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Most Common Causes For Cabin Pressure Changes  
User currently offlineKing767 From , joined Dec 1969, posts, RR:
Posted (13 years 2 months 4 weeks 1 day 23 hours ago) and read 3300 times:

Hello,
I was just wondering, other than ageing pressure bulkheads, what are the main causes for inflight cabin pressure changes.

Thanks alot,
Tom

18 replies: All unread, jump to last
 
User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 1, posted (13 years 2 months 4 weeks 1 day 19 hours ago) and read 3241 times:

I'm assuming you are asking about pressurized aircraft.

Don't know what you mean by ageing pressure bulkheads, but pressurization changes are regulated by the outflow valve(s) which, in modern aircraft, are operated by computer driven pressurization controllers.

The reason for pressurization changes is usually a change in the aircraft operating altitude.

If you can be more specific with your inquiry, you'll get lots more detail from many others besides me!

Best Regards,

Buff



User currently offlineKing767 From , joined Dec 1969, posts, RR:
Reply 2, posted (13 years 2 months 4 weeks 1 day 18 hours ago) and read 3222 times:

Ok, well I thought I explained it well, anyway, you know when you hear, for example : "UA A320 makes emergency landing due to drop in cabin pressure." What I mean by ageing pressure bulkheads is I thought on older aircraft, for example, 727s, 737-200s, as the pressure bulkhead ages, it is more prone to leakage. I thought that a recent incident involving a drop in cabin pressure aboard an ATA 1011 was due to a problem with the pressure bulkhead.

-Tom


User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 3, posted (13 years 2 months 4 weeks 1 day 17 hours ago) and read 3217 times:

I thought that a recent incident involving a drop in cabin pressure aboard an ATA 1011 was due to a problem with the pressure bulkhead

May very well have been - I'm not familiar with that incident. Structural failures to which you refer are extremely rare.

Not so uncommon are pressurization control failures which may cause the requirement for passenger oxygen. Even so, these occurences are very rare by comparison.

Best Regards,

Buff


User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 4, posted (13 years 2 months 4 weeks 1 day 16 hours ago) and read 3218 times:

Duct ruptures are another cause of "failures". Outside the pressurized hull they cause cabin pressure loss. Inside the hull they give overpressure which can cause the safety valve(s) to open which then gives pressure loss until they close again at a predetermined figure causing the pressure to rise again. This can be a bit confusing for the operators as the outflow valves get confused, cabin pressure controller failures occur, cabin altitude can fluctuate, dust and very hot bleed air felt in the cabin etc. Not pretty!
Another problem that can occur is that the cabin altitude can rise during descent when power is reduced because high pressure bleeds don't open when commanded.
Hope this makes sense.
Cheers.


User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 5, posted (13 years 2 months 4 weeks 1 day 16 hours ago) and read 3210 times:

Good additions Feret and very accurate. BTW, what kind of handle is that?!

Normal operations on the DH8 could be very uncomfortable during descent from hi altitude (FL250) if the descent is done too quickly. Because of the low max differential on the DH8, if the pressurization control is not set to "increased rate of descent", it is possible to "catch the cabin". What this means is that the pressurization system can go to zero differential, i.e. inside = outside pressure at an altitude significantly higher than airport elevation. This is not a malfunction, just an operating technique idiosyncracy. The aircraft is then depressurized and further descent causes the cabin pressure to increase at the same rate of the aircraft's vertical speed. If this is in excess of 500'/minute, it is very uncomfortable for all concerned, especially the passengers.

Best Regards,

Buff


User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 6, posted (13 years 2 months 4 weeks 1 day 14 hours ago) and read 3199 times:

Buff,
It's an acronym for Flight Engineer (retired).  Smile

Cheers.


User currently offlineBuff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 7, posted (13 years 2 months 4 weeks 1 day 14 hours ago) and read 3197 times:

Well G'Day Mate!

Buff


User currently offlineFeret From , joined Dec 1969, posts, RR:
Reply 8, posted (13 years 2 months 4 weeks 1 day 10 hours ago) and read 3188 times:

Gidday mate! BTW, I learnt to speak Canadian by flying (and drinking) with some of those ex Ward Air piss-pots who are over this way.  Nuts
Cheers.


