Qantas 744 Depressurisation

[Dr Illitout]

Ozthai 999
That brings us back to my theory (Expressed weeks back on this very forum) http://www.pprune.org/rumours-news/336528-qantas-744-depressurisation-13.html#post4289735That If there was a fastener of incorrect length fitted to that fairing and the tail of the fastener had damaged the pressure hull causing a weak spot....... Would the subsequent failiure cause the O2 cylinder to disintergate aswell? and what damage would that cause?

Rgds Dr I

[lomapaseo]

I believe that the oxygen bottle is pretty impervious to extremely rough handling, pressure changes etc. The most I could see is the fittings at the top failing.

However since I still have not seen confirmed facts that the bottle itself exploded, all theories are still guesses

[arcniz]

Is there any possibilty that the hull could have failed first, (for some unknown reason). Subsequently the rapid decompression of the cargo hold caused an extreme pressure difference between the bottle and ambiant pressure then the faulty fitting blew off the bottle and the bottle torpedoed out increasing the hull demage.

Along the same lines: A possibly more likely mechanism if one considers the scenario of hull-failure preceding O2 bottle failure, is that some object or objects in the cargo hold were caught up in the outflow of pressure-hull air following the breech. Accelerated in the wave of outflow, an object hits the O2 cylinder with considerable force at just the point where the valve stem meets the flask. Effect of this collision is to break the valve stem or the threaded section of bottle just below it, causing the liberated valve to depart upward on the path observed in the airframe damage. Subsequently the bottle might possibly have remained roughly in place as the pressure released, thrashing around and perhaps tearing out its attaching tethers, until it was ultimately carried out the starboard airframe hole by buffeting turbulence (and suction) from external airflow or by cabin air outflow.

[Falcon124]

Is there any possibilty that the hull could have failed first, (for some unknown reason). Subsequently the rapid decompression of the cargo hold caused an extreme pressure difference between the bottle and ambiant pressure then the faulty fitting blew off the bottle and the bottle torpedoed out increasing the hull demage.


The pressure differential wouldn't do it. It would be more like a part of the hull failed and, in the process of things going out or the hull opening outwards in the decompression, the top of the O2 bottle got damaged causing the fittings to get blown off and up into the cabin.

CASA have just released an urgent AD for improved inspections of lap joints in the area of the wing/fuselage join (eg: right where this occurred).

[lomapaseo]

CASA have just released an urgent AD for improved inspections of lap joints in the area of the wing/fuselage join (eg: right where this occurred).

Perhaps somebody can post a copy of the words that CASA used to justify the AD in order to see if there is any linkage with this thread discussion.

It seems that if this is not unique to Qantas than the FAA as the regulator of the certicate holder is bound to verify and reissue a broader AD .

I'm not sure yet if this is a clue in this thread.

[Capt Kremin]

The cabin crew in the first class section reported seeing something akin to a blast wave of dust and condensation coming forward from the area of the hole at R2, which then reversed itself as the air was sucked out of the hole.

The clear inference is that the bottle exploded first, causing the hole which then caused the depressurisation.

[Falcon124]

Perhaps somebody can post a copy of the words that CASA used to justify the AD in order to see if there is any linkage with this thread discussion.I posted a full link to the AD last night but got told by the system it was being held for a moderator - haven't seen it since.

Here's the text:

Applicability:
Model 747-100, -100B, -100B SUD, -200B, -200C, -200F, -300, -400, 747SR, and 747SP series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-53A2312, Revision 3, dated February 8, 2007 or later FAA approved revision.

Requirement:
Action in accordance with the technical requirements of FAA AD 2008-16-14 Amdt 39-15632.

Note:
Boeing Alert Service Bulletin (ASB) 747-53A2312 Revision 3 or later FAA approved revision refers.

Compliance:
As specified in the requirement document.

This Amendment becomes effective on 17 September 2008.

Background:
This Directive was prompted by reports of cracking in the stringer 34 lap joint near the interface with the wing-to-body fairing. This condition, if not corrected, could result in an in-flight depressurisation of the aircraft.

Amendment 1 reduced the number of aircraft to be inspected and widened the inspection area to include all lap splice upper rows under the wing-to-body fairing.

