Airliners.net

Hi all

Tonight I flew from Paris to Oslo onboard a 737-600 and there was something weird with the pressurisation. When I flushed the toilets the toilet paper got blown out of the toilet instead of being sucked in. I did not think that was possible. Second there was allot of air coming out as I was trying to wash my hands after the toilet experience. I notified the cabin crew, who told me there was a pressurisation failure onboard. I got a terrible headache, which I almost never get on planes, but the flight continued to Oslo as nothing unusual was going on. They also needed external power from a truck at CDG because the airplanes APU was not working properly. So my question is. What could have been wrong with this airplane, that caused the toilet experience, air in the water system and high altitude pressure?

I am not a mechanic, engineer or an attorney. So don't take any of this information or advice as exact. I do have a few opinions so I'll share them with you. It's not too uncommon for a flight to operate without pressurization. Under specific conditions an inoperative pressurization may be deferred. The problem is typically the pressurization controller or one of the outflow valves or possibly an HP valve in the pressurization failed.

A few obvious clues are a much lower cruise altitude, a much warmer or colder cabin than usual, louder than normal air noise in the cabin. But when the crew tells you the pressurization failed, you can declare that as your 'final answer' without having to poll the audience.

If a flight is operated unpressurized they can operate up to 10,000 feet or 12,500 for a limited time without providing supplemental oxygen for the passengers. A pressurized airliner has a cabin pressure of typically 5,500 feet. So the environmental effect on you is greater as you will feel climbs and descents more readily unless the crew makes an effort to keep the aircraft climb/descent rate reduced but actually in practise it's not always that easy to meet ATC's expectations. If you have any type of allergy or sinus problem the difference in 300 and 1,500 feet per minute can dramatically impact your sinus passages and potentially cause a severe ear ache and/or head ache.

The air in the water supply typically indicates the line wasn't purged after servicing or the water holding tank is low or empty. Pressurization is used to provide the pressure to feed water to your faucet. If the HP valves are manually closed chances are there was no pressure in the supply line. On the other hand, the pressurization problem could be in a leak in the air pressure line to the water system and the tech's just haven't made it that far down the list to find it.

As for the toilet, I can't imagine a vacuum toilet ever having a differential over that of the cabin. If there was a negative delta from the toilet to the cabin then count your blessings all you experienced was floating toilet paper. Pressurized toilets contain raw sewage with very little water. It's not the same formula as the recycle systems which to me are about the nastiest thing known to mankind.

P.S. A new mechanic was servicing the water on an aircraft when the lunch bell rang. During lunch a guy walks by the aircraft and wondered why water was pouring from the engine nacelle? What happened was a one way check valve failed and water entered the entire pressurization system. We referred to the aircraft as a flying U Boat!

Thank you for your answers FlyMatt2Bermud.

Quoting FlyMatt2Bermud (Reply 1): It's not too uncommon for a flight to operate without pressurization. Under specific conditions an inoperative pressurization may be deferred. The problem is typically the pressurization controller or one of the outflow valves or possibly an HP valve in the pressurization failed.

I thought all flights was cancelled if there was something wrong with the pressure onboard, I guess not.

Quoting FlyMatt2Bermud (Reply 1): A few obvious clues are a much lower cruise altitude, a much warmer or colder cabin than usual, louder than normal air noise in the cabin. But when the crew tells you the pressurization failed, you can declare that as your 'final answer' without having to poll the audience.

I did not notice the altitude we where having it was dark and the captain did not announce the altitude while flying. I think we used about the same time to get to OSL as I would have expected, so we where flying just as fast as regular. The noise was not louder than I expected.

The crew did not specify if the pressurization failure was only related to the water system, or if it was also related to the pressure onboard. That is why I thought it would be a good idea to ask about this on here.

Quoting FlyMatt2Bermud (Reply 1): The air in the water supply typically indicates the line wasn't purged after servicing or the water holding tank is low or empty.

According to the crew the tank had sufficient with water.

Quoting FlyMatt2Bermud (Reply 1): As for the toilet, I can't imagine a vacuum toilet ever having a differential over that of the cabin. If there was a negative delta from the toilet to the cabin then count your blessings all you experienced was floating toilet paper. Pressurized toilets contain raw sewage with very little water. It's not the same formula as the recycle systems which to me are about the nastiest thing known to mankind.

