Qantas 744 Depressurisation

[CallBell]

"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.

[Litebulbs]

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.

[Pontius Navigator]

"What caused so many passengers to activate more masks? "

It may also be explained by passengers grabbing more than one mask, thinking the first one is not working.

I suspect this is more likely.

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.

[GroundScot]

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.....

[Intruder]

is 4000ft/min a normal rate of descent in case of decompression ?
Yes. Normal idle descent is 3000-3500 fpm at high altitude (above 30,000'), and decreases to around 2000 fpm at low altitude. Add speedbrakes (another 1000-1500 fpm), and that's just right.

[uncle_maxwell]

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! :ok:

[alanwoodie]

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.

[ChristiaanJ]

...Maybe the lifejackets should all have a survival kit attached - say foil blanket, firelighters, flares, knife, etc.Maybe...
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?

[glhcarl]

Just above the regulators on all of the bottles is the first officers back up aileron cables covered in grease.

Flight control, throttle and all other cables should be grease free.

Grease on cables allows them to pick up dirt and lint, which leads to premature wear of the pulleys and cables themselves.

[NickNavarro]

The real acronym for QANTAS is:

Queensland And Northern Territory Air Service


I don't know if there is a humorous equivalent......

[forget]

Close - but no cigar. :hmm:

Queensland and Northern Territory Aerial Services.

And I'm a Pom.

[Aerolex]

Ancient Obs,

Some HUF if you like.

TUC (time of useful consciousness) or EPT (effective performance time) for minimal activity (sitting in a seat) are as follows:

18,000' - 30 mins
22,000' - 10 mins
25,000' - 3 mins
28,000' - 1.5 mins

my guess is that most healthy PAX would not have even needed supplimental O2.

[NSEU]

oxygen and grease

--------------------------------------------------------------------------------

Just above the regulators on all of the bottles is the first officers back up aileron cables covered in grease.

Thank god you said BACKUP cables... or the media would go into an unjustified frenzy.

Here's a pic of the cables on another aircraft, sans grease, I prepared earlier...

http://members.ozemail.com.au/~b744er/ControlCablesAboveO2Bottle.jpg

This was the pic which prompted my question about corrosion inhibitor (unless that is coffee seeping through the floorboards :E )
As previously mentioned, the inhibitor dries into a waxy substance. The brown stains are perfectly dry. The same stuff is used throughout the aircraft, sometimes making it hard to spot real hydraulic (and other) leaks.

Note the brass and stainless steel fittings of this typical (non-lightweight) Qantas bottle.

[Litebulbs]

Hmm, Astrolan (spelling?), great stuff. Its like toffee in a spray can

[arcniz]

Looking for a failure mechanism... pure conjecture, only.

From the pix at #703 (and before), it would appear that a looseness or failure of the single restraining strap on the bottle, so it is not held securely in position, would allow the top portion of the 13-odd kilos of object+contents to wobble or orbit around on the footplate with considerable freedom, restrained principally by the stainless-steel exit feed line that (presumably) runs over to the adjacent distribution panel.

An extended cycle of such movement would exert strong "working" forces on the bottle's valve-regulator assembly in a variety of directions and angles. Heavy stress applied to a high-pressure valve assembly is a no-no in general, because this eventually promotes some kind of failure.

Continued long enough, the cycling abnormal flexing would seem likely to cause a crystalisation fracture of the metals somewhere in the assembly. This might occur at the valve stem-to-bottle junction, in the valve body, or in the feed line or its fitting. Effect of any of these failures would likely be an initial crack, then a more dramatic break caused by releasing gas pressure. In the process, the increasingly unrestrained bottle would likely tilt enough to come clear of the curved footplate, even while the releasing gas from the degenerating valve assembly would cause increasingly eccentric and powerful motions.

As the top of the valve assembly broke loose, headed upward to punch through the cabin floor and diddle the door handle, the bottle proper would likely be drilling or bashing a hole in the airframe with the blunt end thrashing and battering wide an opening already perhaps started with tears higher up from the pressure of escaping gas. Eventually the liberated cylinder shoots out through the wall opening and through the lightweight fairing, still accelerating as it descends below and under the leading edge of the wing.

Seems like this scenario could make a strong argument for a secondary retaining strap and possibly also smaller-bore flow-limiting exit holes in the cylinders.

[Kiwiguy]

So correct me if I am wrong but the O2 bottle could still have been sucked out secondary to a rupture in the fuselage and the valve fittings could have simply been ejected upwards in the process of being ripped off the cylinder.

There still appears no evidence of an actual cylinder rupture does there ?
No fragments ejected sideways or into the hold perchance ?

[lomapaseo]

I love the photos so keep them coming.

Do we have an idea of which way the valve stem was launched through the floor and into the ceiling panel. The trajectory might give an idea as to whether the bottle was loose or in place at the time. I'm guessing that a + or - 15 deg cone angle trajectory would be inconclusive, but if it was greater it might be a significant pointer.

I am also reminded that we still don't have a reason for the very large hole in the fuselage, without lesser shrapnel damage holes visible.

The ATSB certainly has their work cut out for them to identify the cascading damages as well as the chicken and the egg.

[infrequentflyer789]

Maybe...
Won't happen ... weighs and costs too much. And a KNIFE? You crazy?


You missed the smiley. As I said, a reasonable survival kit won't get past security, and won't be put in the aircraft for pax for same reasons. The possible increase in post-crash survivability won't outweigh the perceived risks (these days) of equiping pax with anything useful.

Even wearing warm clothing in case of crash might not be a good idea if it's hot at the ends of your trip - grounds for suspicion (or worse) from security...

[Litebulbs]

Kiwiguy, I agree.

The last picture in post #751 shows the mount that the bottle is strapped against and it clearly shows a failure of where each side of the strap is attached. You would expect the strap to fail, or one of the strap mounts, but not both strap mounts to have sheared at the same time due to their own failure. There is no obvious sign of damage to the adjacent bottle or the cabling that is visible (although this cabling may have moved to its current position after the event).

Now if it was a failure of the skin beneath the wing to body fairing, then the base where the bottle sits could have ejected when the skin failed as it would be attached to either stringer or frame. The bottle would then pivot outward, ripping the strap from the strap mount and disappear out of the hole. The weak point in this 1am theory is that you would imagine that the charge line/ring main supply lines would fail before the brass regulator fitting, which would not allow the regulator to enter the passenger cabin and cause the damage that it is stated it has.

[infrequentflyer789]

Being an 'infrequent flyer' you might not be aware that there are extra masks in every PSU (pax service unit: above your head). For example, the 3 seats outboard of a 747, there will be 4 masks drop from the PSU in a depresurisation event. Plenty of masks for all even if yours dont drop.

The location of where the masks failed to deploy will be the issue, not the number, trust me. :ok:


I am aware that there are extras (I worked in the industry for a while, although not for Mr Boeing). I think one pax (can't find the article now) story implied that the whole row (whole PSU?) failed to drop.


As far as numbers go, 418 out of 484 masks for 346 PAX sounds pretty good to me. :)

That's 418 activated - question is why did 50+ passengers activate more than one mask (or 20 activated several, etc.). Maybe that's about par for a planeload of panicing pax, or maybe it points to 50+ masks not working.

[Smilin_Ed]

Yes, I understand ANFE.

Ed

[SUB]

The cables above the bottles I looked at the other day had lots of grease and were covered in thick dust.

[SUB]

The 747-400F Passenger and Crew Oxygen System supply source is a bank of
high-pressure cylinders. Each cylinder has a quantity of oxygen
equivalent to 115 cubic feet (3030 liters), when charged to 1850 psig at
760 mm Hg and 70 degrees F. The cylinders are retained firmly in place
with clamps.


Cylinder positions 1 through 7 are located in the forward cargo
compartment right hand sidewall between STA 720 and STA 880.
Because cylinders from position 4 to position 7 are customer
options, actual passenger system cylinder quantities in the sidewall
may vary.

Cylinder positions 8 through 21 are located in the forward cargo
compartment ceiling, between STA 620 and STA 780. Because cylinders
from position 8 to position 21 are customer options, actual
passenger system cylinder quantities in the ceiling may vary.

Cylinder positions 1 through 2 are located in the forward cargo
compartment right hand sidewall between STA 680 and STA 720.
Because cylinder position 2 is a customer option, actual Crew system
cylinder quantities in the sidewall may vary.

Older in-service steel cylinders are interchangeable with the graphite
composite cylinders.

Every cylinder has an associated high-pressure regulator, which
reduces the pressure for reasons of safety, to the intermediate
system working pressure of 600-680 psig.

C_A_U_T_I_O_N_: DO NOT TIGHTEN THE FITTINGS AND CONNECTIONS MORE THAN
THE TORQUE WHICH IS PERMITTED. THIS CAN CAUSE DAMAGE
TO THESE PARTS.

[Rolling-Thunderbird]

In the 5th picture of post #745, which shows the o2 tank valve imbedded into the cabin interior, does it not look like a transfer mark ( the green smear of paint) from the o2 bottle itself ?

It almost seems to me as if the o2 bottle came up through the cabin floor and struck the door handle and cabin interior, then sheared the valve and exited downward and out though the side of the aircraft.

However, the pictures of the cabin floor are not clear enough to lend further credibility to this idea.

What else could have left this green streak (smudge) on the cabin interior?

http://i6.photobucket.com/albums/y205/steve1995/a-quantas-finterior4vl2.jpg

[SUB]

At the bottom of that partition is a portable oxygen cylinder mounted at floor level at a 45deg angle. Had a look at another aircraft and the bottle is pointing exactly in line with the door handle.

The door handle which was hit by ?? would of tried to open but the upper and lower gate pushrods would of broken and this is why it looks like the door cracked oped during flight, but I think the gates are just hanging down because there is no pushrod to hold them closed. After the aircraft depressurized the upper gate is open more that the lower as you would expect, chk out that pic of the door upper gate. My thoughts only.

[Mark in CA]

Am I imagining things, or is there another green streak on the lower portion of the door, opposite the one you're talking about? You might have to blow up the first photo in the series to see it. Looks like it's about a foot off the floor.

[privateer]

QANTAS

One 'humorous' version of the acronym is

<censored> and nymphomaniacs travel as staff.

[NSEU]

Someone said the "regulator" shot through the cabin floor. Did they mean the regulator or the the valve at the top of the bottle?

The regulator is separate item on a "T" piece shown on the right hand side of my* picture in post #764 (i.e. the "T" piece is shown, not the regulator).

*NB: Picture not for media use.

[Machaca]

Rolling T-Bird -- good eye on the green stripe! The oxy cylinder valve knob is metal with a molded green plastic cover that could have left such a mark.


SUB -- in one photo (poor quality) of vestibule & door, the portable oxy bottle appears in its cubby in partition near floor but opposite angle you describe. May have been returned there post-descent.


NSEU -- from ATSB Media Release 2008/28: "The ATSB can confirm that it appears that part of an oxygen cylinder and valve entered the passenger cabin and impacted the number 2 right door frame handle..." [empahsis mine]


Mark in CA -- yes, could be a second green mark. Perhaps one was caused by the cylinder fragment and the other by the knob cover.


Anyone have a clear photo of the floor penetration? Lower half of door? Noddys Car? NSEU?

[pacplyer]

Yesterday, 18:37 #773 (permalink)
SUB

The cables above the bottles I looked at the other day had lots of grease and were covered in thick dust.

Sub, and chemists,

Hypothetical question only here:

Let's say some new guy at Haeko decides he's going to help out and lube up those dry overhead control cables that he's spotted. All he can find is Lithium Grease. He really slops it on there and nobody knows he's done this.

On the next flight a big blob of this stuff drips/flakes off down and hits a leaking Valve/line/regulator.

Spontaneous Combustion possible?

[NSEU]

The oxy cylinder valve knob is metal with a molded green plastic cover that could have left such a mark.

Actually, they appeared to be metal, painted with green paint. I opened and closed half a dozen of them last week ;)

Thanks for the heads up on the valve.

Rgds.
NSEU

[Machaca]

Lomapaseo -- was this what you had in mind?

http://i337.photobucket.com/albums/n385/motidog/QF30-PathSTA810c.jpg


http://i337.photobucket.com/albums/n385/motidog/QF30-fusebuild3.jpg

[HotDog]

Machaca,-- The missing cylinder resided vertically between stations 800 and 820. The picture on #751 would suggest otherwise, i.e. horizontal, if that is the rack of the missing bottle.

[spannersatKL]

Hot Dog they are retained vertically.......

[NSEU]

Hot Dog.. the last pic of post #745 shows the bottle and cabin floor panelling above. Only the tech crew bottles are mounted horizontally (and the other pax ones along the centreline of the cargo ceiling).

If the cargo centreline pax ones let go, they would probably fly sideways, not up/down.

Machaca wins the PPRuNe best technical illustration award :ok:

[Blacksheep]

I am also reminded that we still don't have a reason for the very large hole in the fuselage, without lesser shrapnel damage holes visible.The valve assembly going up and the bottle ejecting down are one plausible explanation for some of the damage signature, but the bottle is mounted vertically between two frames; a section of each of these frames has departed the airframe, what is the failure mode for that to happen?

[snowfalcon2]

The valve assembly going up and the bottle ejecting down are one plausible explanation for some of the damage signature, but the bottle is mounted vertically between two frames; a section of each of these frames has departed the airframe, what is the failure mode for that to happen?

Wing fairing coming off and taking skin panels with it, dislodging the frames and the lower retaining cup of the oxygen bottle.

Note this is just a theoretical possibility which I'm not sure can be entirely discounted yet. Is the composite wing fairing secured to the fuselage otherwise than along its edges, i.e. are there any other tie-rods or other supports affixing it? But if the fasteners are only along its edges, this theory seems to have little merit.

[GOLF_BRAVO_ZULU]

pacplyer. I can't imagine anyone slapping grease on a control cable that wasn't actually passing through a pulley or fairlead; but who knows. Your point about grease in proximity to an oxygen leak has been made previously but disregarded. I'm not a plumber nor an expert but, many years ago, I had a safety brief in a Naval Armament Depot. Part of that was concerned with Oxygen safety. Having made the point about liquid Oxygen and the formation of LOX Gel from its contact with oil, fat, wax or grease, mention was made of similar hazards from high pressure gaseous Oxygen. Mention was also made of Oxygen in contact with such materials through misuse or leaks. As I remember it, oil and grease could absorb significant amounts of Oxygen, particularly at low temperatures, and form a LOX gel like substance. These substances could be ignited by impact or friction.

What I was told was not in the papers nor on television so could have been complete bowlox; or I could have remembered it wrongly. Anyway, offered for what it's worth.

[Chardy]

Great work Mach - but I think I have missed something. ATSB said the O2 bottle is missing - from your EXCELLENT diagram it would appear that the O2 bottle is still inside the fuselage???

As I said, I think I've missed something...

[Barkly1992]

If you deleted all of the speculative and stupid contributions to this thread and only left the ones where experts have made a serious discussion of the likely events - you have the ATSB Report.

Well done chaps - and chapeeses.

:D

[forget]

.... from your EXCELLENT diagram it would appear that the O2 bottle is still inside the fuselage??? As I said, I think I've missed something...

Get a grip Chardy. That's where the bottle was. But I'm sure you knew that. :rolleyes:

PS. Top marks Machaca. :ok:

[beamender99]

If you deleted all of the speculative and stupid contributions to this thread and only left the ones where experts have made a serious discussion of the likely events - you have the ATSB Report.



If you deleted all the moans from "experts" it would make easier reading.

I have been an expert in my field for several decades but am still open to ideas from others.
I have experienced the holes in the cheese situation which ensured that I always listened to non experts.

[Chardy]

I'll forgive your rudeness, Forget - I was only trying to qualify what Mach was trying to portray in in the diagram.

Had a CRM eval recently? Damn glad you don't fly on my right.

[HotDog]

Machaca, Spanners & NSEU, thank you; I stand corrected. I agree the bottle was vertical in that position but it leaves a lot of unexplained questions still.
I have a total of 18,680 hours operating as a F/E on CV880, B707, L1011, B747-100-200-300 pax and cargo. In 32 years have never encountered a problem with pax or crew oxygen. This incident is a bit of a worry, to say the least.

[chris weston]

pacplyer 781

Yes in principle.

ppO2 at contact point with hydrocarbon would be key.

CW

[chris weston]

Macha,

Splendid photos/graphics sir.

CW

[Barkly1992]

Beamender99

Get a grip - I am talking about contributors who say things like: 'what IF - the cylinder expolded and generated a fire source - WHAT IF - those that assume O2 explodes. WHAT IF - Qantas is trying cover up a crime - WHAT IF -

The experts - maybe including you but I haven't checked your posts - have kept the discussion within the bounds of physics and not the paranormal.

What sort of expert are you?

I'm one too too. Some years as an aviation safety expert.

Gees !!

[Chris Scott]

Quote from forget:
Get a grip Chardy. That's where the bottle was. But I'm sure you knew that.

