Qantas 744 Depressurisation
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BBC Reporting - ATSB have confirmed that it was the oxy bottle that caused the hole, but no closer to a reason as to why it exploded
BBC NEWS | World | Asia-Pacific | Oxygen bottle behind Qantas blast
BBC NEWS | World | Asia-Pacific | Oxygen bottle behind Qantas blast
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No obvious failure mode?
From my limited understanding, it appears that these cylinders are of the type that are cast in one single piece (which can't be simple) and then the plumbing is added at the neck. So there are no joins, no seams etc to rupture at the bottom, which is where the failure appeared to have happened a/c to the report and the diagrams.
I can't see that dropping it, even from a significant height, as has been mentioned, would have caused such a clean separation of the bottom from the rest of the cylinder. The weakness would have already had to be there. So possibly there was a fault in the casting process above that produced a slightly weaker circumferential line at the bottom. Feel free to flame my reasoning.
Don't know if they do x-rays on these as part of q.a. or regular maintenance checks, but if so, then this didn't even show up on x-ray which is disturbing.
I can't see that dropping it, even from a significant height, as has been mentioned, would have caused such a clean separation of the bottom from the rest of the cylinder. The weakness would have already had to be there. So possibly there was a fault in the casting process above that produced a slightly weaker circumferential line at the bottom. Feel free to flame my reasoning.
Don't know if they do x-rays on these as part of q.a. or regular maintenance checks, but if so, then this didn't even show up on x-ray which is disturbing.
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Speculation alert!
If a cylinder had been dropped from significant height onto a concrete surface then it is no surprise (at least to me) that a subsequent catastrophic failure should occur. Of course, this would be more plausible if the cylinder received a subsequent 'injury' (and there is no suggestion so far that this was the case in this incident).
As a separate consideration, it is, in my opinion, unreasonable (I hesitate to state unacceptable) to have no non-return valves (NRVs) in the supply system, but you have to ask where these need to be located (as anywhere beyond the NRVs would not be protected. You have to consider the likelihood of a failure at a particular location (in the circuit) and in the case of a rigidly installed pipework and cylinders this is 'unlikely', especially as this would need to be associated with a need for oxygen (ie a depressurisation incident).
Of course, you can always create a scenario (such as ballistic damage) which could take out significant essential equipment beyond retention of a safe system. You have to deal with likely wear and tear (and likely accidental damage). Such events shouldn't result in loss of an essential 'service' through a single failure (ie control systems have backups or redundant mechanisms.
As far as a (theoretical) failure of an oxygen cylinder is concerned you'd have to postulate something as severe as a bullet impact as the initiating event (the cylinders are shrouded from general cargo intrusion and even then the inertia would need to be 'immense' to cause sufficient trauma). Displacement of a cylinder (however unlikely) is unlikely (!) to result in catastrophic failure (unless there has been prior injury) and also unlikely to cause structural damage to the pressure hull (again, assuming no previous trauma or weakness).
Holes, cheese, spring to mind, although if there had been an incident such as dropping a cylinder from significant height onto a hard surface then you've already got a piece of emmentaler (or at least the constituent ingredients):-
As a separate consideration, it is, in my opinion, unreasonable (I hesitate to state unacceptable) to have no non-return valves (NRVs) in the supply system, but you have to ask where these need to be located (as anywhere beyond the NRVs would not be protected. You have to consider the likelihood of a failure at a particular location (in the circuit) and in the case of a rigidly installed pipework and cylinders this is 'unlikely', especially as this would need to be associated with a need for oxygen (ie a depressurisation incident).
Of course, you can always create a scenario (such as ballistic damage) which could take out significant essential equipment beyond retention of a safe system. You have to deal with likely wear and tear (and likely accidental damage). Such events shouldn't result in loss of an essential 'service' through a single failure (ie control systems have backups or redundant mechanisms.
