Tests done on oxygen bottles to find answers to Qantas blast

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There is no evidence of there being a systematic safety problem with aircraft oxygen bottles, says Australian investigators in their latest report into the July 2008 accident in which an oxygen bottle on a Qantas Airways 747 exploded.

The Australian Transport Safety Bureau's (ATSB) second interim report on this accident, released today, says to date there is no evidence of systematic problems with oxygen bottles of this type.

On 25 July last year the Qantas 747-400, local registration VH-OJK, was cruising at 29,000ft while on a flight from Hong Kong to Melbourne when one of 94 oxygen cylinders on board exploded causing a rupture of the forward fuselage and depressurisation of the cabin.

The rupture was approximately 2m along the length of the aircraft and 1.5 metres vertically.

ATSB says the cylinder that exploded was lost but, for the purposes of its investigation, it has obtained five cylinders from the same manufacturing lot.

It says all the pressure tests of the cylinders met or exceeded safety specifications.

"The minimum allowable rupture pressure prescribed ....was 4,111 psi and all the test cylinders exceeded that value", it says.

Today's report also provided details on how the cabin crew and cabin equipment responded to the depressurisation of the cabin.

It says "the passenger address tape reproducer - the automatically activated system for addressing passengers in the event of a depressurisation - did not function."

It also says "not all the oxygen masks deployed and as a result two passengers did not immediately start using oxygen and displayed symptoms of hypobaric hypoxia," a condition resulting from oxygen deprivation.

The ATSB says Qantas has since taken action to address these cabin issues.

As for why one of the aircraft's oxygen cylinders exploded, the bureau says it will complete its investigation early next year.