Merely an occasional browser of this fascinating discussion, I'm finally having to admit to being mildly confused like Chardy is (or was at 0906z Thursday). Still can't find any ATSB reference to the "part of an oxygen cylinder and valve (which) entered the passenger cabin and impacted the number 2 right door frame handle" having been found. So has it?

At risk of provoking public humiliation, could someone briefly enlighten me – and any others labouring under similar ignorance – in a slightly less cryptic fashion than the above?

[pacplyer]

Gee,

I must have gotten lost. Is this the private pilot expert forum? (That's what is listed on your profile bark old boy (PPL) :cool:

I thought it was the Flight Deck section of Rumours and News of the professional pilots Rumour network. :}

No one said anything about a crime being committed; you wildly exaggerate. If it was unclear, my examples where meant to be strictly hypothetical and in no way imply anything that has happened at Qantas. All my posts are just my own opinion only, and unlike you, I do not profess to be an expert. I am just a reader.

But please tell us, oh great sage of aviation safety, HYPOTHETICALLY what happens when a shipper does not declare lithium batteries in boxes loaded next to leaking oxidizer?

Nothing?

[FlexibleResponse]

Machaca,

Excellent photos and visual depiction of possible failure mode.

Just one point for clarity...are you saying that:

1. The oxy valve separated and the valve only was vertically propelled by expanding gases vertically into the cabin.
2. That the main body of the oxy cylinder itself then push hard into its' concave base plate but having nowhere to go, it started to rotate on the base plate
3. That the top of the body of the oxy cylinder with the broken and end then rotated inboard towards the centre of the cargo compartment.
4. That the oxy cylinder was then propelled by expanding gases out through the side of the fuselage.

[G-CPTN]

Still can't find any ATSB reference to the "part of an oxygen cylinder and valve (which) entered the passenger cabin and impacted the number 2 right door frame handle" having been found. So has it?
As I understand, the hole in the cabin floor is (almost) directly above the hole in the fuselage wall.
Various items were reported as being sucked across the cabin by the depressurisation, and any debris that 'came up' could realistically have fallen and gone down and flown out of the big hole to the outside world.
After all, some of the hold cargo ended up jammed in the hold, so it is reasonable to assume that other material might have preceded it . . .

[NSEU]

ok.. I'm confused. Didn't the early reports say that the oxygen valve was found in the roof. Like "Flexible Response", I assumed that the neck of the bottle had shattered, a section of bottle (with the valve) caused the green marks in the cabin and damaged the door assembly... and the rest of the oxygen bottle went down (due jet propulsion), angled off something and went out of the side of the aircraft.

One of the earlier pictures shows a bracket for the wing-to-body fairing as an additional attachment point (other than the fasteners around the circumference). There may be more, accounting for the tearing.

I have a total of 18,680 hours operating as a F/E on CV880, B707, L1011, B747-100-200-300 pax and cargo. In 32 years have never encountered a problem with pax or crew oxygen. This incident is a bit of a worry, to say the least.

That's what makes aviation so interesting. As an engineer for a similar period of time, I regularly come across things that I haven't seen before and have to come up with solutions. When I find one, I say to myself.. ."I'll remember that for next time it happens".... but most of the time it doesn't.. .or it's so long between these unusual events, I forget the solution :O

Aircraft are getting safer and safer (that's why we are so surprised when things like this do happen).

I'm still trying to work out why the "Captain's FMC" and 3 ILS's failed (yet the VOR did work). :confused: I assume the crew switched to the Right FMC to allow that to tune the navigation radios(?)

[Vertiginous]

Yes, it's possible that Li grease + O2 in fair concentration could give you a fire.

There seems to be a drift towards the idea that the tank 'pushed' its way through the hull by jet propulsion, having ignominiously lost its valve. This really doesn't wash: the forces involved are not high enough, and are broadly downwards rather than outwards. However, the failure / loss of the valve is very likely to compromise the rest of the tank's structure. It would be strange if it didn't. We are then looking at sudden explosive failure a very short time after the loss of the valve, as a result of the considerable pressure that remains inside the tank blowing out the damaged tank structure. The resulting explosion would account for the observed damage to the a/c: a sudden, violent force outwards, powerful enough not just to hole the skin nearby but also to fracture neighbouring structural elements.

[FlexibleResponse]

An appreciation of the forces involved in an unrelated ground accident involving an oxygen cylinder explosion during maintenance.

O2 CYLINDER EXPLOSION
YouTube - O2 CYLINDER EXPLOSION (http://www.youtube.com/watch?v=9lw_fhNAIQc)

Edit to sanitize and keep it as factual as possible.

[Chardy]

FORGET - do you want to play nicely or just play on the number of postings you do here?

Most of us do NOT guess. We make decisions. That includes all people associated with our ship-o-the-day. We talk, we collaborate.

If you don't want to play nicely, and bag posters who, like many of us, are a little too busy doing our job up the pointy end and are seriously interested in what happened to QF30, then back to your postings.

I see from your profile your in avionics, so thanks for keeping our avionics working :) You people are great.

Just settle, petal. We're all in this for the good, not ego.

Now, can we get back on topic?

[Blacksheep]

...powerful enough not just to hole the skin nearby...Or in one case where the shut-off valve was jammed and a chap tried to release the oxygen pressure by loosening the valve stem with an adjustable spanner, the blast was powerful enough to break the chain vice, take off his arm, embed the cylinder cap in the workshop wall and in addition, the temperature generated by tearing the cylinder apart melted the inner surface of the cylinder and fused the threads in the cyclinder neck.

But the fact remains that gas bottles do not spontaneously burst; they do so when they are being interfered with in some way, during handling or charging. This cylinder was sitting in its stowage out of the way of any normal "interference".

[Aerolex]

Chris Scott,

ATSB has commented on O2 components hitting door handle. The info you seek (or have failed to find) is available from the link in post #707 or from an excerpt from the report in post #708. :)

[RatherBeFlying]

Many thanks for the excellent pictures and image enhancements, much beyond my skills.

The trajectory of the valve shows that the cylinder was still fastened in its original position when it departed -- caveat that a hull failure directly below may have sucked the bottle straight down and caused the valve to part company -- 5% probability?

The more likely case is that the valve departed while the bottle was still in situ. The equal and opposite reaction would have loaded the lower cup fitting which seems to be supported by two rods from the ends of the upper tank support. Note that both rods are gone and that a recent photo shows one rod for the adjacent tank hanging from its upper tank support but no longer connected to the lower cup. Note that the remaining rod was sufficient to retain that tank:ok:

It's been too many decades since uni physics for me to calculate the thrust from an 1800 psi tank with missing valve -- that would apply only if the tank held together.

A fragment comprising the bottom of the tank would likely have a higher velocity while an intact tank would have a greater duration of banging against the fuselage structure. But in the case of tank fragmentation, other bits of the tank would likely be found imbedded in baggage (caveat some sucked out) and adjacent structure, or at least marks, perhaps with green smears.

The hoop frames seem cleanly cut; so likely at a joint. Was that the bottle banging at them, or the baggage pushing them, or something dislodging a piece spanning the frames at the joints, or???

Note also that the metal curled up against the fuselage shows erosion of the interior paint in a number of panels. The boundary in one area shows the perimeter of a spray pattern -- oxidation of the paint???

[Chris Scott]

Thanks for your reply, Aerolex. Had already read your post #707 and that particular ATSB media release (from which I quoted). Also looked at all the other ATSB releases on their website. Unless I've missed something, it looks as if they hadn't yet found the object(s) that hit the door handle; hence Chardy's and my question.

G-CPTN (#802) suggests it might have reversed direction, and then "flown out of the big hole to the outside world." Machaca suggests it may have ricocheted into the upper-deck floor. My tuppence is on something like the latter. On the other hand, like Chardy (unless I'm misunderstanding his #790), I'm assuming that it would have been found quickly by the investigators. Fascinating.

[G-CPTN]

But the fact remains that gas bottles do not spontaneously burst; they do so when they are being interfered with in some way, during handling or charging. This cylinder was sitting in its stowage out of the way of any normal "interference".

http://members.ozemail.com.au/~b744er/SidewallO2PaxBottles.jpg
http://i37.tinypic.com/2wp7di9.jpg
http://i337.photobucket.com/albums/n385/motidog/QF30-Cargo-Hold-01.jpg
http://img294.imageshack.us/img294/9103/dsc02332fi5.jpg
http://img222.imageshack.us/img222/3011/qfo2tankplacementdd2.jpg
http://i337.photobucket.com/albums/n385/motidog/QF30-ViewUp.jpg

Without doubt the oxygen cylinder is a crucial element of the incident. As stated above, there had to be a 'discontinuity' (either physical or chemical) that induced the failure of the mounting bracket(s) and severed the valve and/or the regulator (with or without part of the cylinder) which then flew upwards through the cargo hold ceiling and the cabin floor. It is (IMO) inconceivable that an intact cylinder could inflict the damage seen in the cabin (ie there is no way a complete cylinder could levitate with sufficient force) therefore at some stage either the valve became detatched from the cylinder or part of the cylinder with the valve still attached was propelled from its original storage location.
Although plausible, I do not believe that a simple displacement of the cylinder (as shown in http://i337.photobucket.com/albums/n385/motidog/QF30-Cyl4breach-1.jpg would, in itself, cause sufficient damage to the structure of the cylinder to cause separation of the valve. Furthermore, (IMO) I don't believe that an external 'explosion' (or rapid burning) caused by leakage of oxygen from connecting pipework or valves could inflict destructive damage on an otherwise previously intact and undamaged cylinder. Such events usually occur when a flaw exists in a fitting fitted into the cylinder or an attempt to remove the fitting has been made. Failure of external pipework is unlikely to 'destroy' the cylinder itself, although dropping the cylinder could 'knock off' the valve screwed into the cylinder.
If the cylinder was properly fixed into the support brackets and clamped in place then failure of any of the external connecting pipework is most unlikely (improbable - maybe impossible) to cause the catastrophic failure that occurred.
Therefore, either the cylinder was displaced from its mountings prior to the 'explosion', or the cylinder itself fractured. The former suggests that the mounting bracket(s) either simultaneously failed (unlikely) or that some mechanical force (such as part of the cargo) impinged on the cylinder, or that an 'explosion' displaced the cylinder from its stowage location. Subsequently (and maybe simultaneously) damage to the valve (and/or the cylinder) allowed the valve to detach itself.
Simple failure of the fuselage skin (ie no primary failure of the cylinder) could cause rotation of the cylinder in its clamp as it was sucked out of the breach, but (IMO) the valve wouldn't detach until it struck something solid (such as the flange along the bottom of the 'curtain' or the edges of the remaining upper support bracket - there should be witness marks) and the state of the remaining pipework would indicate how the cylinder 'departed'.
I'd love to be able to view the scene (and it would help to know exactly what debris has been recovered).
It's easy to assume that 'cylinders don't fail spontaneously', yet should a cylinder fail . . .
. . . the result would be as seems to have occurred here.

[Dairyground]

Re post #771

I recall having heard sometime in the distant past that one of the reasons for the apparent overprovision of passenger oxygen masks is to make it possible for cabin crew (or even passengers) to breathe if they needed to move around the cabin. Assuming that someone was on their feet several rows away from an empty aisle seat, or their own seat, when the masks dropped, they might well sample several on their journey back to their own seat. The cabin crew might also have reason to use dangling masks rather than their own portable cylinders if their duties took them away from the crew seats, for example to check that all passengers were wearing masks and were otherwise OK.

So I don't see the excess of activated masks over number of passengers as indicative of a significant problem.

[G-CPTN]

After further examination of the above illustrations, what if the retaining clamp wasn't fitted . . .
http://i24.photobucket.com/albums/c19/GroupCaptain/UpperBracket.jpg
(full image at http://img65.imageshack.us/img65/49/dsc023391sq0.jpg )

. . . allowing the cylinder to displace, tearing the pipework and subsequently striking the valve against something 'solid' . . .

(The upper bracket of the missing cylinder location seems 'incomplete' rather than torn - either it is flimsy and designed only to stop the cylinder from rattling or there are parts missing from the 'clamp'?)

(Recall the Virgin train derailment - and the Potters Bar crash - where fixing nuts were 'missing'. Such omissions can occur due to human 'failures', despite inspection procedures . . . )


OTOH, that piece of (broken?) pipe in the middle of the above photograph looks 'discoloured' . . .

[international hog driver]

Well guys (Machaca, Spanners & NSEU & Others) I think that your collective knowledge and inquisitive natures have got most of it.

Seriously, I would put money down that the ATSB reads identically!

The only thing that worries me is what caused the O2 Bottle to rupture in the first place to have it rocket into then out of the fuselage?

What if this had occured on L888 sometime after NOLEP...

Interesting stuff....CSI Pprune indeed!


(for those that dont know see http://www.planningchart.de/Hongkong.gif)

[Litebulbs]

G-CPTN,

Two well thought out posts. The thing that does not seem right to me, is that the bottle support mount shown in your last post shows no damage apart from where the support straps would normally be. If the complete bottle was to fail, then there should be at lease some deformation of the mount. If the bottle ruptured, it would do so in all directions, not just towards the straps.

Now if the bottom mount was to move for whatever reason?

[L-38]

Truly good forensic knowledge has been contributed to these many posts.

"The only thing that worries me is what caused the O2 Bottle to rupture in the first place to have it rocket into then out of the fuselage?"

Was taught in A&P school that one of the closest lethal combinations to create a near spontaneous combustion, was the proximity mix of aviator's breathing oxygen (color coded green), with aviation Mil-Spec grease, no matter how small in quantity. (note - aviators breathing oxygen is simply medical grade oxygen (color coded grey?) with moisture removed).

[Smilin_Ed]

In Post #813, I perceive that we are looking at the half of the tank restraint which is normally behind the tank and closest to the pressure hull. It appears that the bolt holes, to which the strap which encircles the tank is fastened, have been torn out.

If the strap had not been adequately tightened, over time those bolt holes would have elongated and eventually failed, allowing the tank to lean out of it's proper position. This might then possibly have allowed the valve body to strike something firm and break off.

Of course, those bolt holes could have been torn out by some other mechanism.

[lomapaseo]

Many thanks Machca a good sketch engenders a good discussion:ok:

I not entirely sure of what has started this (chicken and the egg). There are some excellent pro and cons on multiple theories. Obviously if one could examine the details close up, I could eliminate some theories and concentrate on the rest.

My current musings do consider that to launch the valve straight up implies to me that the cyclinder was still intact and a pure jet force was along the axis of the valve. I might have thought that a fractured cyclinder would have launched multiple fragments randomly (like the workbench video).

An axial propulsive force that launches the valve implies a reverse axial propulsive force against the memaining cyclinder. Somehow, I can't imagine this force beng enough to fracture the fueslage albeit it likely is enough to fracture the upper cylinder supports.

Some really good thoughts by some on here so I await some more iteration of ideas.

Just for some food for follow on thought. Eventually we are going to need a sound safety related recommendatiuon (not just an interim inspection). If we ascribe to an extermely rare tank fracture, we don't have a lot to work with trying to chase a one in a billion chance. On the other hand if the tank is secondary we need to concentrate on this aspect and either strengthen its supports or eliminate the primary cause. (More thoughts on this later as new details emerge)l

[Ancient Observer]

No.s of O2 masks used.
My point was far simpler - whether or not they physically need it, they'll take it. The role of "authority" in a crisis is well known. Authority told them to pull at a mask, and put it on their face. Some might well grab 2, believing that to be better for them. Don't forget, very few pax have been in a sim., and even fewer would be able to work out their need for/use of and availability of O2. That's what HF is s'posed to remind us about....

[Litebulbs]

Please read post #186 again about possible damage repairs around where the missing bottle mount was.

[G-CPTN]

What seemed surprising was how few masks had had the elastic retaining straps adjusted.
Only a small number of masks appeared to have had the elastic retaining strap adjusted by the passengers
(From:- MEDIA RELEASE : 30 July 2008 - Investigation into Boeing 747- 400 depressurisation and diversion to Manila, Philippines (http://www.atsb.gov.au/newsroom/2008/release/2008_28.aspx)
Audio version:- http://www.atsb.gov.au/newsroom/2008/release/files/QF30_media_300708.wav there's some interesting Q&As at the end where the ATSB guy states that they do have 'part of the cylinder'.)

Do passengers merely hold the mask in place?

Incidentally, also from the above release:- The ATSB can confirm that it appears that part of an oxygen cylinder and valve entered the passenger cabinwhich seems specific that 'a part of the cylinder' left the cargo hold . . .
although they merely state 'appears' . . .


and:- The team have confirmed that the aircrafts three Instrument Landing Systems (ILS) and the anti-skid system were not available for the arrival and landing at Manila.
Was this merely more holes in the cheese, or is there a logical explanation?

[Ancient Mariner]

Let me get this clear, an oxy cylinder pressurised to, say 150 bar is secured by ONE tiny looking clamp. It also looks like the clamp is locked by some quick-locking device? This on a platform that vibrates and are subject to G-forces in all directions.
Not good enough on any ship I was on.
Per

[G-CPTN]

'Typical' cylinder mount (first and second 'passenger' oxygen):- http://i24.photobucket.com/albums/c19/GroupCaptain/CylinderMount.jpg

The 'fourth' cylinder installation:- http://i24.photobucket.com/albums/c19/GroupCaptain/No4Cylinder.jpg

[lomapaseo]

Please read post #186 again about possible damage repairs around where the missing bottle mount was.