As far as a (theoretical) failure of an oxygen cylinder is concerned you'd have to postulate something as severe as a bullet impact as the initiating event (the cylinders are shrouded from general cargo intrusion and even then the inertia would need to be 'immense' to cause sufficient trauma). Displacement of a cylinder (however unlikely) is unlikely (!) to result in catastrophic failure (unless there has been prior injury) and also unlikely to cause structural damage to the pressure hull (again, assuming no previous trauma or weakness).
Holes, cheese, spring to mind, although if there had been an incident such as dropping a cylinder from significant height onto a hard surface then you've already got a piece of emmentaler (or at least the constituent ingredients):-
I still haven't seen or read any conclusive evidence that the bottle actually ruptured.
So all I can discern is that a add-on part to the bottle was found and that the bottle is missing.
I may have missed something myself in my read so I await further coments
So all I can discern is that a add-on part to the bottle was found and that the bottle is missing.
I may have missed something myself in my read so I await further coments
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No Obvious Failure Mode? You Reckon?
"The ATSB says investigations are continuing into the functioning of the cabin oxygen masks and into the design and manufacture of the failed oxygen cylinder."
.
Not disclosed in this report is the reason why the oxygen bottle may have failed. I cannot believe the ATSB is that dumb. In fact they've been unable to come to any conclusions. However a very simple conjecture can address the distinct probabilities.
Every aircraft type I've ever flown has had a minimum oxygen pressure below which you should never allow the contents to drop. The reason for that is simply that, at low pressures (say <300psi) moisture then readily gathers inside the bottle and it can then corrode undetected from the inside out (recalling that the lower and outer part of this bottle failed - where the water would tend to gather on the fuselage-mounted and slightly inclined cylinder's outermost wall). The exploding bottle eventually completed its jet-about final fling and departed via a final trickle-down through the hole in VH-OJK's fuselage - so no proof of this having been a corrosion incident is now available (except perhaps in other bottles of the same and "other" fleet systems). If a bottle (or "bottles" as part of a plumbed-together system) ever drops below that min pressure, it (they) has to be removed, evacuated, refilled and re-installed or kept (full) in storage as a spare. In consequence, engineers are usually careful not to allow oxygen systems to drop to those levels (unless it's within a closed/plumbed and therefore humidity-controlled environment). You cannot tell whether (or not) an oxygen bottle or system has been allowed to accumulate moisture. There are no in-tank dessicants and no water-collecting low points and drainage ports as in a pitot-static system. Compared to aviation's dehumidified dry breathing oxygen, medical oxygen is humidified and therefore hospital oxygen bottles are regularly evacuated and drained before being refilled.
My theory is that at some stage some systems (including this system on VH-OJK) was allowed to drop to a low or zero pressure and accumulated water via atmospheric moisture ingress and that it's been corroding at an accelerated rate over time. When and why might this have happened? Well you may recall that a year or so ago (see article below) QANTAS was found to have been mistakenly filling/topping off oxygen systems with Nitrogen over a lengthy period - due to a task delegation to a lowly qualified engineer who changed out a connector and enabled this alarming mistake to occur - not only to QANTAS aircraft but to a whole bunch of transient international aircraft that they (QANTAS) were in-transit servicing contractors for. Nitrogen, unlike dry breathing oxygen, is not really a zero humidity-controlled gas. It's normally used only for servicing tyres and oleos etc.
Read the thread below and judge for yourself. The nitrogen fiasco was uncovered in Dec 2007 but had been going on long before that. How long (after being emptied and refilled with guaranteed pure oxygen - but not water-checked) does it take corrosion to weaken a tank in a pressurized oxygen rich (and nitrogenized) H2O environment? The corrosion rate is about 5 times as fast as in a normally corrosive environment at sea-level pressures - and that is why people who work with oxygen should be as conscious of water contamination and low bottle pressures as they are about flammability of oil and grease contamination.
The question now is: "How many more oxygen bottles are going to be cooking off inflight before CASA/ATSB and QANTAS 'fesses up" to the OTHER complication of their little gaseously malfeasant Nitrogen escapade? An explosion that causes both an explosive decompression at high altitude AS WELL AS compromising the then critical emergency oxygen system is a matter for considerable concern. 365 very lucky people?
