Qantas 744 Depressurisation
Join Date: Jul 2002
Location: UK
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
Maintenance personnel used a nitrogen cart filled with nitrogen. No mixup there.
The problem was, they were using it to top up the oxygen tanks. And since the fittings didn't, well, fit, they exchanged them for ones that did.
Bernd
The problem was, they were using it to top up the oxygen tanks. And since the fittings didn't, well, fit, they exchanged them for ones that did.
Bernd
Join Date: Feb 2004
Location: Australia
Posts: 1,307
Likes: 0
Received 0 Likes
on
0 Posts
Can anyone in the know tell me.... along with the auto announcement, does anything display on the pax screens aside from the 'fasten seatbelt' diagram (that is, if it doesn't, perhaps the steps for oxygen mask use should be displayed as well) I've never actually bothered to look at the screens when the announcement was playing on the ground...
Cockpit headset to oxygen mask microphone switching is automatic when the mask is pulled from its stowage box on QF 747-400's.
Second Law
Join Date: Jan 2008
Location: Wirral
Age: 77
Posts: 113
Likes: 0
Received 0 Likes
on
0 Posts
Chemist here and not chlorites in O2 generators, thread creep I know and I'm very happy for moderators to decide if the following needs removal.
The core chemistry of the oxygen generators I'm familiar with is based mainly on sodium chlorate (V) ie NaClO3, together with a few % of sodium chlorate (VII) ie NaClO4, together with a few % of barium peroxide BaO2.
That little lot is initiated with a percussion cap. The chemical reaction that follows is properly exothermic.
I can't find Delta H Standard Data as I am sure they will vary according to the mix but reacting can temperatures of > 200C are normal. They need careful packaging.
A final comment. These are seriously hazardous materials and any risk assessment I did would recognise the possibility of a terrorist misusing them.
Nuff said.
CW
The core chemistry of the oxygen generators I'm familiar with is based mainly on sodium chlorate (V) ie NaClO3, together with a few % of sodium chlorate (VII) ie NaClO4, together with a few % of barium peroxide BaO2.
That little lot is initiated with a percussion cap. The chemical reaction that follows is properly exothermic.
I can't find Delta H Standard Data as I am sure they will vary according to the mix but reacting can temperatures of > 200C are normal. They need careful packaging.
A final comment. These are seriously hazardous materials and any risk assessment I did would recognise the possibility of a terrorist misusing them.
Nuff said.
CW
Last edited by chris weston; 3rd Aug 2008 at 18:36. Reason: putting a second t in together
Join Date: Jan 2008
Location: Denver, CO
Posts: 265
Likes: 0
Received 0 Likes
on
0 Posts
Attn. Rottenray
‘What if the bottle blew in the direction of the pressure vessel (fuselage) and caused a failure which allowed the concentration of oxygen to exit? The fluid dynamics work, from a scientific point of view. Large pressure wave, failure, and immediate flow and escape aided by pressure within the vessel. Any comments?’
Yes, I agree entirely. All we need is to verify an earlier story that O2 bottle débris was found in the hold.
[Later] Oops — looks as though it has been verified. Could we be facing the end of the thread? Rainboe will have to take his self-importance elsewhere.
‘What if the bottle blew in the direction of the pressure vessel (fuselage) and caused a failure which allowed the concentration of oxygen to exit? The fluid dynamics work, from a scientific point of view. Large pressure wave, failure, and immediate flow and escape aided by pressure within the vessel. Any comments?’
Yes, I agree entirely. All we need is to verify an earlier story that O2 bottle débris was found in the hold.
[Later] Oops — looks as though it has been verified. Could we be facing the end of the thread? Rainboe will have to take his self-importance elsewhere.
I'm not a pilot, and I'm not a frequent flyer, and I'm not a "journo" attempting to incite bu**sh*t statements to take to press later this week...
But it really seems that the more any given operator outsources maintenance, the worse the maintenance becomes.
(Hopefully I won't have my feet held to a torch by folks who work for 3rd party maintenance outfits....)
Qantas has worked diligently to keep their reputation, and they've also spent great gobs of money following that same goal - and it's respectable.
I really think the industry needs to find a way to go back to the "golden days" - 30 to 40 years ago - when an operator took pride in its reputation and aggressively pursued protecting its reputation.
Carriers now don't really give a s**t - delays and poor service and crashes are sort of "expected," something for the insurance folks to worry about.
I miss the glory days of flying in the 1960s and 1970s (before deregulation in the US) and I have to say that getting on one of these stellar, over-built, normally safe jetliners is now a real disappointment. They're operated like cattle haulers, and traveling by Greyhound bus is now a more pleasant experience (except in Canada this week...)
Are we taking the whole miracle for granted? Making a flight from "A" to "B" happen is a very involved process, starting with the build of the craft and ending with the [safe] landing at the destination.
