Safety Board to Release Second Report of Qantas A330 Accident

Following Tuesday’s release of the Australian Transport Safety Bureau’s (ATSB) tests on oxygen bottles, tomorrow the ATSB will release its final second interim report on the Qantas A330 that dived 1000 feet in a matter of minutes over Western Australia.

Let’s have a recap of the event and the first interim report (opens as PDF).

Basics

  • Flight: Qantas 72 from Singapore to Perth (2420 miles), 7 October 2008
  • Aircraft: A330-300 VH-QPA
  • On board: 303 passengers, 9 cabin crew, 3 flight crew
  • Injuries: 11 passengers and 1 flight attendant sustained serious injuries, others had less serious injuries. Most occurred as the individuals were standing or not wearing seat belts. No fatalities.

  • There was no structural damage, but the centre and rear cabin sustained damage. See photos:

VH-QPA Damage1.jpgVH-QPA Damage2.jpg(ATSB)



Timeline (in local time)

  • 9:32 am Aircraft departs Singapore
  • 12:40:24 pm At cruise altitude of 37,000 feet, autopilot disconnects, cockpit gives system failure notifications
  • 12:42:27 Flight crew evaluating situation when aircraft pitches nose-down at a maximum angle of 8.4 degrees, descends 650 feet. Crew brings aircraft back to 37,000 feet, deals with failure messages

  • 12:45:08 Aircraft commences second commanded plunge, this time at a maximum angle of 3.5 degrees, and descends 400 feet (approx 160 seconds after first plunge)

  • 12:49 Flight crew declare PAN urgency, begin diversion
  • 12:54 Flight crew learn from cabin crew of serious injuries, declare mayday
  • 13:50 Aircraft lands at Learmonth

Aircraft’s flight path (ATSB):

QF 72 Tracking.jpg

What’s at fault?

The preliminary report (“interim factual”) identified two concerns

  1. One of the three air data inertial reference units (ADIRUs) “started providing erroneous data (spikes) on many parameters to other aircraft systems”. The other two ADRIUs functioned normally.
  2. The second concern is a bit more technical: “Spikes in angle of attack data were not filtered by the flight control computers, and the computers subsequently commanded the pitch-down movements”.

More simply, as our Kieran Daly on the safety beat summarised the accident, “the crew was trying to control a fly-by-wireaircraft which didn’t ‘understand’ what it [the aircraft] was doing or what washappening to it”.

ADIRU.jpgThe ADIRU in question from VH-QPA



Significance

At the time, the ATSB was investigating two similar incidents involving “anomalous ADIRU behaviour” but which didn’t involve an “in-flight upset”.

  1. One incident involved a Malaysia Airlines B777-200 240 km from Perth. The ADIRU was from a different manufacturer. (Read the report in PDF here.)
  2. A second incident involved the same aircraft, VH-QPA, as the one concerned in this aircraft. The incident, in September 2006, involved the exact same ADIRU. After the  flight, the unit was inspected and re-set.

Additionally, on a December 2008 flight from Perth to Singapore, a different Qantas A330-300 received a fault message regarding the ADIRU. While it was a different ADIRU from the other incidents, it was in the same position (the #1 ADIRU).

ATSB map of the three Qantas A330 incidents (not included is the Malaysian 777 incident):

 Map of QF 330 Incidents.jpgA greater incident would occur three months, with the complete loss of Air France flight 447. While that incident focused on faulty pitot tubes, an ACARS message reported a fault in an ADIRU.

Report’s Influence

The report ruled out the dive as being a result of simple turbulence and advanced military operations that interfered with the aircraft’s systems. It also ruled out the rumour a laptop or wireless headphones (media speculation couldn’t settle on which one) was at fault.

The algorithms used to calculate data relating to the ADIRU are also featured on the A340. EASA and the FAA issued air worthiness directives. Of the 900 A330 and A340 aircraft in operation at the time, 397 had the same ADIRU model as the one involved in the accident and other incidents.

For its investigation, Airbus searched for similar incidents within a designated time frame. It could only identify four: the Malaysian 777, the previous incident on VH-QPA, the incident in December 2008 on another Qantas A330-300, and finally an incident on a Jetstar A330-200 (VH-EBC) from Sydney to Ho Chi Minh.

What’s going on with A330s in the skies around Australia?

Check back here tomorrow for an update on the second report.

, , ,

Leave a Reply