Cylinder information
All passenger oxygen cylinders installed in VH-OJK were of a single piece, heat-treated alloy steel construction. The missing (presumed failed) oxygen cylinder, part number 801307-0012, serial number 535657, was one of a batch of 94 cylinders manufactured in February 1996 to the DOT13 3HT1850 specification. The cylinders measured 22.8 cm outside diameter by 75.1 cm long (8.98 inches x 29.56 inches) and had a minimum 2.87 mm (0.113 inch) wall thickness.
Merged: Oxygen tanks topped up with Nitrogen
--------------------------------------------------------------------------------
Probe after Qantas pumps wrong gas into jets
Matthew Benns
December 16, 2007
POTENTIALLY fatal gas being pumped into passenger jet emergency oxygen tanks in Australia has sparked a worldwide safety investigation.
The Australian Safety Transport Bureau confirmed yesterday that Qantas engineers accidentally put nitrogen into the emergency oxygen tanks of a Boeing 747 passenger jet at Melbourne Airport.
The Australian carrier immediately checked the oxygen supplies of more than 50 of its planes that had been serviced by the mislabelled nitrogen cart at the airport. But an aviation source said: "This could have affected hundreds of planes worldwide. Any international jet that passed through Melbourne and was serviced by Qantas could have had nitrogen pumped into its oxygen tanks."
Health experts warned that in an emergency the effects of nitrogen in the oxygen tanks could have potentially fatal results.
Dr Ian Millar, hyperbaric medicine unit director at The Alfred hospital, said: "If there was an emergency and the pilot took nitrogen instead of oxygen, instead of gaining control of the aircraft he would black out and it would be all over. It's a pretty serious mistake."
Nitrogen, which is non-flammable, is commonly used at airports to fill aircraft tyres. The aviation source said: "Qantas took delivery of the new nitrogen cart 10 months ago. It looked exactly like the old oxygen cart. When the attachments did not fit they went and took them off the old oxygen cart and started using it."
The mistake was eventually spotted by an aircraft engineer. "He was walking around the plane and asked what they were doing. When they said they were topping up the oxygen, he said, 'No you're not, that's a nitrogen cart'," said the source.
The incident was reported to the Civil Aviation Safety Bureau, which confirmed that an investigation detected nitrogen in the crew oxygen tanks on the Boeing 747-300. A bureau spokeswoman said it was a one-off incident.
But the aviation source said: "This has affected at least 175 planes and Qantas has had to tell any other airline that has been serviced in Melbourne to check out its oxygen supplies."
Air New Zealand was told about the problem six weeks ago. "As a result of receiving that letter we did take some precautionary measures," a spokeswoman said. "The oxygen tanks on a small number of planes were removed, checked, reserviced and refilled. No irregularities were found."
A spokeswoman for the Australian Transport Safety Bureau said: "Very clearly they (Qantas) needed to carry out a risk assessment because there was a chance that other aircraft were affected.
"They identified 21 that were at risk because they had had a reasonable amount of oxygen top-up, so there was a reasonable chance they had been contaminated. There were another 30 aircraft at minor risk because they have had minor top ups," said the spokeswoman. The planes were inspected and no positive results found.
She said the airline had turned the error into a learning exercise and informed engineers all over the world about the mistake. "They have talked to thousands of their engineers around Australia and overseas, informing them about this lesson that has been learnt," she said.
Qantas engineering executive general manager David Cox said: "We had a guy using a new rig and he inadvertently serviced the crew oxygen with nitrogen. He realised what he was doing and flagged it."
Mr Cox said that once the mistake had been realised, extensive safety checks were put in place to ensure no other aircraft had been contaminated and that it could never happen again.
"Every aircraft, including customer aircraft, that could have been touched with this rig has been checked," he said after confirming the rig had been in use at the airport for several months. Mr Cox said the airline had been completely open in informing all safety authorities, staff and other airlines about the mistake.
