your help with the link.

Regards

Bellerophon


User currently offlineDrJetMech From United States of America, joined Jan 2004, 44 posts, RR: 0
Reply 23, posted (10 years 10 months 3 weeks 1 day 6 hours ago) and read 3944 times:

I was on a flight from Tinker AFB heading to Turkey, about an 18 hr flight and 2 in-flight refuels. Well, I was sleeping about 4 hours into the flight and all of a sudden I hear a loud bang. I woke up and my ears were hurting, I looked around and all the flight crew had put on there O2 masks. whatt happened was the Auto mode of the press. controller had fualted and opened the outflow valve to full opened in a hurry.
The flight eng. performed the correct actions and went to manual mode and closed the outflow valve even faster. The whole ordeal took no more than 2 minutes, but I did start feeling a little woozy becuase by the time I realized what had happened it was to late to put on O2. It was on a boeing 707 E-3 AWACS, the best looking A/C flying today.


User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6536 posts, RR: 54
Reply 24, posted (10 years 10 months 3 weeks 1 hour ago) and read 3840 times:

I have been away from this thread for some days, and it really surprises me that it is not common knowledge that water boils at +37C at extreme altitude pressure.

In fact water (H2O) acts exactly the same way as carbon dioxcide (CO2). Only the temperature values are different. With CO2 we can observe the process at ambient temperature at sea level atmospheric pressure.

CO2 freezes to white ice at around -70C (H2O at zero). In a telescope we see the CO2 atmosphere on Mars freeze on the North and South poles as Martian winter and summer alternates.

Our bar tender keeps it as a liquid in a pressurized container, but when he blows it into our drink, then it boils.

Same way we can take butane gas (C4H10) as used in a cigaret lighter. It boils at normal ambient temperature and that way builds up pressure so it can be kept in liquid state in the lighter.

But put the lighter into your freezer, and then try to light it. It won't. C4H10 boils at sea level pressure at just around zero degrees C, so no gas will flow when the valve is opened on your frozen lighter.

The gasoline you put on your car is basically a mixture of C6H14 and more complex hydrocarbon molecules which boils at between roughly +40 and +200C. It needs the heat from the compression in the cylinder to boil and evaporate so the spark plug can ignite it.

But back to the Armstrong line: Well above 60,000 feet your blood will boil. Steam bobbles will form and obstruct the blood flow within you brain, and you will die very quickly.

At such altitude a pressure suit (space suit) or pressurized cabin is absolutely mandatory for man to survive.

Happy landing, Preben Norholm



Always keep your number of landings equal to your number of take-offs, Preben Norholm
25 OE-LDA : I have to disagree with Preben Norholm: Altitudes between FL100 and FL 150 cannot be described as "no problem". In fact, everything above FL 100 has t
26 Delta-flyer : I have been away from this thread for some days, and it really surprises me that it is not common knowledge that water boils at +37C at extreme altitu
27 Vikkyvik : According to the standard atmosphere tables in one of my textbooks, the pressure at 65,000 feet is 118.93 psf, or 0.826 psi. Outside air temp is ~ -56
28 Post contains images Prebennorholm : Thanks OE-LDA for the detailed information. Sure your data are valid. When I wrote "Below 15,000 no problem", then I was more or less thinking about t
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