Investigators probing the 25 July fuselage rupture and rapid decompression involving a Qantas Boeing 747-400 are focusing their attention on what appears to have been an oxygen cylinder explosion.

Australian Transport Safety Bureau investigators say the aircraft's emergency oxygen system is being looked at most closely, because one of 13 cylinders in the area of the 747 where the fuselage rupture occurred was found missing after the aircraft's emergency landing in Manila.

Qantas-fuselage-hole 
 

Investigations later determined that parts from the missing cylinder blasted into the passenger cabin. Qantas had already been ordered days earlier to inspect the oxygen system bottles on its 29 other 747-400s.

"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, thereby moving the handle part way towards the open position," says the safety bureau, although it added that "there was never any danger of the door opening".

It also says the aircraft's three instrument landing systems "were not available" for the emergency landing at Manila nor was its anti-skid system as a result of the suspected oxygen tank explosion, which it says if confirmed would probably be the first of its kind involving a 747-400. But it says all main systems including engines and hydraulics were functioning normally and the approach to Manila airport was conducted smoothly in visual conditions.

The incident occurred on the morning of 25 July as the 747-400 was operating as flight QF30 from Hong Kong to Melbourne. At around 29,000ft (8,840m) part of the fuselage separated at the forward cargo hold on the right side of the aircraft, which led to the rapid decompression. A rapid descent was carried out to 10,000ft, after which the aircraft made an emergency landing in Manila. There were no injuries.

The ATSB says the descent from 29,000ft to 10,000ft took around 5min, with an average descent rate of around 4,000ft/min (20.3m/s).

Some of the 346 passengers reported their oxygen masks were not working. The ATSB says it is continuing to look into this, but adds that it has determined that most of the masks deployed as intended.

A preliminary factual report is to be released by late August, but "should the need for urgent safety action by any agency be identified, the ATSB will immediately notify the relevant agencies".




Source: Flight International

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