I read it the first time and was concerned that the repairs might have allowed the frame to flex more and induce more rapid normal fatigue crack progression.l However, not being an expert in repair terminology I awaited other LAMEs to confirm the statements or refute the suggestions.

Apparently nobody understands well enough to comment, so perhaps the originator should comment further.

[speedbump59]

One idea for a failure mechanism.

Lets assume for the moment that the regulator did suddenly fail while the oxygen tank was standing upright. Perhaps due to a one-in-a-million reason (bad threading, damage during the last inspection, corrosion, grease contamination, whatever).

The regulator flies upwards, and the oxygen tank tries to go downwards. The escaping gas from the tank would put a rather huge load on the bottom support bracket. Athough we don't have any really clear photos yet, it appears that the bottom support bracket for the oxygen tank is directly attached to the longitudinal ribs on the fuselage (see the photos of the tanks sitting on the bottom brackets and also the closeup photos of the adjacent bottom support bracket some posts back).

If the tank's bottom support bracket is directly attached to the fuselage, the huge downward force from the tank may have bent the bottom support bracket sufficiently to split open a seam in the fuselage. Perhaps that skinny little band clamp was strong enough to hold the oxygen tank vertical, but I suspect it would not have prevented the tank from putting a large vertical downwards force on the lower support bracket.

If that did cause a split in the hull, escaping pressure from the interior would have rapidly enlarged the split and thus the oxygen tank was perhaps propelled and/or sucked out of the opening. Any thoughts on this as possibly being the breach initiation mechanism?

Engineering school was a long time ago, but depending on the design and attachment of the bottom support bracket, a unexpectedly large load on the bracket could have put a very great stress on some part of the fuselage.

Anybody in a position to get a better photo of how the bottom support bracket is actually attached to the airplane?

speedbump

[arcniz]

Interesting to note in CPTN's post #823 upper photo that the two adjacent O2 cylinders are significantly different in appearance and somewhat different in fixturing:

Even with allowance for perspective in the photo, it would seem the cylinder on the left is taller and newer than the one on the right. It is differently marked, a different shade of green, and possibly has some differences in the pipe attachments and fixings.

The cylinder mounting arrangement is clearly designed to optimize quick & easy installation & removal, consistent with the requirements described for certain cases where cylinders must be physically removed for charging. The clamp in contact with the bottle appears to be a standard stainless-type aircraft clamp material with a cam-over lever handle for latching. One might expect the handle to be safety-wired in place when closed, but no visual confirmation can be seen of any such safety tie-down, so it is either not present or is very hard to casually inspect for security.

For the bottle on the right, one can see that the hook side of the clamp (on the left side of the right bottle, as seen) engages the opposing loop side in a skewed manner, as compared to the bottle seen on the left in this image. This suggests that either a spring mechanism may be present for tensioning in the back, out of view, or that the clamp metal itself imposes enough spring tension to average out variations in mating angle between the sides. It also suggests that there might exist some clamps that are less secure in their grip than others - especially after years of use.

One might surmise that the bottle on the right is possibly one of the older metal-type O2 cylinders, and the one on the left a newer composite model.

One wonders if these types are considered to be interchangeable in general usage, despite minor differences in size and significant differences in weight?

One also wonders what kind of engineering analysis was done, and when, to determine the suitability of the original holder-bracket design and associated structures and fittings for use with the newer bottle style?

[alright jack]

What would happen if the fuselage failed at an area near the oxygen bottle lower support bracket causing a twisting motion to the regulator assembly enough to snap it off .Was the bottle a steel one or composite type ? Food for thought...............................

[Aerolex]

No probs Ancient,

I've got a novel idea that might help crew. Some PAX should not be so complacent and maybe pay a little extra attention to the pilots or cabin crew pre-flight briefing and read that laminated thingie in the pocket in front of them. A wealth of info on that plastic thingameebob:=

[NSEU]

The cylinder mounting arrangement is clearly designed to optimize quick & easy installation & removal, consistent with the requirements described for certain cases where cylinders must be physically removed for charging. The clamp in contact with the bottle appears to be a standard stainless-type aircraft clamp material with a cam-over lever handle for latching. One might expect the handle to be safety-wired in place when closed, but no visual confirmation can be seen of any such safety tie-down, so it is either not present or is very hard to casually inspect for security.

You are correct about the clamp. There is a small safety pin, however, to prevent the spring-loaded latch releasing.

One might surmise that the bottle on the right is possibly one of the older metal-type O2 cylinders, and the one on the left a newer composite model.

On this particular aircraft (not the damaged one), the pax tanks were all the same. The difference in size may be an optical illusion due to the irregular/uneven edge of the white plastic above the bottle. The colour change may be due to the light drop off (When I took the photograph, the only significant source of light was the open cargo door)

Gentlemen, don't confuse the term "regulator" with "valve". The regulator is separate from the bottle on a T-piece attached to the right (aft) side of the bottle. The shutoff "valve" is on top of the bottle (normally wound fully open). However, looking at the pictures of the damage, the regulator, thermal compensator, pressure sensor/transducer and bottle valve (as well as the bottle) are completely missing. Only half the electrical plug for the pressure sensor remains.

Note that, without the spring clamp, the bottle will still be held in place with the rather rigid stainless pipework attached to both sides of the neck of the bottle. The pipework will flex to a degree, but when I changed a bottle last week, I found that the bottle had to be in a precise position to get the nuts on both pipes to thread properly.

[pacplyer]

Attn. Pacplyer re. 781
Yes, it's possible that Li grease + O2 in fair concentration could give you a fire.

There seems to be a drift towards the idea that the tank 'pushed' its way through the hull by jet propulsion, having ignominiously lost its valve. This really doesn't wash: the forces involved are not high enough, and are broadly downwards rather than outwards. However, the failure / loss of the valve is very likely to compromise the rest of the tank's structure. It would be strange if it didn't. We are then looking at sudden explosive failure a very short time after the loss of the valve, as a result of the considerable pressure that remains inside the tank blowing out the damaged tank structure. The resulting explosion would account for the observed damage to the a/c: a sudden, violent force outwards, powerful enough not just to hole the skin nearby but also to fracture neighbouring structural elements.

Thanks Vertiginous,

I agree with you. What makes the thrust of the bottle less likely a cause of the lattice work side-wall failure is the fact that this "rocket" is only potentially dangerous because of it's mass; and only if that mass can get time/space to accelerate the bottle into something with enough kinetic energy going to punch a whole through the side. Sitting in it's bracket venting isn't going to do it. If something else first knocked the valve off the bottle (or it fell) and then that cylinder, was free out of the bracket and looped around and hit...... man, sounds so problematical.... but I guess, if the tank threading was offset it might be possible.

And none of this really explains why people in business class reported that the floor buckled up (if that's true)..... does it?

Right now I'm in the camp that the popped-cork happened after and as a result of a seperate explosion or repair failure of some sort. But... I'm leaning toward complete cylinder disintegration as a primary cause for the first time in history because of those green smears at the R-2 door post. What we need to see is a picture of the fragments or get a report about what they are comprised of: fiberglass, bottle metal, bottle neck or just attached hardware?

Here's a fun exercise:
Could someone analyze the green tank color at the R2 doorpost for a color wavelength signature of that particular shade of green and see if it even comes close to the tank color vs. the green zinc chromate sprayed everywhere?) Note: we are just readers not safety experts. Don't quote anything in this thread in your newspaper.

What we need around here is more acurate press reports! :rolleyes:

[NSEU]

Quote:
The team have confirmed that the aircrafts three Instrument Landing Systems (ILS) and the anti-skid system were not available for the arrival and landing at Manila.

Was this merely more holes in the cheese, or is there a logical explanation?

The defects would most likely be caused by the damage to the aircraft wiring in the vicinity of the exploding bottle (note the large loom hanging down in some shots).... or perhaps by shrapnel flying out to further areas. Unfortunately, I don't think the investigation reports will tell us the full story about the "collateral damage".

Finding shrapnel damage in an aircraft this complex is not going to be easy. Somehow, I don't think this aircraft is going anywhere in a hurry ;)

Let me get this clear, an oxy cylinder pressurised to, say 150 bar is secured by ONE tiny looking clamp. It also looks like the clamp is locked by some quick-locking device? This on a platform that vibrates and are subject to G-forces in all directions.
Not good enough on any ship I was on.

I'd have to agree. Unfortunately, on aircraft, compromises have to be made to keep them as light as possible.

[geemul]

As a way of visual perspective this is what happens to a motor vehicle when an industrial oxygen cylinder of about the same physical dimensions as the aircraft units has a catastrophic failure in a confined space. It occured in a suburb of Newcastle, NSW, Australia in about December 2005.
The owner was in the flats at the back asleep and was uninjured as the failure occured at night.
Notice the lack of glass in the buildings windows and the absence of a rear door on the building, now just an opening.
There was no fire, just a massive release of stored gaseous energy.
Two pictures of the damage and one of a similar specified vehicle for perspective.

http://i46.photobucket.com/albums/f111/gmullard/Junk/breakable.jpg

http://i46.photobucket.com/albums/f111/gmullard/Junk/breakable2.jpg

http://i46.photobucket.com/albums/f111/gmullard/Junk/4107540.jpg

[triton140]

No expert here, just SLF with an interest in aviation, flying since the sixties.

But a thought - and perhaps some LAMEs can comment.

There seems to be two stays running from the top cradle of the oxygen cylinders back to the stringers, as shown in this pic:

http://farm4.static.flickr.com/3220/2720619231_59b03354b3_o.jpg

If the cylinder ruptured, might not these pull back on the stringer (against the pressure differential pushing the hull out) causing it to separate from the skin and perhaps opening up a fracture in the hull?

Just a thought ......

[NotPilotAtALL]

Hi,

Let me get this clear, an oxy cylinder pressurised to, say 150 bar is secured by ONE tiny looking clamp. It also looks like the clamp is locked by some quick-locking device? This on a platform that vibrates and are subject to G-forces in all directions.The clamping system for retain those bottles is very safe and it's nothing like vibrations or G forces who will open them (the handle have a insignifiant weight).The only way to them open is to applicate a great force on the handle.Of course if they broke .. the bottle will be free .. but this apply for any type of retainer.
I tell this by my experience with such retainers.

Two pictures of the damage and one of a similar specified vehicle for perspective.

One remarkable thing in those photos is the car just aside is pratically intact ....
Seem's to indicate the blow destructions are dependent of the bottle position in the car ....

Cheers.

[nonsense]

Can anyone seriously look at those photos of a Hilux ute, where a cylinder rupture in the rear load area, only contained by a fibreglass canopy, has utterly demolished the cabin area as well, and still feel a need to explain what direction the Qantas cylinder was facing, etc, when it failed?

The cylinder failed.
Some of it, including the valve, went upwards and was found in and around the door in the passenger cabin.

The escaping gas (not a rocketing near intact cylinder) blew a hole in the aircraft fuselage.

There was no fire. The oxygen was all gone, dissipated in a fraction of a second, long before any fire had a chance to get started.

Have another look. Gas, not cylinder fragments, did the damage.

http://i46.photobucket.com/albums/f111/gmullard/Junk/breakable.jpg


Mechanical engineer.
No aircraft industry experience, but a healthy respect for compressed gases.

[pacplyer]

Gee Mr nonsense,

Was this a pressurized pick up truck? Structured to fly at 45,000 feet and handle over 9.2 internal differential before it failed?

Complete with a plumbed in aviation oxygen system with a known history of leaking at a bottle pressure of [up to] 1800 psi? Sitting next to unknown pallets of god-knows-what being shipped in huge pallet positions?

The Toyota picture may be appropriate to outline the destructive force possible with bottle structural failure, O.K. But your conclusions if stated non-hypothetically, are poor and without reasonable foundation.

Is that what you meant to do? Solve the investigation with proof from Toyota?

(I agree, however, that the "rocketeer theory" sounds unlikely. The problem is that your "cylinder failure theory" is statistically unheard of in reported jet aviation history of over fifty years. We can't find one case of this ever happening in millions of flight hours.)

Sometimes though, even Peter Sellers is right for the wrong reasons.....


.

[vortsa]

If it is confirmed that the bottle caused the incident or was a result of an incident which ruptured the oxy bottle presenting missile type debris inside an aircraft, we have a serious problem and one that is going to present itself as a headache for commercial aircraft designers, on all continents.

How many other unexplained hull losses over the years could have been caused by just such an event?

Was this the real cause of the TWA disaster, a bottle projecting itself into the centre fuel tank?

The list is endless, are we as passengers playing Russian Roulette and flying around on time bombs?

Is the only answer to a safer aircraft can be unpressurized stowage and the use of oxygen generators?

[Chardy]

Interesting point, Vortsa - particularly the TWA accident.

As tech crew I'm not overly concerned given the number of miles flown vs accident/incident rates, however as you say, it's a headache for designers, not to mention what happens to existing a/c already in service.

[EDIT: Also the issue regarding O2 generators is covered in this thread too - quite a few pages back but I recall it was a very good point]

Cheers, Chardster

[Milt]

Missing factors.

We don't yet know the oxygen pressure in the bottles before the event. Top pressure is believed to be 1800 psi and a recharge reportably required if 1300 psi or less. Ultimate design strength another unknown yet. Charge pressure could have been anywhere between 1300 and 1800 psi..

Other unknown yet in this thread is the metallurgy of the bottle material.

Oxygen under pressure is a powerful oxident. An internal bottle scratch/blemish/flaw in manufacture may be all that is necessary as a crack starter particularly if there is any propensity for "stress corrosion cracking". A crack in steel under stress will grow at the tip of the crack as hydrogen ions migrate to the crack tip resulting in corrosion slowly extending the crack.

Every square inch of the bottle will have a force on it of up to 1800 pnds. If the valve in the neck of the bottle breaks away leaving a 3 square inch hole then the immediate thrust to propell the bottle will be say 3 X 1500 = 4,500 pnds.

Recall the MythBusters playing around with a bottle of compressed air. When the valve departed, the bottle went through a solid brick wall at high speed..

Another unknown is the life of the bottle and the number of pressure change cycles it will have experienced.. Could fatigue of the bottle material be a factor?

[Teal]

The clamping system for retain those bottles is very safe and it's nothing like vibrations or G forces who will open themI've seen these types of straps in automotive and gas applications, and have also seen them simply snap within 24 hours of being attached through expansion and contraction.

[soupisgoodfood]

"Was this a pressurized pick up truck? Structured to fly at 45,000 feet and handle over 9.2 internal differential before it failed?"

No, but it was a modern car, which has to pass modern safety standards, made of steel, not thin aluminum alloy. I'm sure if you sealed it up properly, took care of the windows, it would be able to stand much higher pressure than a 747.

"The problem is that your "cylinder failure theory" is statistically unheard of in reported jet aviation history of over fifty years."

Stats are great, but they are also just that. They don't mean rare things can't happen, they just make them rare. Many accidents are caused by things that haven't happened before.

Besides, I don't think nonsense meant to imply that the bottle exploded on it's own, just that if it did rupture, the orientation might not have mattered compared to the bottle rocket theory. Then there's the possibility that it was a bit of both.

[Short_Circuit]

The installation strap have a spring to allow for expansion / contraction.

The release clip is safetied with a pin.

But anything is possible.

[geemul]

Might be worth a read for known failures of aluminium (in statistically insignificant numbers) SCUBA and rescue type cylinders.

Luxfer: Technical Bulletins: October 22, 2007 (http://www.luxfercylinders.com/support/bulletins/20071022usa.htm)

These units develop neck cracks up into the thread region and have been known (again in statistically insignificant numbers) to expel valves at high velocity. Most of these cylinders have been condemned at their regular inspection cycles.

These are most likely different styles of cylinders and different grades of aluminium to the ones on aircraft and are treated far worse than aircraft kit.

Like the car photo's, it's just an illustration of what can happen in this world.

[pacplyer]

No, but it was a modern car, which has to pass modern safety standards, made of steel, not thin aluminum alloy. I'm sure if you sealed it up properly, took care of the windows, it would be able to stand much higher pressure than a 747.


Certainly, Soupman,

Your rebuttal sounds fair. But may I point out, a flaw in that argument. A modern automobile in compliance with modern DOT highway safety standards is not designed to withstand pnematic expansion forces from within the vehicle. That's why it flew apart so dramatically. It is only designed (with any significant magnitude) to withstand the opposite: external compression and energy absorption from outside the vehicle (a crash.)

You guys are mixing apples and Oranges imho. The material chosen for design is not the only factor in strength. The Toyota in that picture (not some "Chitty-Chitty-Bang-Bang" sealed window pickup you've imagined) is incapable of being pressurized. Ergo, the damage we see in the photo is not representative of what would happen in a reverse stress-engineered structure like a 747 pressure containment hull.

