Global alert after Qantas dive

[Rockville]

EUROPEAN plane-maker Airbus has warned A330 operators around the world to guard against potential computer problems after last week's roller-coaster ride by a Qantas jet.
The global alert comes after investigators found that a faulty unit that provides information about the plane's movement and position resulted in the autopilot disconnecting and prompted flight control computers to pitch the plane's nose downward.
More than 70 people were injured, 14 seriously, when they were thrown around the cabin as the plane pitched down violently near Learmonth, in Western Australia northwest, while en route from Singapore to Perth.
The jet diverted to Learmonth and the worst injured were airlifted to Perth by the Royal Flying Doctor Service.
Investigators said last night the false information from an air data inertial reference unit (ADIRU) fed "very high, random and incorrect values".
The ADIRU supplies information such as air speed, altitude and position.
The fault led to the flight control computers pitching the aircraft's nose down by about 8.5 degrees and led to a fault in the flight control primary computer.
"The crew's timely response led to the recovery of the aircraft trajectory within seconds," ATSB air safety investigations director Julian Walsh said last night.
"During the recovery the maximum altitude loss was 650ft. As far as we can understand, this appears to be a unique event and Airbus has advised that it is not aware of any similar event over the many years of operation of the Airbus."
The faulty unit continued to generate random spikes after the first drop, causing the plane to pitch down a second time about 70 seconds later, although not as badly. This is the first time an Airbus aircraft has been affected by a problem with this type of unit but it is the second incident involving an ADIRU on a plane travelling to or from Perth.
A global alert was issued in 2005 after a Malaysia Airlines Boeing 777 en-route to Kuala Lumpur from Perth experienced similar problems.
Investigators found a software glitch in a unit made by the same US manufacturer as the one in the Qantas plane combined with a mechanical problem.
The findings quash any suggestion of pilot error.

The Australian | October 15, 2008