Qantas 744 Depressurisation
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Still can't find any ATSB reference to the "part of an oxygen cylinder and valve (which) entered the passenger cabin and impacted the number 2 right door frame handle" having been found. So has it?
Various items were reported as being sucked across the cabin by the depressurisation, and any debris that 'came up' could realistically have fallen and gone down and flown out of the big hole to the outside world.
After all, some of the hold cargo ended up jammed in the hold, so it is reasonable to assume that other material might have preceded it . . .
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ok.. I'm confused. Didn't the early reports say that the oxygen valve was found in the roof. Like "Flexible Response", I assumed that the neck of the bottle had shattered, a section of bottle (with the valve) caused the green marks in the cabin and damaged the door assembly... and the rest of the oxygen bottle went down (due jet propulsion), angled off something and went out of the side of the aircraft.
One of the earlier pictures shows a bracket for the wing-to-body fairing as an additional attachment point (other than the fasteners around the circumference). There may be more, accounting for the tearing.
That's what makes aviation so interesting. As an engineer for a similar period of time, I regularly come across things that I haven't seen before and have to come up with solutions. When I find one, I say to myself.. ."I'll remember that for next time it happens".... but most of the time it doesn't.. .or it's so long between these unusual events, I forget the solution 
Aircraft are getting safer and safer (that's why we are so surprised when things like this do happen).
I'm still trying to work out why the "Captain's FMC" and 3 ILS's failed (yet the VOR did work).
I assume the crew switched to the Right FMC to allow that to tune the navigation radios(?)
One of the earlier pictures shows a bracket for the wing-to-body fairing as an additional attachment point (other than the fasteners around the circumference). There may be more, accounting for the tearing.
I have a total of 18,680 hours operating as a F/E on CV880, B707, L1011, B747-100-200-300 pax and cargo. In 32 years have never encountered a problem with pax or crew oxygen. This incident is a bit of a worry, to say the least.
Aircraft are getting safer and safer (that's why we are so surprised when things like this do happen).
I'm still trying to work out why the "Captain's FMC" and 3 ILS's failed (yet the VOR did work).
I assume the crew switched to the Right FMC to allow that to tune the navigation radios(?)
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Attn. Pacplyer re. 781
Yes, it's possible that Li grease + O2 in fair concentration could give you a fire.
There seems to be a drift towards the idea that the tank 'pushed' its way through the hull by jet propulsion, having ignominiously lost its valve. This really doesn't wash: the forces involved are not high enough, and are broadly downwards rather than outwards. However, the failure / loss of the valve is very likely to compromise the rest of the tank's structure. It would be strange if it didn't. We are then looking at sudden explosive failure a very short time after the loss of the valve, as a result of the considerable pressure that remains inside the tank blowing out the damaged tank structure. The resulting explosion would account for the observed damage to the a/c: a sudden, violent force outwards, powerful enough not just to hole the skin nearby but also to fracture neighbouring structural elements.
There seems to be a drift towards the idea that the tank 'pushed' its way through the hull by jet propulsion, having ignominiously lost its valve. This really doesn't wash: the forces involved are not high enough, and are broadly downwards rather than outwards. However, the failure / loss of the valve is very likely to compromise the rest of the tank's structure. It would be strange if it didn't. We are then looking at sudden explosive failure a very short time after the loss of the valve, as a result of the considerable pressure that remains inside the tank blowing out the damaged tank structure. The resulting explosion would account for the observed damage to the a/c: a sudden, violent force outwards, powerful enough not just to hole the skin nearby but also to fracture neighbouring structural elements.
Last edited by Vertiginous; 31st Jul 2008 at 12:34.
An appreciation of the forces involved in an unrelated ground accident involving an oxygen cylinder explosion during maintenance.
O2 CYLINDER EXPLOSION
YouTube - O2 CYLINDER EXPLOSION
Edit to sanitize and keep it as factual as possible.
O2 CYLINDER EXPLOSION
YouTube - O2 CYLINDER EXPLOSION
Edit to sanitize and keep it as factual as possible.
Last edited by FlexibleResponse; 31st Jul 2008 at 13:55.
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Thanks Flex...
FORGET - do you want to play nicely or just play on the number of postings you do here?
Most of us do NOT guess. We make decisions. That includes all people associated with our ship-o-the-day. We talk, we collaborate.
If you don't want to play nicely, and bag posters who, like many of us, are a little too busy doing our job up the pointy end and are seriously interested in what happened to QF30, then back to your postings.
