Qantas 744 Depressurisation
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Critter down
wasn't there an oxygen bottle explosion on a plane over the Everglades a few years ago? If my memory is correct that cost the lives of everyone on the plane. I think these were being illegally transported from one base to another.
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Re: posts 352 and 358
One person close to the investigation, who was not permitted to speak to the media while the inquiry was under way, said Saturday that “some kind of explosion” might have occurred, because the floor above the cargo hold had been pushed up. Two oxygen bottles that supply the pilots are stored in that area.
Australian investigators, who got their first look inside the plane Saturday, discovered shards of an oxygen bottle throughout the cargo hold and in the floor above, which sits below the cabin, this person said. Officials cautioned that it was too soon to know if the oxygen canister had caused the damage, but theorized that it might have played a role, this person said.
Australian investigators, who got their first look inside the plane Saturday, discovered shards of an oxygen bottle throughout the cargo hold and in the floor above, which sits below the cabin, this person said. Officials cautioned that it was too soon to know if the oxygen canister had caused the damage, but theorized that it might have played a role, this person said.
Assuming that the O2 tanks are approximately the size or diameter of SCUBA tanks (my assumption), it seems that the bottom part of a tank blew through the fuselage and then tore off the composite wing root fairing.
The weakest part of an O2 or compressed gas tank is at the valve fitting assuming no defect in manufacture.
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Xyzzy:
Due to the possibility of press being on board:
"In the even of a loss of cabin pressure, masks will drop from the ceiling. Pull towards you and place the elastic around your head. Fit yours first before helping other people. The plastic bag will not inflate. The plane will then plummet uncontrollably while the pilot attempts to avoid schools for blind orphans until an altitude at which you can breath normally has been reached."
Serious questions now: if it is an o2 cylinder rupturing (seen a Diving cylinder at around 200bar rupture ... it hurt!*) for some reason then the question is what reasons...what are the conditions like around the cylinders: moisture levels (water ingress similar to Oantas' electrical incident), oil (!!!), hydraulic lines etc? I don't have any good idea about the 747 so could someone (Rainboe?) give us an idea of what can be found in the vicinity of that area.
fc101
*at a distance and it made a mess of the shed where the cylinders were being pressurised - makes me wonder now what they'd have done to my E145...
Why isn't the safety briefing changed? ``In the event of a loss of cabin pressure, masks will drop from the ceiling. Pull towards you and place the elastic around your head. Fit yours first before helping other people. The plastic bag will not inflate. The plane will then descend to an altitude at which you can breath normally.''
"In the even of a loss of cabin pressure, masks will drop from the ceiling. Pull towards you and place the elastic around your head. Fit yours first before helping other people. The plastic bag will not inflate. The plane will then plummet uncontrollably while the pilot attempts to avoid schools for blind orphans until an altitude at which you can breath normally has been reached."
Serious questions now: if it is an o2 cylinder rupturing (seen a Diving cylinder at around 200bar rupture ... it hurt!*) for some reason then the question is what reasons...what are the conditions like around the cylinders: moisture levels (water ingress similar to Oantas' electrical incident), oil (!!!), hydraulic lines etc? I don't have any good idea about the 747 so could someone (Rainboe?) give us an idea of what can be found in the vicinity of that area.
fc101
*at a distance and it made a mess of the shed where the cylinders were being pressurised - makes me wonder now what they'd have done to my E145...
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QF has had some conspicuous bad luck with O2 bottles recently, they were filled with Nitrogen on 51 planes a year or so ago. Perhaps just a coincidence, we'll see...
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Oxygen-powered missiles
Almost 50 years experience as SLF, but no formal training in any aspect of aviation. However, I do have experience of system design in other fields and some exposure to mechanical design.
If I were designing a piping system fed by multiple high-pressure gas bottles, I would expect to connect each bottle through a non-return valve. That way it would be possible to remove a bottle whilst leaving others in place and without depressurising the whole system.
Can anyone advise us whether oxygen gas systems on aircraft in general and on the 744 in particular have such fittings? If they do, that could explain why one bottle could escape without the emergency oxygen system failing completely.
If a free-flying oxygen cylinder turns out to have contributed to this event, can we expect to see AD to move all such potential missile outside the pressure vessel?
If I were designing a piping system fed by multiple high-pressure gas bottles, I would expect to connect each bottle through a non-return valve. That way it would be possible to remove a bottle whilst leaving others in place and without depressurising the whole system.
Can anyone advise us whether oxygen gas systems on aircraft in general and on the 744 in particular have such fittings? If they do, that could explain why one bottle could escape without the emergency oxygen system failing completely.
If a free-flying oxygen cylinder turns out to have contributed to this event, can we expect to see AD to move all such potential missile outside the pressure vessel?
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Jamesair,
I believe the Florida crash was the result of improperly packed emergency oxygen generators (not bottles) that caused a raging fire after one or two were bumped and accidently triggered.