Amendment 2 allowed use of ASB 747-53A2312 Revision 3 as an alternative method of compliance with the requirements of FAA AD 94-15-06.

Amendment 3 is issued to change the requirement document. FAA AD 94-15-06 Amdt 39-8977 is superseded by FAA AD 2008-16-14 Amdt 39-15632. This results in a change to the High Frequency Eddy Current inspection method due to possible faulty results when inspecting Alodine-coated rivets; adds an additional one time inspection for cracking; and terminates the adjusting factor for the inspection compliance times based on cabin differential pressure.

[Falcon124]

And here's the URL (posted separately in case it's the URL that's causing the moderator flag):

http://www.casa.gov.au/airworth/airwd/ADfiles/over/b747/b747-128.pdf

[HotDog]

This confirms my suspicions of the pressure hull breach being caused by an exploding oxygen cylinder. Still does not explain the fact that the overpressure valves were activated?

[ampclamp]

I think a couple of cubic feet of oxy turning into many times that in an instant is enough to pop the Op valves.The rate of expansion would imho exceed the rate at which the entire hull could absorb or release the pressure.The hull breach itself may have come very shortly after the initial explosion with parts of the cylinder likely belting around violently.Even if the hull went straight away the instantaneous increase in pressure would likely pop the valves too being the weak point in an OP situation and relatively nearby the source.

Heard an interesting rumour regarding the reason why it went off.Pretty conclusive if its a fact.And not surprising it did go off..... if true.:oh:

[lomapaseo]

Thanks for the AD link.

Personaly I don't see a direct link to this thread.

It appears that Boeing simply issued a modification to an existing service bulletin and the CAA in an abundance of caution in their current fishbowl raised this to an AD.

No where does it cite new information based on formal investigative findings.

BTW Hotdog

The judges have decided that it is premature to award you a gold medal for the best theory about what caused this incident :}

[forget]

Heard an interesting rumour regarding the reason why it went off.Pretty conclusive if its a fact. And not surprising it did go off..... if true.

Come on then! This is a Rumour network.

As a complete aside- John Coates, the head of Australian Olympic Committee, has conceded publicly that the Poms might edge out the Aussies. "Not bad for a country that has no swimming pools and very little soap." Pom :)

[Falcon124]

It appears that Boeing simply issued a modification to an existing service bulletin and the CAA in an abundance of caution in their current fishbowl raised this to an AD.

No where does it cite new information based on formal investigative findings.

True that - but it is interesting that it's the area of the blow out, thus my reason for bringing it up :)

[lomapaseo]

True that - but it is interesting that it's the area of the blow out, thus my reason for bringing it up

Agree and thanks for the tip off. By now the excellent metalurgists at the AAIB have covered this aspect so keep your eye on what and if the FAA says about this.

[CAAAD]

Iomapaseo - The CAA encouraged by AAIB often found it necessary to raise ADs on US products when the FAA approach seemed insufficiently robust.
But the glass bowl residents in this case are CASA, Aussies, nothing to do with the Brits.

[moa999]

comment from crikey.com.au reporting on the Qantas AGM today

"However he did say all of the 737s in question were back in service, and that the damage to the 747-400 that made an emergency diversion to Manila last month would cost less than $10 million to repair and would return to service in October. "

[ampclamp]

The rumour was, allegedly the bottle was dropped onto concrete during servicing elsewhere and refitted.

[lomapaseo]

The rumour was, allegedly the bottle was dropped onto concrete during servicing elsewhere and refitted.

Shouldn't have bothered the bottle and the refitting should have addressed the externals.

[Private jet]

As a complete aside- John Coates, the head of Australian Olympic Committee, has conceded publicly that the Poms might edge out the Aussies. "Not bad for a country that has no swimming pools and very little soap." Pom

forget.....

Maybe it should be remembered that the australians ancestors were handpicked by the best english judges?? lol

[ampclamp]

That of course depends from what height the cylinder was dropped.
From what I hear it was not insignificant.
Anyway just a strong rumour and subject to confirmation.

