Qantas 744 Depressurisation
Join Date: Oct 2001
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Hotdog,
I know what a pallet is and I know its location with regard to the bottles. I have seen LD containers jammed, broken and the damage that can cause. This is not a regular occurrence, but it is a far more common event than an O2 bottle uncontained failure. What is a more likely event, an O2 bottle rupture due to an unnoticed mechanical failure or an incorrectly loaded and strapped down pallet allowing whatever is on it to move? Cargo hold sidewall panel blowout panels get dislodged regularly, O2 bottle explosions do not.
I know what a pallet is and I know its location with regard to the bottles. I have seen LD containers jammed, broken and the damage that can cause. This is not a regular occurrence, but it is a far more common event than an O2 bottle uncontained failure. What is a more likely event, an O2 bottle rupture due to an unnoticed mechanical failure or an incorrectly loaded and strapped down pallet allowing whatever is on it to move? Cargo hold sidewall panel blowout panels get dislodged regularly, O2 bottle explosions do not.
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O2
Lots of comments about O2 on this thread. I wanted to clairify what most already know, O2 will NOT burn on its own. O2 needs a 'fuel' to oxidize. Without something to oxidize, no fire/explosion is possible.
Atmospheric O2 is about 21%. Even in a 100% O2 atmosphere most materials react no different to the naked eye. If anyone has seen Li, it is stored in a liquid (oil????) becuase if it contacts air, the 21% O2 is enough for it to 'burn', while the O2 in liquid is not enough and thus it is more stable.
The same is true in air. There are SOME materials that will self ignite in a 100% O2 atmosphere that do not in a 21% atmosphere. Chemically this comes down to more O2 molecules being able to 'touch' the surface of the material in a given time and thus raise the heat enough to 'sustain' the reaction. (over simple I know but gets the point across)
As a SLF with a first degree in BioChem, I know little of the chemical make ups of materials in the area of the 747 O2 tanks, but would be very surprised to learn any material used on an airframe itself would self ignite even in a 100% O2 atmosphere. I may be wrong, but that is a guess in part based on the very few materials that actualy can self ignite in a 100% O2 enviroment but are 'safe' in a 21% enviroment.
Thus the idea that a leak itself CAUSED an explosion is very unlikly. I can not see pure O2 contacting any material in an aircraft and thus causing a fire. The idea obove of an O2 leak causing a fire by 'touching' a fuel source (Hat on O2 tank in cockpit, O2 leak on rust inhibitor) seems very unlikly, but I would of course not deny it without testing/research. However, if a leak were present and thus an atmosphere with high O2 concentration existed, an ignition source would have a much higher chance of causing an explosion. From posts above, THIS DOES NOT SEEM to be the case.
I would suggest that whatever caused this sitaution is independent of the actual gas compressed in the tank. (unless caused by some interaction of the gas and tank/fittings itself).
TME
Edited to correct O2 concentration to 21% from 16% (16% is after breathing and a mix up from my CPR training
)
Atmospheric O2 is about 21%. Even in a 100% O2 atmosphere most materials react no different to the naked eye. If anyone has seen Li, it is stored in a liquid (oil????) becuase if it contacts air, the 21% O2 is enough for it to 'burn', while the O2 in liquid is not enough and thus it is more stable.
The same is true in air. There are SOME materials that will self ignite in a 100% O2 atmosphere that do not in a 21% atmosphere. Chemically this comes down to more O2 molecules being able to 'touch' the surface of the material in a given time and thus raise the heat enough to 'sustain' the reaction. (over simple I know but gets the point across)
As a SLF with a first degree in BioChem, I know little of the chemical make ups of materials in the area of the 747 O2 tanks, but would be very surprised to learn any material used on an airframe itself would self ignite even in a 100% O2 atmosphere. I may be wrong, but that is a guess in part based on the very few materials that actualy can self ignite in a 100% O2 enviroment but are 'safe' in a 21% enviroment.
Thus the idea that a leak itself CAUSED an explosion is very unlikly. I can not see pure O2 contacting any material in an aircraft and thus causing a fire. The idea obove of an O2 leak causing a fire by 'touching' a fuel source (Hat on O2 tank in cockpit, O2 leak on rust inhibitor) seems very unlikly, but I would of course not deny it without testing/research. However, if a leak were present and thus an atmosphere with high O2 concentration existed, an ignition source would have a much higher chance of causing an explosion. From posts above, THIS DOES NOT SEEM to be the case.
