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How To Fly An Airliner If Pressurization Fails?  
User currently offlineA380900 From France, joined Dec 2003, 1102 posts, RR: 1
Posted (9 years 5 months 3 weeks 1 day 4 hours ago) and read 5004 times:

What would be the characteristic of a fly without pressurization for a jetliner?

What altitude should it be? What speed? Is it specified in the operating handbook for all aircraft?

How often are such flights performed?

[Edited 2005-02-04 18:26:39]

22 replies: All unread, jump to last
 
User currently offlineAirWillie6475 From United States of America, joined Jan 2005, 2448 posts, RR: 1
Reply 1, posted (9 years 5 months 3 weeks 1 day ago) and read 4904 times:

The highest that a human can legally fly without oxygen aid is 15k feet and only about 30 minutes at that altitude. Also I think at night the altitude limit is lower.

User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 2, posted (9 years 5 months 3 weeks 1 day ago) and read 4893 times:

Normally, if you lose cabin pressure you're going to descend to atleast 14,000 feet, 10,000 feet if possilbe. Most likely you would divert to the closest airport at that point.

If it were an explosive decompression, you would have some people who experienced some minor injuries and you'd want to get them on the grouned.

There is no speed restriction, assuming you haven't had structural damage. And these flights aren't all that common. An aircraft can't be dispatched with the cabin pressure system in op. However, I have ferried several aircraft that have sustained damage from jetways, catering trucks, fuel trucks, etc. In these situations the flights were with no pax and unpressurized. In most cases, there was no speed restrictions. Sometimes, in the case of an aircraft that has damage to say a cargo door, the mfg will put an airspeed restriction as part of the ferry permit.


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 3, posted (9 years 5 months 3 weeks 23 hours ago) and read 4861 times:

As loss of pressurization is a symptom rather than a fault in and of itself, I'd say it depends.

There are two major possibilities; with or without structural damage.

If you have nothing more than the inability to control cabin pressure (outflow valve stuck open for example) you must get down to an altitude that permits passengers to remove their little yellow nosebags, and then you must find a suitable place to land and fix it.

If a door blows off or a bulkhead ruptures you want to do these things in such a way as to not add any stress to the airframe.

In any event you are not going to be overflying a suitable airport to proceed.

You probably don't have enough fuel.
You might have other problems.
etc.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineBobster2 From , joined Dec 1969, posts, RR:
Reply 4, posted (9 years 5 months 3 weeks 23 hours ago) and read 4836 times:

This is a pretty good article on the subject. It includes the story of the BAC-111 captain who got partially blown out of the plane when a window popped out and the crew members had to hold on to his feet until they landed.

http://www.casa.gov.au/avreg/fsa/download/00mar/page42-44.pdf


User currently offlineLeanOfPeak From United States of America, joined Oct 2004, 509 posts, RR: 1
Reply 5, posted (9 years 5 months 3 weeks 23 hours ago) and read 4833 times:

I believe the question was about unpressurized ferry flights.

They tend to be done when there is an uncertainty about either the structural soundness of the pressure vessel, the capabilities of the pressurization system, or both and the aircraft needs to be repositioned where there is equipment better suited for the diagnosis and/or repair of the situation.

As long as the flight crew and any passengers aboard (Generally engineers or mx workers, not paying passengers) are willing to wear oxygen masks, I would anticipate the flight envelope to be affected more by the underyling reason for the flight being undertaken unpressurized than by the fact that the flight was being undertaken unpressurized. The one significant point is that the cabin pressure is no longer a reliable means of keeping plug doors secure, and all must be properly latched.

If for some reason supplemental oxygen is not to be used, then the altitude restrictions above would come into play.


User currently offlineBobster2 From , joined Dec 1969, posts, RR:
Reply 6, posted (9 years 5 months 3 weeks 22 hours ago) and read 4822 times:

If the ferry flight is at normal altitude, wouldn't it be very cold inside? Is there heated air without pressurization?

And the article I cited above says there is a risk of decompression illness after exposure to altitudes above 18000 ft.