[flynerd]

"... and that the damage to the 747-400 that made an emergency diversion to Manila last month would cost less than $10 million to repair and would return to service in October. Well I hope they convert it to a freighter and fly it (only over un-populated areas) using remote control. :hmm:

[Tankengine]

Why nerd??
If rivetted back together properly and the wiring etc fixed this A/C will be in the same condition as hundreds or thousands of airliners around the world!:ugh:

[flynerd]

If rivetted back together properly and the wiring etc fixed this A/C will be in the same condition as hundreds or thousands of airliners around the world!
In retrospect, I think you are correct :ouch: Seeing an AC through a major refit would likely make me pause before flying in it! In this particular case I would guess that 99% of the AC is in as good condition as before the event. So, yes, I would fly in it once fixed :)

Flynerd

[Grunf]

Flynerd,

What's bad about "major refit"? I can assure you where I work we cover for the next 16K cycles (747-400 "refit" = conversion)

Regards

[flynerd]

They just look so bad at the time with all those covers and bits missing. I know it is all for the better!

[aussiepax]

SAFETY investigators will tomorrow release an initial report into the mid-air explosion that left a Qantas jet with a hole in its fuselage and forced it to make an emergency landing in Manila.
The explosion late last month (http://www.news.com.au/story/0,23599,24076175-2,00.html) tore through part of the fuselage of the Melbourne-bound Boeing 747-400 plane with 365 people on board, causing depressurisation.
The Australian Transport Safety Bureau will release its preliminary factual report in Canberra tomorrow.

Report on Qantas explosion tomorrow | The Daily Telegraph (http://www.news.com.au/dailytelegraph/story/0,22049,24256171-5001028,00.html)

[gulfboy]

The Sydney Morning Herald reported likewise.

Qantas 'explosion' report to be released - Breaking News - National - Breaking News (http://news.smh.com.au/national/qantas-explosion-report-to-be-released-20080828-44va.html)

Well, what goes around comes around......
Remember how the mighty Qantas was acting whan Ansett had some problems a few years ago? Always good when the spouse of the (at the time) Minister for Transport was sitting on the board of QF:ugh:

[beamender99]

MEDIA ALERT : 28 August 2008 - ATSB Preliminary Factual Report, Depressurisation 475 km north-west of Manila, Philippines, 25 July 2008 (http://www.atsb.gov.au/newsroom/2008/alert/2008_32.aspx)

says

MEDIA ALERT 2008/32

ATSB Preliminary Factual Report, Depressurisation 475 km north-west of Manila, Philippines, 25 July 2008

28 August 2008

A media conference to release the Preliminary Factual Report on the investigation into the circumstances surrounding the depressurisation 475 km north-west of Manila, Philippines on 25 July 2008, will be held: Friday 29 August 2008
Where: 15 Mort Street, CANBERRA Time: 10:30 am (local time)

Mr Julian Walsh, acting Executive Director will discuss factual information known to the investigation team at this time and will outline the investigation process

Media release when available should be at Media Releases and Alerts (http://www.atsb.gov.au/newsroom/media.aspx)

[ZAGORFLY]

last Thu 21 August I photographed the plane still in Manila. With a black ducted tape (apparently) right side covering the hole and the door .

question: Since partial door opening in fly is possible in 747s for smoke removal i wonder why ad how the doors did not open when the Flying valve did hit the handle in more than 12 o'clock position..

any comment about?

[flynerd]

The report by the Australian Transport and Safety Bureau (ATSB) contains a detailed account of how the passenger oxygen cylinder - one of seven carried on the flight - failed and then exploded in the aircraft hold.
It says the cylinder ruptured the fuselage, punctured the cabin floor and entered the cabin before falling to the cabin floor and falling out of the aircraft through the ruptured fuselage.
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.
<- from abc.net.au news site

Nothing surprising there!

Flynerd

[cjsyd]

The 2.5MB prelim report is at:
http://www.atsb.gov.au/publications/investigation_reports/2008/AAIR/pdf/AO2008053_Prelim.pdf

Abstract:
On 25 July 2008, at 0922 local time, a Boeing Company 747-438 aircraft (registered VH-OJK) with 365 persons on board, departed Hong Kong International airport on a scheduled passenger transport flight to Melbourne, Australia. Approximately 55 minutes into the flight, while the aircraft was cruising at 29,000 ft (FL290), a loud bang was heard by passengers and crew, followed by the rapid depressurisation of the cabin.