...
Join Date: Jan 2008
Location: Australia
Posts: 125
Likes: 0
Received 0 Likes
on
0 Posts
Have a look at this file, I just uploaded the PDF of the damage as it was sent to me....pics up close and personal.
RapidShare: Easy Filehosting
RapidShare: Easy Filehosting
Join Date: Dec 2000
Location: Off track, again
Posts: 68
Likes: 0
Received 0 Likes
on
0 Posts
Carriers now don't really give a s**t - delays and poor service and crashes are sort of "expected," something for the insurance folks to worry about.
Join Date: Aug 2005
Location: London, UK
Posts: 196
Likes: 0
Received 0 Likes
on
0 Posts
In the PDF there are two photos, 10 and 11 which I presume are the left side of the aircraft.. Is the picture included just for reference, or is there damage on that side of the aircraft too?
Download was fine, pictures worth a hundred words.
Fracture of supporting strips at top of the hole illuminating.
but did they ever find a top of the bottle (not just the valve)
I wonder how significant the blanket covering the bottles is to creating a significant local overpressure against the hull.
In the end I'm still concerned how to address preventive actions on what might be a one-off event.
Fracture of supporting strips at top of the hole illuminating.
but did they ever find a top of the bottle (not just the valve)
I wonder how significant the blanket covering the bottles is to creating a significant local overpressure against the hull.
In the end I'm still concerned how to address preventive actions on what might be a one-off event.
Join Date: Oct 2003
Location: Canberra Australia
Posts: 1,300
Likes: 0
Received 0 Likes
on
0 Posts
Photps show that the valve assy from the oxy bottle almost made it out through the side of the fuselage after trying to open a door. That bottle was very intent on its escape.
Early reports had some of the pax floor buckling. Serious if this is fact as it would indicate that the floor vents are inadequate or were partially blocked by loose debris during the decompression.
Early reports had some of the pax floor buckling. Serious if this is fact as it would indicate that the floor vents are inadequate or were partially blocked by loose debris during the decompression.
Join Date: May 2008
Location: Australia
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
The photo's 10 and 11 are Showing the left hand side of the aircraft just below door #2.
They show the two outward relief valves to be fully open, these valves open when the pressure inside the cabin becomes dangerously high compared to the pressure outside.
which could provide some information as to the actual sequence of events.
Cheers, a great photo sequence.
They show the two outward relief valves to be fully open, these valves open when the pressure inside the cabin becomes dangerously high compared to the pressure outside.
which could provide some information as to the actual sequence of events.
Cheers, a great photo sequence.
The Reverend
Join Date: Oct 1999
Location: Sydney,NSW,Australia
Posts: 2,020
Likes: 0
Received 0 Likes
on
0 Posts
When compartment to ambient differential pressure reaches 9.2psi, pressure relief valves open allowing compartment air to flow overboard. There is a backup servo that opens the relief valves at a diff. pressure of 9.65psi, should the 9.2psi remote servo signal fail to open the relief valves. When the over pressure condition is relieved, the valves close but the external flapper doors remain open, as shown on the photograph. So what caused the over pressure?
So what caused the over pressure
my initial thoughts were that the total volumn change from a bursting bottle wouldn't be enough.
I also considered wave reflection and felt that the blankets would have defeated that one.
I do however suspect that I am probably wrong at least in one of my considerations
lomapaseo,
How much can the contents of an 1850 psi bottle of oxygen expand to when those same contents are suddenly let free? Say the bottle contained 50 litres of volume and the pressure at sea level was 14.7 psi but the cargo compartment was at 8000 feet (10 psi or so?).
Would the contents suddenly expand to say 150 times (7500 litres). That would seem to be enough without any need to consider explosive ignition forces?
I would postulate that the outflow valves could NOT react in time to compensate for that sudden increase in gas volume and subsequent rise in pressure, without triggering the positive pressure safety valves.
What does the engineering mathematics indicate?
How much can the contents of an 1850 psi bottle of oxygen expand to when those same contents are suddenly let free? Say the bottle contained 50 litres of volume and the pressure at sea level was 14.7 psi but the cargo compartment was at 8000 feet (10 psi or so?).
Would the contents suddenly expand to say 150 times (7500 litres). That would seem to be enough without any need to consider explosive ignition forces?
I would postulate that the outflow valves could NOT react in time to compensate for that sudden increase in gas volume and subsequent rise in pressure, without triggering the positive pressure safety valves.
What does the engineering mathematics indicate?
Join Date: May 2000
Location: Seattle
Posts: 3,196
Likes: 0
Received 0 Likes
on
0 Posts
They show the two outward relief valves to be fully open, these valves open when the pressure inside the cabin becomes dangerously high compared to the pressure outside.
which could provide some information as to the actual sequence of events.
which could provide some information as to the actual sequence of events.