This story was found at: http://www.theage.com.au/articles/20...568332267.html
NITROGEN USED TO FILL AIRCRAFT OXYGEN SYSTEMS
Airlines all over the world are being warned to check to make sure there’s actually oxygen in their aircraft oxygen systems after an embarrassing mix-up by Qantas Airlines at Melbourne International Airport. For ten months, crews have been filling airliner oxygen systems from a nitrogen cart that’s supposed to be used to fill tires. The mistake went unnoticed until a couple of weeks ago when an observant aircraft engineer spotted service workers using the cart. "He was walking around the plane and asked what they were doing. When they said they were topping up the oxygen, he said, 'No you're not, that's a nitrogen cart,'" an unnamed source told The Age. As anyone who works with industrial gases knows, oxygen tanks have different fittings than other gases to prevent exactly this kind of mix-up. However, when the crews discovered the fittings on what they thought was their new oxygen cart didn’t fit, they swapped them for the ones on the old cart they were retiring. Of course, Australian officials are looking into the error and Qantas has been busy notifying other airlines that use its services in Melbourne. Hundreds of aircraft may be affected.
.
Not disclosed in this report is the reason why the oxygen bottle may have failed. I cannot believe the ATSB is that dumb. In fact they've been unable to come to any conclusions. However a very simple conjecture can address the distinct probabilities.
Every aircraft type I've ever flown has had a minimum oxygen pressure below which you should never allow the contents to drop. The reason for that is simply that, at low pressures (say <300psi) moisture then readily gathers inside the bottle and it can then corrode undetected from the inside out (recalling that the lower and outer part of this bottle failed - where the water would tend to gather on the fuselage-mounted and slightly inclined cylinder's outermost wall). The exploding bottle eventually completed its jet-about final fling and departed via a final trickle-down through the hole in VH-OJK's fuselage - so no proof of this having been a corrosion incident is now available (except perhaps in other bottles of the same and "other" fleet systems). If a bottle (or "bottles" as part of a plumbed-together system) ever drops below that min pressure, it (they) has to be removed, evacuated, refilled and re-installed or kept (full) in storage as a spare. In consequence, engineers are usually careful not to allow oxygen systems to drop to those levels (unless it's within a closed/plumbed and therefore humidity-controlled environment). You cannot tell whether (or not) an oxygen bottle or system has been allowed to accumulate moisture. There are no in-tank dessicants and no water-collecting low points and drainage ports as in a pitot-static system. Compared to aviation's dehumidified dry breathing oxygen, medical oxygen is humidified and therefore hospital oxygen bottles are regularly evacuated and drained before being refilled.
My theory is that at some stage some systems (including this system on VH-OJK) was allowed to drop to a low or zero pressure and accumulated water via atmospheric moisture ingress and that it's been corroding at an accelerated rate over time. When and why might this have happened? Well you may recall that a year or so ago (see article below) QANTAS was found to have been mistakenly filling/topping off oxygen systems with Nitrogen over a lengthy period - due to a task delegation to a lowly qualified engineer who changed out a connector and enabled this alarming mistake to occur - not only to QANTAS aircraft but to a whole bunch of transient international aircraft that they (QANTAS) were in-transit servicing contractors for. Nitrogen, unlike dry breathing oxygen, is not really a zero humidity-controlled gas. It's normally used only for servicing tyres and oleos etc.
Read the thread below and judge for yourself. The nitrogen fiasco was uncovered in Dec 2007 but had been going on long before that. How long (after being emptied and refilled with guaranteed pure oxygen - but not water-checked) does it take corrosion to weaken a tank in a pressurized oxygen rich (and nitrogenized) H2O environment? The corrosion rate is about 5 times as fast as in a normally corrosive environment at sea-level pressures - and that is why people who work with oxygen should be as conscious of water contamination and low bottle pressures as they are about flammability of oil and grease contamination.