Oxygen masks dropped from the overhead compartments shortly afterward, and it was reported that most passengers and crew commenced using the masks. After donning their own oxygen masks, the flight crew carried out the 'cabin altitude non-normal' checklist items and commenced a descent to a lower altitude, where supplemental breathing oxygen would no longer be required. A MAYDAY distress radio call was made on the regional air traffic control frequency. After levelling the aircraft at 10,000 ft, the flight crew diverted to Ninoy Aquino International Airport, Manila, where an uneventful visual approach and landing was made. The aircraft was stopped on the runway for an external inspection, before being towed to the terminal for passenger disembarkation.
Subsequent inspection of the aircraft by the operator's personnel and ATSB investigators, revealed an inverted T-shaped rupture in the lower right side of the fuselage, immediately beneath the wing leading edge-to-fuselage transition fairing (which had been lost during the event). Items of wrapped cargo were observed partially protruding from the rupture, which extended for approximately 2 metres along the length of the aircraft and 1.5 metres vertically.

After clearing the baggage and cargo from the forward aircraft hold, it was evident that one passenger oxygen cylinder (number-4 from a bank of seven cylinders along the right side of the cargo hold) had sustained a sudden failure and forceful discharge of its pressurised contents into the aircraft hold, rupturing the fuselage in the vicinity of the wing-fuselage leading edge fairing. The cylinder had been propelled upward by the force of the discharge, puncturing the cabin floor and entering the cabin adjacent to the second main cabin door. The cylinder had subsequently impacted the door frame, door handle and overhead panelling, before falling to the cabin floor and exiting the aircraft through the ruptured fuselage.

The investigation is continuing.

[cirrus32]

link to the report ...


200804689 (http://www.atsb.gov.au/publications/investigation_reports/2008/AAIR/aair200804689.aspx)

[NSEU]

The report by the Australian Transport and Safety Bureau (ATSB) contains a detailed account of how the passenger oxygen cylinder - one of seven carried on the flight -

Already a misquote of the official report? :ugh:

It's interesting to note that the bulk of the bottle went through the ceiling including the valve. This seems to suggest that the bottle fractured at the bottom. Strange.

Also of note is the recent fitment date (the bottle was installed only a few months prior to the incident).

Did the Right A/P disconnect because of the sudden movement of the F/O's aileron cables or because an electrical signal was lost due to the damaged wiring looms?

Rgds.
NSEU

[Yamagata ken]

The reports states that the cables were severed.

Do the oxygen systems have non-return valves? That is, does the loss of integrity allow the entire system to leak down, or is there something to prevent this?

[Bolty McBolt]

question: Since partial door opening in fly is possible in 747s for smoke removal i wonder why ad how the doors did not open when the Flying valve did hit the handle in more than 12 o'clock position..

any comment about?

The door handle mechanism or shaft sheared during the violent movement of the handle when it was struck by the oxy cylender :ok:
Check the pics of the handle embedded in the door bustle, handle at 12 oclock postion.

[Short_Circuit]

Yamagata ken
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. :}


NSEU
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. However it is possible with an unusually large and rapid manual input the internal regulated pressure momentarily pressure locked causing the A/P piston to hold against manual input arm whilst the output rod moved creating an error signal between A/P LVDT pos & output LVDT enough to cause the A/P to disengage.

OR a wire was taken out. Unlikely as the Right A/P drives the Left CLCP and I would suggest the wiring would route down the left side of the cargo hold.:ooh:

[ExSp33db1rd]

ZAGORFLY # 1030

from the report:~


Cabin door

All main cabin doors of the 747-400 aircraft type were designed as outward opening‘plug doors’. A plug door is designed to be physically larger than the doorway opening, and mates with the frame around the full circumference when in position. It is designed to increase the security of the pressurised fuselage, with pressurisation loads serving to force the door more tightly against the frame.
Retractable gates at the top and bottom of the door serve to allow it to move inward and then sideways through the door frame during the opening and closing process when the aircraft is not pressurised. The plug door design provides for a level of protection against inadvertent or intentional attempts to open the door while the aircraft is in flight. A latch mechanism holds the door in the closed position whenthe aircraft is not pressurised.

[Yamagata ken]

Thanks Short Circuit. :ok:

That's what I suspected. It would still take some time to leak down, and better than nothing at max altitude.