I see from your profile your in avionics, so thanks for keeping our avionics working
You people are great.
Just settle, petal. We're all in this for the good, not ego.
Now, can we get back on topic?
Most of us do NOT guess. We make decisions. That includes all people associated with our ship-o-the-day. We talk, we collaborate.
If you don't want to play nicely, and bag posters who, like many of us, are a little too busy doing our job up the pointy end and are seriously interested in what happened to QF30, then back to your postings.
I see from your profile your in avionics, so thanks for keeping our avionics working
You people are great.Just settle, petal. We're all in this for the good, not ego.
Now, can we get back on topic?
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...powerful enough not just to hole the skin nearby...
But the fact remains that gas bottles do not spontaneously burst; they do so when they are being interfered with in some way, during handling or charging. This cylinder was sitting in its stowage out of the way of any normal "interference".
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ATSB Report.
Chris Scott,
ATSB has commented on O2 components hitting door handle. The info you seek (or have failed to find) is available from the link in post #707 or from an excerpt from the report in post #708.
ATSB has commented on O2 components hitting door handle. The info you seek (or have failed to find) is available from the link in post #707 or from an excerpt from the report in post #708.
Many thanks for the excellent pictures and image enhancements, much beyond my skills.
The trajectory of the valve shows that the cylinder was still fastened in its original position when it departed -- caveat that a hull failure directly below may have sucked the bottle straight down and caused the valve to part company -- 5% probability?
The more likely case is that the valve departed while the bottle was still in situ. The equal and opposite reaction would have loaded the lower cup fitting which seems to be supported by two rods from the ends of the upper tank support. Note that both rods are gone and that a recent photo shows one rod for the adjacent tank hanging from its upper tank support but no longer connected to the lower cup. Note that the remaining rod was sufficient to retain that tank
It's been too many decades since uni physics for me to calculate the thrust from an 1800 psi tank with missing valve -- that would apply only if the tank held together.
A fragment comprising the bottom of the tank would likely have a higher velocity while an intact tank would have a greater duration of banging against the fuselage structure. But in the case of tank fragmentation, other bits of the tank would likely be found imbedded in baggage (caveat some sucked out) and adjacent structure, or at least marks, perhaps with green smears.
The hoop frames seem cleanly cut; so likely at a joint. Was that the bottle banging at them, or the baggage pushing them, or something dislodging a piece spanning the frames at the joints, or???
Note also that the metal curled up against the fuselage shows erosion of the interior paint in a number of panels. The boundary in one area shows the perimeter of a spray pattern -- oxidation of the paint???
The trajectory of the valve shows that the cylinder was still fastened in its original position when it departed -- caveat that a hull failure directly below may have sucked the bottle straight down and caused the valve to part company -- 5% probability?
The more likely case is that the valve departed while the bottle was still in situ. The equal and opposite reaction would have loaded the lower cup fitting which seems to be supported by two rods from the ends of the upper tank support. Note that both rods are gone and that a recent photo shows one rod for the adjacent tank hanging from its upper tank support but no longer connected to the lower cup. Note that the remaining rod was sufficient to retain that tank
It's been too many decades since uni physics for me to calculate the thrust from an 1800 psi tank with missing valve -- that would apply only if the tank held together.
A fragment comprising the bottom of the tank would likely have a higher velocity while an intact tank would have a greater duration of banging against the fuselage structure. But in the case of tank fragmentation, other bits of the tank would likely be found imbedded in baggage (caveat some sucked out) and adjacent structure, or at least marks, perhaps with green smears.
The hoop frames seem cleanly cut; so likely at a joint. Was that the bottle banging at them, or the baggage pushing them, or something dislodging a piece spanning the frames at the joints, or???
Note also that the metal curled up against the fuselage shows erosion of the interior paint in a number of panels. The boundary in one area shows the perimeter of a spray pattern -- oxidation of the paint???
Where did the phantom door-knocker go?
Thanks for your reply, Aerolex. Had already read your post #707 and that particular ATSB media release (from which I quoted). Also looked at all the other ATSB releases on their website. Unless I've missed something, it looks as if they hadn't yet found the object(s) that hit the door handle; hence Chardy's and my question.
G-CPTN (#802) suggests it might have reversed direction, and then "flown out of the big hole to the outside world." Machaca suggests it may have ricocheted into the upper-deck floor. My tuppence is on something like the latter. On the other hand, like Chardy (unless I'm misunderstanding his #790), I'm assuming that it would have been found quickly by the investigators. Fascinating.
G-CPTN (#802) suggests it might have reversed direction, and then "flown out of the big hole to the outside world." Machaca suggests it may have ricocheted into the upper-deck floor. My tuppence is on something like the latter. On the other hand, like Chardy (unless I'm misunderstanding his #790), I'm assuming that it would have been found quickly by the investigators. Fascinating.
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But the fact remains that gas bottles do not spontaneously burst; they do so when they are being interfered with in some way, during handling or charging. This cylinder was sitting in its stowage out of the way of any normal "interference".
Without doubt the oxygen cylinder is a crucial element of the incident. As stated above, there had to be a 'discontinuity' (either physical or chemical) that induced the failure of the mounting bracket(s) and severed the valve and/or the regulator (with or without part of the cylinder) which then flew upwards through the cargo hold ceiling and the cabin floor. It is (IMO) inconceivable that an intact cylinder could inflict the damage seen in the cabin (ie there is no way a complete cylinder could levitate with sufficient force) therefore at some stage either the valve became detatched from the cylinder or part of the cylinder with the valve still attached was propelled from its original storage location.
Although plausible, I do not believe that a simple displacement of the cylinder (as shown in
would, in itself, cause sufficient damage to the structure of the cylinder to cause separation of the valve. Furthermore, (IMO) I don't believe that an external 'explosion' (or rapid burning) caused by leakage of oxygen from connecting pipework or valves could inflict destructive damage on an otherwise previously intact and undamaged cylinder. Such events usually occur when a flaw exists in a fitting fitted into the cylinder or an attempt to remove the fitting has been made. Failure of external pipework is unlikely to 'destroy' the cylinder itself, although dropping the cylinder could 'knock off' the valve screwed into the cylinder.If the cylinder was properly fixed into the support brackets and clamped in place then failure of any of the external connecting pipework is most unlikely (improbable - maybe impossible) to cause the catastrophic failure that occurred.
Therefore, either the cylinder was displaced from its mountings prior to the 'explosion', or the cylinder itself fractured. The former suggests that the mounting bracket(s) either simultaneously failed (unlikely) or that some mechanical force (such as part of the cargo) impinged on the cylinder, or that an 'explosion' displaced the cylinder from its stowage location. Subsequently (and maybe simultaneously) damage to the valve (and/or the cylinder) allowed the valve to detach itself.
Simple failure of the fuselage skin (ie no primary failure of the cylinder) could cause rotation of the cylinder in its clamp as it was sucked out of the breach, but (IMO) the valve wouldn't detach until it struck something solid (such as the flange along the bottom of the 'curtain' or the edges of the remaining upper support bracket - there should be witness marks) and the state of the remaining pipework would indicate how the cylinder 'departed'.
I'd love to be able to view the scene (and it would help to know exactly what debris has been recovered).
It's easy to assume that 'cylinders don't fail spontaneously', yet should a cylinder fail . . .
. . . the result would be as seems to have occurred here.
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Excess activated masks - not a problem?
Re post #771
I recall having heard sometime in the distant past that one of the reasons for the apparent overprovision of passenger oxygen masks is to make it possible for cabin crew (or even passengers) to breathe if they needed to move around the cabin. Assuming that someone was on their feet several rows away from an empty aisle seat, or their own seat, when the masks dropped, they might well sample several on their journey back to their own seat. The cabin crew might also have reason to use dangling masks rather than their own portable cylinders if their duties took them away from the crew seats, for example to check that all passengers were wearing masks and were otherwise OK.
So I don't see the excess of activated masks over number of passengers as indicative of a significant problem.
I recall having heard sometime in the distant past that one of the reasons for the apparent overprovision of passenger oxygen masks is to make it possible for cabin crew (or even passengers) to breathe if they needed to move around the cabin. Assuming that someone was on their feet several rows away from an empty aisle seat, or their own seat, when the masks dropped, they might well sample several on their journey back to their own seat. The cabin crew might also have reason to use dangling masks rather than their own portable cylinders if their duties took them away from the crew seats, for example to check that all passengers were wearing masks and were otherwise OK.
So I don't see the excess of activated masks over number of passengers as indicative of a significant problem.
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After further examination of the above illustrations, what if the retaining clamp wasn't fitted . . .