This is why aeronautical engineering is quite a different thing altogether than engineering the stresses involved in a simple soup-can (even a four wheel drive one from Japan.)

Granted, I will concede that IF the cylinder itself goes off that close to the 747 skin and fuselage structure: we are going to loose some skin baby. Thank God for great aeronautics aloft in Boeing Aircraft (built like tanks.) They've repeatedly come home safe with huge portions of the aircraft gone.

Repeat after me everybody: "If it's not Boeing, I'm not Going." :}

Vortsa is dead-balls-on imho with his post, BTW. And agree with his preventative failure post below as well;

Aviation post-accident/incident investigation, however, does factor stats in for likelyhood, but does not rule out anything outside those stats. If the evidence leads off in a certain unlikely direction (like the DC-10 #2 eng uncontained N1 hub failure, or structural O2 cylinder failure) then the industry has changed and new AD's NPRM's etc result.

[vortsa]

"The problem is that your "cylinder failure theory" is statistically unheard of in reported jet aviation history of over fifty years."

That's not the way we work in Aviation, we look for a potential problem and try to address it before it becomes an event.

see below


Compliance: 1. Before 28 February 2005
2. After 26 February 2004
Effective Date: 26 February 2004
DCA/EMY/27A Oxygen Reserve Cylinders – Inspection and Replacement
Applicability: Oxygen Cylinders P/Ns GLF(XXX)-(X), GLD(XXX)-(X), PC2300 and SLF300, which
are known to be installed on, but not limited to Airbus A300 series aircraft, Dassault
Aviation (AMD-BA) Mystère-Falcon 20, Mystère-Falcon 50, Falcon 200 and Falcon
900 aircraft, Pilatus aircraft, Eurocopter SA 315 B and AS 350 B3 helicopters and
Hindustan Aeronautics Limited helicopters.
Note 1: This AD has been revised to extend the compliance time for oxygen cylinders
operated in normal climatic conditions from 6 months to 12 months.
Note 2: These types of oxygen cylinders are an optional equipment fit for use during
operations at high altitudes or to provide respiratory aid for passengers.
Requirement: To prevent oxygen cylinders exploding due to aging and deterioration of the
Aluminium Alloy 5283 (AA5283) cylinder shell material, identify the year of
manufacture of each affected P/N oxygen reserve cylinder made from AA5283 and
replace per the instructions in Eurocopter AS 350 Alert Service Bulletin No. 05.00.54.
Immediately after removing the oxygen cylinder from the aircraft, empty the cylinder
per the instructions in Intertechnique Service Bulletin (SB) GLD/GLF-35-150 dated 20
September 2006.
Note 3: Oxygen cylinders with P/Ns listed in this AD may only be used if the service life is
within the limitations of the compliance of this AD.
Note 4: Oxygen cylinders with P/Ns listed in this AD and which are held as spares are to be
inspected per the requirements of this AD. Identify the year of manufacture of the
cylinder and empty all oxygen reserve cylinders that have reached or exceeded 2

[Deaf]

One point that has to be borne in mind with the assorted horror pics etc is the dynamic behavior of metal cracks with gas pressure. A crack normally propagates slowly with fatigue etc. When it gets to a certain length (dependant on material, stress etc) it will propagate at 1/3 speed of sound in metal ie much faster than pressure relief which happens at the speed of sound in gas.

Thus if something like Al skin designed for a few psi pressure suddenly get hit with a slug of gas at high velocity there will be a localised pressure which well may cause the skin to fail and the crack will spread very fast. The airflow does the rest.

Poor explanation I know but modelling this sort of thing is not easy.

[Pontius Navigator]

It was said many pax masks were not adjusted.

Maybe the pax were happy to hold the mask in place, much as is see on many hospital dramas? It gives them something to do with one hand.

If you have never donned an oxygen mask before you may not have the confidence to fiddle around with the straps and then let go in what you may perceive as a d***h dive.

How many of you when you were first trained got any sort of mask on right first time? and how many had to be assisted?

IMHO holding a mask in place with one hand is a smart move.

[pacplyer]

Vortsa,

I concede the point to you. O2 problems are tracked and prevented.

You guys so a great job of making flying safe. :ok:

pac

[Machaca]

Pacplyer
The problem is that your "cylinder failure theory" is statistically unheard of in reported jet aviation history of over fifty years. We can't find one case of this ever happening in millions of flight hours.)


Well, er, not quite. I did a quick search a few days ago and found a similar incident from 2006 -- cylinder rupture & pressure hull penetration. I even shared it back in post #678 (http://www.pprune.org/forums/rumours-news/336528-qantas-744-depressurisation-34.html#post4297481), with a link to the AAIB bulletin.


Reported, but unheard of by all but a few.;)

[BOAC]

No wish to restart any wild theories about TWA800, and I apologise for not reading all the posts here, but does anyone know if the 'inconclusive' accident findings looked at bottle explosion, or even if the initial rupture was near any bottles? This from a PPrune archive:

<‘AAR-00/03 "It was clear from the wreckage recovery locations that the FIRST pieces to depart the airplane were from the area in and around the airplane's wing center section (WCS), which includes the CWT, and therefore that the breakup must have initiated in this area.”

That statement refuted by TWA 800 public docket:: Docket Number SA-516, Exhibit No. 22A, Trajectory Study, page 3: "The wreckage distribution shows that parts were initially shed from the area just forward of the wing."

"...the red zone (the wreckage zone closest to JFK along the airplane's flightpath and, therefore, containing the earliest pieces to depart the airplane) consisted primarily of pieces from the WCS front spar and spanwise beam (SWB) 3, the manufacturing access door from SWB 2, the two forward air conditioning packs, large pieces of a ring of fuselage structure just in front of the wing front spar, and main cabin floor beams and flooring material from above the WCS and from the fuselage in front of the WCS....

The forward cargo door is ‘from the fuselage in front of the WCS....’>

There was also a recent thread in this forum about TWA800 which is now here (http://www.pprune.org/forums/aviation-history-nostalgia/337040-twa-800-investigation-hearing-soon.html).

I am braced for the howls of protest!

[pacplyer]

Thanks Machaca.

I missed your post
BUT.....

It's not an oxygen cylinder if I read your link correctly. The pic on page 13 is a completely different animal: a (machined out of solid bar stock) metal relatively Low pressure (1000 psi IIRC) back up to normal 2000-3000 psi hydraulics (IIRC generally speaking)

Hydraulic accumulator information
There are two hydraulic accumulators located under
the BAe 146 fuselage floor close to the main landing
gear installation and inside the pressure hull, and these
are fitted so that the hydraulic system can cope with
fluctuations in demand. The accumulator consists of a
pressure cylinder with a piston inside. On one side of
the piston is hydraulic fluid and on the other is nitrogen,
nominally at 1,000 psi.

That's how I read it anyway. Are Metal O2 tanks stamped out of thick sheets and then welded at the neck? Not sure.

Machaca, great photos; you are one of the best contributors to this thread thanks. :ok:

[Machaca]

All Avox Systems lightweight steel 801307 series cylinders that apply to Boeing aircraft meet DOT 3HT-1850 regs.

Title 49: Transportation
PART 178—SPECIFICATIONS FOR PACKAGINGS


§ 178.44 Specification 3HT seamless steel cylinders for aircraft use

(http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=0f30f8f36cc6d9d089c6e90c1a02eacf&rgn=div5&view=text&node=49:2.1.1.3.13&idno=49#49:2.1.1.3.13.3.39.7) (a) Type, size and service pressure. A DOT 3HT cylinder is a seamless steel cylinder with a water capacity (nominal) of not over 150 pounds and a service pressure of at least 900 psig.

(b) Authorized steel. Open hearth or electric furnace steel of uniform quality must be used. A heat of steel made under the specifications listed in Table 1 in this paragraph (b), a check chemical analysis that is slightly out of the specified range is acceptable, if satisfactory in all other respects, provided the tolerances shown in Table 2 in this paragraph (b) are not exceeded. The maximum grain size shall be 6 or finer. The grain size must be determined in accordance with ASTM E 112–88 (IBR, see §171.7 of this subchapter). Steel of the following chemical analysis is authorized:

Table 1 — Authorized Materials

..........................AISI 4130
Designation............(percent)

Carbon.................0.28/0.33
Manganese...........0.40/0.60
Phosphorus...........0.040 maximum
Sulfur..................0.040 maximum
Silicon.................0.15/0.35
Chromium.............0.80/1.10
Molybdenum..........0.15/0.25


Table 2 — Check Analysis Tolerances

.........................................................Tol erance %
Element..........Limit or max %............over max.....under min

Carbon...........Over 0.15 to 0.40 incl.....03............04
Manganese.....To 0.60 incl...................03............03
Phosphorus*...All ranges.....................................01
Sulphur..........All ranges.....................................01
Silicon...........To 0.30 incl...................02............03
...................Over 0.30 to 1.00 incl......05............05
Chromium......To 0.90 incl....................03............03
...................Over 0.90 to 2.10 incl......05............05
Molybdenum...To 0.20 incl...................01............01
...................Over 0.20 to 0.40 incl......02............02

*Rephosphorized steels not subject to check analysis for phosphorus.

(c) Identification of material. Material must be identified by any suitable method. Steel stamping of heat identifications may not be made in any area which will eventually become the side wall of the cylinder. Depth of stamping may not encroach upon the minimum prescribed wall thickness of the cylinder.

(d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished container appreciably. The general surface finish may not exceed a roughness of 250 RMS. Individual irregularities such as draw marks, scratches, pits, etc., should be held to a minimum consistent with good high stress pressure vessel manufacturing practices. If the cylinder is not originally free of such defects or does not meet the finish requirements, the surface may be machined or otherwise treated to eliminate these defects. The point of closure of cylinders closed by spinning may not be less than two times the prescribed wall thickness of the cylindrical shell. The cylinder end contour must be hemispherical or ellipsoidal with a ratio of major-to-minor axis not exceeding two to one and with the concave side to pressure.

(e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited, except that welding by spinning is permitted to close the bottom of spun cylinders. Machining or grinding to produce proper surface finish at point of closure is required.

(f) Wall thickness.
(1) Minimum wall thickness for any cylinder must be 0.050 inch. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure may not exceed 75 percent of the minimum tensile strength of the steel as determined from the physical tests required in paragraph (m) of this section and may not be over 105,000 psi.
(2) Calculations must be made by the formula:
S = [P(1.3D2 + 0.4d2 )] / (D2 − d2 )
Where:
S = Wall stress in psi;
P = Minimum test pressure prescribed for water jacket test;
D = Outside diameter in inches;
d = Inside diameter in inches.
(3) Wall thickness of hemispherical bottoms only permitted to 90 percent of minimum wall thickness of cylinder sidewall but may not be less than 0.050 inch. In all other cases, thickness to be no less than prescribed minimum wall.

(g) Heat treatment. The completed cylinders must be uniformly and properly heated prior to tests. Heat treatment of the cylinders of the authorized analysis must be as follows:
(1) All cylinders must be quenched by oil, or other suitable medium.
(2) The steel temperature on quenching must be that recommended for the steel analysis, but may not exceed 1750°F.
(3) The steel must be tempered at a temperature most suitable for the particular steel analysis but not less than 850°F.
(4) All cylinders must be inspected by the magnetic particle or dye penetrant method to detect the presence of quenching cracks. Any cylinder found to have a quenching crack must be rejected and may not be requalified.

(h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads conforming to the following are required on openings:
(1) Threads must be clean cut, even, without cracks, and to gauge.
(2) Taper threads, when used, must be of length not less than as specified for National Gas Tapered Thread (NGT) as required by American Standard Compressed Gas Cylinder Valve Outlet and Inlet Connections.
(3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear stress of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required.

(i) Hydrostatic test. Each cylinder must withstand a hydrostatic test, as follows:
(1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. Pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent of 0.1 cubic centimeter.
(2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 psig, which ever is the lower.
(3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure.
(4) Each cylinder must be tested to at least5/3times service pressure.

(j) Cycling tests. Prior to the initial shipment of any specific cylinder design, cyclic pressurization tests must have been performed on at least three representative samples without failure as follows:
(1) Pressurization must be performed hydrostatically between approximately zero psig and the service pressure at a rate not in excess of 10 cycles per minute. Adequate recording instrumentation must be provided if equipment is to be left unattended for periods of time.
(2) Tests prescribed in paragraph (j)(1) of this section must be repeated on one random sample out of each lot of cylinders. The cylinder may then be subjected to a burst test.
(3) A lot is defined as a group of cylinders fabricated from the same heat of steel, manufactured by the same process and heat treated in the same equipment under the same conditions of time, temperature, and atmosphere, and may not exceed a quantity of 200 cylinders.
(4) All cylinders used in cycling tests must be destroyed.

(k) Burst test. One cylinder taken at random out of each lot of cylinders must be hydrostatically tested to destruction.

(l) Flattening test. A flattening test must be performed on one cylinder taken at random out of each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60° included angle, rounded to1/2-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder.

(m) Physical tests. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows:
(1) Test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of cylinders.
(2) Specimens must conform to the following:
(i) A gauge length of at least 24 times the thickness with a width not over six times the thickness. The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with the record of physical tests detailed information in regard to such specimens.
(ii) Heating of a specimen for any purpose is not authorized.
(3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length.
(i) The yield strength must be determined by either the “offset” method or the “extension under load” method as prescribed in ASTM E 8 (IBR, see §171.7 of this subchapter).
(ii) In using the “extension under load” method, the total strain (or “extension under load”) corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset.
(iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 psi, the strain indicator reading being set at the calculated corresponding strain.
(iv) Cross-head speed of the testing machine may not exceed1/8inch per minute during yield strength determination.

(n) Magnetic particle inspection. Inspection must be performed on the inside of each container before closing and externally on each finished container after heat treatment. Evidence of discontinuities, which in the opinion of a qualified inspector may appreciably weaken or decrease the durability of the cylinder, must be cause for rejection.

(o) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by dry gas or dry air pressure after the bottom has been cleaned and is free from all moisture, subject to the following conditions and limitations:
(1) Pressure, approximately the same as but not less than service pressure, must be applied to one side of the finished bottom over an area of at least1/16of the total area of the bottom but not less than3/4inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (q) of this section, a cylinder must be rejected if there is leakage.
(2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process.
(3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug.
(4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer should design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas.

(p) Acceptable results of tests. Results of the flattening test, physical tests, burst test, and cycling test must conform to the following:
(1) Flattening required without cracking to ten times the wall thickness of the cylinder.
(2) Physical tests:
(i) An elongation of at least 6 percent for a gauge length of 24 times the wall thickness.
(ii) The tensile strength may not exceed 165,000 p.s.i.
(3) The burst pressure must be at least4/3times the test pressure.
(4) Cycling-at least 10,000 pressurizations.

(q) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. For each cylinder subjected to reheat treatment during original manufacture, sidewall measurements must be made to verify that the minimum sidewall thickness meets specification requirements after the final heat treatment.

(r) Marking. (1) Cylinders must be marked by low stress type steel stamping in an area and to a depth which will insure that the wall thickness measured from the root of the stamping to the interior surface is equal to or greater than the minimum prescribed wall thickness. Stamping must be permanent and legible. Stamping on side wall not authorized.
(2) The rejection elastic expansion (REE), in cubic cm (cc), must be marked on the cylinder near the date of test. The REE for a cylinder is 1.05 times its original elastic expansion.
(3) Name plates are authorized, provided that they can be permanently and securely attached to the cylinder. Attachment by either brazing or welding is not permitted. Attachment by soldering is permitted provided steel temperature does not exceed 500 °F.

(s) Inspector's report. In addition to the requirements of §178.35, the inspector's report must indicate the rejection elastic expansion (REE), in cubic cm (cc).
[Amdt. 178–114, 61 FR 25942, May 23, 1996, as amended at 62 FR 51561, Oct. 1, 1997; 65 FR 58631, Sept. 29, 2000; 66 FR 45385, Aug. 28, 2001; 67 FR 51652, Aug. 8, 2002; 68 FR 75748, 75749, Dec. 31, 2003]

[Machaca]

pacplyer
Are Metal O2 tanks stamped out of thick sheets and then welded at the neck?
Deep-drawn and hot-spun -- have a look! (http://fr.youtube.com/watch?v=Z8R-I5I1Dgo)

[Machaca]

Dodgy cylinder maintenance has happened before:

http://www.ntsb.gov/Recs/letters/1995/A95_148.pdf

A review of the oxygen cylinder's maintenance records indicated that it had been serviced by Tec-Air Services, Incorporated's (Tec-Air), East Northport, New York, repair station on November 30, 1990, and again at Tec-Air's Macon, Georgia, repair station on January 11, 1994. According to Tec-Air records, the service included removing the cylinder valve, inspecting and cleaning the cylinder's interior, testing the cylinder hydrostatically, cleaning and overhauling the cylinder valve, purging/recharging the cylinder, and checking for leakage.

The operator of N66JE, Professional Jet Management, reported that the oxygen cylinder in another of its corporate jet airplanes, a Hawker Siddeley 125-700A, had also been serviced by Tec-Air, but upon reinspection was found unserviceable because of internal corrosion.