The question now is: "How many more oxygen bottles are going to be cooking off inflight before CASA/ATSB and QANTAS 'fesses up" to the OTHER complication of their little gaseously malfeasant Nitrogen escapade? An explosion that causes both an explosive decompression at high altitude AS WELL AS compromising the then critical emergency oxygen system is a matter for considerable concern. 365 very lucky people?
Cylinder information
All passenger oxygen cylinders installed in VH-OJK were of a single piece, heat-treated alloy steel construction. The missing (presumed failed) oxygen cylinder, part number 801307-0012, serial number 535657, was one of a batch of 94 cylinders manufactured in February 1996 to the DOT13 3HT1850 specification. The cylinders measured 22.8 cm outside diameter by 75.1 cm long (8.98 inches x 29.56 inches) and had a minimum 2.87 mm (0.113 inch) wall thickness.
Merged: Oxygen tanks topped up with Nitrogen
--------------------------------------------------------------------------------
Probe after Qantas pumps wrong gas into jets
Matthew Benns
December 16, 2007
POTENTIALLY fatal gas being pumped into passenger jet emergency oxygen tanks in Australia has sparked a worldwide safety investigation.
The Australian Safety Transport Bureau confirmed yesterday that Qantas engineers accidentally put nitrogen into the emergency oxygen tanks of a Boeing 747 passenger jet at Melbourne Airport.
The Australian carrier immediately checked the oxygen supplies of more than 50 of its planes that had been serviced by the mislabelled nitrogen cart at the airport. But an aviation source said: "This could have affected hundreds of planes worldwide. Any international jet that passed through Melbourne and was serviced by Qantas could have had nitrogen pumped into its oxygen tanks."
Health experts warned that in an emergency the effects of nitrogen in the oxygen tanks could have potentially fatal results.
Dr Ian Millar, hyperbaric medicine unit director at The Alfred hospital, said: "If there was an emergency and the pilot took nitrogen instead of oxygen, instead of gaining control of the aircraft he would black out and it would be all over. It's a pretty serious mistake."
Nitrogen, which is non-flammable, is commonly used at airports to fill aircraft tyres. The aviation source said: "Qantas took delivery of the new nitrogen cart 10 months ago. It looked exactly like the old oxygen cart. When the attachments did not fit they went and took them off the old oxygen cart and started using it."
The mistake was eventually spotted by an aircraft engineer. "He was walking around the plane and asked what they were doing. When they said they were topping up the oxygen, he said, 'No you're not, that's a nitrogen cart'," said the source.
The incident was reported to the Civil Aviation Safety Bureau, which confirmed that an investigation detected nitrogen in the crew oxygen tanks on the Boeing 747-300. A bureau spokeswoman said it was a one-off incident.
But the aviation source said: "This has affected at least 175 planes and Qantas has had to tell any other airline that has been serviced in Melbourne to check out its oxygen supplies."
Air New Zealand was told about the problem six weeks ago. "As a result of receiving that letter we did take some precautionary measures," a spokeswoman said. "The oxygen tanks on a small number of planes were removed, checked, reserviced and refilled. No irregularities were found."
A spokeswoman for the Australian Transport Safety Bureau said: "Very clearly they (Qantas) needed to carry out a risk assessment because there was a chance that other aircraft were affected.
"They identified 21 that were at risk because they had had a reasonable amount of oxygen top-up, so there was a reasonable chance they had been contaminated. There were another 30 aircraft at minor risk because they have had minor top ups," said the spokeswoman. The planes were inspected and no positive results found.
She said the airline had turned the error into a learning exercise and informed engineers all over the world about the mistake. "They have talked to thousands of their engineers around Australia and overseas, informing them about this lesson that has been learnt," she said.
Qantas engineering executive general manager David Cox said: "We had a guy using a new rig and he inadvertently serviced the crew oxygen with nitrogen. He realised what he was doing and flagged it."
Mr Cox said that once the mistake had been realised, extensive safety checks were put in place to ensure no other aircraft had been contaminated and that it could never happen again.
"Every aircraft, including customer aircraft, that could have been touched with this rig has been checked," he said after confirming the rig had been in use at the airport for several months. Mr Cox said the airline had been completely open in informing all safety authorities, staff and other airlines about the mistake.
