Report: In-flight upset of Airbus A330 near Australia

December 19, 2011

The Australian Transport Safety Bureau (ATSB) issued the final report of their investigation into an in-flight upset accident involving an Airbus A330 in 2008.

On 7 October 2008, an Airbus A330-303 aircraft, registered VH-QPA and operated as Qantas flight 72, departed Singapore on a scheduled passenger transport service to Perth, Western Australia. While the aircraft was in cruise at 37,000 ft, one of the aircraft’s three air data inertial reference units (ADIRUs) started outputting intermittent, incorrect values (spikes) on all flight parameters to other aircraft systems. Two minutes later, in response to spikes in angle of attack (AOA) data, the aircraft’s flight control primary computers (FCPCs) commanded the aircraft to pitch down. At least 110 of the 303 passengers and nine of the 12 crew members were injured; 12 of the occupants were seriously injured and another 39 received hospital medical treatment.

Although the FCPC algorithm for processing AOA data was generally very effective, it could not manage a scenario where there were multiple spikes in AOA from one ADIRU that were 1.2 seconds apart. The occurrence was the only known example where this design limitation led to a pitch-down command in over 28 million flight hours on A330/A340 aircraft, and the aircraft manufacturer subsequently redesigned the AOA algorithm to prevent the same type of accident from occurring again.

Each of the intermittent data spikes was probably generated when the ADIRU’s central processor unit (CPU) module combined the data value from one parameter with the label for another parameter. The failure mode was probably initiated by a single, rare type of internal or external trigger event combined with a marginal susceptibility to that type of event within a hardware component. There were only three known occasions of the failure mode in over 128 million hours of unit operation. At the aircraft manufacturer’s request, the ADIRU manufacturer has modified the LTN-101 ADIRU to improve its ability to detect data transmission failures.

At least 60 of the aircraft’s passengers were seated without their seat belts fastened at the time of the first pitch-down. The injury rate and injury severity was substantially greater for those who were not seated or seated without their seat belts fastened.

The investigation identified several lessons or reminders for the manufacturers of complex, safety‑critical systems.

More information:

ATSB Report: oxygen cylinder rupture on Boeing 747 was unique event

November 22, 2010

Part of the fuselage was ruptured (Photo: ATSB)

The rupture of an oxygen cylinder on board a Qantas Boeing 747 in 2008 was a unique event and highly unlikely to happen again according to the Australian Transport Safety Bureau (ATSB).

On 25 July 2008, an oxygen cylinder ruptured in the plane’s forward cargo hold about an hour into a flight from Hong Kong to Melbourne. Part of the ruptured cylinder punctured the fuselage wall and damaged the cabin, causing the plane to rapidly depressurise. The plane then made an emergency descent and landed at the nearest suitable airport in Manila, Philippines. None of the 369 passengers and crew on board were injured.

The key piece of evidence, the ruptured cylinder, was ejected from the plane and is at the bottom of the South China Sea, which made the investigation challenging.

Investigators exhaustively tested and evaluated identical cylinders, including cylinders from the same manufacturing batch. Through these tests it was not possible to  identify any aspect of the cylinder design or manufacture that could pose a threat.

Given the widespread and long-term use of this type of cylinder, it was clear that this occurrence was a unique event.

More information:

Qantas grounds four DHC-8-400Q’s due to cracks in landing gear component

August 22, 2010

Qantas reported that five De Havilland Canada DHC-8-402Q Dash 8 aircraft operated by its regional airline QantasLink had been temporarily removed from service following an inspection by the airline of a main landing gear component.

During these inspections cracks were discovered in a major component of a landing gear fitting in five of its 21 DHC-8-Q400 aircraft, with the remaining 16 unaffected and to remain in service, according to the Australian Associated Press.

The inspections were probably carried out following two recent Airworthiness Directives:

  • CF-2010-22 Main Landing Gear Stabilizer Extension Spring (August 10, 2010)
  • CF-2010-23 Main Landing Gear – Failure to Extend (August 16, 2010)

%d bloggers like this: