Qantas 744 Depressurisation
I might very have overlooked this but is there any mention in the preliminary report that cargo did exit the hull ?
As many others I find the "magic bottle" theory hard to believe (i.e ascending and reversing course as described).
As many others I find the "magic bottle" theory hard to believe (i.e ascending and reversing course as described).
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Well guys, as hard as it might be to believe a bottle could follow such a trajectory, the evidence is there that it did just as described. The green paint smears and the impact damage prove it.
What is incredible though, is that to cause such a trajectory, the bottle will had to rupture at the bottom. I'd assumed the thing would have failed at the weakest point - the neck/valve section, but there's no way the bottle would have been propelled upwards in that event. This thing must have exploded out its hemispherical bottom. Incredible stuff.
It is seriously unfortunate that they haven't recovered the bottle or sufficient pieces of the bottle to figure out why. Unless they can identify flaws in other bottles manufactured at the same time, this one could end up in the unknown category.
I note no.2 bottle was fitted at the same time as the exploding no. 4. I bet they've looked closely at that bottle, although it means little if the suspicion is that the failure was due to a casting flaw.
I also, along with others, have been wondering about the integrity of the remaining oxygen supply. The report notes the residual pressure, when inspected, was zero. I'd expect that, given the system remains on with masks dangling until well after landing. The big question though is (and the report doesn't get into it - it is a factual report only at this stage) whether the oxy supply to passengers went rapidly to zero due to the failure. Big ramifications if that was the case.
An incredible event, and incredibly good luck that no one was hurt, or worse.
p.s. atakacs: No, the report states that some cargo shifted towards the breach but nothing exited.
What is incredible though, is that to cause such a trajectory, the bottle will had to rupture at the bottom. I'd assumed the thing would have failed at the weakest point - the neck/valve section, but there's no way the bottle would have been propelled upwards in that event. This thing must have exploded out its hemispherical bottom. Incredible stuff.
It is seriously unfortunate that they haven't recovered the bottle or sufficient pieces of the bottle to figure out why. Unless they can identify flaws in other bottles manufactured at the same time, this one could end up in the unknown category.
I note no.2 bottle was fitted at the same time as the exploding no. 4. I bet they've looked closely at that bottle, although it means little if the suspicion is that the failure was due to a casting flaw.
I also, along with others, have been wondering about the integrity of the remaining oxygen supply. The report notes the residual pressure, when inspected, was zero. I'd expect that, given the system remains on with masks dangling until well after landing. The big question though is (and the report doesn't get into it - it is a factual report only at this stage) whether the oxy supply to passengers went rapidly to zero due to the failure. Big ramifications if that was the case.
An incredible event, and incredibly good luck that no one was hurt, or worse.
p.s. atakacs: No, the report states that some cargo shifted towards the breach but nothing exited.
Ron & Edna Johns
Incredible
In the end, the only thing that counts is the prevention scenario for future events. If it's something as simple as a coin tap test on the bottom of each bottle, as-installed, then I'm sure the industry will be happy to do it and put this extremely unlikely scenario behind us. If they can't come up with a simple prevention strategy then I expect that there is going to be several counter theories offered outside the official investigation.
Well guys, as hard as it might be to believe a bottle could follow such a trajectory, the evidence is there that it did just as described. The green paint smears and the impact damage prove it.
What is incredible though, is that to cause such a trajectory, the bottle will had to rupture at the bottom. I'd assumed the thing would have failed at the weakest point - the neck/valve section, but there's no way the bottle would have been propelled upwards in that event. This thing must have exploded out its hemispherical bottom. Incredible stuff.
It is seriously unfortunate that they haven't recovered the bottle or sufficient pieces of the bottle to figure out why. Unless they can identify flaws in other bottles manufactured at the same time, this one could end up in the unknown category.
What is incredible though, is that to cause such a trajectory, the bottle will had to rupture at the bottom. I'd assumed the thing would have failed at the weakest point - the neck/valve section, but there's no way the bottle would have been propelled upwards in that event. This thing must have exploded out its hemispherical bottom. Incredible stuff.
It is seriously unfortunate that they haven't recovered the bottle or sufficient pieces of the bottle to figure out why. Unless they can identify flaws in other bottles manufactured at the same time, this one could end up in the unknown category.
Incredible
In the end, the only thing that counts is the prevention scenario for future events. If it's something as simple as a coin tap test on the bottom of each bottle, as-installed, then I'm sure the industry will be happy to do it and put this extremely unlikely scenario behind us. If they can't come up with a simple prevention strategy then I expect that there is going to be several counter theories offered outside the official investigation.