In December 1994, the Federal Aviation Administration (FAA) inspected Tec-Air's East
Northport facility, Repair Station No. MAlR315K, and found that Tec-Air had violated or failed to demonstmte compliance with 10 sections of the Federal Aviation Regulations relating to Parts 21, 43, and 145. The investigation cited numerous occasions on which Tec-Air had approved oxygen cylinder assemblies and aircraft fire extinguishers for return to service, including parts utilized on passenger-carrying aircraft under Part 121, when such equipment was unairworthy.

Based on Tec-Air's inadequate record system, it could not be determined whether Tec-Air replaced parts as required during overhaul, utilized old parts, or changed the parts at all.

---

http://www.dot.gov/affairs/cair.htm

FOR IMMEDIATE RELEASE OIG 28-95
Friday, October 27, 1995 Contact: Todd Zinser
Tel.: (202) 366-0681

DOT INSPECTOR GENERAL ANNOUNCES
GUILTY PLEA IN AIRCRAFT EMERGENCY
EQUIPMENT FRAUD CASE


Inspector General A. Mary Schiavo of the U.S. Department of

Transportation today announced that Tec-Air Services, Inc., and

two of its top executives pled guilty to charges of conspiracy,

mail fraud and making false statements to the federal government

in connection with a long-running fraudulent scheme involving the

failure to properly service aircraft emergency equipment.

Tec-Air Services, Inc. (Tec-Air), based in East Northport,
Long Island, and its two vice presidents, Jack Caloras and Steven
Metal, pled guilty on Oct. 12 to five felony counts before U.S.
District Judge Jacob Mishler in Uniondale, N.Y.

Tec-Air was an aircraft repair station licensed by the
Federal Aviation Administration (FAA) to service emergency
equipment such as fire extinguishers, smoke detectors and the
oxygen supply system used during emergency cabin depressurization
on commercial aircraft.

The charges relate to Tec-Air's failure, between 1990 and
1994, to properly test, overhaul and repair aircraft emergency
equipment for customers who were primarily civilian airlines. In
order to reduce costs and increase profits, Tec-Air, at the
direction of Caloras and Metal, routinely failed to properly test
the emergency equipment for defects or to replace needed parts as
required by the manufacturers' specifications and by FAA
regulations. Tec-Air billed its customers for the services
although they were not performed. Tec-Air then falsified
documents to indicate the required testing and repair work had
been performed.

The defendants also pled guilty to mail fraud for failing to
properly overhaul and replace necessary parts in the oxygen
system emergency equipment provided to one of their customers,
Boeing Defense and Space Group, for use on Air Force One and Air
Force Two, the aircraft used to transport the President and Vice
President.

Caloras and Metal face a maximum sentence of five years in
prison and a $250,000 fine on each count. As part of their plea
agreement with the government, they have each agreed to pay a
fine and to be barred for life from operating or being employed
at any business that holds an FAA license.

Tec-Air faces a maximum fine of $500,000 on each count. As
part of its plea agreement, Tec-Air has agreed to pay a $100,000
fine and to be permanently barred from holding any FAA license.

The trial of another defendant named in the superseding
indictment, Domenick Leonardi, who was Tec-Air's production
coordinator, is scheduled to begin on Nov. 13.

The case was investigated by DOT's Office of Inspector
General in New York, N.Y., the Federal Bureau of Investigation
and the Defense Criminal Investigative Service.

The prosecution was handled by Assistant U.S. Attorneys Sean
F. O'Shea and Ronald G. White and former Assistant U.S. Attorney
Mark S. Cohen, of the U.S. Attorney's Office for the Eastern
District of New York.

[pacplyer]

Interesting stuff Machaca,

Especially the bottle inspection pencil whipping. Can in fact cause fires since the tank contamination plus oxidizer (oxygen) is dispersed together when old flying leatherman sets off an ignition source (static) in that corporate jet case.

You're getting really warm buddy, I'll give you that. Still no documented oxygen tank failure. :)

(But don't give up now! You're bound to find one if anybody can.) :D

[DozyWannabe]

pacplyer:
Thank God for great aeronautics aloft in Boeing Aircraft (built like tanks.) They've repeatedly come home safe with huge portions of the aircraft gone.

Repeat after me everybody: "If it's not Boeing, I'm not Going."
Now now, that's not exactly fair - the DHL Airbus A300 landed successfully after a sodding missile took out a significant chunk of the port wing's trailing edge and the hydraulics to boot!

That said, hats off to any aircraft manufacturer that builds beasts that can take that kind of punishment and still bring you home.

[airship]

You guys are mixing apples and Oranges imho. The material chosen for design is not the only factor in strength. The Toyota in that picture (not some "Chitty-Chitty-Bang-Bang" sealed window pickup you've imagined) is incapable of being pressurized. Ergo, the damage we see in the photo is not representative of what would happen in a reverse stress-engineered structure like a 747 pressure containment hull. Is that why apparently solid houses literally "explode" when a tornado passes overhead? Is that why human-beings suffer 'the bends' if they don't respect the proper depth/time tables when ascending? Is that why fish caught at great depths have never been brought up to the surface alive (even those that are hooked at depths of a mere 100m. will end up with their gas-bladders in their mouths and succomb rapidly)...?! You're missing the point. Which is that we're discussing an almost instantaneous escape of highly-pressurised gas locally and in a relatively-confined space, leaving no appreciable time for a normal (or natural) equilibrium to reinstate itself...?! Perhaps, we're all (aircraft and living creatures) more fragile than you might think...?! :ok:

[Wingover68]

A slight deviation from the very informed ongoing technical discussion. I can’t remember which but one of the ATSB’s safety investigation reports during the past 6 months or so included the statement “Sooner or later it will happen, as long as the probability is greater than zero”

Well said I thought, and stuck it on my computer desktop as a reminder that zero probability could be a bit elusive.

[airship]

All the examples you site are not metal machines at 29,000 feet. At least one of the examples I cited involved a naturally-occuring phenomenom that are normally associated with cumulonimbus, a type of cloud that can be found anywhere between 2,000 - 16,000 meters altitude. If you need any help making the conversion or otherwise, please do contact Duck Rodgers! :eek::eek::eek:

[Conan The Barber]

In threads like this one, there is always at least one poster who becomes a bit too prolific and a bit too possessive.

Taking a bit of time off for some reflection, is good for both poster and thread.

[airship]

Well, I'm off to feed the stray cats now anyway. :ok: :zzz:

[soupisgoodfood]

pacplyer: I pretty much agree with you, but I think you still missed the point. That exploded car still shows how much damage one of those bottles can do -- it still takes a large force to blow a car apart like that even though they're not designed to be pressurised and have quite a different structure design compared to an airliner. And Boeings aren't built like tanks, as tanks are designed to withstand external compression, like a car :}

[FrequentSLF]

Repeat after me everybody: "If it's not Boeing, I'm not Going."

SLF Here.
Is this the opinion of an expert?
A statement such this should be deleted from the thread as many other as being deleted. Such statement does not add anything to the thread discussion.
No facts to validate it, or...the a/c is falling apart but I am able to land it, that's a great a/c. Sounds good? not to me.
Note I am not saying anything about the a/c manufacturer...just commenting the post.
regards

[bobusse]

Fully concur

[DozyWannabe]

Nah, let it stand. Everyone's entitled to their opinion, even if the facts don't necessarily bear it out. Much better to let the facts speak for themselves!

[r75]

I concur with #845, I in fact did an inspection very similar to this on a 744 today, in this job we try our very best to get to the problem (if there is one) before it gets to us.

[sevenstrokeroll]

BOEING SUCKS

AIRBUS SUCKS

happy now?

by the way, DOUGLAS RULES!

[eight16kreug]

LIFE SUCKS

JOB SUCKS

WIFE DOESN'T

by the way, girlfriend does!

[Brakes on]

pcplayer,
in post #844 you say:
Quote: They've repeatedly come home safe with huge portions of the aircraft gone. Unquote, followed by the name of an aircraft manufacturer.

Do you mean you'd rather go on an aircraft manufacturer's planes which repeatedly have developed holes (and come home safely) than on a manufacturer's planes who do not repeatedly develop holes (and come home safely(?

Sorry for thread drift.

[vortsa]

Thank you r75 a point that has been missed by many. The very essence of our profession is to look to prevent a system failure that will cost lives. We rely heavily on testing,procedures,technology,science and experience. Each of these is important in what we call preventative maintenance. Those in the industry understand the term redundant system but even the maintaining of these systems follow the same principle. We don't just rely on the design, every element is important and that is why we will learn from this event and our experience and awareness will profit.

[Vertiginous]

Glad someone reads my posts!! I'd go further, actually. I think the top fitting of the bottle failed when the bottle was held in position. Why? Because the valve travelled on a vertical trajectory. This suggests that either

1. The assembly failed spontaneously; or

2. An item of baggage forcefully contacted the upper part of the tank assy when the latter was in its right and proper place.

The alternative — that the bottle was swinging around all over the place, and the valve assy took off at an angle that exactly compensated for the bottle's leanings — is too daft to contemplate.

My money is on option 1. — spontaneous failure of the cylinder-valve assembly.

[Vertiginous]

The fact that a Hilux is not designed to be pressurised is beside the point. Leakage of window- and door-seals when the world outside goes low-pressure is something that you experience over a matter of whole seconds. If pressure were built up gradually inside the truck it would leak out. But this is not what we are dealing with. An O2 tank takes a few milliseconds to fail. The pressure-wave from this event completely demolished the vehicle, a robust structure.

This incident also demonstrates that spontaneous failures happen. (I acknowledge that we do not know the history of this particular bottle.)

[NSEU]

We don't yet know the oxygen pressure in the bottles before the event. Top pressure is believed to be 1800 psi and a recharge reportably required if 1300 psi or less. Ultimate design strength another unknown yet. Charge pressure could have been anywhere between 1300 and 1800 psi..

More likely to be in the upper region. Because QF 744's fly over high terrain in Asia, the miniumum pressure ex-Australia is 1800psi cockpit (EICAS) indication (strongly enforced by the pilots as it's in their manuals). The pressure is not going to drop 500 psi on a trip to Europe and back under normal circumstances.

When filling the bottles at the remote fill port near the Forward Cargo door, the engineers use the gauge at the remote fill port to assess tank oxygen pressure. Although the cockpit indication is supposed to be a repeater (as it uses the same oxygen tank averaging system) the cockpit indications always read lower than the fill point gauge (+/-100psi difference is allowable), so the engineers have to put extra pressure in the tanks to get 1800psi in the cockpit. You might say that the fill point gauge is underreading, but this gauge reading is always closer to the gauge reading on the regularly calibrated oxygen servicing cart. Normally the fill pressure from the cart is higher still. I have, on occasions, on other operators, seen cockpit indications over 2000psi on warm days, so I can only imagine the pressures in the bottles on very hot days. I think the highest pressure I've seen in the cockpit on QF is in the mid 1900's (ex-Sydney).

Anyway, these pressures are all well below the design limits of the bottle and the pressure relief blow out disc value (2650~3083psi) ;)

[banana head]

gauge reading is always closer to the gauge reading on the regularly calibrated oxygen servicing cart

Regularly calibrated, and for a time regularly filled with Nitrogen :ugh:

I wonder if any other 'non-standard' maintenance has been carried out on QF -400 O2 systems that may have contributed to an O2 bottle failure?

[pacplyer]

SLF Here.
Is this the opinion of an expert?
A statement such this should be deleted from the thread as many other as being deleted. Such statement does not add anything to the thread discussion.
No facts to validate it, or...the a/c is falling apart but I am able to land it, that's a great a/c. Sounds good? not to me.
Note I am not saying anything about the a/c manufacturer...just commenting the post.
regards

FrequentSLF: Ya gotta allow us a little humor once in a while! "If it's not Boeing, I'm not going", was an industry tongue-in-cheek sales slogan; boeing used to give free stickers out that said this in ground school. I should have put a smiley to it. And no, I'm not an expert at anything, I'm just a retired pilot with an A&P. There are those who want the rumours and news section open to only licenced airman because of these kind of misconceptions. But me, personally? I think this forum as is, presents a unique dynamic between those who ride and those who make it possible. But SLF, if I was a patient, and you were a heart surgeon, I wouldn't come on Medical rumours and news and tell you to delete medical posts I didn't understand. Right? :8 But there's nothing wrong with putting things in the form of a question as moderator Sick Squid has pointed out on stickies many times.

But it's amazing to me just how many times the printed english language fails to convey intended meaning isn't it? I'll have to be more attentive to it.

Good point Soup, Airship and others. (Boeing tank; good one!:))

Thanks for taking my barbs, everybody. The localized pressure wave of a cylinder exploding O2 tank is clearly is something you don't want in a confined space. Yes, it's a plausible theory imho.

And lastly, Conan the Barber is correct in his post.

I yield the floor to others.

pac

[NSEU]

banana head said:
Regularly calibrated, and for a time regularly filled with Nitrogen

No, oxygen carts are filled with oxygen. Only nitrogen carts are filled with nitrogen.

[pasoundman]

NSEU
No, oxygen carts are filled with oxygen. Only nitrogen carts are filled with nitrogen.

IIRC there was a little bit of a mix up on that point a while back.

[moa999]

A few more photos of the door area in this article (u/f very shoddy quality) - experts go to work :ok:

New pictures show interior damage to Qantas plane - News - Travel - smh.com.au (http://www.smh.com.au/news/news/qf30-blast-new-photos/2008/08/01/1217097515197.html)

[bsieker]

No, oxygen carts are filled with oxygen. Only nitrogen carts are filled with nitrogen.

IIRC there was a little bit of a mix up on that point a while back.


Then you might have cared to look for the incident again, before referring to it.

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

[spannersatcx]

That's probably one of the reasons we don't fill from the charging point, pressure low change a bottle. So if QF charges from the remote point, the bottles could be sat in there for quite sometime then?

[LapSap]

Is there any record of the rogue McCormack working on OJK?

[FlexibleResponse]

So it would be fair to say:

1. That some airlines change the oxy bottles when the pressure is low...for safety reasons?

2. And other airlines recharge the oxy bottles from a central remote charge point for economic reasons?

But doesn't QANTAS put safety and security first? Help me here. I am confused.

[Fargoo]

So it would be fair to say:

1. That some airlines change the oxy bottles when the pressure is low...for safety reasons?

2. And other airlines recharge the oxy bottles from a central remote charge point for economic reasons?

But doesn't QANTAS put safety and security first? Help me here. I am confused.

We at BA also charge our Oxy in-situ.
Some might say there is more risk involved in disturbing the systems and changing bottles than there is in charging from a remote point - horses for courses ;)

[Weapons_Hot]

May I recommend the following to your observation/experience:

Mellow on the first

Ditch the second and third

The fourth - keep her!:ok:

On a slightly off-topic question:
Aren't Boeing and Airbus designed and built to meet FAA/JAA certification requirements? Aren't both flying over/on most of the continents?

[PaperTiger]

"If it's not Boeing, I'm not going", was an industry tongue-in-cheek sales slogan; boeing used to give free stickers outAnd it ceased to be even remotely amusing a long, long tme ago.

[pasoundman]

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

Ah, that's how they did it. Thanks for the charification. It's almost more bizarrre though.

[NotPilotAtALL]

Hi,

And since the fittings didn't, well, fit, they exchanged them for ones that did.A common mistake that people make when trying to make something completely foolproof is to underestimate the ingenuity of complete fools...

I hope those who exchanged the connections fittings are now discharged of all responsible job and are whipping the dust of the runway at Wagga Wagga.

Cheers.

[NSEU]

Some might say there is more risk involved in disturbing the systems and changing bottles than there is in charging from a remote point - horses for courses

Precisely. The more you pull the bottles in and out, the more wear and tear on the threaded connections(safety), more risks of dropping the bottles from a great height onto the tarmac(safety), the less chance of getting contaminants on the connections(safety), the less chance of personnel getting injured by lifting the cumbersone bottles in confined spaces (safety), much greater turnaround speed (happier pax), etc....

[Joetom]

Oxygen systems get loads of care and attention.

Nitrogen systems get much much less attention and find themselves in dirty, greasy,wet oily places, am sure they will be trying to find out if said aircraft or bottle/bottles were involved with the nitrogen misshapp !!!

[Swedish Steve]

That's probably one of the reasons we don't fill from the charging point, pressure low change a bottle

Yes I agree with you in principle, and in fact in ARN we are not allowed oxygen charging rigs on the ramp. But the B744 pax oxy system has around 20 bottles. They are used in parallel, so that when the pressure is low you have to refill all the bottles at once. Maybe you keep 20 charged bottles in stock, I have one (for the crew). So if I had low pax oxy pressure on a B744, I would have to remove all the bottles and take them to the workshop and charge them one at a time. Oxy bottles charge very slowly because they can get hot. I would be much happier charging all 20 at once through an outside rig.