[Oilandgasman]

Interesting report. Can anyone confirm if these metal cylinders have a threaded plug in the base? Other cylinders do, but not clear if this type had.

[triton140]

No threaded plug in base ......

[raffele]

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 (http://news.bbc.co.uk/1/hi/world/asia-pacific/7587383.stm)

[Spotted Reptile]

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.

[G-CPTN]

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):-
http://www.cartoonstock.com/lowres/dre0220l.jpg

[lomapaseo]

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

[UNCTUOUS]

"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.

[Hbr]

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.

Probably because it's a PRELIMINARY Report. In which they clearly state under 'ONGOING INVESTIGATION ACTIVITIES';

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.)

[Volume]

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.

[r1ch]

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.

[Diesel Fitter]

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?

[Manoka]

ATSB slides:
http://www.atsb.gov.au/newsroom/2008/release/files/QF30_1mediaPP.pdf
Awesome pictures.
They were absolutely very lucky...

[arcniz]

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.

Similar circumstances (CVR stays on until overwritten) seem to often occur quite often when "incidents" do not progress to "accidents". One may draw one's own conclusions...

[beamender99]

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.

[EXBIGGLES]

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

[NSEU]

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.

Short Circuit...
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.

Interesting... The way I undestood it was that if the autopilot LVDT signals disagreed with the output LVDT signals, a camout would develop.... or are the autopilot LVDT signals tracking the manual override input? The plumbing on those CLCP's is a proverbial rats nest and difficult to understand.

Cheers.
NSEU

[Mark in CA]

...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.
Not really reversing trajectory. Rather, just either falling straight down or perhaps bouncing back down after hitting the overheads. I'd imagine most of its energy had been spent after rocketing through the floor, hitting the door frame and handle and impacting the overhead bin.

[NSEU]

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?

[G-CPTN]

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.
Whilst I'm prepared to believe that the missing cylinder exited through the hole in the pressure hull, I'm sceptical that an exploded (ie fractured) cylinder could result in all fragments being evacuated (though clearly the vacuum effect of the hull rupture would be considerable and anything loose could be sucked out). Such combinations of events do happen (miracle?), but the probability is pretty remote, especially when you add in the 'evidence' that parts entered the passenger cabin (through a hole punched in the cabin floor), reached the overhead locker (punching out a clean cylinder-diameter segment) then retraced its path precisely.
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 . . . :E

[CALB756]

Here's the full ATSB preliminary report:
http://www.atsb.gov.au/publications/investigation_reports/2008/AAIR/pdf/AO2008053_Prelim.pdf

[Cartmen]

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.

[WET]

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. :ooh:

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.]

[lomapaseo]

What're the odds? (100% apparently, but I would never have guessed it.)


about the same odds as having a winglet cut another planes wing clean off in the air.

I sure hope that the final report describes in detail on how these one of a kind events occured

[DC2 slf]

Whilst I'm prepared to believe that the missing cylinder exited through the hole in the pressure hull, I'm sceptical that an exploded (ie fractured) cylinder could result in all fragments being evacuated (though clearly the vacuum effect of the hull rupture would be considerable and anything loose could be sucked out). <snip>
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.

<snip> :E

The aircraft did a fair amount of manouvering with the hole in its side before it landed. The broken bottle need not have fallen out immediately. In any case it seems to be gone. and something made that nice round hole.

People speak of the bottles being castings. but steel forgings seem possible. The bottle was more than ten years old; what happened to it in the meantime?

[Flash2001]

I think you'll find that this type of bottle is always deep drawn.

After an excellent landing you can use the airplane again!

[RatherBeFlying]

Whoever was seated on the upper deck above the cylinder is extremely fortunate that: It did not go straight up as it may have penetrated the upper deck
Energy was dissipated hitting the door handle
the cylinder assumed an oblique trajectory to the upper deck so that it bounced off rather than penetrate.

[NSEU]

Anyone know where the CVR CB is on the 744?

It's located on the P6 panel on the lower, right hand side of the cockpit ;)

[L1011GE]

The aircraft is still AOG in MANILA I see it every day on the way to work

[Spotted Reptile]

Similar circumstances (CVR stays on until overwritten) seem to often occur quite often when "incidents" do not progress to "accidents". One may draw one's own conclusions...And what conclusions are those you have evidently drawn, but are not prepared to state?