I thought that most if not all drop down oxygen came from OG's but, maybe not.
gh
I believe the Florida crash was the result of improperly packed emergency oxygen generators (not bottles) that caused a raging fire after one or two were bumped and accidently triggered.
I thought that most if not all drop down oxygen came from OG's but, maybe not.
gh
Cunning Artificer
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Oxygen systems are designed in the way you suggest Dairyground. The bottles are lifed and also subjected to regular inspections, being removed from the aircraft and subjected to non-destructive examination and proof testing. It would be very unusual for a bottle to "explode" in service, though it is not completely unknown. As one poster has revealed, the QF "Longreach" configuration includes a customer selectable option for supplementary oxygen bottles. These would be to permit operation on routes where terrain prevents the aircraft from immediately descending to 10,000 feet in the event of de-pressurisation. It seems that this option installs supplementary oxygen bottles mounted in the location where the hull rupture occured.
Placed under deliberate pressure, a poster whom I presume to be a QF management pilot has revealed that the event was not as routine as first appears (such incidents seldom proceed exactly as rehearsed in the simulator) and that the crew had additional un-stated system problems to handle. Perhaps an oxygen system problem is included among these?
Placed under deliberate pressure, a poster whom I presume to be a QF management pilot has revealed that the event was not as routine as first appears (such incidents seldom proceed exactly as rehearsed in the simulator) and that the crew had additional un-stated system problems to handle. Perhaps an oxygen system problem is included among these?
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oxygen bottles as suspect were mentioned as early as post 22 and 61...
one must ask, if the bottles that supplied that pilots were both ruptured, what the outcome of the flight might have been
can you imagine some poorly paid baggage handler accidently bumping a bottle and having it come apart later that day?
glad they are down safely.
one must ask, if the bottles that supplied that pilots were both ruptured, what the outcome of the flight might have been
can you imagine some poorly paid baggage handler accidently bumping a bottle and having it come apart later that day?
glad they are down safely.
Warning Toxic!
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The bottles are a major maintenance item only. I don't remember any hatch or access to that part of the aeroplane. The bottles occupy a small space between the central wing carry through box and the rear of the hold. You obviously want as much hold space as possible, so the rear of the hold will come down as close as possible to the wing box. The bottles are quite large. I do not think aircon plumbing comes through here- I think it goes under the wing box- the engineers here will know. I have checked my Pilot Technical Manual, but these are not pilot accessible areas so the manual gives scant information. The bottles feed into a universal cabin ring main, so there would be NRVs at each bottle as well as pressure reducing valves, and a big stopcock on each bottle. Can any divr say what happens if all the gubbins on the end of an Oxygen cylinder blows off suddenly? Or the end blows off? What happens to the bottle?
It did occur to me that the TWA accident began in this general location, but I am quite sure that the investigators would have discovered if a similar cause could be involved. But the bottles are very close to the wing box which is the largest fuel tank on the aeroplane.
It did occur to me that the TWA accident began in this general location, but I am quite sure that the investigators would have discovered if a similar cause could be involved. But the bottles are very close to the wing box which is the largest fuel tank on the aeroplane.
Oxygen Bottles Well Restrained
1. I'm not a 747 mechanic.
2. I am an industrial engineer and a retired military pilot.
3. I would expect that, due to their weight, oxygen bottles would be well restrained simply to ensure that they don't bounce around due to in flight G loadings. A unrestrained bottle which lost its top end, valves, etc., would, of course take off like a rocket, but I can't imagine a bottle properly installed in the aircraft would do anything but sit there and vent its contents. On the other hand, wherever the top end was pointed when it came off, it would knock quite a hole in anything it hit (like the pressure hull).
2. I am an industrial engineer and a retired military pilot.
3. I would expect that, due to their weight, oxygen bottles would be well restrained simply to ensure that they don't bounce around due to in flight G loadings. A unrestrained bottle which lost its top end, valves, etc., would, of course take off like a rocket, but I can't imagine a bottle properly installed in the aircraft would do anything but sit there and vent its contents. On the other hand, wherever the top end was pointed when it came off, it would knock quite a hole in anything it hit (like the pressure hull).
It did occur to me that the TWA accident began in this general location, but I am quite sure that the investigators would have discovered if a similar cause could be involved. But the bottles are very close to the wing box which is the largest fuel tank on the aeroplane.
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with regard to the theory that an oxygen bottle failed of it's own accord,well i'm fairly sure that they are pressure tested at manufacture to about 2-3x operating pressure so a bottle failing on it's own would be quite a rare event!
Having personally carried and fitted these to many BA 747/777 aircraft over the past 30 years,i have never known one to "let go" as it were!.
Personally i do not know the Qantas set up on the 400s,so it is possible that there are extra bottles fitted near to the damaged area,which i am led to believe has a galley unit directly above it.
Personally i would go for the following scenario.....Oxygen bottle fitted in position but has for some reason developed a small leak,(insecure fittings/seal failure etc),....contaminant from galley above finds it's way to bottle and "explosion" occurs!!