[glhcarl]

Yes I agree with you in principle, and in fact in ARN we are not allowed oxygen charging rigs on the ramp. But the B744 pax oxy system has around 20 bottles. They are used in parallel, so that when the pressure is low you have to refill all the bottles at once. Maybe you keep 20 charged bottles in stock, I have one (for the crew). So if I had low pax oxy pressure on a B744, I would have to remove all the bottles and take them to the workshop and charge them one at a time. Oxy bottles charge very slowly because they can get hot. I would be much happier charging all 20 at once through an outside rig.

Could someone explain why Boeing would design such a heavy, complacated, maintenance intentsive and possibility dangerous system, when oxygen generators were available?

[forget]

Could someone explain why Boeing would design such a heavy, complacated, maintenance intentsive and possibility dangerous system, when oxygen generators were available?

Oxygen generators don't last long enough for flight operations over high terrain. Himalayas etc.

[Buster Hyman]

Had a chat to the Brother in law last night...

1. He had a crying FA (don't know if its the same one from before) and this was when it was all happening. After thy'd levelled out, a more senior FA came along & gave her a duty which snapped her back into composure.

2. He had just been served a beer before it happened & when they did level out, not a drop had been spilled! Plunge my arse!:=

3. Note to QF & Crews: He said he had trouble understanding the announcements from the flight deck. Possibly due the masks, possibly a faulty PA as a result of the incident. Only every second or third word was clear.

4. He reiterated that the QF staff in MNL were excellent. They enacted an emergency plan & they were being assisted by staff from all other carriers (such as CX...possibly a local OneWorld agreement) They handled themselves well when confronted by a bunch of boisterous, adrenaline fuelled Aussies!!!

[Finn47]

This article makes some new claims and has a few previously unseen pictures:

The damage inside QF30 - Travel - smh.com.au (http://www.smh.com.au/news/travel/the-damage-inside-qf30/2008/08/02/1217097606087.html)

"electric cables cut" & "Pax were breathing just cabin air instead of oxygen through the masks"....

[Capt Kremin]

If the plane had been higher than 29,000 feet [8839 metres], there almost certainly would have been fatalities in the time it took to get down to 10,000 feet," an aviation expert said.


Total crap.

[Milt]

Does anyone know what indications were presented on the flight deck as to the extent of the problem or did the crew think they had lost a door because of the rapid depressurisation. Would it have been prudent to shut down cabin air flow.

Must have been somewhat puzzling until they were on the ground.

[Little_Red_Hat]

Buster, re: #3- yes masks the most likely cause of garbled PA's... also, having heard the auto depressurisation PA on the ground a number of times, it's sufficiently loud in 'normal' circumstances but I doubt anyone would hear it very well what with people shouting, the step descent and the disturbed airflow....

If I recall correctly, one of the crew on the UAL 801 flight commented that she couldn't hear the crew member seated next to her, let alone anything else. (Different incident I know, but it probably gives an idea of just how much noise there might have been 'during the event')

Did your brother mention if it was more audible 'after' the descent (in level flight), maybe that will give an idication as to whether any improvement is needed....

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...

[Buster Hyman]

LRH. He actually did mention that it was still garbled when they were told that masks were no longer required. As I mentioned, he's a seasoned traveller, ex AN CSO & Flight Service officer and not prone to exagerration.

does anything display on the pax screens
When the crewed informed the punters that they were diverting, they didn't mention a destination however, the chap next to my BIL had the moving map screen on & it showed them turning to MNL. So, I'd say that there was no specific on screen warnings but you raise a good point. If it's difficult to hear or see in an emergency, that would be an excellent way to communicate to the great unwashed!

[forget]

Great unwashed here! :) Improved emergency announcements to passengers could be a very useful outcome of this incident. LHR’s idea of automatically using IFE screens has huge potential.

Voice PAs are full of trip wires. Remember the BA 747 and the volcanic ash, all four quit in the cruise. The flight crew took an age to switch from Boom Mics to Mask - so, in the interval, PAs didn’t get through to the cabin. (Is switching automatic now?)

There has to be a better way. On PA volume levels I remember a flight out of Singapore, early 80s, oddly enough a QF 747. Boarding was complete but people were still attacking overheads. A taped PA came on - and it was deafening.

‘Stop what you are doing and listen’. So loud the passengers froze solid – and listened. It then went on the say that the Safety Brief would commence in one minute and if you didn’t pay attention you’d get a serious slap from a Flight Attendant.:uhoh:

I only heard it the once on Qantas and I wonder if it was an experiment that got knocked on the head by the PR people. Too scary perhaps? I liked it. The point is - PA Systems can produce a huge volume - if you want them to.

[Little_Red_Hat]

PA Systems can produce a huge volume - if you want them to.

As evidenced by many a ground delay (no pax of course) filled with impromptu karaoke sessions over the PA... oops did I just say that out loud? :E

Yes I think a simple addition of basic diagrams for this eventuality to the IFE would do the trick nicely... especially if said Auto announcement is only in English (can't recall it now but I think it can be done in other languages but I'm not sure if this is dependent on the route) and whether it's something which has to be manually done through the IFE control system... on newer aircraft I'm sure it's automatic but you just never know!

Something to the effect of the pictures on the safety card, flashing on the screen with maybe the words 'DO THIS NOW' in a few major languages might help...

[Tinymind]

Oxygen generators as well as not giving a long supply are also dangerous in their own right, burning iron and sodium chlorite (I think) in a small canister to make oxygen is a risky business. They can get very hot and have been known to melt out of seat backs when not installed correctly.

[PeePeerune]

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

It has been known that oxy bottles have been installed into nitrogen rigs and vice versa.Therefore the rig would then easily connect to aircraft systems!!!!

[NSEU]

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...

The video system is automatically shut down during decompression. The boarding music (and old-type safety announce) player makes the very loud and authoritative announcements. Decompression cranks up the volume automatically.

Cockpit headset to oxygen mask microphone switching is automatic when the mask is pulled from its stowage box on QF 747-400's.

[chris weston]

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

[rottenray]

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.




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.


...

[Willoz269]

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 (http://rapidshare.com/files/134686598/Qantas.pdf.html)

[Chardy]

Hey WillOz - tried that link a couple of times - it doesn't appear to be working. Could you do me a favour and double check it please? Thanks! Chardster!

[Tjosan]

Download works fine for me.

[aerostatic]

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.
Can't say I agree with this. Flying now is much safer now than it was 30 years ago, it's just not very special any more. There have been massive advances in technology and human factors. Sorry for the thread drift.

[Chardy]

Tks TJ - must just be the link here at WSSS. Will try again later. Chards

[oversteer]

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?

[BrissySparkyCoit]

Positive pressure relief doors.

[lomapaseo]

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) :confused:

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.

[Milt]

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.

[edoil]

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.

[Nepotisim]

BrissySparkyCoit:Negative pressure relief doors.

You really are a sparky. They are POSITIVE pressure relief doors.

The negative ones are in the cargo doors.;)

[HotDog]

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?

[lomapaseo]

So what caused the over pressure

I think that we need an explosive expert here

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 :}

[justawanab]

Is it too fanciful to suggest that the explosion of the O2 bottle caused a momentary overpressure situation high enough to trigger the relief flaps?

[FlexibleResponse]

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?

[Intruder]

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.
Those doors are simply indicator flaps or covers for the relief valves -- not the valves themselves. It is possible the relief valves did not open, but the doors got jostled open during the fray...

[atakacs]

Just wondering - is there any significant thermal implication of discharging 1850 psi oxygen bottles ?! I gather it should provide some cool into that cargo bay, but anything that could impact the mechanical performances of the nearby structure ?!

[kansasw]

Just wondering - is there any significant thermal implication of discharging 1850 psi oxygen bottles ?! I gather it should provide some cool into that cargo bay, but anything that could impact the mechanical performances of the nearby structure ?!

Atakacs, this is slightly peripheral to your questions but raises a related issue that has been lingering with me for a while.

The escaped gas as it expands will absorb a lot of heat, or provide cooling, by principles familiar to anyone who understands how a refrigeration system works. In a word, when you compress a gas, the total heat energy it contains is confined to a smaller space and so it gets hotter. By the time it gets into the service bottle on the plane, it has cooled to ambient. So when you let it out of the bottle, it has less heat than before it was initially compressed, so gets cooler. So there we have cooling.

Now my lingering puzzle: Some posts back (I'm not going to search 900+ posts, can anybody link?) there were pictures of an exploded oxygen tank. They showed melted female threads where the valve had screwed in, perhaps other melted elements of the tank, but did not specify why. I think these melted from the friction created by the oxygen whizzing at high speed past the orifice. So there we have heating.

Can anybody speak authoritatively to this? And while we're at it, can anybody tell me how to make quoted text appear in blue?

[Vertiginous]

‘Just wondering - is there any significant thermal implication of discharging 1850 psi oxygen bottles ?! I gather it should provide some cool into that cargo bay, but anything that could impact the mechanical performances of the nearby structure?!’

Not in a few milliseconds it wouldn't. This is a bang not a hiss.

[pasoundman]

And while we're at it, can anybody tell me how to make quoted text appear in blue?

Copy it into you your reply - highlight it and press the 'quote' icon - the last on the right of the bar of them.

Took me a while to figure too !

[Buster Hyman]

The video system is automatically shut down during decompression.

The moving map was still running on this flight though... I'm assuming it is separate from the IFE then?

[kansasw]

"Not in a few milliseconds it wouldn't. This is a bang not a hiss."

I think that depends, how big is the orifice through which the oxygen is escaping? If the bottom suddenly falls off the tank, clearly it is a bang not a hiss. If the orifice is of a certain smaller size, like if the valve broke off, I think the gas could escape fast enough to generate a lot of friction = heat, and possibly long enough to melt some stuff locally. If the orifice is much smaller still, it could leak very little and generate only a 1"/25.4mm soap bubble a minute (a typical actual spec for gas leakage from pipes) which would generate no appreciable heat.

I happily proclaim that I haven't the knowledge to calculate this myself, though it can be done. My real questions are, A) Can somebody link the post showing the exploded O2 tank (NOT from the incident aircraft, but previous in this thread as an example) that showed melted threads, B) Why did the threads melt, C) (Excuse if I missed something, but) I have seen no information that the presumed exploded tank was steel or aluminum or composite, has this information been released? I am sure that failure modes differ according to tank type.

I hope I am not drifting the thread excessively. Answers to these questions appear to me relevant to the case.

[kansasw]

"Quote:
And while we're at it, can anybody tell me how to make quoted text appear in blue?
Copy it into you your reply - highlight it and press the 'quote' icon - the last on the right of the bar of them.

Took me a while to figure too !"

Thanks pasoundman, but I have nothing on my screen that looks like what you direct me to. Down below as I compose, I have three rows of "Post Icons," none of which is labelled "quote." Browser is Firefox, is it eliminating something from my view? Or am I just too ignorant?

[Intruder]

The manual method is to enclose the quoted text in

[quote ... [/quote

tags. Put in the closing ] in each to make them work.

[Fris B. Fairing]

Works in Firefox for me

The icon for this is at the end of the second row. It looks like a squared off thought bubble.

[NSEU]

The moving map was still running on this flight though... I'm assuming it is separate from the IFE then?

Not separate. The backlighting for all seat video screens is supposed to be switched off (making the screens blank).

Interesting... Perhaps the wiring between the oxygen flow control valves and the video system was damaged.

[bsieker]

The moving map was still running on this flight though... I'm assuming it is separate from the IFE then?

Has anyone seen, and can point to, video footage of the actual descent? The ones I have seen show an altitude display of ca. 10,000ft, so must have been after the descent. I have no way of telling if the IFE system was active and lit during the emergency descent.


Bernd

[pasoundman]

kansasw wrote: "Quote:
And while we're at it, can anybody tell me how to make quoted text appear in blue?
Copy it into you your reply - highlight it and press the 'quote' icon - the last on the right of the bar of them.

Took me a while to figure too !"

Thanks pasoundman, but I have nothing on my screen that looks like what you direct me to. Down below as I compose, I have three rows of "Post Icons," none of which is labelled "quote." Browser is Firefox, is it eliminating something from my view? Or am I just too ignorant?

None of them has a label, even if you hover the mouse over them.

It's the one that looks like square box with text in it and a little pointy arrow at the bottom. I use Opera so I can't say how Firefox might render it.

[pasoundman]

Intruder posted

The manual method is to enclose the quoted text in

[quote ... [/quote

tags. Put in the closing ] in each to make them work.

Yes, this will work equally well but as you say don't forget the closing ] after each use of 'quote'.

[aussiepax]

Has anyone seen, and can point to, video footage of the actual descent? The ones I have seen show an altitude display of ca. 10,000ft, so must have been after the descent. I have no way of telling if the IFE system was active and lit during the emergency descent.






No , it probably doesn't exist, as on an australian flight , any w@nk&r with a video camera during such a descent would have had his camera wrenched off him and thrown into the gaping hole in the fuselage. We don't have time for cowboys and jerks wanting to film their impending demise. (LOL, we're too busy putting our passports in our pockets!)

[Xeque]

bsieker

The clip showed the passengers still wearing their masks so it could be that the first part of the video was taken whilst the descent was still in progress.
I was interested to see a meal tray sitting firmly on a passengers tray table so the angle of descent certainly wasn't the 'death plunge' that the journo's would have you believe.
There was also the report from a pax on the flight who said, as the aircraft levelled out at 10,000 feet, his glass of beer was still where he had placed it when the masks dropped with not a drop spilled.
Further into the clip the masks are off, cabin crew are out and about and the IFE shot shows the altitude at 10,000.

[HotDog]

Intruder,

I can assure you that the doors do not get jostled open unless the pressure relief valves are opened.

[rogerd]

Regarding IFE during decompression, all screens are turned OFF, PSS (Reading and call functions) still available at passenger control unit. This condition is supposed to remain unless the whole system is restarted, then, and provided no active decompression signal from Pressurisation Controller, IFE returns to normal.

[Intruder]

I can assure you that the doors do not get jostled open unless the pressure relief valves are opened.
OK... What is the mechanism that holds the doors closed? What trips that mechanism? How is it made fail-safe?

[Dairyground]

Re post #927

"Not in a few milliseconds it wouldn't. This is a bang not a hiss."

I think that depends, how big is the orifice through which the oxygen is escaping? If the bottom suddenly falls off the tank, clearly it is a bang not a hiss. If the orifice is of a certain smaller size, like if the valve broke off, I think the gas could escape fast enough to generate a lot of friction = heat, and possibly long enough to melt some stuff locally. If the orifice is much smaller still, it could leak very little and generate only a 1"/25.4mm soap bubble a minute (a typical actual spec for gas leakage from pipes) which would generate no appreciable heat.

I would be surprised if friction from a gas flow would raise the orifice temperature significantly. The hot connector that some of us may remember from pumping up bicycle tyres is a result of the adiabatic compression of the air in the pump body. A more likely cause of a high degree of heating is that when the pressure differential across the orifice is so high that the exit speed would be supersonic, a shock wave appears and limits the speed of the outflow. It would be the flow across the shock wave that produced the metal-melting temperature apparently observed in some cases. It's almost 50 years since I last looked at the mathematics of the situation in detail, so I'm not going to bore most of you with even further off-thread computational minutiae.

[cockney steve]

Re-posts 923 &927- (kansasw)

The exploding cylinder was on U-tube-it appeared to be a standard medical-type aluminium cylinder.

The explosive force of a large cylinder, as fitted to the aircraft,would, IMHO, be sufficient to rupture the hull-skin....the several hundred mile an hour slipstream would take care of this distinctly un-aerodynamic intrusion into it's smooth progress.
the argument about the hull being designed as a pressure-vessel, is a bit fatuous.....it was already loaded!...at cruise altitude, pressurised internally....suddenly hit by an enormous shockwave and simultaneous over-pressure,to an already once-repaired area.

buildings where pyrotechnics,ordinance,explosives etc. are prepared/assembled,,-are designed that the roof will readily blow off in order to minimise any blast-damage in event of an "incident"- a luxury not available to the designer of a pressurised aircraft.

[Mech-prentice]

Atmospheric pressure at 30 000' : ~ 4psi.

Assume adiabatic expansion:
Pressure x (Volume ^ 1.4) = constant. [1.4 is a typical value for a diatomic gas, like oxygen]

Therefore:
Pressure1 x (Volume1 ^ 1.4) = Pressure2 x (Volume2 ^ 1.4)

(Volume2 / Volume1) ^ 1.4 = (Pressure1 / Pressure2)

(Volume2 / Volume1) = (Pressure1 / Pressure2) ^ (1/1.4)

P1 = 1800 psi
P2 = 4 psi

Therefore:
(Volume2 / Volume1) = (1800 / 4) ^ (1/1.4)
(Volume2 / Volume1) = 78.6

That is, the gas in the cylinder will expand to almost 80 times its compressed volume if the cylinder ruptures.

That assumes that the cylinder didn't lose any heat while it climbs to altitude - fairly reasonable, I think.


If I've messed up the maths, someone please let me know.

[infrequentflyer789]

OK... What is the mechanism that holds the doors closed? What trips that mechanism? How is it made fail-safe?