[Edited 2005-02-05 00:18:51]

User currently offlineWoodreau From United States of America, joined Sep 2001, 1020 posts, RR: 6
Reply 7, posted (9 years 5 months 3 weeks 22 hours ago) and read 4807 times:

I was wondering about the temp as well...

Any of the pax wouldn't be using the oxygen that comes from the overhead since it only provides oxygen for a very limited time. I think just enough to get the aircraft down to an altitude below 12,500ft.




Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 8, posted (9 years 5 months 3 weeks 22 hours ago) and read 4800 times:

You will not be carrying paying passengers on an upressurized flight.

Just because we cannot control the cabin altitude does not mean we don't have temperature control. We may be able to use the packs.

Once, out of curiosity I ferried a plane with the temperature controller set at full cold, then backed off just off the stop. (I don't like to operate machines against the stops.)

Took off out of an 85 or so degree airport. After an hour and ten minutes of flight and a landing at a 70 degree airport, the cabin temp was only down in the mid 50s.

On the other hand I once saw an ONA DC-9 freighter bring in a load of live penguins for SeaWorld. That cabin was cold. The pilots were wearing some kind of warm suits.





Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineAir2gxs From , joined Dec 1969, posts, RR:
Reply 9, posted (9 years 5 months 3 weeks 22 hours ago) and read 4791 times:

We have flown unpressurized revenue flights before (cargo). We don't like to do it, but if you don't have a spare aircraft, you do what you can. The flight is slower, lower and costs a whole in fuel. Also requires quite a bit of coordination with enroute ATC.

User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 10, posted (9 years 5 months 3 weeks 20 hours ago) and read 4769 times:

On 747, I have done several flights unpressurized. I remember the last one from MAN-LUX to have the aft cargo door fixed after the ground handling agent tried to close the door on the loader. Didn't quite make it.

The flight was planned at 110 and 320 kias. No packs and the cockpit was actually quite stuffy.

There was no speed restriction, no revenue payload (people or cargo). Nice way to sightsee along the way.


User currently offlineInbound From Trinidad and Tobago, joined Sep 2001, 851 posts, RR: 2
Reply 11, posted (9 years 5 months 3 weeks 18 hours ago) and read 4736 times:

On the Dash8, engage autopilot if it isn't already on, don oxygen masks and initiate an emergency descent.

simultaneously, turn 45degrees off course for 1 minute,then turn back to original heading to parallel the airway.

declare and emergency and descend to 14,000' or 10,000' if available.



Maintain own separation with terrain!
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 12, posted (9 years 5 months 3 weeks 18 hours ago) and read 4737 times:

For a long time here in the US we practiced emergency descents in the simulator by making a turn off course before starting down. The idea was to get off the airway.

It took the training departments a lot longer than it took line pilots to realize that you were as likely to turn into traffic as you were away from it. Not all traffic is on YOUR airway. Once they finally got it, you get a clearance for any turn or descent.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 13, posted (9 years 5 months 3 weeks 14 hours ago) and read 4680 times:

The flight was planned at 110 and 320 kias. No packs and the cockpit was actually quite stuffy
What is the Altitude flown normally.
regds
MEL



Think of the brighter side!
User currently offlinePhilSquares From , joined Dec 1969, posts, RR:
Reply 14, posted (9 years 5 months 3 weeks 13 hours ago) and read 4679 times:

Hawk21M,

The normal altitude would have in the upper 30's. So there was quite a big difference.



User currently onlineSilver1SWA From United States of America, joined Mar 2004, 4769 posts, RR: 26
Reply 15, posted (9 years 5 months 3 weeks 11 hours ago) and read 4658 times:
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This is interesting to me. I do know of one flight about 4 months ago that did fly a revenue flight from SJC-LAX at 10000 feet because of pressurization problems on the flight before. Just took a bit more fuel that's all...


ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
User currently offlineMandala499 From Indonesia, joined Aug 2001, 6761 posts, RR: 76
Reply 16, posted (9 years 5 months 3 weeks 3 hours ago) and read 4576 times:

What's annoying is when you have to fly a plane with a problematic outflow valve that won't keep the pressure in... when you descend, u gotto keep the thrust above flight idle... can give an intesting ASI figure sometimes... like 330KIAS (a 732)! LOL, well somewhere near the barberpole! Gotta do it otherwise the pax might start passing out!

