Quantas oxygen cylinder caused explosion
08-28-2008 | 08:48 PM
#1
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Che Guevara
Joined: Aug 2005
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Quantas oxygen cylinder caused explosion
I can't imagine what would make that tank blow. I seen scuba tanks dropped 25ft and nothing.
CANBERRA, Australia - An oxygen cylinder caused the explosion that blew a car-sized hole in a Qantas jet last month, forcing an emergency landing, air safety officials said Friday.
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The release of the interim report by Julian Walsh, acting executive director of the Australian Transport Safety Bureau, confirmed earlier suspicions by investigators that an exploding oxygen tank was the cause.
The Boeing 747-438 aircraft, carrying 365 people, was flying over the South China Sea July 5 when the explosion blew a hole in the fuselage five-feet in diameter, causing a loss of cabin pressure.
Walsh said one of the seven emergency oxygen cylinders below the cabin floor had exploded, but did not say what caused the tank to burst.
"On the basis of the physical damage to the aircraft's forward cargo hold and cabin, it is evident that the number 4 passenger oxygen cylinder sustained a failure that allowed a sudden and complete release of the pressurized contents," Walsh told reporters in releasing the report.
The plane — en route from London to Melbourne, Australia — rapidly descended thousands of feet and flew about 300 miles to Manila, where it made a successful emergency landing.
No one was injured, but questions were raised about the much-lauded safety of Qantas Airways, which has never lost a jet aircraft because of an accident.
In the weeks after the incident, Qantas planes experienced a number of other problems, including a loss of hydraulic fuel that led to an emergency landing, failure of landing gear, and detached panels.
The problems prompted the Civil Aviation Safety Authority, Australia's aviation agency, to launch a review of Qantas Airways' safety standards.
Qantas earlier this month temporarily pulled six planes from service because of irregularities in maintenance records. Qantas said it was a record-keeping issue and there were no safety implications for the aircraft.
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The release of the interim report by Julian Walsh, acting executive director of the Australian Transport Safety Bureau, confirmed earlier suspicions by investigators that an exploding oxygen tank was the cause.
The Boeing 747-438 aircraft, carrying 365 people, was flying over the South China Sea July 5 when the explosion blew a hole in the fuselage five-feet in diameter, causing a loss of cabin pressure.
Walsh said one of the seven emergency oxygen cylinders below the cabin floor had exploded, but did not say what caused the tank to burst.
"On the basis of the physical damage to the aircraft's forward cargo hold and cabin, it is evident that the number 4 passenger oxygen cylinder sustained a failure that allowed a sudden and complete release of the pressurized contents," Walsh told reporters in releasing the report.
The plane — en route from London to Melbourne, Australia — rapidly descended thousands of feet and flew about 300 miles to Manila, where it made a successful emergency landing.
No one was injured, but questions were raised about the much-lauded safety of Qantas Airways, which has never lost a jet aircraft because of an accident.
In the weeks after the incident, Qantas planes experienced a number of other problems, including a loss of hydraulic fuel that led to an emergency landing, failure of landing gear, and detached panels.
The problems prompted the Civil Aviation Safety Authority, Australia's aviation agency, to launch a review of Qantas Airways' safety standards.
Qantas earlier this month temporarily pulled six planes from service because of irregularities in maintenance records. Qantas said it was a record-keeping issue and there were no safety implications for the aircraft.
08-29-2008 | 09:17 AM
#4
On Reserve
Joined: Jun 2008
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From: B757/767 F/O
Here's the report from the Aussie gov't. It's pretty detailed and has some interesting pics of the damage.
http://www.atsb.gov.au/publications/...053_Prelim.pdf
http://www.atsb.gov.au/publications/...053_Prelim.pdf
08-29-2008 | 09:48 AM
#5
Prime Minister/Moderator
Joined: Jan 2006
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From: Engines Turn or People Swim
The usual problem in these cases is internal corrosion, probably due to water build up. A manufacturing defect is unlikely since the bottle was hydo-tested before entering service, and on a routine basis thereafter. It should have had routine borescope inspections too.
Static could not ignite the contents inside a metal bottle...no flow path for the current. Also (except for really exotic applications like spacecraft monopropellants), flammable mixtures are never stored in bottles...otherwise ignition at the output would likely flash back into the bottle
Oxygen itself is not flammable or explosive anyway. It would be almost unbelievable if a breathing oxygen bottle were accidentently filled with a flammable mixture...there is a higher standard of handling for breathing and medical O2.
If the cyclinder was composite, and not all-metal, it's possible that the composite wrap was damaged by a sharp impact or by corrosive fluids.
If the cyclinder was weakened significantly it's possible that the cyclinder failed at a pressure below the relief valve setting.
Another remote possibility is brittle fracture. Steel can crack spontaneously at cold temperatures. We design steel products to have a low or extremely low risk of BF (depending on the application), but it cannot be totally eliminated.
From an engineering perspective, this is very odd. Given the application (high mx standards, no salt water) the odds are against this event occoring. My guess would physically damaged composite wrap, but those bottles in the pictures look like aluminum from a distance.
08-29-2008 | 11:45 AM
#8
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From: 747 Captain (Ret,)
For those who questioned the bottle construction, the Australian safety report says it was one piece steel. See the link in Posrates post, page 16.
Joe
08-29-2008 | 11:57 AM
#9
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From: LCA, A&P, IA
If you are filling something with a gas by pumping it in with a compressor that will heat it up, but when you fill an O2 bottle from a higher pressure bottle, the O2 coming in will be expanding and cooling off.
For those who questioned the bottle construction, the Australian safety report says it was one piece steel. See the link in Posrates post, page 16.
Joe
For those who questioned the bottle construction, the Australian safety report says it was one piece steel. See the link in Posrates post, page 16.
Joe