Are you saying that the flight crew deliberately left the CVR running in the hope it would overwrite the incident? That seems to be the inference from your statement. That seems to be a ridiculous reasoning based on what we have all read and understood of the actions and character of the pilot and first officer during and after the whole thing.

Please do justify your 'conclusions'.

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.Ah well, you see the ATSB doesn't have a mandate to advance conjecture. They are supposed to state the facts, which so far they have done. Without a bottle to examine, it is extremely difficult to state the cause of the rupture, hence the failure to SPECULATE on what may have happened.

And I suspect they're a lot smarter than you are.

[Capt Kremin]

The CVR is this case would prove nothing except provide a sound bite of the explosion for examination.
The crew performed as per their training and handled the associated mechanical failures correctly and well.

[Short_Circuit]

For clarification on My comments post 1037

AUTOPILOTs,

If the A/P LVDT & the OUTPUT LVDT disagree the A/P will disconnect. How the manual input is allowed by the A/P I can no longer remember exactly. Refresher training would be handy for everyone!

A cam-out only occurs when 2 A/P’s are engaged (Dual Engaged, APP mode only) and one commands different to the other. As the 2 engaged do not distinguish which one is in error the lessor of the same direction output will be the control (fail passive).
Only when there is a large difference will both disengage.

In Triple Engage APP, the one in error is over ridden by the other 2 (fail operational)
Large difference will cause disconnect of the one voted failed A/P by the other 2.

During CRZ only one A/P can be engaged so no cam-out can occur.

OXYGEN REGULATOR
whilst it will probably check the flow, it is mounted on a Tee piece directly onto the shutoff valve outlet of the cylinder and is more robust than the down stream plumbing. This later plumbing will be the first to break and therefore all other cylinders will discharge through the broken pipe.


SC

[arcniz]

As written:
Similar circumstances (CVR stays on until overwritten) seem to often occur quite often when "incidents" do not progress to "accidents". One may draw one's own conclusions...

Spotted reptile's contentious demand as a "reply"
Please do justify your 'conclusions'.

SR - you seem presumptuously argumentative - a bit inappropriate for someone with only 3 posts on the counter... even for an Aussie.

I meant exactly what was said. Clearly many circumstances can occur which cause CVR tapes to be overwritten after a serious incident of this sort. The obvious first responsibility and focus of the flight crew is to assure the safety of passengers, crew and the aircraft itself, an activity that may be very time consuming and may involve long delays before routine housekeeping activities resume.

It probably is true that some airlines do not have an explicit SOP for the protocol to secure the CVR contents following an incident; this might be desirable. Sometimes the elapsed time to the "end" of the incident period (which may be hard to delineate clearly when in the thick of it) is long enough for the CVR to be overwritten anyway - as was nearly always the case with the older, shorter-running CVR's.

I certainly did not and do not mean to suggest that the conduct of the Qantas crew in this odd and complex incident was anything other than exemplary.

[Old Fella]

Don't know if it is still the case, but one of the last items in the Qantas After-shutdown checklist used to be "CVR Erase".

[ExSp33db1rd]

Diesel Fitter # 1050.

The first thing that happens after many accidents is that the crew licences are inspected, and the report starts with a statment that "...... the flight crew licences were inspected and found to be in order.........." if not, the investigation can stop right there,'cos the fact that a crew member might have a licence that could be slightly defective, i.e. maybe not re-issued ( if required, as is by some States ) after a recent medical that was in itself satisfactory, means that that fact alone was the cause of the accident, and the airline and the insurers can breath again. QED

I once attended a Court of Enquiry into a B-747 total loss where the pilot had deviated by 100 ft. from the proscribed departure route on take-off, which had absolutely nothing to do with the subequent mechanical failure, but the Judge immediately stated that the accident was due to 'pilot error' ( you think I'm joking ) :ugh:

[Spotted Reptile]

SR - you seem presumptuously argumentative - a bit inappropriate for someone with only 3 posts on the counter... even for an Aussie.Let's leave the xenophobic remarks out of this.