Having personally carried and fitted these to many BA 747/777 aircraft over the past 30 years,i have never known one to "let go" as it were!.
Personally i do not know the Qantas set up on the 400s,so it is possible that there are extra bottles fitted near to the damaged area,which i am led to believe has a galley unit directly above it.
Personally i would go for the following scenario.....Oxygen bottle fitted in position but has for some reason developed a small leak,(insecure fittings/seal failure etc),....contaminant from galley above finds it's way to bottle and "explosion" occurs!!
Paxing All Over The World
Pax speaking
slats11
I then asked:
Boeing certainly did build them tough 30 years ago. But - do they build them as tough now...?
787FOCAL replied
I understand that 747s are built the same way, due to design spec, but what is the spec of the 787?
Some of the passenger accounts mentioned a "hole appeared in the floor". It is possible that the 2R door (I think it was) was partially unseated by the failure below it. To those inside, the movement of the door would appear to be the primary fauly as it was the only one that they could see. Whereas, it may well have been a secondary failure.
As to pax experiencing nausea - this may have been to do with the oxygen (lack or use of) but also sheer nerves as they had no means of knowing how serious it was and fearing for their life.
One bit of GOOD REPORTING is in the UK paper The Independent. Simon Calder points out that all went according to plan and that you are still safe in the airplane than on the roads. He says:
No other industry is so tightly regulated, nor staffed with such safety-conscious people, as aviation. Life in the danger zone? Take a spin on the M1. But to prolong your life expectancy, take off.
Simon Calder: You're still safer up there than down here - Simon Calder, Travel - The Independent
slats11
and we all know Boeing builds em Tonka tough.
Boeing certainly did build them tough 30 years ago. But - do they build them as tough now...?
787FOCAL replied
yes. 747 skins, etc are still the same
Some of the passenger accounts mentioned a "hole appeared in the floor". It is possible that the 2R door (I think it was) was partially unseated by the failure below it. To those inside, the movement of the door would appear to be the primary fauly as it was the only one that they could see. Whereas, it may well have been a secondary failure.
As to pax experiencing nausea - this may have been to do with the oxygen (lack or use of) but also sheer nerves as they had no means of knowing how serious it was and fearing for their life.
One bit of GOOD REPORTING is in the UK paper The Independent. Simon Calder points out that all went according to plan and that you are still safe in the airplane than on the roads. He says:
No other industry is so tightly regulated, nor staffed with such safety-conscious people, as aviation. Life in the danger zone? Take a spin on the M1. But to prolong your life expectancy, take off.
Simon Calder: You're still safer up there than down here - Simon Calder, Travel - The Independent
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hello, im just a passenger enthusiast with an engineering background earlier in this thread someone pointed out a small area where the skin appears to be folded inwards as if an external impact event initiated the failure,or was at least present, this seems to have been largely passed by in subsequent posts...seems very significant to me
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Speculation alert - please read no further if facts are required -
Looking at the pictures in #358, it seems that the luggage visible is of two colours, greeny/black and red. There is no visibly obvious remains of a ULD, but something that looks like a pallet. I have seen stuff bagged up like this when I was on a flight bringing a rescue party back from Bam, after the earthquake a few years back. The equipment was not pallet loaded, but there was some pretty high tech stuff included. No problem with this but again, you would have thought that oxygen generators should be safe to transport, if all precautions were followed.
Now if it turns out that it was exhibition or expedition kit, all sorts of items could be on the pallet. All individually safe and manifested, but who knows?
Speculation over - In the second picture of #358, on the left hand side of the hole, I believe you can see what looks like an O2 bottle. I have had the privilege to hump these things off and on B74's in the past, so I have been up close and personal with them, so I believe that I am at least qualified to suggest that it could be a bottle.
I await a flame!!
Looking at the pictures in #358, it seems that the luggage visible is of two colours, greeny/black and red. There is no visibly obvious remains of a ULD, but something that looks like a pallet. I have seen stuff bagged up like this when I was on a flight bringing a rescue party back from Bam, after the earthquake a few years back. The equipment was not pallet loaded, but there was some pretty high tech stuff included. No problem with this but again, you would have thought that oxygen generators should be safe to transport, if all precautions were followed.
Now if it turns out that it was exhibition or expedition kit, all sorts of items could be on the pallet. All individually safe and manifested, but who knows?
Speculation over - In the second picture of #358, on the left hand side of the hole, I believe you can see what looks like an O2 bottle. I have had the privilege to hump these things off and on B74's in the past, so I have been up close and personal with them, so I believe that I am at least qualified to suggest that it could be a bottle.
I await a flame!!
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Wondering
a times online article indicated that the pilots had trouble with their oxygen supply...and that there was a secondary supply
I would like details on that from a 747 guy.
while I can imagine a "walk around bottle" being part of the cockpit stuff, I'd just like to know.
I would like details on that from a 747 guy.
while I can imagine a "walk around bottle" being part of the cockpit stuff, I'd just like to know.