Qantas 744 Depressurisation

[vee-tail-1]

747 "Classic" flight engineer.
Excellent photo of damage over on Flyer. Certainly looks like a corrosion induced failure of the skin under the wing root fairing.

[Xeque]

Thanks BelArgUSA

You answered John R's question perfectly which, strangely, no-one else did. Too busy pumping up their flame guns I guess.

[cambruzzo]

What if it let go at 39,000 instead?

I am interested in comments from those in the know on the impact if any of a greater air pressure differential had this hole developed say at max altitude. It seems to my uneducated mind that the greater the pressure difference the greater the forces when it let go. Could this have been a total loss in that circumstance?

[nonsense]

Oxygen masks failed: passengers | theage.com.au

The Age newspaper is now reporting that passengers' oxygen masks did not operate correctly and quotes:

"However, a source close to the Civil Aviation Safety Authority said exploding oxygen cylinders were the likely cause of the rupture, and would be the main focus of the investigation, as they were stored in the exact location of the explosion and there were no signs of fire."

[GlueBall]

Airframe corrosion not likely. But conceivable corrosion or failure of one of several oxygen bottles mounted along the sidewall.

[lomapaseo]

What if it let go at 39,000 instead?

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

I am interested in comments from those in the know on the impact if any of a greater air pressure differential had this hole developed say at max altitude. It seems to my uneducated mind that the greater the pressure difference the greater the forces when it let go. Could this have been a total loss in that circumstance?

Too many unknown variables (since we don't know the cause yet). If it's a structural failure in the pressure vessel then the altitude pressure differential is likely not significant to the damage. The most significant mitigation to ruptures under pressure is the rib structure in the airplane that limits the size of the hole.

[Ejector]

Does anyone have a link to this plane spotters forum listed below?



BBC NEWS | Asia-Pacific | Plane hole 'not due to corrosion'

'Fingers crossed'

In an online planespotters' forum in February, participants referred to the detection of "serious corrosion issues" in the 17-year-old Boeing 747-438 Longreach during a maintenance check at Avalon airport in March.

Aviation experts say corrosion could have been enough to have caused the 2.5-3m hole in the fuselage - if even a small section of the plane's aluminium skin was able to break free, the enormous pressures generated at cruising altitude could have done the rest.

[Leodis737]

Rainboe:

yet the passengers evidently used oxygen during the descent?

There are some suggestions it failed (at least in parts of the cabin):
Oxygen masks failed: passengers | theage.com.au

Mention of lack of oxygen, some masks not dropping, breathing problems.

[glhcarl]

The Aloha incident was caused by a series of small fatigue cracks that after a period of time joined together to cause the rapid decompression and major structural failure. These fatigue cracks were caused by a voids in the Aloha 737 fuselage lap joints.

If you look at the pictures of the damaged area on the Qantas 747, there is a lap joint running right through the middle of the damaged area. Could a faulty lap joint have caused this failure, I don't know its just a thought.

However, there is an AD that requires all lap joints to be inspected to insure they are sound. But this is done externally using untra-sonic testing and since the area that failed was under the fairing, maybe the area was missed or it was just too much trouble to remove the fairing and do the test?

[xyzzy]

Better Safety Briefings would help

Why is it that when an incident like this occurs it's totally beyond the British press to report it correctly...is a de-pressurisation followed by an emergency descent and landing not exciting enough for them?

Why isn't the safety briefing changed? ``In the event of a loss of cabin pressure, masks will drop from the ceiling. Pull towards you and place the elastic around your head. Fit yours first before helping other people. The plastic bag will not inflate. The plane will then descend to an altitude at which you can breath normally.''

I fly as a passenger regularly, and the closest I've come to ``an event'' was when I was inbound to LHR T4 when the IRA mortars went in. I know, as a hopefully educated passenger, that a fairly rapid descent is a checklist item following depressurisation. Most people don't know that, and they assume that the loss of inflow and/or sudden outflow, plus the masks, has caused the plane to dive uncontrollably, hence all the general purpose hysteria amongst passengers and media.

How hard would the extra sentence in the briefing be? Job done, and the cabin crew will have fewer hysterics to deal with.