I meant exactly what was said. Clearly many circumstances can occur which cause CVR tapes to be overwritten after a serious incident of this sort. The obvious first responsibility and focus of the flight crew is to assure the safety of passengers, crew and the aircraft itself, an activity that may be very time consuming and may involve long delays before routine housekeeping activities resume. I'm glad that's what you meant to say, unfortunately it sounded to me very close to an accusation about cover-ups and improper use of recording equipment. Perhaps next time you might state those conclusions upfront, so we are all clear on what you mean, instead of leaving them up in the air like you did and getting me hot under the collar, which I admit I did.

I certainly did not and do not mean to suggest that the conduct of the Qantas crew in this odd and complex incident was anything other than exemplary.I'm very glad to hear that.

[Bullethead]

CVRs are not erased, ever, by the crew it's not part of any shutdown procedure that I know of. It used to be back in B707 days.

If any of the data was erased it is because the CVR only records about the last 25 minutes of flight and anything prior to that will be overwritten, again and again. Originally designed before decent solid state memory and to capture take off or landing incident data.

The depressurisation event occurred 54 minutes before the aircraft landed so the likelyhood of anything useful remaining on the tape is remote, and further the CVR wasn't shut down until well over 2 hours after the event.

Regards,
BH.

[ACMS]

The 777 CVR records 2 hrs ( I think it's 2, but a lot more than 25 mins ) before starting again.

The crew can erase it on the ground if they wish.

In the QF incident the tape had already runout and started to tape over the initial event. Just bad luck for the investigators, nothing sinister.

[capt.cynical]

200804689 (http://www.atsb.com.au/publications/investigation_reports/2008/AAIR/aair200804689.aspx)

Preliminary report

[Barkly1992]

Cynical

I think everyone knows this - plus have read all of the media reports.

:ugh:

[capt.cynical]

Barkly, read the report it only came out yesterday.:oh:

[India Four Two]

Capt.cynical,

I think what Barkly could have said, if he was less "Grumpy" ;), was that the report was referenced yesterday by cjsyd in Post 1032.

I42

[Barkly1992]

Cynical

Yes it was referenced earlier as was mentioned by India Four Two.

But I used to work for the then BASI and later CAA and have a real interest and read the report online in detail every single line. It was availble online from Thursday.

The series of events are well known - in fact this thread picked it early.

What no one knows is why the cylinder 'let go'.

This is what the ongoing investigation will concentrate on. It will be difficult without some remnants of then cylinder.

[atakacs]

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).

[Ron & Edna Johns]

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.

[lomapaseo]

Ron & Edna Johns

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.



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.

[Buster Hyman]

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.

[sooty655]

at least this has given us insight into another potentially dangerous piece of equipment that was previously considered innocuous.

I would be rather surprised if any charged pressure vessel was "considered innocuous" by the maintenance and inspection schedules. Anything which is holding that amount of stored energy must be treated with both respect and suspicion.

If they really have been considered innocuous, then the aviation industry is well out of step with my (non-aviation) industrial experience.

[ozslf]

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 :E)

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.

[Buster Hyman]

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.

[NSEU]

Cynical

I think everyone knows this - plus have read all of the media reports.

Then why do they keep asking questions that were clearly answered in the report and making statements that contradict the report ;)

Another reminder...

http://www.atsb.com.au/publications/investigation_reports/2008/AAIR/pdf/AO2008053_Prelim.pdf :E

[VH-Cheer Up]

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.

Sorry, how does that work?

[Selenajade]

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

[triton140]

"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 think the evidence so far is that the floor first ruptured upwards (Capt Kremin somewhere in this thread reported pax at the pointy end noticing a blast of air towards them first, followed by air exhausting through the hole). Backed up by evidence of the track of the cylinder as set out in the report.

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).

[llondel]

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.

[Milt]

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..

[Oldlae]

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.

[Oilandgasman]

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)

[ampclamp]

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:)

[Kiwiguy]

O2 Bottle does not have to fail in the base to fly upwards.

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.

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. :ugh:

[llondel]

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.

Except that if you have a crack in the vertical wall that doesn't go through at right-angles, it could well direct the escaping gas downwards, pushing the bottle up. Of course, it'll be well off-balance, I doubt if a sudden crack of that severity would provide symmetrical thrust.

