Buff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 1, posted (14 years 6 days 15 hours ago) and read 6760 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!
King767 From , joined Dec 1969, posts, RR:
Reply 2, posted (14 years 6 days 14 hours ago) and read 6741 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.
Feret From , joined Dec 1969, posts, RR:
Reply 4, posted (14 years 6 days 12 hours ago) and read 6737 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.
Buff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 5, posted (14 years 6 days 12 hours ago) and read 6729 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.
Prebennorholm From Denmark, joined Mar 2000, 6690 posts, RR: 54
Reply 10, posted (14 years 4 days 16 hours ago) and read 6694 times:
Main causes for inflight cabin pressure changes...
Well, for me the ONLY reason is easy: Flying on a Tu-134
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
JohnM From United States of America, joined Feb 2001, 358 posts, RR: 0
Reply 11, posted (14 years 4 days 11 hours ago) and read 6682 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!
242 From United States of America, joined Oct 2000, 498 posts, RR: 1
Reply 12, posted (14 years 4 days 8 hours ago) and read 6676 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.