Mandala499



When losing situational awareness, pray Cumulus Granitus isn't nearby !
User currently offlineAirplay From , joined Dec 1969, posts, RR:
Reply 17, posted (9 years 5 months 3 weeks 2 hours ago) and read 4559 times:

There was an incident years ago with a Crossair SAAB 340 that had the outflow valve freeze up. It's failure caused the cabin to dump. Unfortunatly, the airplane was over the Alps in an area where they couldn't descend immediatly. Since there is no pax oxygen in the SAAB 340 (not required for airplanes who's ceilings are 25,000 feet or less) the passengers suffered some oxygen starvation.

Nobody was killed or seriously injured but it did cause an AD and subsequent re-design. The outflow valves were moved from the tail cont to the rear cabin bulkhead. A tube was added between the outflow valve and the tailcone.

Many modern aircfraft (including the SAAB 340) have a limited amount of cabin pressure available from a ram-air source. Of course it doesn't help if the outflow valve is open or there is a hole in the side of the fuselage.

A great many modern airliners are built to very stringent standards with respect to depressurization. Any airliner with a max certified ceiling above 410 has been required to meet additional "high altitude" airworthiness standards where the calculated probability of a depressurization due to system malfunction or structural failure is extremely remote. These newer "high altitude" fuselages have very miniscule leak rates under normal conditions.



User currently offlineInbound From Trinidad and Tobago, joined Sep 2001, 851 posts, RR: 2
Reply 18, posted (9 years 5 months 2 weeks 6 days 18 hours ago) and read 4473 times:

SlamClick,
Seeing as we still follow some older british based regulations during our training in the caribbean, even at the sim in toronto, I wouldn't doubt that a new regulation exists that allows you to descend through your own airway.

but with the new RVSM regs in effect, it might be twice as possible to collide with traffic on your airway now as compared to those who may be off of it.

perhaps?



Maintain own separation with terrain!
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 19, posted (9 years 5 months 2 weeks 6 days 14 hours ago) and read 4444 times:

What would the Max Altitude be in a Commercial Aircraft [eg B737] if it has to Ferry fly from A to B with U/s Pressurisation & Oxygen system.
regds
MEL



Think of the brighter side!
User currently offlineLongHauler From Canada, joined Mar 2004, 4913 posts, RR: 43
Reply 20, posted (9 years 5 months 2 weeks 6 days 6 hours ago) and read 4416 times:

HAWK21M, for extended periods, without oxygen, the maximum altitude would be 10,000 feet. I did it once in the DC-9 from YQB to YYZ.

No passengers, and not all that cold, it was July, but as mentioned above, it was very stuffy and humid.



Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night
User currently offlineOPNLguy From , joined Dec 1969, posts, RR:
Reply 21, posted (9 years 5 months 2 weeks 6 days 5 hours ago) and read 4396 times:

>>>What would the Max Altitude be in a Commercial Aircraft [eg B737] if it has to Ferry fly from A to B with U/s Pressurisation & Oxygen system.

It also depends upon what you're authorized for....

For unpressurized ferries, we usually stay at 9,000 or 10,000 depending upon direction of flight, but if MEAs/terrain are an issue, we have the option of operating up to 17,000 (with the flightcrew on oxygen) not to exceed one hour's time between 10,000 and 17,000.

Unpressurized revenue flights at/below 10,000 are rare, but still possible in some cases, as long as pax count is low (for cabin temp considerations) and that MEAs can be complied with. The flight that Silver1SWA mentioned in post #15 is a good example, and SJC-LAX is one leg where it's possible to be done. You wouldn't have the same luck coming out of RNO...  Big grin


User currently offlineL-188 From United States of America, joined Jul 1999, 29791 posts, RR: 58
Reply 22, posted (9 years 5 months 2 weeks 4 days 21 hours ago) and read 4260 times:

Assuming that nothing else in the equasion changes. It will fly just the same, except maybe lower and slower, or under the mask.


OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
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