Says Computer Fault Led To Wild Ride
Transport Safety Bureau says it knows why an Airbus A330-300
dropped about 650 feet within seconds over Western Australia last
week. Investigators have pinpointed the cause of the incident to a
fault in the aircraft's flight data computer, which shut off the
As ANN reported, dozens of passengers were
injured when the aircraft violently lurched during an October 7
flight from Singapore to Perth, falling several hundred feet from
its 37,000-foot cruising altitude. Speculation initially pointed to
clear air turbulence, but days later
Qantas curiously pointed a finger at potential
electronic interference from a passenger's laptop computer.
It now appears both hypotheses were in error. Bloomberg reports
Airbus SAS immediately issued an alert Tuesday after the ATSB
issued its preliminary report, advising operators of the advanced
widebody airliner -- and its larger A340 sibling -- to be aware of
an apparent glitch in air data computers manufactured by Litton
Industries, a subsidiary of Northrop Grumman.
"This appears to be a unique event," the ATSB noted in its
report, adding the advisory issued by Airbus is "aimed at
minimizing the risk in the unlikely event of a similar
ATSB says its preliminary analysis determined one of the A330's
three Air Data Inertial Reference Unit sent incorrect information
to the aircraft's fly-by-wire flight control system, which caused
the autopilot to disconnect due to warnings of an imminent stall.
The jet dropped when the air data unit triggered "a nose-down
aircraft movement, which resulted in the aircraft pitching down to
a maximum of about 8.5 degrees."
The Board added the ADIRU "generated very high, random and
incorrect values for the aircraft's angle of attack," and triggered
repeated stall and speed warnings over a two-minute period
following the incident. By that time, the pilots had taken manual
control of the airliner.
"Airbus has advised that it is not aware of any similar event
over the many years of operation of the Airbus," the ATSB said.
Operators of the A330 and A340 may select air data computers
manufactured by Litton, or Honeywell. The fault appears confined to
the Litton models, according to the ATSB.