(full image at http://img65.imageshack.us/img65/49/dsc023391sq0.jpg )
. . . allowing the cylinder to displace, tearing the pipework and subsequently striking the valve against something 'solid' . . .
(The upper bracket of the missing cylinder location seems 'incomplete' rather than torn - either it is flimsy and designed only to stop the cylinder from rattling or there are parts missing from the 'clamp'?)
(Recall the Virgin train derailment - and the Potters Bar crash - where fixing nuts were 'missing'. Such omissions can occur due to human 'failures', despite inspection procedures . . . )
OTOH, that piece of (broken?) pipe in the middle of the above photograph looks 'discoloured' . . .
(full image at http://img65.imageshack.us/img65/49/dsc023391sq0.jpg )
. . . allowing the cylinder to displace, tearing the pipework and subsequently striking the valve against something 'solid' . . .
(The upper bracket of the missing cylinder location seems 'incomplete' rather than torn - either it is flimsy and designed only to stop the cylinder from rattling or there are parts missing from the 'clamp'?)
(Recall the Virgin train derailment - and the Potters Bar crash - where fixing nuts were 'missing'. Such omissions can occur due to human 'failures', despite inspection procedures . . . )
OTOH, that piece of (broken?) pipe in the middle of the above photograph looks 'discoloured' . . .
Last edited by G-CPTN; 31st Jul 2008 at 15:43.
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CSI Pprune!
Well guys (Machaca, Spanners & NSEU & Others) I think that your collective knowledge and inquisitive natures have got most of it.
Seriously, I would put money down that the ATSB reads identically!
The only thing that worries me is what caused the O2 Bottle to rupture in the first place to have it rocket into then out of the fuselage?
What if this had occured on L888 sometime after NOLEP...
Interesting stuff....CSI Pprune indeed!
(for those that dont know see http://www.planningchart.de/Hongkong.gif)
Seriously, I would put money down that the ATSB reads identically!
The only thing that worries me is what caused the O2 Bottle to rupture in the first place to have it rocket into then out of the fuselage?
What if this had occured on L888 sometime after NOLEP...
Interesting stuff....CSI Pprune indeed!
(for those that dont know see http://www.planningchart.de/Hongkong.gif)
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G-CPTN,
Two well thought out posts. The thing that does not seem right to me, is that the bottle support mount shown in your last post shows no damage apart from where the support straps would normally be. If the complete bottle was to fail, then there should be at lease some deformation of the mount. If the bottle ruptured, it would do so in all directions, not just towards the straps.
Now if the bottom mount was to move for whatever reason?
Two well thought out posts. The thing that does not seem right to me, is that the bottle support mount shown in your last post shows no damage apart from where the support straps would normally be. If the complete bottle was to fail, then there should be at lease some deformation of the mount. If the bottle ruptured, it would do so in all directions, not just towards the straps.
Now if the bottom mount was to move for whatever reason?
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Truly good forensic knowledge has been contributed to these many posts.
"The only thing that worries me is what caused the O2 Bottle to rupture in the first place to have it rocket into then out of the fuselage?"
Was taught in A&P school that one of the closest lethal combinations to create a near spontaneous combustion, was the proximity mix of aviator's breathing oxygen (color coded green), with aviation Mil-Spec grease, no matter how small in quantity. (note - aviators breathing oxygen is simply medical grade oxygen (color coded grey?) with moisture removed).
"The only thing that worries me is what caused the O2 Bottle to rupture in the first place to have it rocket into then out of the fuselage?"
Was taught in A&P school that one of the closest lethal combinations to create a near spontaneous combustion, was the proximity mix of aviator's breathing oxygen (color coded green), with aviation Mil-Spec grease, no matter how small in quantity. (note - aviators breathing oxygen is simply medical grade oxygen (color coded grey?) with moisture removed).
Torn Mounting Holes?
In Post #813, I perceive that we are looking at the half of the tank restraint which is normally behind the tank and closest to the pressure hull. It appears that the bolt holes, to which the strap which encircles the tank is fastened, have been torn out.
If the strap had not been adequately tightened, over time those bolt holes would have elongated and eventually failed, allowing the tank to lean out of it's proper position. This might then possibly have allowed the valve body to strike something firm and break off.
Of course, those bolt holes could have been torn out by some other mechanism.
If the strap had not been adequately tightened, over time those bolt holes would have elongated and eventually failed, allowing the tank to lean out of it's proper position. This might then possibly have allowed the valve body to strike something firm and break off.