I can imagine that. What happened was there was almost like i small hurricane, when I flushed inside the toilet. Some paper disappeared. But the turbulence caused more paper to go outside of the toilet rather than being sucked in.

Quoting FlyMatt2Bermud (Reply 1): P.S. A new mechanic was servicing the water on an aircraft when the lunch bell rang. During lunch a guy walks by the aircraft and wondered why water was pouring from the engine nacelle? What happened was a one way check valve failed and water entered the entire pressurization system. We referred to the aircraft as a flying U Boat!

Hehe. A good one. Again thank you for the answer.

Quoting OyKIE (Reply 2): The crew did not specify if the pressurization failure was only related to the water system, or if it was also related to the pressure onboard. That is why I thought it would be a good idea to ask about this on here.

From what you are describing it is not an oxygen issue, probably just isolated with pluming of the toilet. Cabin pressure problems are serious and are announced to the pax. A plane can not fly unless it can hold an 8000 cabin pressure. You will never see a pax plane fly with no pressure because they tend to climb/descend at high rates. If you go anywhere above 500ftp climb/descend unpressurized you head will feel like it will explode.

Quoting FlyMatt2Bermud (Reply 1): It's not too uncommon for a flight to operate without pressurization

Maybe an Islander or a Skyvan, but airliners do not depart with pressurisation inoperative. It just isn't done.
Yes they can fly with it inop, but as a ferry flight back to base at low altitude, but we would never dispatch an airliner with the pressurisation system inoperative.

Quoting OyKIE (Thread starter): When I flushed the toilets the toilet paper got blown out of the toilet instead of being sucked in. I did not think that was possible. Second there was allot of air coming out as I was trying to wash my hands after the toilet experience.

If you are saying that there was no water coming out the taps, just air, then this would be due to an empty water tank. Perhaps the gauge in the cabin showed full, but it was empty so they didn't service it in CDG. The water tank is pressurised with engine bleed air so with an empty water tank you get a lot of air coming out of the taps.
When you flush a vacuum toilet, a short spray of water is taken from the same tank first, before the flush valve opens to empty the bowl. As the tank was empty of water, this short spray would have been high pressure (40psi) air instead.

Quoting OyKIE (Thread starter): who told me there was a pressurisation failure onboard. I got a terrible headache, which I almost never get on planes, but the flight continued to Oslo as nothing unusual was going on

If there had been a pressurisation FAILURE the flight would not have continued normally. Perhaps the cabin crew meant pressurisation failure of the water system, and you took it to mean failure of the aircraft system?

Quoting OyKIE (Thread starter): They also needed external power from a truck at CDG because the airplanes APU was not working properly

The APU is shut down after engine start, so has no bearing on this story.

Quoting AirWillie6475 (Reply 3): From what you are describing it is not an oxygen issue, probably just isolated with pluming of the toilet. Cabin pressure problems are serious and are announced to the pax. A plane can not fly unless it can hold an 8000 cabin pressure. You will never see a pax plane fly with no pressure because they tend to climb/descend at high rates. If you go anywhere above 500ftp climb/descend unpressurized you head will feel like it will explode.

Thank you. I did not think we flew without pressurisation, but with something weird going on with the pressure because of the headache, but this could be because of a rapid climb out of CDG.

Quoting TristarSteve (Reply 5): If you are saying that there was no water coming out the taps, just air, then this would be due to an empty water tank. Perhaps the gauge in the cabin showed full, but it was empty so they didn't service it in CDG. The water tank is pressurised with engine bleed air so with an empty water tank you get a lot of air coming out of the taps. When you flush a vacuum toilet, a short spray of water is taken from the same tank first, before the flush valve opens to empty the bowl. As the tank was empty of water, this short spray would have been high pressure (40psi) air instead.

Thank you for a good answer. My first thought was that this was the tank being low on water, but since there where many weird things going on, it made me wonder. The high pressure air seems plausible to throwing out the toilet paper. I am sure there weren't any water coming out when I flushed. Some water came out as I tried to wash my hands, but mostly air.

