Aviation Safety Investigation Report - Interim Factual

This report provides an update to the first Interim Factual Report on this occurrence that was released on 6 March 2009.

The interim report should be read in conjunction with the first interim report. The contents of this second interim report focus on summarising new activities conducted since the previous report, providing information on relevant topics not released in the previous report, and updating information on relevant topics where there have been significant changes. Further details of new and ongoing activities will be provided in the Australian Transport Safety Bureau's (ATSB) final report.

The information contained in this interim factual report is derived from the ongoing investigation of the occurrence. Readers are cautioned that there is the possibility that new evidence may become available during the remainder of the investigation that alters the circumstances as depicted in this report.

The investigation is continuing.

At 0932 local time (0132 UTC) on 7 October 2008, an Airbus A330-303 aircraft, registered VH-QPA, departed Singapore on a scheduled passenger transport service to Perth, Australia. On board the aircraft (operating as flight number QF72) were 303 passengers, nine cabin crew and three flight crew. At 1240:28, while the aircraft was cruising at 37,000 ft, the autopilot disconnected. From about the same time there were various aircraft system failure indications. At 1242:27, while the crew was evaluating the situation, the aircraft abruptly pitched nose-down. The aircraft reached a maximum pitch angle of about 8.4 degrees nose-down, and descended 650 ft during the event. After returning the aircraft to 37,000 ft, the crew commenced actions to deal with multiple failure messages. At 1245:08, the aircraft commenced a second uncommanded pitch-down event. The aircraft reached a maximum pitch angle of about 3.5 degrees nose-down, and descended about 400 ft during this second event.

At 1249, the crew made a PAN urgency broadcast to air traffic control, and requested a clearance to divert to and track direct to Learmonth. At 1254, after receiving advice from the cabin of several serious injuries, the crew declared a MAYDAY. The aircraft subsequently landed at Learmonth at 1350.

One flight attendant and 11 passengers were seriously injured and many others experienced less serious injuries. Most of the injuries involved passengers who were seated without their seatbelts fastened or were standing. As there were serious injuries, the occurrence constituted an accident.

The investigation to date has identified two significant safety factors related to the pitch-down movements. Firstly, immediately prior to the autopilot disconnect, one of the air data inertial reference units (ADIRUs) started providing erroneous data (spikes) on many parameters to other aircraft systems. The other two ADIRUs continued to function correctly. Secondly, some of the spikes in angle of attack data were not filtered by the flight control computers, and the computers subsequently commanded the pitch-down movements.

Two other occurrences have been identified involving similar anomalous ADIRU behaviour, but in neither case was there an in-flight upset.

Download Interim Factual report [ PDF 1.6 MB]

At 0932 local time (0132 UTC) on 7 October 2008, an Airbus A330-303 aircraft, registered VH-QPA, departed Singapore on a scheduled passenger transport service to Perth, Australia. On board the aircraft (operating as flight number QF72) were 303 passengers, nine cabin crew and three flight crew. At 1240:28, while the aircraft was cruising at 37,000 ft, the autopilot disconnected. That was accompanied by various aircraft system failure indications. At 1242:27, while the crew was evaluating the situation, the aircraft abruptly pitched nose-down. The aircraft reached a maximum pitch angle of about 8.4 degrees nose-down, and descended 650 ft during the event. After returning the aircraft to 37,000 ft, the crew commenced actions to deal with multiple failure messages. At 1245:08, the aircraft commenced a second uncommanded pitch-down event. The aircraft reached a maximum pitch angle of about 3.5 degrees nose-down, and descended about 400 ft during this second event.

At 1249, the crew made a PAN emergency broadcast to air traffic control, and requested a clearance to divert to and track direct to Learmonth. At 1254, after receiving advice from the cabin crew of several serious injuries, the crew declared a MAYDAY. The aircraft subsequently landed at Learmonth at 1350.

Currently available information indicates that one flight attendant and at least 13 passengers were seriously injured and many others experienced less serious injuries. Most of the injuries involved passengers who were seated without their seatbelts fastened. This constituted an accident under the ICAO definition outlined in Annex 13 to the Chicago Convention and as defined in the Transport Safety Investigation Act 2003.

Examination of flight data recorder information indicates that, at the time the autopilot disconnected, there was a fault with the inertial reference (IR) part of the air data inertial reference unit (ADIRU) number 1. From that time, there were many spikes in the recorded parameters from the air data reference (ADR) and IR parts of ADIRU 1. Two of the angle-of-attack spikes appear to have been associated with the uncommanded pitch-down movements of the aircraft.

Download Preliminary report [ PDF 1.2 MB ]