Qantas 744 Depressurisation
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Originally Posted by Smilin_Ed
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Terminology
For those of us who are professional pilots but not airline pilots, what do the terms SLF and MEL mean?
Terminology
For those of us who are professional pilots but not airline pilots, what do the terms SLF and MEL mean?
In view of your number of posts, I can only just about believe you're not taking the mickey....
SLF: Self Loading Freight. The part of the payload you do not have to tie down on pallets, although, if you're cabin crew, you occasionally wish you could.
MEL: Minimum Equipment List. There are bits on the aircraft that are duplicated, triplicated and even quadruplicated. You ARE allowed to operate with some, but not all, of them inoperative. The MEL sets out in considerable detail what kind of defects you are allowed to carry, and under what conditions.
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from the Brisbane Times
A piece of an exploding oxygen tank is believed to have pushed the handle of an emergency door into the opening position, after smashing through the floor on a Qantas flight from Hong Kong.
Last Friday a Qantas international jet was forced to make an emergency landing at Manila after a mid-air explosion tore a hole in the plane's fuselage.
Passengers were not in danger of the doors opening because they are designed so they cannot be opened mid-flight, The Australian reports today.
But after examining photographs, industry observers were surprised the door was pushed into the opening position.
"It's an incredibly rare event for the oxygen tank to explode and for it to hit the door handle and rotate it open is just eye-watering," a source told The Australian.
The aircraft's controls were not affected but some computer functions and electrics were disrupted, including three of the plane's supposedly independent landing systems.
Sources said the emergency descent from 29,000 feet to 10,000 feet took about four minutes.
Last Friday a Qantas international jet was forced to make an emergency landing at Manila after a mid-air explosion tore a hole in the plane's fuselage.
Passengers were not in danger of the doors opening because they are designed so they cannot be opened mid-flight, The Australian reports today.
But after examining photographs, industry observers were surprised the door was pushed into the opening position.
"It's an incredibly rare event for the oxygen tank to explode and for it to hit the door handle and rotate it open is just eye-watering," a source told The Australian.
The aircraft's controls were not affected but some computer functions and electrics were disrupted, including three of the plane's supposedly independent landing systems.
Sources said the emergency descent from 29,000 feet to 10,000 feet took about four minutes.
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Herald Sun latest suggestions
Yesterday Qantas and the ATSB refused to comment on an engineer's claim that 346 passengers on the jumbo forced to make the emergency landing in Manila were starved of oxygen for several minutes after supplies were lost.
And an ATSB investigator said the jet's black box voice recorder did not capture the explosion that tore a hole in its fuselage.
The engineer, who can't be identified, said the three intact passenger oxygen cylinders emptied into the atmosphere after a regulator blew off the top of a fourth tank.
Passengers said several children wearing gas masks turned blue in the 10 minutes it took the aircraft to descend from 29,000ft to a safe breathing level of 14,000ft.
An aircraft engineer said there must have been some oxygen available because the doors that release the masks are oxygen-operated.
Sources said the steel regulator penetrated the cabin floor of the 747/400 after blowing off the cylinder in the cargo hold.
and the final info
The tank then flew around the hold like a rocket until it smashed through the outer skin.
And an ATSB investigator said the jet's black box voice recorder did not capture the explosion that tore a hole in its fuselage.
The engineer, who can't be identified, said the three intact passenger oxygen cylinders emptied into the atmosphere after a regulator blew off the top of a fourth tank.
Passengers said several children wearing gas masks turned blue in the 10 minutes it took the aircraft to descend from 29,000ft to a safe breathing level of 14,000ft.
An aircraft engineer said there must have been some oxygen available because the doors that release the masks are oxygen-operated.
Sources said the steel regulator penetrated the cabin floor of the 747/400 after blowing off the cylinder in the cargo hold.
and the final info
The tank then flew around the hold like a rocket until it smashed through the outer skin.
Retiring in 110 days - Probably one of my last posts.