Evertonian
Whilst we are all very greatful to the skill of the crew & the manufacturing techniques of Boeing for bringing this one home, I can only wonder at what they would have made of this if, in fact, it went into the drink.
Would anyone have ever determined the cause of this incident if they couldn't see it with their own eyes, or pieced it all together. I'm thinking of how many Comets were lost before a cause was determined (granted, the relativity of the events & the time), at least this has given us insight into another potentially dangerous piece of equipment that was previously considered innocuous.
Would anyone have ever determined the cause of this incident if they couldn't see it with their own eyes, or pieced it all together. I'm thinking of how many Comets were lost before a cause was determined (granted, the relativity of the events & the time), at least this has given us insight into another potentially dangerous piece of equipment that was previously considered innocuous.
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at least this has given us insight into another potentially dangerous piece of equipment that was previously considered innocuous.
If they really have been considered innocuous, then the aviation industry is well out of step with my (non-aviation) industrial experience.
Last edited by sooty655; 31st Aug 2008 at 17:09. Reason: remove un-necessary "quote"
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Cylinder fragments leaving the aircraft
Given the depressurisation took 20-25 seconds (App C of ATSB Prelim Report), it's not that surprising to me that loose materials near the hole below R2, including cylinder fragments, were sucked out of the aircraft. I would imagine that, within the first second or two of the incident, the main fragment of the exploded cylinder landed on the top of the main deck near the hole in the floor it had just made, and was then sucked back through the floor by the air rushing out.
I haven't read of any eyewitness reports from that part of the plane. Perhaps a passenger in that area might have glimpsed the cylinder's movements?
Figure 11 of the report (photo of hole in main deck taken from below) shows that the edges of the hole are pointing downwards - this is in the direction of the escaping air, not the initial passage of the cylinder fragment through the main deck floor. The downward curve would make it much easier for the cylinder to go back through the hole in created (if only the cups in putting greens were like this
)
Other fragments of the cylinder below the main deck are also likely to have been dragged overboard by the air exiting the aircraft in that initial half minute. That is, if they didn't leave the aircraft when they caused the hole...
As a scuba diver and an engineer (who's never worked for an airline, but used to work for an industrial gases company with millions of cylinders worldwide), I have a huge respect for gas cylinders, especially pressurised ones. I have no wish to see one fail first hand, but have seen failed cylinders, watched videos of exploding cylinders, and met a couple of people who've narrowly survived cylinder failures. Few of us have enough time in this life to make all the mistakes possible - please learn from other people's and treat cylinders with respect.
I haven't read of any eyewitness reports from that part of the plane. Perhaps a passenger in that area might have glimpsed the cylinder's movements?
Figure 11 of the report (photo of hole in main deck taken from below) shows that the edges of the hole are pointing downwards - this is in the direction of the escaping air, not the initial passage of the cylinder fragment through the main deck floor. The downward curve would make it much easier for the cylinder to go back through the hole in created (if only the cups in putting greens were like this
)Other fragments of the cylinder below the main deck are also likely to have been dragged overboard by the air exiting the aircraft in that initial half minute. That is, if they didn't leave the aircraft when they caused the hole...
As a scuba diver and an engineer (who's never worked for an airline, but used to work for an industrial gases company with millions of cylinders worldwide), I have a huge respect for gas cylinders, especially pressurised ones. I have no wish to see one fail first hand, but have seen failed cylinders, watched videos of exploding cylinders, and met a couple of people who've narrowly survived cylinder failures. Few of us have enough time in this life to make all the mistakes possible - please learn from other people's and treat cylinders with respect.
Evertonian
Innocuous in the sense that they are a known quantity & have rarely, if ever, caused this much of an issue on an aircraft. Besides, most items on an aircraft can be volatile, including the punters, so there are varying degrees by which they are considered.
I doubt that anyone at the coal face would treat them without respect.
I doubt that anyone at the coal face would treat them without respect.
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Cynical
I think everyone knows this - plus have read all of the media reports.
I think everyone knows this - plus have read all of the media reports.
Another reminder...
http://www.atsb.com.au/publications/...053_Prelim.pdf
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If it's something as simple as a coin tap test on the bottom of each bottle, as-installed, then I'm sure the industry will be happy to do it and put this extremely unlikely scenario behind us.
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O2 tanks and aircraft pressurization
Greetings.
When the news came out about the O2 tank that may have caused the depressurization of this a/c, the first question that entered my mind was:"Did the exploding tank cause the a/c to depressurize, or was it the depressurization of the a/c ITSELF that caused the O2 tank to fail?"