[G-CPTN]

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."
(From:- BBC NEWS | England | Beds/Bucks/Herts | Explosion man in critical state (http://news.bbc.co.uk/1/hi/england/beds/bucks/herts/7714038.stm) )
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.
(From:- FireNet Forums / "Argonite" cylinder explosion at Welwyn Garden City (http://www.fire.org.uk/punbb/upload/viewtopic.php?pid=38453) )

[Buster Hyman]

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.:ok: Good to see that some QF staff are keen to go the extra mile...

[7x7x70]

Buster now let me guess ....that must be.....um.... how about... um......... J & K from bb ???? :rolleyes:

[Buster Hyman]

Hmmm....could be.....;)

BTW. He's still rapped about the beer.

(PS. I might have missed the discussion *sorry* amongst the 1100 odd posts, but was it true about nil instruments for landing?):ooh:

[Spotted Reptile]

Heard from a close source that hundreds of little packets of peanuts and other similar sealed snacks exploded during the decompression. Peanuts everywhere apparently, quite a mess.

Buster, the Captain's ILS was disabled.

[Buster Hyman]

Righto SR...cheers.:ok:

[two green one prayer]

Everyone who has read the Hitchhiker books knows how important it is to eat peanuts before the difficult part of a journey.
Peanut assisted or not, well done the crew.

[FlexibleResponse]

Possible Mechanism and Mode of Failure?

I thought it was interesting to note loose cargo partly sucked out of the hole in the fuselage. On page 22 of the preliminary report I note that the cargo loaded adjacent to the hole in the fuselage was not a container, but rather, a plasctic wrapped netted pallet of general freight.

The thought I pose is...What is the chance that during autoloading (powered floor rollers) that a partly collapsed or misshapen cargo pallet load rubbed against the curtains screening the oxgen cylinders, snagged the subject restraining clamp and unclipped it (or pulled it wholly from the structure) during the rearward movement of the subject pallet?

Furthermore, what are the chances that following loss of restraint by the clamp, that the now loose oxygen cylinder (restrained only by oxygen plumbing) was dislodged by further snagging by the pallet load under the forces generated by the powered cargo loading system thereby causing mechanical distress and damage to the oxygen piping and valve attachments on the head of the cylinder?

Only the (Hong Kong?) cargo loader would have known if the cargo fouled during loading. This type of event happens fairly often and is normally cured by loader chap reversing and backing up the pallet loading system and going at it again at speed.

I did not see any reference to any interviews with cargo loading personnel in the report?

Just pure speculation of course...but magic oxygen bottles need a head start.

Edited for clarity

[captainspeaking]

Not sure if you all spotted this: Bird cannot keep its nose out of trouble - News - Travel - smh.com.au (http://www.smh.com.au:80/news/news/bird-cannot-keep-its-nose-out-of-trouble/2008/11/25/1227491548530.html)

[mrdeux]

I might have missed the discussion *sorry* amongst the 1100 odd posts, but was it true about nil instruments for landing?

I'm sure this is covered in the ATSB report somewhere.

All three ILS systems failed. Some of the Captain's instrumentation failed initially, but the displays were brought back to life by the use of the alternate source switches. The aircraft was maintained in VMC from the time of the failure until landing, but both pilots had full attitude and air data displays, and a number of alternatives were available had an instrument approach been needed.

In any event, the ILS on Manila 06 has been out of service for a few months.

[RobShan]

The ATSB final report (http://www.atsb.gov.au/newsroom/2010/201023.aspx) for this incident will be released Monday 22-November-2010. It will be interesting reading, but unfortunate timing for Qantas, another reminder off a serious unusual incident during the uncontained engine failure incident.

[aussiepax]

Media Releases: 22 November 2010 - Risk of aviation oxygen cylinder rupture extremely remote: ATSB report (http://www.atsb.gov.au/newsroom/2010/201024.aspx)

[IFixPlanes]

Executive summary and Links to the Final Report can be found here:
Investigation: AO-2008-053 - Oxygen cylinder failure and depressurisation - 475 km north-west of Manila, Philippines, 25 July 2008, Boeing 747-438, VH-OJK (http://www.atsb.gov.au/publications/investigation_reports/2008/aair/ao-2008-053.aspx)