They are "plug" doors. The pressure difference holds them closed. The whole door is therefore the fail-safe. See eg. Plug door - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Plug_door)

In contrast, the forward cargo doors on a 747 are not of this type. They are held closed by mechanical locks/latches (well, most of the time...).

[Intruder]

We are discussing the "doors" on the positive pressure relief valves -- 2 small butterfly doors on the forward left side of the fuselage, both of which are open in the pix shown (link in post #906, page 10).

[lomapaseo]

I would be surprised if friction from a gas flow would raise the orifice temperature significantly. The hot connector that some of us may remember from pumping up bicycle tyres is a result of the adiabatic compression of the air in the pump body. A more likely cause of a high degree of heating is that when the pressure differential across the orifice is so high that the exit speed would be supersonic, a shock wave appears and limits the speed of the outflow. It would be the flow across the shock wave that produced the metal-melting temperature apparently observed in some cases. It's almost 50 years since I last looked at the mathematics of the situation in detail, so I'm not going to bore most of you with even further off-thread computational minutiae.

I'm stumped:confused:

All of the above seems to assume flow. How does one define flow in an explosive rupture removing all definition of an orifice

I'm still waiting for confirmation that the body of the O2 bottle actually exploded and then I can limit my own speculation somewhat:}

[bsieker]

rogerd,

thanks for the info on the IFE operation during depressurization events.

Xeque,

The clip I had in mind, this one (http://fr.youtube.com/watch?v=Adkqtljz3-s&feature=related), shows people still wearing their masks, although it also shows the IFE screen displaying the altitude as 10,000ft, so it must be after the emergency descent, and the masks would no longer be required.

Probably cabin crew haven't told them yet that the ambient air is fine to breathe; they may not even have realised it, wearing portable masks themselves.

The comment on this one (http://fr.youtube.com/watch?v=woNkk2eYJ90&feature=related), on the other hand, is BS. ("Watch the altitude drop", showing the descent for landing, coming down from 10,000ft, and not the emergency descent. I've seen no video of that.)


Bernd

[cockney steve]

I'm stumped

All of the above seems to assume flow. How does one define flow in an explosive rupture removing all definition of an orifice

I think he was referring to the u-tube vid. alloy cylinder where the valve came out....most odd, in itself,as theoperative appeared to be unscrewing the valve in order to get a controlled leakage past the threads (presumably the spindle was sheared/siezed) . In the event, I can visualise the valve ripping-out the last few threads ,I can also see a resultant split from the orifice to the main body..but I don't understand how the body exploded in the bench-vice merely as a result of the valve being unscrewed.

Sorry, this is off topic,but associated with the explosive force of the cylinder in the frame of the main thread theory.

Mech Prentice. Thanks for the maths (way over my head) but I DO understand the 80-fold expansion and the force with which it would slam against the fuselage....not forgetting that it could well have slammed a large chunk of flattened bottle against said skin.

[Machaca]

Mech-prentice -- Assuming the cylinder ruptured prior to the hull breach then Volume 2 would be the pressurized fuselage, which was closer to 12 psi.

What about the potential energy?

The cylinder should have contained 3,260,000 cc (115 cubic feet) Oxygen @ 128 barg (1850 psig), 21 deg C (70 deg F).

Generally, for a diatomic gas whose volume is V, the internal energy is (1.4)PV 1.4 * 128 * 3,260,000 = 584,192,000 cubic cm-atm

...............................= 59,193,254 joules

...............................= 8 kg dynamite

.
Corrections are invited!

[treblemaker]

but I don't understand how the body exploded in the bench-vice merely as a result of the valve being unscrewed.

Considering everything else he did wrong, it wouldn't surprise me if he put penetrating oil on the threads to loosen it up a bit.

[wilyflier]

I have observed that a high pressure gas cylinder when leaking through a small constriction,(in this case a partly opened oxygen supply cock) can generate a static charge sufficient to discharge a 3 inch spark.
I saw this happen on 2 different flights , fortunately there was no subsequent ignition.
Transferring fuel without an earth connection comes to mind.

[chris weston]

Macha 948

The cylinder should have contained 3,260,000 cc (115 cubic feet) Oxygen @ 128 barg (1850 psig), 21 deg C (70 deg F).


Generally, for a diatomic gas whose volume is V, the internal energy is (1.4)PV 1.4 * 128 * 3,260,000 = 584,192,000 cubic cm-atm


...............................= 59,193,254 joules


...............................= 8 kg dynamite


pV = nRT based sums agreed but ........being properly pedantic, ......no allowance is being made here for rate of expansion, so 8 kg of an NG based explosive is an absolute i.e. instantaneous discharge limit case.

Time dependence is critical methinks.

Yes, yes we have inadequate data.

CW

[G-CPTN]

Perhaps it would be advantageous to consider two extremes - one being leakage of the gas through an orifice (varying in size from a minor leak, through a 'venturi' that restricted flow, to a 'porthole' large enough to empty the contents (almost) instantaneously) and the other being instantaneous rupture of the container (as happens with a child's balloon).
It's obvious (even to the layperson) that different conditions (as far as dissipation of energy) apply to the extremes.

It is a fact that the expansion of the pressurised gas requires heat from the surroundings which will be chilled by the escaping gas - this in itself could alter the ductility of the metal of the struture of the aircraft making it brittle and subject to 'snapping' rather than deforming, so a jet of escaping oxygen could 'blast' a hole in the skin of the hull.
Of course, the cylinder itself would also chill and (conceivably) become fragile (regardless if it was metal or polycarbonate or whatever its material). I believe that the composite cylinders have aluminium liners, and, being highly conductive (as regards heat) the aluminium would reach a lower temperature more rapidly than the outer skin of 'plastic'. Differential contraction (despite the residual pressure) could cause delamination in extreme circumstances (IMO). Thus an initial 'controlled' leak could develop into explosive expansion because of failure of the cylinder structure.

Once 'uncontrolled' expansion of the previously contained pressurised oxygen occurs generating shock-waves, probably supersonic in propagation (which is why we hear a bang from a ruptured child's balloon . . . ).

It's not beyond reasonable speculation to imagine a combination of a leak causing localised supercooling of the hull wall ('weakening' it) followed by rapid acceleration of the leak into a rupture of the cylinder.

The rest (part of the cylinder exiting through the hull wall with another piece 'blowing' up through the cabin floor followed by debris being sucked-out of the breach in hull after the shock-wave has triggered the pressure doors in the cabin wall) is 'inevitable' - when the holes in the cheese line up . . .

[Machaca]

When the holes in the cheese line up you can make out the image of William of Ockham ;)

[Xeque]

bsieker

I think you're right. All the clips I've seen seem to be from the same source but your first one is longer - the others have been edited with 'journospeak' added. Watch the altitude drop from 10,000 FEET not Metres. Maybe the reporter made that error.

[justawanab]

Seems someone at the Cairns Post reads PPrune too ...

Cairns.com.au - Qantas blast (http://tools.cairns.com.au/photo_gallery/photo_gallery_popup.php?category_id=2915)

I'm sure I saw these photos here first.

[HotDog]

Intruder,OK... What is the mechanism that holds the doors closed? What trips that mechanism? How is it made fail-safe?
http://i106.photobucket.com/albums/m246/adamtakach/Image0002-1.jpg
The butterfly doors are held in place by a spring mechanism and forced open by escaping air pressure from the valves. The valves close after pressure relief but the doors have to be manually reset.

[Intruder]

That is, the gas in the cylinder will expand to almost 80 times its compressed volume if the cylinder ruptures.

That assumes that the cylinder didn't lose any heat while it climbs to altitude - fairly reasonable, I think.

If I've messed up the maths, someone please let me know.

Sanity check works: Bottle is rated at 114 cu ft. Bottle itself looks to be around a couple cu ft. That's about right.

[Intruder]

The butterfly doors are held in place by a spring mechanism and forced open by escaping air pressure from the valves. The valves close after pressure relief but the doors have to be manually reset.
OK. Then it is possible the valves opened briefly due to a pressure pulse. Only 0.35 psi would be needed, and that would hardly be noticed by the SLF.

Other possibility is that the valves rebounded off their seats when the valve impacted the door frame not too far away -- the "jostling" I mentioned earlier.

[forget]

Other possibility is that the valves rebounded off their seats when the valve impacted the door frame not too far away.

They're on opposite sides of the aircraft.

[Intruder]

Scratch that theory, then... I initially thought the valve hit the L1 door.

[Litebulbs]

I do apologise if this has been discussed before, but I do find the door handle damage quite strange. It has been bent inwards toward the door, but not upwards, as you would imagine, if it had been hit from directly below. Their is no other visible damage to the bottom edge of the handle. It had been hit with enough force to deform it inwards and move it towards the open position, breaking the internal mechanism and then embedding itself into the door panel, but you imagine that you would see chips or dents on the lower edge.

Discuss!

[PeePeerune]

where is the small portable oxygen bottle that should be stowed next to the door at floor level?.it appears to be missing in that photo.

[Spotted Reptile]

Would imagine it's at the bottom of the South China sea along with the fire bottle that it sits next to?

[Millski]

Maybe the crew used it ?

[Buster Hyman]

Litebulbs. I too noticed that damage & was thinking about questioning it, but after some thought about how the handle could have bent like that, I came to the conclusion that it was more than likely the door panelling that buckled into the handle. Naturally, I don't know this for fact, and all I can go by is that one photo where the damage is evident.:confused:

[Litebulbs]

I admit that the door panel may have moved, but the angle of bend does not look normal (compared to other Boeings), but it has been 10 years since I opened a -400 door.

[vortsa]

Peepeerune

where is the small portable oxygen bottle that should be stowed next to the door at floor level?.it appears to be missing in that photo.

My thoughts too I even suggest that there may have been a second projectile in the cabin and the green skid mark may have come from the portable bottle.

Maybe the crew used it ?

I can't see anybody would have been game enough to approach that door in flt. note the oxygen masks still in packs.

[vortsa]

Their is no other visible damage to the bottom edge of the handle. It had been hit with enough force to deform it inwards and move it towards the open position,

The position of the handle when in locked mode puts the tip directly above the damaged floor area, makes me think that any damage to the handle will be on the tip, out of site in door shroud.

[Litebulbs]

Still does not explain why the handle is bent in though.

[vortsa]

I think it does.... the handle took the full force of the ??bottle?? and fortunately reduced its force... if it hadn't have been hit the damage around the upper door hinge point may have been more catastrophic . If the R2 door had failed then we would not have pictures to discuss all of the 'What If's'

[Buster Hyman]

http://aviation-safety.net/photos/exits/990120-E-d-1-500.jpg

Ah...Lightbulbs, while my post still stands, I misunderstood your question. That handle is actually designed that way. The top quarter (I suppose) angles into the door, but clears it of course. So, the shape of the handle has not been affected by the incident.

[vortsa]

JAMES REASON

I have a new theme for another thread " Australian Cheddar"

By now we all know what the "Swiss cheese theory" is and how important it has been in our industry in preventing serious incidents/loss of life. Well I propose in Qantas there is another theory or phenomenon and that should be the " Aussie Cheddar" .

Cheddar has no holes and that way a catastrophic event is prevented. This theory doesn't require many slices of cheddar only one placed at random somewhere amongst all the slices of swiss cheese.

Read on and you will understand.

1. Extremely bad weather enough to cause errors in judgement, procedures and operation. But wait the golf course is soaked in water the ground is boggy and the fairways are clear. Enter one 747 which failed to stop on the runway because of the holes in the cheese but stops stuck in the bog, NO LOSS OF LIFE

2. A leaking tap/drain in the forward galley directly above the equipment bay full of avionics boxes and computers, but not a problem splash guards and drip trays will prevent damage, regular/scheduled inspections will locate damaged drip trays before anything serious happens.....NOT. So what happens when the aircraft looses all power in the middle of the Pacific or Indian Ocean??? Never fear the aircraft happens to be less than an hour away from landing and the Battery power is JUST sufficient enough to allow for safe landing NO LOSS OFF LIFE

3. A never before event in aviation HAPPENS ?? when an oxygen bottle explodes in flight on a passenger aircraft. How many slices of cheese before it got to this stage.

But wait 'Aussie Cheddar' to the rescue the bottle doesn't go through the fuel tank, the debris doesn't take out #3 engine, no one is sucked out the hole, just a couple of old bags( I didn't say old boilers). Parts of the bottle are projected into the next compartment and heavy impact on the door handle dissipates the force and prevents more serious damage to structure and possibly Door R2. The crew declare MayDay and divert to an air port that was only hours early closed due to a typhoon, fortunately this aircraft has all the latest landing instruments that will make a bad weather approach less difficult. Not need ( and didn't have all available anyway) fine weather landing. NO LOSS OF LIFE

BREAKING NEWS
Qantas have announced that they are making a take-over for the Kraft Cheese Company.

[vortsa]

Sorry Buster have to agree with Lightbulb on this one, handle has definitely taken a pounding and instead of 15 degree bend more like 80 degrees.

[Buster Hyman]

vortsa. Fair enough. I can't see that much (80 degrees?) myself, but maybe I'm not looking at the same pics as you guys. :ok:

[Litebulbs]

Download and look at the pic's #906 and especially the 4th from last one.

[HotDog]

Nobody has commented so far on the outward bulge of the top right hand R2 door hinge panel on the exterior view on post #745. That panel is supposed to be flush with the fuselage skin.:confused:

[Buster Hyman]

Hmm...still not seeing 80 degrees. The handle is designed with an inward 'bend' at the tip & that's all I see. I am seeing an armed door (if down is armed...I can't recall) in the Open position though...if comparing that KLM door to the QF one. The handle looks ok to me.

Anyway, the people that count will know what they are looking at.:ok:

[Machaca]

HotDog -- this may help:


http://i337.photobucket.com/albums/n385/motidog/QF30-D2Rinout.jpg

[PickyPerkins]

I am just a private pilot with no special knowledge of oxygen systems. My trade is (was) Physics.

This is a fascinating thread generated by many smart and knowledgably people.
But I am curious about some reactions.

Lack of curiosity
For instance, several comments have been along the lines of “an explosion of an oxygen cylinder in flight has never happened before, so how could it possibly have happened now“?

Yet when presented with a case of an oxygen cylinder exploding in a vehicle on the ground, complete with a photo in glorious Technicolor (from geemul in Post #832 on 31st July 2008), nobody seems to have expressed curiosity about how that could have happened.
http://pickyperkins.home.infionline.net/breakable.jpg
The vehicle was said to be unoccupied and no one was hurt. Nobody was doing anything to the cylinder. There was no turbulence. No G-forces. Maybe the temperature in the vehicle was exceptionally high (less likely since the explosion occurred at night).

Question: what was determined to be the cause of the explosion? Did the insurance company investigate, and pay out on the loss? Where were the fractures in the cylinder? Presumably the fragments were available to re-construct the cylinder. Was any defect found in the cylinder? Even more interesting, was no defect found in the cylinder (other that its failure to hold pressure). Why is nobody interested enough to ask?

A perfect cylinder
One aspect which has not been mentioned yet (maybe I missed it) is the fact that for a perfect cylinder of uniform thickness under internal pressure, the circumferential tensile stress in the cylinder wall is about twice the tensile stress in the cylinder wall parallel to the cylinder axis. So a “good” cylinder should fail by a crack developing parallel to the cylinder axis. This seems to have happened to the failed cylinder shown by Manchaca (Post #832 on July 31st 2008), part of that photo is reproduced below.
http://pickyperkins.home.infionline.net/cyl_frag.jpg
The circumferential stress would be somewhat lower towards the cylinder ends, but once the crack starts it could tend to continue in a perfect cylinder in the same direction and end by splitting the neck containing the valve (even though its considerably thicker than the walls). Which is what seems to have happened to the cylinder in the photo above. In which case the valve might be released from the cylinder.

Cylinder failure in any other mode (such as the top half of the cylinder separating from the bottom half) seems to me to imply the presence of a significant defect or external influence. The cylinder necks are considerably thicker than the walls and look to be hard to “knock off”. The valve found on the aircraft was reported to be still attached to part of the cylinder, so the valve did not “pop out of the neck”.

Don’t believe everything you read
Posts #948 &951 discuss a cylinder “containing 115 cubic feet of oxygen @ 1,850 psig at 70ºF”. A cylinder of the proportions shown in photographs of typical installations with an internal volume of 115 cubic feet would have to be approximately 4 ft in diameter and 9 ft long internal dimensions. If this 115 number comes from a published specification, either the specification is wrong or it is not relevant to this thread. Possibly the volume quoted may be for the gas content at atmospheric pressure, or maybe a decimal point is missing. In contrast, the specifications for “3HT seamless steel cylinders for aircraft use” in Post #852 is for “seamless steel cylinders with a water capacity (nominal) of not over 150 pounds”, or about 2.4 cubic feet - nothing like 115 cubic feet.