I am not an expert, AT ALL. Moreover, I am not one of those who instantly thinks that every a/c incident is due to sabotage, terrorists, or conspiracy. But, seriously.
You have an a/c with positive internal pressure and an O2 tank with positive internal pressure; the walls of the O2 tank are possibly weakened by invisible corrosion. If the normal internal pressure of an a/c is suddenly disrupted, is it possible that the exploding O2 tank is a symptom and not a cause?
It would take someone with more understanding than mine to answer.
SJ
When the news came out about the O2 tank that may have caused the depressurization of this a/c, the first question that entered my mind was:"Did the exploding tank cause the a/c to depressurize, or was it the depressurization of the a/c ITSELF that caused the O2 tank to fail?"
I am not an expert, AT ALL. Moreover, I am not one of those who instantly thinks that every a/c incident is due to sabotage, terrorists, or conspiracy. But, seriously.
You have an a/c with positive internal pressure and an O2 tank with positive internal pressure; the walls of the O2 tank are possibly weakened by invisible corrosion. If the normal internal pressure of an a/c is suddenly disrupted, is it possible that the exploding O2 tank is a symptom and not a cause?
It would take someone with more understanding than mine to answer.
SJ
"Did the exploding tank cause the a/c to depressurize, or was it the depressurization of the a/c ITSELF that caused the O2 tank to fail?"
Plus I guess the additional cabin pressure is tiny compared to the cylinder pressure, and these things are presumably designed for many, many pressure cycles (albeit slow not sudden).
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VH-Cheer Up:
The coin test is probably similar to the wheeltappers' test for railway wheels - hit the metal and if it's good it will ring with a clean note. If there's a crack then it won't.
The coin test is probably similar to the wheeltappers' test for railway wheels - hit the metal and if it's good it will ring with a clean note. If there's a crack then it won't.
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Dangers with High Pressure Energy.
Before this thread subsides we should ponder the potential havoc that high pressures can cause in our aircraft built to be as light as possible within the limiting design parameters learned during aviation's short developmental period.
As a TP I have mostly taken pressurised oxygen cylinders in aircraft for granted and am now prompted to review their potential for creating mayhem. Formerly the cylinders were just expected to be somewhere near their external charging point/s and of course I knew where the pressure gauges and controls happened to be. Now it all takes on a new dimension and we should be wary of where the cylinder/s are positioned and safely contained.
Other similar high pressure/temperature energy sources occasionally exhibit their destructive capabilities. These are
1. Portable oxy bottles
2. Air/nitrogen bottles for emergency back up to hydraulics,
3. Air bottles for floatation vest,slides and dinghies.
4. Nitrogen/gas bottles for replacing air in fuel tanks.
5. High temperature air bleed ducting from engines,
6. Hydraulic tubing more often at pressures over 3,000 psi.
7. Pressured bottles in freight.
8. The pressurised aircraft hull.
Hopefully we can continue to take most of the above for granted in the belief that the design parameters take care of most of our doubts and for some life dependent oxygen supplies there is a gradual change over to LOX (liquid oxygen).
There must be many reports now in the archives of oxygen cylinders being punctured by weapons during and since WW2 and the subsequent effects. I know of one Spitfire pilot whose aircraft and oxy bottle was hit by flack, the resulting fire from burning oil/fuel being most unhealthful. He survived and ended up marying his nurse. The RAAF lost an F-111 after a hot bleed air duct failed and caused a fire.
Where was the oxygen bottle in a Spitfire and what was the max pressure in those days?. Where are the bottles in your aircraft? Most of us probably don't recall where those incidental things are placed - sometimes it helps to know..
Before this thread subsides we should ponder the potential havoc that high pressures can cause in our aircraft built to be as light as possible within the limiting design parameters learned during aviation's short developmental period.
As a TP I have mostly taken pressurised oxygen cylinders in aircraft for granted and am now prompted to review their potential for creating mayhem. Formerly the cylinders were just expected to be somewhere near their external charging point/s and of course I knew where the pressure gauges and controls happened to be. Now it all takes on a new dimension and we should be wary of where the cylinder/s are positioned and safely contained.
Other similar high pressure/temperature energy sources occasionally exhibit their destructive capabilities. These are
1. Portable oxy bottles
2. Air/nitrogen bottles for emergency back up to hydraulics,
3. Air bottles for floatation vest,slides and dinghies.
4. Nitrogen/gas bottles for replacing air in fuel tanks.
5. High temperature air bleed ducting from engines,
6. Hydraulic tubing more often at pressures over 3,000 psi.
7. Pressured bottles in freight.
8. The pressurised aircraft hull.
Hopefully we can continue to take most of the above for granted in the belief that the design parameters take care of most of our doubts and for some life dependent oxygen supplies there is a gradual change over to LOX (liquid oxygen).
