Melbourne, Oct.14 : Air investigators have blamed a faulty computer system for the terrifying mid-air plunge of a Qantas flight between Singapore and Perth last week.
A fault in the Airbus A330-300's air data inertial reference system is believed to have led to erroneous information being sent to its flight control computer, causing the autopilot to shut down.
The aircraft was cruising at 37,000 feet when the fault occurred, causing it to descend up to 650 feet in seconds.
More than 70 people were injured when the plane, carrying 303 passengers and 10-crew, suddenly dropped altitude, hurling people around the cabin and forcing the pilot to make an emergency landing at Learmonth in Western Australia.
Australian Transport Safety Bureau investigation director Julian Walsh said the faulty unit continued to feed "erroneous and spike values" to its primary computers.
Walsh said analysis of the digital flight recorder showed the faulty air data system continued to generate false information, leading to a second, less serious "nose down aircraft movement".
The ATSB is expected to provide a preliminary factual report within three weeks.