This story was found at: http://www.theage.com.au/articles/20...568332267.html
NITROGEN USED TO FILL AIRCRAFT OXYGEN SYSTEMS
Airlines all over the world are being warned to check to make sure there’s actually oxygen in their aircraft oxygen systems after an embarrassing mix-up by Qantas Airlines at Melbourne International Airport. For ten months, crews have been filling airliner oxygen systems from a nitrogen cart that’s supposed to be used to fill tires. The mistake went unnoticed until a couple of weeks ago when an observant aircraft engineer spotted service workers using the cart. "He was walking around the plane and asked what they were doing. When they said they were topping up the oxygen, he said, 'No you're not, that's a nitrogen cart,'" an unnamed source told The Age. As anyone who works with industrial gases knows, oxygen tanks have different fittings than other gases to prevent exactly this kind of mix-up. However, when the crews discovered the fittings on what they thought was their new oxygen cart didn’t fit, they swapped them for the ones on the old cart they were retiring. Of course, Australian officials are looking into the error and Qantas has been busy notifying other airlines that use its services in Melbourne. Hundreds of aircraft may be affected.
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Not disclosed in this report is the reason why the oxygen bottle may have failed. I cannot believe the ATSB is that dumb. In fact they've been unable to come to any conclusions.
Cylinder failure
The ongoing engineering investigation into the apparent oxygen cylinder failure
will focus on (but not be limited to) the following:
• cylinder design, manufacturing methods and type testing procedures
• manufacturing quality control processes and results
• modes and mechanisms of cylinder failure
• historical oxygen and pressurised cylinder failure experiences, civil and military,
aviation and industrial
• cylinder degradation mechanisms
• the adequacy and efficacy of inspection, maintenance and repair processes,
procedures and equipment prescribed by the manufacturer and implemented by
maintenance organisations
• cylinder filling processes and procedures.
As the failed cylinder was not recovered, the ATSB is currently working with the
aircraft manufacturer, other aircraft operators and the oxygen cylinder
manufacturer, to obtain samples of cylinders from the same manufacturing batch as
the failed item, to facilitate the ongoing investigation of all relevant issues.
(And yes, I'm only SLF.)
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Didn´t the ATSB report state, that the ATSB is trying to inspect oxygen bottles from the same production batch as the failed one, if they can get them from other operators ?
I am really confident they will investigate further, now they are sure a failure of the bottle body was the first event in the sequence.
I am really confident they will investigate further, now they are sure a failure of the bottle body was the first event in the sequence.
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Does the CVR normally just run constantly or is it usually shut down when the aircraft isn't in use? I'm surprised that the CVR wasn't shut down until nearly an hour after the chocks were on. Unfortunately this delay means that the CVR has overwritten the recording from around the time of the depressuration as it only had a 2 hour capacity and it was left running for about 2.5 hours after the event.
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Rather Odd I thought
That the ATSB Prelim RPT thought it relevant to include the date of the Captain's last medical - but NOT the date of any of the ageing oxy cylinders last inspections and tests in accordance with CAR.
QANTAS of course has these records readily on hand....don't they?
QANTAS of course has these records readily on hand....don't they?
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ATSB slides:
http://www.atsb.gov.au/newsroom/2008...0_1mediaPP.pdf
Awesome pictures.
They were absolutely very lucky...
http://www.atsb.gov.au/newsroom/2008...0_1mediaPP.pdf
Awesome pictures.
They were absolutely very lucky...
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I'm surprised that the CVR wasn't shut down until nearly an hour after the chocks were on. Unfortunately this delay means that the CVR has overwritten the recording from around the time of the depressuration as it only had a 2 hour capacity and it was left running for about 2.5 hours after the event.
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Path of the lost cylinder.
From the report photos and diagrams it seems almost unbelievable that the cylinder having already inverted within the cabin, impacted above the door would then reverse its trajectory and exit via the same hole in the floor and thence into the blue yonder.