Quoting TristarSteve (Reply 5): If there had been a pressurisation FAILURE the flight would not have continued normally. Perhaps the cabin crew meant pressurisation failure of the water system, and you took it to mean failure of the aircraft system?

I think they meant the water-system, but I thought it might had something to do with the irregular pressure onboard the plane. I have never experienced that kind of headache.

Quoting TristarSteve (Reply 5): The APU is shut down after engine start, so has no bearing on this story.

The APU was just to give an insight on how troublesome the flight was.

Quoting AirWillie6475 (Reply 3): You will never see a pax plane fly with no pressure because they tend to climb/descend at high rates.

I can tell you I have travelled as a passenger on a COMAIR flight with the pressurization inop, I think it was about 8 years ago on a CRJ from CVG-CAE. I don't recall the altitude we flew. I'm not saying it's a good idea (it was a presumption on my part to say a pressurization failure could be deferred) but at least it used to happen.

On Thursday Sept 28th I was a passenger on an ASA CRJ operating between APF-ATL with the lavatory deferred. They announced the problem prior to flight and no passenger indicated they did not want to go (at least on the aircraft) and no one wanted a two hour delay so off we went.

One or two of the packs could have failed in flight. If one failed, there's a limitation how high it can fly on one. If both failed, then it would be limited to below 12,500 or whatever is said in the SOP for failed presszuriation.

The packs provide alot of cabin pressure so that the outflow valve always remain partically open venting excess pressure.

I can defer one pack if I don't have time to fix it and it has to go out. I could defer both but that's only if the dispatch approves it since they have to rewrite the flight plan for lower altitudes. Each company has it's own MEL book which has it's own prodecures assoicated with the AMM manual if it's needed to do an corrective action for deferrals, and that applies to each type of aircraft they operate.
IE like a ERJ-145 and ERJ-170 have different MEL listings according to the type.

Most of the time they don't like more than one pack deferred so I'd take it out of service and fix the failed pack so they can fly high but limited to the limitation in the MEL book.

Quoting AirWillie6475 (Reply 3): A plane can not fly unless it can hold an 8000 cabin pressure. You will never see a pax plane fly with no pressure because they tend to climb/descend at high rates. If you go anywhere above 500ftp climb/descend unpressurized you head will feel like it will explode.

The Dash can be flown unpressurized in revenue service up to 10,000 ft. I've done it on numerous occassions. We just limit the climb to around 1000 fpm, and the descent to 500 fpm.

Quoting FlyMatt2Bermud (Reply 1): A pressurized airliner has a cabin pressure of typically 5,500 feet.

Sorry to nitpick, I'm not an expert either, but typical airliner cabin altitude is around 8,000 feet, though the 747 uses 7,000 and the 787 will drop even lower to 6,000.

Quoting AirWillie6475 (Reply 3): If you go anywhere above 500ftp climb/descend unpressurized you head will feel like it will explode.

Maybe if you are congested--but then regular pressurization will bother you anyway.


I've never been above 10,000 feet in an unpressurized aircraft so I can't speak about this if their are physiological differences at higher altitudes in terms of the sensation of pressure changes, but I've routinely managed 500 to 700 fpm up from sea level past 8,000 feet and never felt uncomfortable.

Quoting DashTrash (Reply 9): The Dash can be flown unpressurized in revenue service up to 10,000 ft. I've done it on numerous occassions. We just limit the climb to around 1000 fpm, and the descent to 500 fpm.

That's interesting. I thought there is a limit by the FAA and ICAO to 8000 cabin altitude on pressurized aircraft.

Quoting Dw747400 (Reply 10): Sorry to nitpick, I'm not an expert either, but typical airliner cabin altitude is around 8,000 feet, though the 747 uses 7,000 and the 787 will drop even lower to 6,000.

It's only 8000 at the aircrafts cervice ceiling. So if an aircraft has a max 41K feet ceiling but is cruising at 37, it's going to have a much lower maybe 6500 cabin altitude. It depends on the aircraft cabin psi. The 747 for example has a ceiling of 45K. But it cruises at around 35K so cabin is only about 5000.