There must be many reports now in the archives of oxygen cylinders being punctured by weapons during and since WW2 and the subsequent effects. I know of one Spitfire pilot whose aircraft and oxy bottle was hit by flack, the resulting fire from burning oil/fuel being most unhealthful. He survived and ended up marying his nurse. The RAAF lost an F-111 after a hot bleed air duct failed and caused a fire.
Where was the oxygen bottle in a Spitfire and what was the max pressure in those days?. Where are the bottles in your aircraft? Most of us probably don't recall where those incidental things are placed - sometimes it helps to know..
A coin tap on an empty vessel is OK. But who in their right mind would tap a charged high pressure vessel which might be cracked with anything, it could set it off. Good result then if it goes, but not if you are close to it.
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O2 Bottle does not have to fail in the base to fly upwards. Good pics of hole in factory roof with intact bottle lying 10 m away.Also some detail on initial velocity on neck connection failure and possible distance of travel if not adequately restrained.
http://www.oseh.umich.edu/OSEH%20Presentations/Rhonda.pdf
http://www.oseh.umich.edu/OSEH%20Presentations/Rhonda.pdf
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coin tap
The coin tap maybe ok on seperations in certain laminated type structures, but I think 1800 psi would find something sooner than a tapped coin.
X ray HFEC magnaflux borescope etc maybe better.
I digress but....I am reminded of the bugs bunny show where one of the characters is tap testing bombs and labelling the ones that dont explode as duds.lol.
I miss bugs bunny and the crew , when cartoons were funny
X ray HFEC magnaflux borescope etc maybe better.
I digress but....I am reminded of the bugs bunny show where one of the characters is tap testing bombs and labelling the ones that dont explode as duds.lol.
I miss bugs bunny and the crew , when cartoons were funny
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Illogical thinkers
O2 Bottle does not have to fail in the base to fly upwards.
Ooooh sorry but that's probably too complex a concept for the level of debate here.
The O2 bottle was stowed sitting on it's base. Pray please show me how an intact gas cylinder sitting on it's base flies upwards ?
I suppose if an accident report concluded the earth was flat, PPRuNers would spend months debating how they got it wrong about the earth being round.
If the cylinder went up through the floor before the fuselage ruptured, how did the bottle get "sucked" back down ?
PPRuNe raises illogical thinking to new highs.
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Well the laws of physics for a gas bottle aren't much different from a balloon. If you want a balloon to fly upwards you have to invert the balloon with the neck beneath so that air rushed out the bottom.
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Argonite cylinder(s) explode.
The explosion is believed to have been caused by an argonite cylinder used in a fire suppression system which exploded inside the building.
Group commander of Hertfordshire Fire and Rescue Service, Jon Smith, said a cylinder of the inert gas depressurised, acting like a missile and setting off other cylinders.
He said: "Each cylinder weighs about 50kg and is about 5ft tall, they've made a real mess of the inside of the building, they've taken down walls and floors.
"The external structure is intact, but 50% of the internal structure has been affected, walls are down, floors are up and walls knocked out.
"These cylinders have become missiles and fired around randomly."
Group commander of Hertfordshire Fire and Rescue Service, Jon Smith, said a cylinder of the inert gas depressurised, acting like a missile and setting off other cylinders.
He said: "Each cylinder weighs about 50kg and is about 5ft tall, they've made a real mess of the inside of the building, they've taken down walls and floors.
"The external structure is intact, but 50% of the internal structure has been affected, walls are down, floors are up and walls knocked out.
"These cylinders have become missiles and fired around randomly."
For some reason the valve was sheared off one of six 47kg 'argonite' cylinders being installed for fire protection purposes while the cylinders were being moved. The cylinder became a 'missile' and in flying around the building knocked the valves off the other cylinders which also took off, some ending up to 40m away from their original position.
Evertonian
Small world eh?
One of the pilots is the neighbour of my Brother in Law...although, not the B.I.L. on the flight....
...And, he's made a very nice gesture too.
Good to see that some QF staff are keen to go the extra mile...
One of the pilots is the neighbour of my Brother in Law...although, not the B.I.L. on the flight....
...And, he's made a very nice gesture too.
Good to see that some QF staff are keen to go the extra mile...