Jet lost pilot instruments in blast

The Qantas jumbo jet hit by a mid-air explosion lost critical pilot instruments in the blast, it has emerged.

The explosion last Friday, caused by a faulty oxygen cylinder during a flight from London to Melbourne, forced the crew of the Boeing 747 to make an emergency landing in the Philippines.

Australian Transport Safety Bureau director of aviation safety Julian Walsh said investigators found that the jet's three landing instrument systems and its anti-skid braking mechanism were not working after the accident

"However evidence indicates that all the aircraft's main systems including engines and hydraulics were functioning normally," he said.

"The approach to Manila airport was conducted in visual conditions and it should be noted that the pilot had other navigation instruments available should the conditions not have been visual," he added.

But another ATSB investigator said later that the failed instruments would have made landing "extremely difficult" if conditions over Manila had been cloudy or foggy.

Mr Walsh said: "The ATSB can confirm it appears that part of an oxygen cylinder and valve entered the passenger cabin. Clearly the valve has travelled vertically through the floor of the aircraft, glanced with the door handle and impacted with the ceiling of the cabin," he said.

But he said "there was never any danger of the door opening" because it is designed never to be opened while the plane is in the air. This is a unique event. It's not happened before that we're aware of," he added.

The jet with 365 people aboard was flying at 29,000 feet when the explosion occurred in the cargo bay, rupturing the fuselage and causing rapid decompression in the cabin.

The pilots took about five and a half minutes to bring the jet down to 10,000 feet where oxygen was not needed. The ATSB is examining reports that around 10 passengers were unable to get oxygen from their overhead masks during the steep decent.

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Fonte: Flight Safety Information 20/07/2008.