The diagram seems to indicate that part of the cylinder ruptured the skin but there was still enough pressure to propel the remainder.
That dammed cheese has caused a key bit of evidence to be lost.
The diagram seems to indicate that part of the cylinder ruptured the skin but there was still enough pressure to propel the remainder.
That dammed cheese has caused a key bit of evidence to be lost.
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Hi, The 744 smoke removal drill requires the a/c to be depressurised fully before moving the handle to open the "flapper doors" at the top and the bottom of the main door to remove smoke. So the cabin would have been pressurised to some extent until a period of time after the failure, if that what it was.
Regards
Exbiggles
Regards
Exbiggles
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The bank of cylinders connect to a common medium press supply line to the flow cont units. There are no check valve in the lines so all the cylinder will vent through the ruptured tubing at approx 600 PSI (outlet press of the reducer). The only check valve are in the fill lines.
I discovered a few weeks ago that the regulator(pressure reducer) attached to the plumbing on each bottle acts as a check valve. I hear it's becoming common practice to change a single bottle without shutting off all the other bottles. Didn't believe it until I tried it myself.
A/P Disconnect, My best GUESS.
Normally a manual input overpowers the CLCP's A/P control servo act. internal regulated pressure (internal CLCP stuff) and allows for manual override without A/P disc.
Normally a manual input overpowers the CLCP's A/P control servo act. internal regulated pressure (internal CLCP stuff) and allows for manual override without A/P disc.
Cheers.
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...it seems almost unbelievable that the cylinder having already inverted within the cabin, impacted above the door would then reverse its trajectory and exit via the same hole in the floor and thence into the blue yonder.
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Unctious:
Re nitrogen in the oxygen bottles...Didn't the report say that "The planes were inspected and no positive results found."?
The bottle was fitted to the aircraft only a few months before the incident. If the bottle came from an inspection/test facility, shouldn't they have discovered any corrosion/weaknesses?
Re nitrogen in the oxygen bottles...Didn't the report say that "The planes were inspected and no positive results found."?
The bottle was fitted to the aircraft only a few months before the incident. If the bottle came from an inspection/test facility, shouldn't they have discovered any corrosion/weaknesses?
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it seems almost unbelievable that the cylinder having already inverted within the cabin, impacted above the door would then reverse its trajectory and exit via the same hole in the floor and thence into the blue yonder.
If the cylinder broke into two segments only (speculation) then one piece might have caused the pressure-hull breach whilst another piece broached the passenger cabin before being sucked-out by the escaping cabin air.
I'd need to see the exact shape of the hole(s) in the cabin floor and compare them with the dimensions of the cylinder . . .
Incredible I'd say.
Now, to prove that the failure analysis theory is correct, it's usual to repeat the incident and observe the result . . .
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Here's the full ATSB preliminary report:
http://www.atsb.gov.au/publications/...053_Prelim.pdf
http://www.atsb.gov.au/publications/...053_Prelim.pdf
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Anyone know where the CVR CB is on the 744?
I had a quick look at the overhead panel yesterday but failed to find it.
It'd be a good one to know so you could stop the CVR as soon as you're on chocks after an event.
I had a quick look at the overhead panel yesterday but failed to find it.
It'd be a good one to know so you could stop the CVR as soon as you're on chocks after an event.
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If I read the preliminary report correctly, cylinder 4 (75cm long when intact) punched a hole roughly equal to its diameter (20cm) in the cabin floor near the R2 door, travelled upward about 2.5m - striking surfaces at least twice and changing attitude/direction - then fell again about 2.5m, and exited the cabin through the same 20cm hole. 
Smeg. What're the odds? (100% apparently, but I would never have guessed it.)
Thank goodness there were no casualties!
[Disclaimer: I am SLF and have no relevant engineering or professional accident investigation experience.]
Smeg. What're the odds? (100% apparently, but I would never have guessed it.)
Thank goodness there were no casualties!
[Disclaimer: I am SLF and have no relevant engineering or professional accident investigation experience.]