Air investigators say a faulty computer system was responsible for a
terrifying mid-air plunge on 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.
“This led to several consequences, including false stall and overspeed warnings,” he said.
“About
two minutes after the initial fault (the air data inertial reference
system) generated very high and incorrect values for the aircraft’s
angle of attack.”
This led to the flight control computers commanding the aircraft to pitch down, Mr Walsh said.
“The
crew’s timely response led to the recovery of the aircraft’s trajectory
within seconds, and during the recovery, the maximum altitude lost was
650 feet.”