Happy contrails -
Happy contrails -
BelargUSA--I sincerely hope you continue to share your insights and wisdom with us---I hope this is not truly your last post
PA
Cunning Artificer
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I believe QF were the unlucky recipients of a one off event,
Try as I might, I haven't been able to find a single other instance of an aircraft oxygen cylinder bursting in flight, other then as combat damage in military aircraft, despite them having been in continuous service on civil airliners since the dawn of pressurised flight. Has anyone else has had more luck in searching for one?
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Originally Posted by Smilin_Ed
BTW, what does "taking the mickey" mean?
ChristianJ, I'm a U.S. Navy pilot. We don't use that terminology.
SLF (self-loading-freight) is a somewhat deprecatory term that most people on this forum recognise.... It's the part of your payload that will get on board all by itself, without needing palletting or fork trucks. Aka passengers.....
The MEL (minimum equipment list) is a document that lists in considerable detail what defective items you can carry and for how long.
I'm sure the U.S. Navy has something very similar, but you may be calling it by a different name.
Also, from a very long time back, I know there is a vast difference between what you would accept for a peacetime training mission (when you were expected to bring the aircraft back in a state where it could be used again...) and the day when the balloon went up.
CJ
The O2 Bottle
Consensus appears to be that the bottle in question is one of the newer composite bottles. This has an inner aluminum liner. The regulator would be expected to be brass.
During the 6 months the bottle had been in place I would expect it to have undergone many cycles through a wide temperature range.
The two materials at the threaded top of the bottle would be Aluminum and Brass. These have quite different coefficients of linear expansion (COE). Those being about 24 * 10^-6 per centigrade degree for aluminum, and 19 for Brass.
Cold Aluminum is very brittle and could become cracked over time in the circumstances.
The disparate COE of these metals at this critical joint may be a big factor.
I suspect that this experiment with lighter O2 bottles may be at an end very soon!
During the 6 months the bottle had been in place I would expect it to have undergone many cycles through a wide temperature range.
The two materials at the threaded top of the bottle would be Aluminum and Brass. These have quite different coefficients of linear expansion (COE). Those being about 24 * 10^-6 per centigrade degree for aluminum, and 19 for Brass.
Cold Aluminum is very brittle and could become cracked over time in the circumstances.
The disparate COE of these metals at this critical joint may be a big factor.
I suspect that this experiment with lighter O2 bottles may be at an end very soon!
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The MEL was for the indicating system of the crew oxy. The indication was intermittent though working on the day. Its not relevant to this incident. The brackets holding the pax oxy bottles are not relevant to this incident. Parts of the bottle did indeed strike the door handle and rotate it more than 90 degrees. Think of the force needed to do that.
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Flynerd, think you hit it on the head.
These new weight/space saving devices are great in the purfect world, and that is the problem, we not in the purfect world.
Excuse the slip, but the 717 was developed because we don't live in the purfect world, fuel prices went up and the 717 was put out to grass.
Lets hope jet fuel slips back to $10 and the 717 has a fair run.
The cost of having these lightweight items fitted/re-fitted to aircraft looks like it may out weight the fuel savings in the future.
Keep yours eyes open for the next AD...it can't be far away.......
These new weight/space saving devices are great in the purfect world, and that is the problem, we not in the purfect world.
Excuse the slip, but the 717 was developed because we don't live in the purfect world, fuel prices went up and the 717 was put out to grass.
Lets hope jet fuel slips back to $10 and the 717 has a fair run.
The cost of having these lightweight items fitted/re-fitted to aircraft looks like it may out weight the fuel savings in the future.
Keep yours eyes open for the next AD...it can't be far away.......
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Lucky the door didn't open, with equalised pressure not forcing the door closed. The opening mechanism must have been damaged whilst the cabin was still pressurised, because at the angle the door handle is in, it would be cracked open if normally moved.
litebulbs
Thanks for the explanation re door opening/not opening. I would like to think that airspeed would also be a factor in not allowing the door to open, pressure differential aside. 
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I would be reasonably sure that opening a door whilst in unpressurised flight was not one of the items that was tested during flight testing as could also be said for an oxygen bottle failure of some sort.
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flynerd
Composite cylinders have been in aviation use for decades -- hardly an experiment. I wouldn't be surprised if this aircraft was delivered with them.
Besides oxygen supply, composite cylinders are used for hydraulic accumulators, fire bottles, evacuation slides and more.
If you have knowledge of any newly uncovered issues re COE/CTE between aluminium and brass please do share it with us.
Composite cylinders have been in aviation use for decades -- hardly an experiment. I wouldn't be surprised if this aircraft was delivered with them.
Besides oxygen supply, composite cylinders are used for hydraulic accumulators, fire bottles, evacuation slides and more.
If you have knowledge of any newly uncovered issues re COE/CTE between aluminium and brass please do share it with us.
Last edited by Machaca; 29th Jul 2008 at 23:50. Reason: correction
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A previous cylinder failure and hull breach in a BAe-146:
During the approach a loud bang was heard by the
aircrew, followed by a loss of the yellow hydraulic
system. After the aircraft landed safely a hydraulic
accumulator was found to have burst. The failure
was subsequently attributed to a material defect in the
cylinder wall of the accumulator.
aircrew, followed by a loss of the yellow hydraulic
system. After the aircraft landed safely a hydraulic
accumulator was found to have burst. The failure
was subsequently attributed to a material defect in the
cylinder wall of the accumulator.
The accumulator was . . . installed in the aircraft
10 months prior to the incident...
Probably several similar events over the years that we haven't heard about.
10 months prior to the incident...
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Guaranteed no speculation in this post, just a question.
There's something I don't understand about the VCR. It says this runs for two hours and then starts from the beginning and overwrites what's on it.
Quote from post 624:
Last night the aircraft cockpit voice recorder (CVR), which records crew conversations, radio traffic and cockpit ambient sounds, was downloaded by ATSB specialists in Canberra. Unfortunately, the standard two hour recording which works on an endless loop principle did not contain the event. The oldest recording commences after the descent and diversion into Manila, so the event itself appears to have been overwritten.
Unqote
... the event seems to have been overwritten... By what? From the event (1 hour into the flight) to the end of the VCR is about 1 hour, from start of overwrite to the event is another hour so it should have been recorded.
The information I've used here (times of events, technical info etc.) is based on posts in this forum, so some of it may have to be taken with a grain of salt, but at least the press release quoted in post 624 sounded to be from an official source.
There's something I don't understand about the VCR. It says this runs for two hours and then starts from the beginning and overwrites what's on it.
Quote from post 624:
Last night the aircraft cockpit voice recorder (CVR), which records crew conversations, radio traffic and cockpit ambient sounds, was downloaded by ATSB specialists in Canberra. Unfortunately, the standard two hour recording which works on an endless loop principle did not contain the event. The oldest recording commences after the descent and diversion into Manila, so the event itself appears to have been overwritten.
Unqote
... the event seems to have been overwritten... By what? From the event (1 hour into the flight) to the end of the VCR is about 1 hour, from start of overwrite to the event is another hour so it should have been recorded.
The information I've used here (times of events, technical info etc.) is based on posts in this forum, so some of it may have to be taken with a grain of salt, but at least the press release quoted in post 624 sounded to be from an official source.
Last edited by Brakes on; 30th Jul 2008 at 00:37.
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Quick question (from a passenger flyer only):
Is it not a possibly lucky event that whatever flew off the Oxy Bottle (Presumably the brass regulator?) actually hit the door handle and was therefore able to dissipate some of its energy into a moveable object...rather than hit the roof and possibly hole the aircraft from the inside? That door handle may have saved a bigger event?
Any feedback?
Is it not a possibly lucky event that whatever flew off the Oxy Bottle (Presumably the brass regulator?) actually hit the door handle and was therefore able to dissipate some of its energy into a moveable object...rather than hit the roof and possibly hole the aircraft from the inside? That door handle may have saved a bigger event?
Any feedback?