Adiabatic expansion
The expansion calculation by Mech-prentice in Post #942 looks right. Modifying it along the lines suggested by Machaca in Post #948 for expansion to 12 psi in the cargo hold instead of 4 psi outside the aircraft gives an expansion factor of about 35.8 instead of 78.6. This gas would be very very cold. If I have done my sums correctly (Mech-prentice check?), the adiabatic cooling of oxygen starting at 1,850 psi and room temperature expanding to 12 psia would cool it enough to liquefy some of it at near -170ºC. As the oxygen expands it does work on the surrounding air, adiabatically heating it (a little), but the oxygen itself gets cold in the process. In the case of the cylinder in the car, the oxygen is also does work on the vehicle (as you can see), and this energy comes from that stored in the pressurized oxygen, which consequently cools. As the oxygen warms up to ambient temperature it would expand by another factor of about 4 - 5.

Ignition process
A once heard a speaker at a safety meeting explain how some oxygen accidents occur when grease is present in tubing between the cylinder and the regulator. The operator typically attaches a regulator to a cylinder and then abruptly opens the cylinder valve. The air in the tubing between the cylinder valve and the regulator is thus suddenly adiabatically compressed and heated, and any hydrocarbon ignites, as in the cylinder of a diesel engine. The oxygen itself is cold - it’s the heated air in front of it which initially ignites the grease. Of course, once ignited, the oxygen burns the remaining grease together with the metal tubing, regulator, etc. So the valve should always be cracked open slowly in case grease is present. If there were no adiabatic heating, oxygen at room temperature would not ignite the grease, even under pressure.

Oxygen lances
Hot steel will burn in oxygen. I understand that the standard method of cutting thick (e.g. 1 inch and thicker) steel plates is by an oxygen lance. The cut is started by an oxy-acetylene torch. Once the steel is hot the acetylene is turned off and the cut is continued using pure oxygen - the burning steel provides all the required heat. This is analogous to what happens in grease-initiated accidents - the grease is ignited, after which metal burning in oxygen provides all the required energy.

A completely different case
Below are stills from the Youtube video mentioned by FlexibleResponse in Post #805.
http://www.youtube.com/watch?v=9lw_fhNAIQc (http://www.youtube.com/watch?v=9lw_fhNAIQc)
The voice commentary says that the inside of the top of the cylinder (Photo left below), the cylinder threads (next photo below), and the valve threads (last two photos below), were all melted . This suggests chemical energy to me, involving burning inside the cylinder before it exploded. This cylinder burst consistent with being heated inside near the valve, not by a split parallel to the axis as described above. Quite different from the aircraft incident.
http://pickyperkins.home.infionline.net/burno2.jpg

Final note - I have no idea why the cylinder burst in the aircraft. http://pickyperkins.home.infionline.net/pi.gif

[Machaca]

PickyPerkins
Posts #948 &951 discuss a cylinder “containing 115 cubic feet of oxygen @ 1,850 psig at 70ºF”. A cylinder of the proportions shown in photographs of typical installations with an internal volume of 115 cubic feet would have to be approximately 4 ft in diameter and 9 ft long internal dimensions. If this 115 number comes from a published specification, either the specification is wrong or it is not relevant to this thread. Possibly the volume quoted may be for the gas content at atmospheric pressure, or maybe a decimal point is missing. In contrast, the specifications for “3HT seamless steel cylinders for aircraft use” in Post #852 is for “seamless steel cylinders with a water capacity (nominal) of not over 150 pounds”, or about 2.4 cubic feet - nothing like 115 cubic feet.Don't believe everything you read too quickly :rolleyes: Yes, the stated volume of 115 cubic feet is the gas content (industry standard), not internal volume (2.4 cubic feet of O2 wouldn't provide much relief!).


So a “good” cylinder should fail by a crack developing parallel to the cylinder axis.True. The method/specs for hydrostatic testing are also included in Post #852 (http://www.pprune.org/forums/rumours-news/336528-qantas-744-depressurisation-43.html#post4302526). Cylinder walls are constantly flexing due to changes in pressure differential. When lifespan limit (24 years) is reached or testing indicates excessive "bulging," the cylinder is scrapped. This rupture is considered an "ideal failure" from an over-pressure burst test:

http://i337.photobucket.com/albums/n385/motidog/IdealCylBurst-1.jpg

If QF30's suspect cylinder turns out to be the culprit due to a manufacturing flaw determined from the fragment(s), then I expect we'll see more stringent post-manufacturing testing & inspection. Otherwise, we may see the current 3-year test frequency shortened significantly.

I'd love to know the life & service history of the green meanie!

[Machaca]

From CASA's April 2006 AD on Inspection, Test and Retirement of Compressed Gas Cylinders (http://www.casa.gov.au/airworth/airwd/ADfiles/EQUIP/GAS/GAS-001.pdf):

Permanent volumetric expansion must not exceed
10% of total volumetric expansion at test pressure or a permanent increase in
volume of more than 1/5000 of its original volume.
In accordance with whichever of the following occurs first:
(a) the manufacturer's specification,
(b) for 3HT cylinders:
(i) 4 380 pressurisations (cycles), or
(ii) 24 years from date of manufacture

NSEU -- Does anything besides a complete de-pressurisation & re-pressurisation constitute a cycle?

[lomapaseo]

If QF30's suspect cylinder turns out to be the culprit due to a manufacturing flaw determined from the fragment(s), then I expect we'll see more stringent post-manufacturing testing & inspection. Otherwise, we may see the current 3-year test frequency shortened significantly.


here's the problem, they probably won't find the crucial fragments.

However a camp of folks will say yes to your idea of inspecting more often hoping to quantify the service life based on in-service handling.

But what interval will they choose?

Without new data to design the corrective action program arround, they will just have to ask some willing operators what they can practically do.

Now if the current 3 year inspection program has provided some sort of deterioration data, then one can always monte carlo that into a reduced life program of some sort.

I don't have a warm feeling about this unless data is available.

[PickyPerkins]

Do you have a corresponding (or any) picture of a failed "good" composite cylinder which you can share with us? http://pickyperkins.home.infionline.net/pi.gif

[Machaca]

According to NSEU (who puts his hands on QF oxy cylinders regularly), QF's 744's are equipped with steel cylinders. The damage sustained on QF30 corroborates this, as composite cylinder failures at service pressure have resulted in a body leak or neck failure.

Composite cylinder "good" failure (burst test):
http://i337.photobucket.com/albums/n385/motidog/CFcylinderBurst2.jpg



Failure after intentional damage (burst test):
http://i337.photobucket.com/albums/n385/motidog/CFcylinderBurst1.jpg

[Vertiginous]

No, sorry, but there won't be a 'slight' failure. If there is any flaw in the structure of the bottle at all, the bottle will disintegrate because of the tremendous pressure within. So we'll always be looking at a bang, not a hiss.

(Sorry I've taken so long to get back to you.)

[Vertiginous]

Apologies for the thread-drift, but

...any w@nk&r with a video camera during such a descent would have had his camera wrenched off him and thrown into the gaping hole in the fuselage. We don't have time for cowboys and jerks wanting to film their impending demise. (LOL, we're too busy putting our passports in our pockets!)

Activities that do not cause annoyance or danger are none of your business.

[Oilandgasman]

Is it worth considering that the cylinder itself was not the initiator of this incident and that the initial failure was in one of the HP fittings connected to it?
From the drawings, each bottle has three screwed connections. Cylinder valve to cylinder, cylinder valve to regulator, and a third connection on the LHS which appears to be a test point. All are subject to full cylinder pressure.
Considering the images and the internal damage which appears to be slighty forward of the suspect bottle storage area, it might be worth considering a failure of the cylinder valve to regulator connection.
In this event, the cylinder would be rapidly thrust forward and were the cylinder valve to strike anything substantial would shear off. (Valves in industrial use are protected by a heavy metal shroud on the cylinder to prevent accidental shearing.)
The cylinder valve would then be propelled upwards on shearing, the intact cylinder itself minus valve and now with HP oxygen exiting from the cylinder neck, being thrust down and outwards.
Failures of HP small bore connections are not uncommon in industry, in the last HSE reporting period there were 1034 of them. The failure mechanisms were varied, some were caused by vibration induced fatigue due to inadequately supported fittings and pipework.
If this occurred, evidence of it will be visible on the valve which apparently was recovered.

[aussiepax]

Activities that do not cause annoyance or danger are none of your business


Gee , Vertiginous, you must have missed the LOL in my post. THere is such a thing as ongue in cheek humour or sarcasm here. In fact, maybe you're not from the UK and are actually an american, as most of them don't understand the concept. The British did give us the Goons and Monty Python.

Well back to your point, you actually have no data to suggest that someone filming is not without risk during descent phase. Why are told to turn off these devices at top of descent. And what happened to my right to have an opinion anway ?

[Volume]

the intact cylinder itself minus valve and now with HP oxygen exiting from the cylinder neck, being thrust down and outwards.

This part of the scenario puzzles me most, because the damage to the skin does not at all support this. The lowermost stringer visible is intact, the skin peels outward further down, but clearly it is not bend by an object exiting the Aircraft but by pressurized air (lots of air at low pressure) or by pressurized Oxigen (less ammount, but higher pressure). The skin has been torn from the frames and the stringers further down and ruptured the rivets in tension or pulled them through the countersunk skin. A fuselage skin through which half an oxygen cylinder has rocketed outwards would look completely different. However, the lower part of the cylinder is missing, so it must have fallen out sideways without much force involved, possibly blown out by the stream of pressurized cabin air. This would be more in line with a failure of the cylinder itself, similar to some of the pictures shown here, sending the top of the bottle with the valve and the fittings into the cabin, while the lower support held the lower part in place. The oxygene pressure ruptures the skin, and the pressurized air blows all evidence right into the pacific, never to be found again. The smaller the upper part (the higher the place of rupture) the higher the speed of this fragment compared to the lower part.
Let´s wait for pictures of the cylinder fragments and valve recovered.

[3DAero]

I am a mechanical engineer, working in aerospace, but with little experience of pressure vessel design. However, I know that large pressure vessels are often designed to leak before burst (i.e. any crack, originating from a manufacturing defect, should propagate slowly enough that it leads to a gradual leak, rather than a potentially catastrophic burst). Does anyone know if this design philosophy is adopted for oxygen cylinders?

[Vertiginous]

Are you trying to outdo me for over-reaction? :)

Actually I am British, and fully versed in Monty Python. Your right to a view is something I would chain my self to an oxy cylinder to defend.

They tell you to turn your appliances off because some people are trying to pray.

Cabbage crates over briney...

[bungacengkeh]

Capt Kremin (http://www.pprune.org/forums/members/170332-capt-kremin)

Join Date: Mar 2007
Location: Brisbane
Posts: 257


Quote:
An unnamed senior Qantas pilot
So some engineer rings a tabloid paper and claims to be a senior Qantas pilot? Not only does the Telegraph fall for it, but MAS falls for it and now you do.

How intelligent are you?


The claim by that some engineer did this........is it true? QF has reportedly stopped sending plane to MAS. Also looks like CASA has some issue with QF maintenance practices in their own hangars!

If the above claim is true, wow Captain Gremlin has the scoop on the engineer's underhand practice, ala GAFA land!

[ampclamp]

Whatever part tore thru the floor sheared and bent the door handle and demolished the ceiling panels must be at least the top part of the cyl given the hole and damge incurred.Coming away with such force may indicate that it may have been first to let go & origin of failure ?
Hopefully something can be gleaned from it anyway no matter what parts are found.

[IFIX]

The distance travelled upward into the cabin by the head of the cyllinder requires some mass.
A previous post mentiones the cyllinder retaining clamp is fitted with a spring to provide expansion of the bottle.

It is quite possible that clamp was tightened to such an extent, expansion was no longer possible.
This will cause the cyllinder to be (over)loaded along its entire circumference, which can lead to fatigue cracking.
This could explain the amount of mass propelled both ways, it will effectively cut the bottle in half along a clean cut.
As both halves separate their respective projectory depends upon where the bottles separate last.

just my two cents:suspect:

[G-CPTN]

I don't subscribe to IFIX's simplistic 'logic' about the clamp causing the cylinder to split cleanly in two.

Any fatigue cracking of the cylinder is unlikely to be completely uniform around the circumference, therefore failure under pressure would initiate from a 'point' whereafter the failure would follow the example of the illustration:-
http://i337.photobucket.com/albums/n385/motidog/IdealCylBurst-1.jpg
the circumferential tensile stress in the cylinder wall is about twice the tensile stress in the cylinder wall parallel to the cylinder axis
(From:- http://www.pprune.org/4315892-post979.html )

And, The distance travelled upward into the cabin by the head of the cyllinder requires some mass. doesn't follow. Inertia is all that is required (think of a rifle bullet).

However, Whatever part tore thru the floor sheared and bent the door handle and demolished the ceiling panels must be at least the top part of the cyl given the hole and damage incurred. does suggest (only suggest) that the fragment that penetrated the passenger cabin was 'substantial' (if only because of the size of the hole in the floor).

A detached valve could easily penetrate as has happened. I'm sceptical about a metal cylinder fragmenting (see the above photograph). Of course another fragment (of the pipework) could have penetrated the hull, resulting in the 'evacuation' of objects in the surrounding area (including the cylinder, intact or otherwise).

We need to have an 'event' to initiate the sequence of failure(s) (such as cargo movement), but, following Occam, a spontaneous failure of a previous hull repair in the area of the cylinder support (resulting in displacement of the cylinder and detachment of the top valve(s)) seems favourite to me.

Apart from the vertical travel of the fragment that penetrated the passenger cabin floor . . .
http://i37.tinypic.com/2wp7di9.jpg
. . . this certainly implies that the cylinder was vertical at the time of the 'failure'.

For 'explosion' (ie catastrophic rupture) of the cylinder:-
The circumferential stress would be somewhat lower towards the cylinder ends, but once the crack starts it could tend to continue in a perfect cylinder in the same direction and end by splitting the neck containing the valve . . .
In which case the valve might be released from the cylinder.
(From:- http://www.pprune.org/4315892-post979.html )

[Flexable]

Another improbable cause of the incident...:hmm:

YouTube - Brucie's Press Conference (http://www.youtube.com/watch?v=X5XxO2MuXu8&feature=relat) ed

[Short_Circuit]

For what it's worth, here is a burst from the BMM about oxygen cylinders & installation of the spring loaded clamp.
O__x_y_g_e_n _C__y_l_i_n_d_e_r_s (Fig. 2)
A. Oxygen storage cylinders supply oxygen to the passenger oxygen system.
The cylinders are mounted in the forward cargo compartment ceiling or
sidewall. Each cylinder has a quantity of oxygen equivalent to 114 cubic
feet at 760 mm Hg absolute and 70°F when filled to 1850 psig. Space is
available for additional cylinders.
B. The cylinder assemblies each include a slow opening shutoff valve, a
pressure gage, and a safety outlet device which bursts before pressure
reaches a value that could damage the cylinder, tubing, or components.
The safety outlet devices are manifolded to a line which runs to an
overboard discharge port in the airplane skin. The overboard discharge
port incorporates an indicator (a plastic disc) which normally prevents
dirt, grease, etc., from entering the discharge line, but which ruptures
at a pressure of 500 psig to allow oxygen to discharge overboard. The
overboard discharge line serves both the passenger and crew systems.

Install the passenger oxygen cylinders installed in the sidewall.
(a) Put the bottom of the oxygen cylinder in the support and move
the cylinder head into position.
N_O_T_E_: Lightly pull on the coupling assembly as necessary
for correct installation.
(b) Loosely connect the coupling nut on the high pressure cylinder
to the oxygen cylinder port.
(c) Loosely connect the overboard discharge line at the B-nut.
(d) Install the band strap clamp.
1) Make sure the toggle lever in open position, and connect
the clamp halves.
2) Move the T-bolt head in place through the two holder
assembly fingers.
C_A_U_T_I_O_N_: DO NOT ATTEMPT TO ADJUST THE SPRING TENSION ON
INSTALLATION. THE SPRING TENSION IS
FACTORY-ADJUSTED, AND ANY ADDITIONAL ADJUSTMENT COULD
CAUSE DAMAGE TO THE SPRING.
3) Move the toggle lever closed which is against the spring
tension.
4) Install the safety pin.
(e) Tighten the connection to the overboard discharge line.
(f) Tighten the coupling nut on the high pressure cylinder to a
torque of 650 to 700 pound-inches.
(g) Connect the fill line as follows:
1) Connect the thermal compensator to fill line B-nut.
2) Tighten the fill line connection.

[ankh]

Aside -- metal, but not steel! Just as an example of an investigation, with pictures: http://hazmat.dot.gov/pubs/reports/cylinder/3al3000_pgs1_15.pdf A metallurgical examination of a failed aluminum cylinder DOT-3AL-3000 type.

[Falcon124]

Have you folks caught the latest urgent AD for B747 lap joints:

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

Latest amendment reads:

"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."


Interesting :)

[ozthai]

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.

Make any sense ?

[chris weston]

Ozthai 999

I would doubt it but stand to be corrected by those who know more about this than me.

The additional pressure differential imposed by hull failure would only be circa 0.5 bar - a lot in terms of % of partial pressure of breathable O2 for you and me but relatively small in terms of a cylinder routinely pressurised to and cycled from circa 200 bar.

But I take the subliminal point about straws on camel's backs and holes in cheese .........

CW