Quoting Dw747400 (Reply 10): I've never been above 10,000 feet in an unpressurized aircraft so I can't speak about this if their are physiological differences at higher altitudes in terms of the sensation of pressure changes, but I've routinely managed 500 to 700 fpm up from sea level past 8,000 feet and never felt uncomfortable.

If anything you feel less pressure change the higher you go because there is less pressure.

Quoting AirWillie6475 (Reply 11): It's only 8000 at the aircrafts cervice ceiling.

I was under the impression these numbers were for a typical cruise altitude, thanks for the clarification.

Quoting FlyMatt2Bermud (Reply 7): On Thursday Sept 28th I was a passenger on an ASA CRJ operating between APF-ATL with the lavatory deferred.

Im guessing that you must be with VpBWB

Quoting AirWillie6475 (Reply 3): You will never see a pax plane fly with no pressure because they tend to climb/descend at high rates.

Negative. Some part 121 flights go with MEL'd packs for very short hops, so the cabin is totally unpressurized.

[Edited 2006-10-01 04:59:24]

Do they at least circulate the air inside?

Quoting AirWillie6475 (Reply 15): Do they at least circulate the air inside?

It depends on the a/c and the conditions of the Mel for most of the 737 Mel's the recirc fans need to work along with equipment cooling no cargo in the fwd pit and the fwd pit heat valve locked closed.  

Quoting Dw747400 (Reply 10): Sorry to nitpick, I'm not an expert either, but typical airliner cabin altitude is around 8,000 feet, though the 747 uses 7,000 and the 787 will drop even lower to 6,000

True, the cabin pressure can get up to around 8,000ft. I was just referencing in general. The actual cabin pressurization will depend upon the cruise altitude and selected differential. I figured most airliners don't fly at their highest attainable altitudes except for the longer flights.

There are two ways we'd go unpressurized in the Dash. First would be with a bleed problem or pack problem which would have us using ram air. That would be bleeds off, front outflow valve open, rear closed. Doesn't provide much ventilation.

Other scenario is with the bleeds on, rear outflow valve open. That gives us the air conditioning, but no pressurization. We use that if there is a problem with the pressurization system itself that doesn't allow it to be run in manual mode.

Quoting AirWillie6475 (Reply 3): 500ftp climb/descend unpressurized you head will feel like it will explode.

Huh? I've experienced extended climbs and descents of over +/-2,500 fpm in an unpressurized turboprops (C208) and felt fine.

You must be special.

Quoting Onetogo (Reply 19): I've experienced extended climbs and descents of over +/-2,500 fpm in an unpressurized turboprops (C208) and felt fine.

I don't doubt that you have. But if you were an Airline Captain there is no way to determine that all of your passengers eustation tubes are equally fit.

Quoting AirWillie6475 (Reply 3): A plane can not fly unless it can hold an 8000 cabin pressure

If it is FAA certified, the design must comply with 14CRF25.841

http://ecfr.gpoaccess.gov/cgi/t/text...ode=14:1.0.1.3.11.4.180.71&idno=14

Quoting Dw747400 (Reply 10): Sorry to nitpick, I'm not an expert either, but typical airliner cabin altitude is around 8,000 feet, though the 747 uses 7,000 and the 787 will drop even lower to 6,000.

Very few airlines operate with an 8000 foot cabin pressure. 7000 to 7600 is far more common. Most 747 operators fly with it between 5600 and 6500.

Quoting FlyMatt2Bermud (Reply 1): On the other hand, the pressurization problem could be in a leak in the air pressure line to the water system

Not likely. If you have inadequate bleed air pressure going into the potable water tanks, then the electric compressor should kick in and provide air to the tanks.

My guess is an empty tank. That would explain why air was blowing from the toilet when flushed. There is no way to get positive pressure from the vacuum waste system.

Tod

Quoting AirWillie6475 (Reply 20): You must be special.

Cool!

With regard to the toilet problem. If the a/c is fitted with vacuum toilets it has vacuum generators so the toilets will work on the ground. They are controlled by a diff press switch, so if the a/c was depressurised the toilets would still work normally as there would no diff press.