I would suggest that whatever caused this sitaution is independent of the actual gas compressed in the tank. (unless caused by some interaction of the gas and tank/fittings itself).
TME
Edited to correct O2 concentration to 21% from 16% (16% is after breathing and a mix up from my CPR training
)
Last edited by TeachMe; 30th Jul 2008 at 17:31.
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Some people seem to think that flying around in a metal cylinder at 800kph is perfectly safe.
If your average pax for one second thought it to be unsafe, there wouldn't be an airline industry.
MaxTow said:
Of course he/she expects a serious answer, because it is a serious question. Read the ASTB statement more carefully:
484 masks dropped down and 418 were ACTIVATED. That is 72 more than required for the number of passengers. What caused so many passengers to activate more masks?
PS Infrequent Flyer 789: "Also, 346 passengers, but 418 masks activated - something clearly wasn't right." You expect a serious answer to that?
According to the airline, there were 346 passengers on board. Inspection by the ATSB shows that 484 masks had deployed, that is, dropped from the ceiling. Of those, 418 had been activated by pulling on the mask to activate the flow of oxygen.
Serious concern
As we Brits might say, serious concern would cause that. Try reading up on Human Factors. Some of the issues apply to the PAX aswell.
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HotDog -- The missing cylinder resided vertically between stations 800 and 820. I do agree it would be nearly impossible for a cylinder to tip its top into the load area. Even if not strapped, the connected stainless lines would prevent it.
PJ2 -- thanks for the photos! Yes, remnants of the missing cylinder's mount. This zoom of a previous pic centers it and shows the floor breach:
PJ2 -- thanks for the photos! Yes, remnants of the missing cylinder's mount. This zoom of a previous pic centers it and shows the floor breach:
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"What caused so many passengers to activate more masks? "
Could it be that when masks drop in groups of 3 or 4 that when one mask is activated 02 flows to all masks in the group? So more masks would have been activated than the actual pax number.
It may also be explained by passengers grabbing more than one mask, thinking the first one is not working.
Could it be that when masks drop in groups of 3 or 4 that when one mask is activated 02 flows to all masks in the group? So more masks would have been activated than the actual pax number.
It may also be explained by passengers grabbing more than one mask, thinking the first one is not working.
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On a ring system, each mask has its individual pin, that when pulled, releases flow to that mask. On a generator system, all 2/3/4 masks are connected to 1 pin that when pulled, activates the generator to supply O2 to all the masks connected to it.
I don't own this space under my name. I should have leased it while I still could
In a block of seats, if only two seats were occupied but 4 masks were swinging I would probably grab hold of them and in the process activate them.
Having experienced several rapid descents I can say it is not a comfortable experience even if the angle of dangle is only 6 degrees, the noise level and temperature drop will all contribute to the anxiety factor.
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Masks
If QF cabin refits are like many others, when Business Class and First are retrofitted with new look cabins, the old 3 masks are still in place for sometimes what is now a single or double seat... could this not be the case for the additional deployed .. you know what people in shock are - lets try another mask and see if there is more oxygen flow.....
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is 4000ft/min a normal rate of descent in case of decompression ?
Join Date: Jul 2007
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honours to the crew
ATSB: "From the evidence gathered to date it appears that the flight crew have responded to and managed the emergency situation extremely well."
Finally some official laurels for the crew.
Give them a medal as big as the hole in their hull and as heavy as the missing oxygen cylinder!
Finally some official laurels for the crew.
Give them a medal as big as the hole in their hull and as heavy as the missing oxygen cylinder!
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door 2right
how did the crew react to the door handle being in the position of being nearly opened, ceiling panels down and an unstable floor? As an ex cabin service director operating on B747's this situation would not have been covered in any SEP situation.
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Originally Posted by infrequentflyer789
...Maybe the lifejackets should all have a survival kit attached - say foil blanket, firelighters, flares, knife, etc.
Won't happen ... weighs and costs too much. And a KNIFE? You crazy?
But all of you people that DO live in places where big snowdrifts happen, and multiple pile-ups of semis DO happen, and where people are known to have spent the night out on the road in such circumstances...
How many of you DO have a basic survival kit in the back of the car? A foil blanket for a start?
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Just above the regulators on all of the bottles is the first officers back up aileron cables covered in grease.
Grease on cables allows them to pick up dirt and lint, which leads to premature wear of the pulleys and cables themselves.