Of course, those bolt holes could have been torn out by some other mechanism.
Many thanks Machca a good sketch engenders a good discussion
I not entirely sure of what has started this (chicken and the egg). There are some excellent pro and cons on multiple theories. Obviously if one could examine the details close up, I could eliminate some theories and concentrate on the rest.
My current musings do consider that to launch the valve straight up implies to me that the cyclinder was still intact and a pure jet force was along the axis of the valve. I might have thought that a fractured cyclinder would have launched multiple fragments randomly (like the workbench video).
An axial propulsive force that launches the valve implies a reverse axial propulsive force against the memaining cyclinder. Somehow, I can't imagine this force beng enough to fracture the fueslage albeit it likely is enough to fracture the upper cylinder supports.
Some really good thoughts by some on here so I await some more iteration of ideas.
Just for some food for follow on thought. Eventually we are going to need a sound safety related recommendatiuon (not just an interim inspection). If we ascribe to an extermely rare tank fracture, we don't have a lot to work with trying to chase a one in a billion chance. On the other hand if the tank is secondary we need to concentrate on this aspect and either strengthen its supports or eliminate the primary cause. (More thoughts on this later as new details emerge)l
I not entirely sure of what has started this (chicken and the egg). There are some excellent pro and cons on multiple theories. Obviously if one could examine the details close up, I could eliminate some theories and concentrate on the rest.
My current musings do consider that to launch the valve straight up implies to me that the cyclinder was still intact and a pure jet force was along the axis of the valve. I might have thought that a fractured cyclinder would have launched multiple fragments randomly (like the workbench video).
An axial propulsive force that launches the valve implies a reverse axial propulsive force against the memaining cyclinder. Somehow, I can't imagine this force beng enough to fracture the fueslage albeit it likely is enough to fracture the upper cylinder supports.
Some really good thoughts by some on here so I await some more iteration of ideas.
Just for some food for follow on thought. Eventually we are going to need a sound safety related recommendatiuon (not just an interim inspection). If we ascribe to an extermely rare tank fracture, we don't have a lot to work with trying to chase a one in a billion chance. On the other hand if the tank is secondary we need to concentrate on this aspect and either strengthen its supports or eliminate the primary cause. (More thoughts on this later as new details emerge)l
Aerolex
No.s of O2 masks used.
My point was far simpler - whether or not they physically need it, they'll take it. The role of "authority" in a crisis is well known. Authority told them to pull at a mask, and put it on their face. Some might well grab 2, believing that to be better for them. Don't forget, very few pax have been in a sim., and even fewer would be able to work out their need for/use of and availability of O2. That's what HF is s'posed to remind us about....
My point was far simpler - whether or not they physically need it, they'll take it. The role of "authority" in a crisis is well known. Authority told them to pull at a mask, and put it on their face. Some might well grab 2, believing that to be better for them. Don't forget, very few pax have been in a sim., and even fewer would be able to work out their need for/use of and availability of O2. That's what HF is s'posed to remind us about....
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What seemed surprising was how few masks had had the elastic retaining straps adjusted.
(From:- MEDIA RELEASE : 30 July 2008 - Investigation into Boeing 747- 400 depressurisation and diversion to Manila, Philippines
Audio version:- http://www.atsb.gov.au/newsroom/2008...dia_300708.wav there's some interesting Q&As at the end where the ATSB guy states that they do have 'part of the cylinder'.)
Do passengers merely hold the mask in place?
Incidentally, also from the above release:-
which seems specific that 'a part of the cylinder' left the cargo hold . . .
although they merely state 'appears' . . .
and:-
Was this merely more holes in the cheese, or is there a logical explanation?
Only a small number of masks appeared to have had the elastic retaining strap adjusted by the passengers
Audio version:- http://www.atsb.gov.au/newsroom/2008...dia_300708.wav there's some interesting Q&As at the end where the ATSB guy states that they do have 'part of the cylinder'.)
Do passengers merely hold the mask in place?
Incidentally, also from the above release:-
The ATSB can confirm that it appears that part of an oxygen cylinder and valve entered the passenger cabin
although they merely state 'appears' . . .
and:-
The team have confirmed that the aircrafts three Instrument Landing Systems (ILS) and the anti-skid system were not available for the arrival and landing at Manila.
Last edited by G-CPTN; 31st Jul 2008 at 18:55.