[Rainboe]

747 Pilot 18 years

There are some suggestions it failed (at least in parts of the cabin):

Interesting. The finger of blame is starting to point to the bottle, not atmospheric re-entry of golf clubs, or horses wild in the freight hold! Rather than trying to sort out fatigue issues that really require expert examination and testing, I think of more interest is the connection with extraneous factors- in this case oxygen bottles. Individual mask failures are irrelevant, the question is did supply fail to large areas of the cabin?

I think we can do without the sensationalism of yet another aviation 'writer' in the press:

Aviation writer Ben Sandilands said Qantas and its passengers were lucky the disaster happened near an airport. "If it had happened on some other Qantas routes we'd be reporting that they were sending the warships out to pick up the bodies."

More aviation tosh from someone out for a buck! It would just have meant flying for rather a long time at 10,000' to the nearest suitable airport! Even the Pacific has some in those interminable wastes!

[GlueBall]

Rainboe: . . ."Catastrophic bottle failure without ignition?"

You don't need "ignition" for a high pressure bottle to explode. Metal fatigue from corrosion inside the 1600+psi bottle can cause the bottle to violently explode, or corroded pipe fittings can separate with explosive force and puncture the fuselage.

[PC767]

How hard would the extra sentence in the briefing be? Job done, and the cabin crew will have fewer hysterics to deal with

Only for the few punters who listen to a briefing. If they cannot be bothered to understand simple seatbelt instructions then why waste time explaining SOPs.

[ImpairedHearing]

Ejector,

The claim was in the first post in this thread:
QF VH-OJK Corrosion Issues — Civil Aviation Forum | Airliners.net

Edit: In advance: In case any toes feel like being stepped on, my sincere apologies for linking to 'that site'

[Capot]

hence all the general purpose hysteria amongst passengers and media.

Media, yes...The Times of today "20,000 foot plunge after belly ripped off"...etc, usw, ad nauseam.

Passengers, no; evidently no hysteria or panic whatsoever. And lots of mobile footage to prove it. Alarmed, maybe, but who wouldn't be alarmed? Yoiu would have to be pretty stupid or drunk not to be concerned about what was happening, at least for a moment or two, after a loud bang followed by rapid decompression. Flight 103 probably felt much the same to many in the cabin, in the first seconds after the bomb went off. But the trick is suppressing the alarm and appearing calm, and they achieved that very well, it seems.

It's the message that many of us try to get over in various pprune fora; passengers not only pay the crew's wages, they are typically very well-educated in what happens on board an aircraft. They do not deserve the ritual auto-contempt that so many in the industry give them, for example writing without thought ..............

general purpose hysteria amongst passengers and media.

[lissyfish]

From the AP one hour ago:

"One person close to the investigation, who was not permitted to speak to the media while the inquiry was under way, said Saturday that “some kind of explosion” might have occurred, because the floor above the cargo hold had been pushed up. Two oxygen bottles that supply the pilots are stored in that area.

Australian investigators, who got their first look inside the plane Saturday, discovered shards of an oxygen bottle throughout the cargo hold and in the floor above, which sits below the cabin, this person said. Officials cautioned that it was too soon to know if the oxygen canister had caused the damage, but theorized that it might have played a role, this person said.

“The dangerous goods manifest is going to be very closely inspected to see if there was anything that might have caused the oxygen bottles to explode,” the person said."

[gas path]

The number of oxy. bottles installed is a customer option! If you opt for the total fit they certainly extend as far aft as sta. 880.
The one or two (customer option!) crew cylinders are mounted horizontally immediately aft of the fwd. cargo door about sta. 700
The bottles are either steel or carbon fibre composite.
Looking at the pictures it certainly appears to have unzipped quite nicely although it does look like there is a section of frame 'gone walkabouts'
In the lower of the pictures it looks like you can just about see part of the frame bent aft.

[colsie]

My local paper has reported the best comment on this. A passenger is complaining that she saw her bag's hanging out the hole after touch down, and that bags should not be kept in an area where there is a chance of this occurring.

[Jamesair]

wasn't there an oxygen bottle explosion on a plane over the Everglades a few years ago? If my memory is correct that cost the lives of everyone on the plane. I think these were being illegally transported from one base to another.

[forget]

Capt Kremin.

.....as I posted before, this was not a "simple" emergency descent. This crew had many other problems to contend with which shall become known in due course.

gas path.

The one or two (customer option!) crew cylinders are mounted horizontally immediately aft of the fwd. cargo door about sta. 700

2 + 2 = ??