Saturday, November 21, 2009

Australian Transport Safety Bureau issues interim reports on two Qantas accidents

by B. N. Sullivan

Qantas logoDuring the past week, the Australian Transport Safety Bureau (ATSB) released interim updates on the investigations of two separate accidents involving aircraft operated by Qantas.

QF 30 depressurization, January 25, 2008

The ATSB issued an interim factual report on the investigation into the depressurization of a Qantas Boeing 747-400 aircraft, registration VH-OJK, on July 25, 2008. That aircraft, operating as Qantas Flight QF30, was en-route from Hong Kong to Melbourne; it diverted to Manila where it made a safe emergency landing. Once on the ground, a large hole in the fuselage was discovered. The ATSB concluded that the failure of an oxygen cylinder damaged the pressure hull and led the depressurization.

The newest report focused on a series of tests carried out on several oxygen cylinders from the same manufacturing lot as the failed cylinder, intended to replicate the failure. The ATSB reports that the "various tests have not been able to replicate the cylinder failure that initiated the accident." The ATSB says:
To date, all pressure tests of the cylinders met or exceeded the relevant safety specifications, with recorded rupture pressures being over twice the maximum working pressure of the cylinders.
The investigation continues, and a final report is expected in early 2010.

QF 72 in-flight upset, October 7, 2008

The ATSB also issued a second interim factual report on its investigation into an in-flight upset involving a Qantas Airbus A330-303, registration VH-QPA, on October 7, 2008. The aircraft, operating as Qantas Flight QF 72, was en route from Singapore to Perth when it experienced two uncommanded pitch-down events. The flight diverted to Learmonth, Western Australia, where it landed safely.

The new report describes tests carried out in an attempt to discover what caused anomalous behavior of the aircraft's No. 1 Air Data Inertial Reference Unit (ADIRU), which led to the upset. The tests were inconclusive. The ATSB says:
Despite extensive testing and analysis, the reason why the ADIRU started providing erroneous data (spikes) during the 7 October 2008 flight (or the 27 December 2008 flight) has not been identified to date. Nevertheless, the crew operational procedures that were provided by Airbus in October 2008 (and modified in December 2008 and January 2009) significantly reduced the chance of another in-flight upset by limiting the time that a faulty ADIRU could output angle of attack spikes. Airbus is also modifying the FCPC software used in the A330/A340 fleets to prevent angle of attack spikes leading to an in-flight upset.
The ATSB expects to release a final report into this accident in the second quarter of 2010.

RELATED: Click here to view all posts about Qantas Flt 72 on Aircrew Buzz