A Preliminary Report has just been released by the Australian Transport Safety Bureau (ATSB) in regard to the in-flight upset of Qantas Flight QF72 on October 7, 2008. Readers will recall that on that date the Airbus A330-300 aircraft was en route from Singapore to Perth, Australia with 10 crew and 303 passengers on board, when it experienced two successive uncommanded pitch-down events. A number of individuals in the passenger cabin were seriously injured. The aircraft diverted to Learmonth, Western Australia, where it made an emergency landing.About a week after the accident, the ATSB reported that early analysis of the accident aircraft's Flight Data Recorder data, Post Flight Report data and Built-in Test Equipment revealed that an Inertial Reference System fault had occurred within the Number-1 Air Data Inertial Reference Unit (ADIRU 1). Today's report elaborates further on that finding, and also reports on the overall progress of the investigation, which is ongoing.
A summary of important points is contained in a media release issued by the ATSB in conjunction with the publication of the Preliminary Report. Here is a part of that summary:
Examination of flight data recorder information indicates that, at the time the autopilot disconnected, there was a fault in a flight computer system component known as the air data inertial reference unit number 1 (ADIRU 1) which resulted in a number of spurious spikes in ADIRU parameter values. Further spurious parameter spikes continued to influence a number of system failure indications throughout the flight, resulting in frequent failure messages being provided to the crew. The crew completed required actions in response to the messages, but these actions were not effective in removing the spikes or failure indications. The investigation team is continuing to examine the influence of the spikes in ADIRU parameters on the performance of the flight controls.Still ongoing:
Most components on modern aircraft, including ADIRUs, are highly reliable and there has only been a small number of occasions where ADIRUs of different types made by varying manufacturers have had some form of failure. It is extremely rare for any such failures to have an effect on an aircrafts flight controls. The ATSB has previously investigated an in-flight upset related to ADIRU failure from a different manufacturer in a Boeing 777 which occurred in 2005 and was traced to a software fault. While a software fault has not been ruled out in the current investigation, it seems unlikely that the two events are linked.
- The three ADIRUs will be subject to comprehensive testing at the manufacturer's facilities in the US.
- Review of the ADIRUs' data monitoring capability and management of anomolous ADIRU data, including flight deck indications.
- Review of records of previous occurrences involving ADIRU failures (which did not result in in-flight upsets) and any occurrences where large numbers of spurious messages were generated.
- Subject to the results of the ADIRU testing, examination of other aircraft components may be conducted such as the three flight control primary computers and their software in order to understand why the fault in the ADIRU was able to be translated to flight control movements.
The investigation of cabin safety issues related to this accident also is still underway. This includes interviews with the cabin crew and seriously injured passengers, and responses to questionnaires "seeking passenger observations during the upset events and asking questions in relation to the use of seatbelts, injuries and the use of personal electronic devices."
The ATSB also noted that a number of important safety actions have already been implemented arising from the investigation to date.
Here is the link to the entire document: AO-2008-070: Preliminary Report - ATSB, Nov. 14, 2008 (43-page 'pdf' file)
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