Wednesday, October 15, 2008

Qantas Airbus Accident Caused by Computer Fault

The Australian Transport Safety Bureau in "Qantas Airbus A330 accident Media Conference" has reported that the aircraft's computers causing the aircraft to pitch down violently, injuring passengers on 7 October 2008. While the accident appears due to a faulty a Air Data Inertial Reference Unit feeding incorrect data to the computers, perhaps the computers should have been programmed to detect and reject the erronious data.
... The ATSB has scheduled the media conference this evening to coincide with the release of an Operators Information Telex/Flight Operations Telex, which is being sent by Airbus to operators of all Airbus aircraft. The aim of that telex is to:
  • update operators on the factors identified to date that led to the accident involving QF72,
  • provide operational recommendations to mitigate risk in the event of a reoccurrence of the situation which occurred on QF72.

... The aircraft was flying at FL 370 or 37, 000 feet with Autopilot and Auto-thrust system engaged, when an Inertial Reference System fault occurred within the Number-1 Air Data Inertial Reference Unit (ADIRU 1), which resulted in the Autopilot automatically disconnecting. ...

The faulty Air Data Inertial Reference Unit continued to feed erroneous and spike values for various aircraft parameters to the aircrafts Flight Control Primary Computers which led to several consequences including:

  • false stall and overspeed warnings
  • loss of attitude information on the Captain's Primary Flight Display
  • several Electronic Centralised Aircraft Monitoring system warnings.

About 2 minutes after the initial fault, ADIRU 1 generated very high, random and incorrect values for the aircrafts angle of attack.

These very high, random and incorrect values of the angle attack led to:

  • the flight control computers commanding a nose-down aircraft movement, which resulted in the aircraft pitching down to a maximum of about 8.5 degrees,
  • the triggering of a Flight Control Primary Computer pitch fault.

The crew's timely response led to the recovery of the aircraft trajectory within seconds. During the recovery the maximum altitude loss was 650 ft.

The Digital Flight Data Recorder data show that ADIRU 1 continued to generate random spikes and a second nose-down aircraft movement was encountered later on, but with less significant values in terms of aircraft's trajectory.

At this stage of the investigation, the analysis of available data indicates that the ADIRU 1 abnormal behaviour is likely as the origin of the event. ...

Related Documents: | Audio file of media conference, 14 October 2008 (18 MB)

From: "Qantas Airbus A330 accident Media Conference", Media Release, Australian Transport Safety Bureau, 2008/43, 14 October 2008

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