User currently offlineMax Power From , joined Dec 1969, posts, RR:
Reply 9, posted (13 years 2 months 3 weeks 6 days 21 hours ago) and read 3179 times:

Let's not forget " flagellation!!

User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6374 posts, RR: 54
Reply 10, posted (13 years 2 months 3 weeks 6 days 20 hours ago) and read 3175 times:

Main causes for inflight cabin pressure changes...
Well, for me the ONLY reason is easy: Flying on a Tu-134  Pissed

Twenty years ago during one of the many strikes at SAS I was on an Interflug (East German) Tu-134. It seemed to me that the plane was going steady and level at 27,000 ft (so the captain said - "siebenundtwanzig tausend Füsse"), but the cabin pressure was fluctuating up and down so I had pain in my ears for the next three weeks.

I have only had three flights on Tu-134, my first, last and only flight. Ten wild horses will not be able to pull me on board a 134 again.

Going home I changed my ticket to a Yugoslavian DC-9. Before that flight I noticed that the captain emptied a pint of beer in the transit hall bar and walked directly on the plane. And he didn't walk too steady. But man what a pleasant flight compared to Interflug. I guess that the captain took a nap in his seat and put the co-pilot to work. Isn't that what we have co-pilots for?

Yeah, that's how it was. Fortunately the good, old days have changed to the better.

Best regards, Preben Norholm



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineJohnM From United States of America, joined Feb 2001, 345 posts, RR: 0
Reply 11, posted (13 years 2 months 3 weeks 6 days 15 hours ago) and read 3163 times:

We sometimes have leaking door seals around pax doors and cargo doors. Also leaking ducts that were mentioned earlier. Rather than a decompression, I think a more common writeup is " Aircraft can't maintain cabin pressure" type of thing. When an aircraft comes back with rags sticking out of cracks in doors into the airstream, that is a giveaway. The crew will hear the leaks and stuff rags into the leak area while flying!

User currently offline242 From United States of America, joined Oct 2000, 498 posts, RR: 1
Reply 12, posted (13 years 2 months 3 weeks 6 days 12 hours ago) and read 3157 times:

Another vote for door seals. Usually it's the most used passenger/crew door (the one that gets opened and closed every flight, has the jetway run into it etc..). Service doors as well, have catering trucks bump the seals all the time. Cargo door seals see untold levels of abuse, and I've seen several blown out before.

User currently offlineL-188 From United States of America, joined Jul 1999, 29786 posts, RR: 58
Reply 13, posted (13 years 2 months 3 weeks 6 days 5 hours ago) and read 3150 times:

I'll have to vote for the door seals also....

honorable mention to either a bleed air vavle or an outflow valve getting dirty and sticking.

Other then that on the pressurization system there is this dial that you turn........



OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineMax Power From , joined Dec 1969, posts, RR:
Reply 14, posted (13 years 2 months 3 weeks 6 days 4 hours ago) and read 3145 times:

Let's not forget the loss of all engines!!

User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6374 posts, RR: 54
Reply 15, posted (13 years 2 months 3 weeks 6 days 1 hour ago) and read 3145 times:

Max Power wrote: Let's not forget the loss of all engines!!

Huh, Max Power, did you realize how inappropriate your user name was for this post?  Big thumbs up



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineMax Power From , joined Dec 1969, posts, RR:
Reply 16, posted (13 years 2 months 3 weeks 6 days ago) and read 3136 times:

Sorry, however I was not aware that I had to check with you before selecting a name.

User currently offlinePrebennorholm From Denmark, joined Mar 2000, 6374 posts, RR: 54
Reply 17, posted (13 years 2 months 3 weeks 5 days 22 hours ago) and read 3137 times:

Oh, I like your user name.
But please check with me before you post once more about "loss of all engines" - it gives me nightmares!



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlineMax Power From , joined Dec 1969, posts, RR:
Reply 18, posted (13 years 2 months 3 weeks 5 days 21 hours ago) and read 3128 times:

Ok,you got a "deal". Cheers.

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