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:


Report: Incorrect take-off data causes A340-500 tailstrike and runway overrun at Melbourne

December 16, 2011

The incorrect entry of take-off weight data that resulted in the tailstrike and runway overrun of an Emirates Airbus A340 aircraft in 2009 was not a unique event. Similar events continue to occur throughout the world, according to the Australian Transport Safety Bureau (ATSB).

The ATSB published the final report of its investigation into a 20 March 2009 accident, when flight EK407, with 18 crew and 257 passengers, sustained a tailstrike and overran the runway end on departure from Melbourne Airport.  The aircraft became airborne in the grass clearway but struck a light and several antennae, which damaged and disabled the instrument landing system for the airport.
The flight crew climbed the aircraft to 7,000 ft and circled over Port Phillip Bay, Victoria, while jettisoning fuel to reduce the aircraft’s weight. The flight crew then returned the aircraft to Melbourne for an uneventful landing on runway 34.

The ATSB found that the accident resulted from the use by the crew of incorrect take-off performance parameters. The initial error was likely due to mistyping, when a weight of 262.9 tonnes, instead of the intended 362.9 tonnes, was entered into a laptop computer to calculate the aircraft’s take-off settings. The error passed through several subsequent checks without detection.

Although a number of contributing factors were identified, the ATSB determined that there were two primary factors in the development of the accident as follows:

  • the flight crew did not detect the erroneous take-off weight that was used for the take-off performance calculations, and
  • the flight crew did not detect the degraded take-off performance until very late in the take-off roll.

More information:

ATSB animation of the occurrence.


ATSB concludes investigation into unreliable airspeed indication incident involving an Airbus A330

January 27, 2011

Location of pitot and TAT probes on an A330 (Photo: ATSB)

The Australian Transport Safety Bureau (ATSB) concluded their investigation into an unreliable airspeed indication incident involving an Airbus A330.

On 28 October 2009, an Airbus A330-202 aircraft, registered VH-EBA, was being operated as Jetstar flight 12 on a scheduled passenger service from Narita, Japan to Coolangatta, Australia. Soon after entering cloud at 39,000 ft, there was a brief period of disagreement between the aircraft’s three sources of airspeed information. The autopilot, autothrust and flight directors disconnected, a NAV ADR DISAGREE caution message occurred, and the flight control system reverted to alternate law, which meant that some flight envelope protections were no longer available. There was no effect on the aircraft’s flight path, and the flight crew followed the operator’s documented procedures. The airspeed disagreement was due to a temporary obstruction of the captain’s and standby pitot probes, probably due to ice crystals. A similar event occurred on the same aircraft on 15 March 2009.

The rate of unreliable airspeed events involving the make of pitot probes fitted to VH-EBA (Goodrich 0851HL) was substantially lower than for other probes previously approved for fitment to A330/A340 aircraft.

In it’s investigation into the June 1, 2009 accident involving an Air France A330 (flight AF447),  the French Bureau d’Enquêtes et d’Analyses pour la sécurité de l’aviation civile (BEA) found 36 occurrences between the period 12 November 2003 and 7 August 2009 that the aircraft manufacturer concluded were attributable to the blocking of at least two pitot probes by ice.  27 events involved aircraft fitted with Thales model C16195AA pitot probes, the same model fitted on the AF447. Two events involved aircraft fitted with Goodrich 0851HL probes.

Both of the events involving VH-EBA occurred in environmental conditions outside those specified in the certification requirements for the pitot probes. The French Bureau d’Enquêtes et d’Analyses pour la sécurité de l’aviation civile (BEA) has recommended the European Aviation Safety Agency (EASA) to review the certification criteria for pitot probes in icing environments.

At the time of the occurrence, most of the operator’s A330 pilots had not received unreliable airspeed training. Most of these pilots had transferred from the operator’s A320 fleet, and the third-party training provider had not included the topic in its A320 endorsement training program, even though it was included in the aircraft manufacturer’s recommended program since 2004.

The operator identified the problem and included unreliable airspeed in its recurrent training program for the A320 from May 2009 and the A330 from October 2009. The training provider included the topic in its endorsement program from July 2010. The operator, training provider and the Civil Aviation Safety Authority all initiated safety action to minimise the likelihood of similar problems in the future.


Study: Aircraft loading occurrences July 2003 to June 2010

December 23, 2010

Incorrect unloading can cause an aircraft to pitch up (photo: ATSB)

The Australian Transport Safety Bureau (ATSB) published a study (AR-2010-044) on aircraft loading occurrences from July 2003 to June 2010.

The report documents the number and types of safety occurrences involving loading of high capacity aircraft to raise awareness within the aviation industry of the associated issues.
Incorrect loading of containers, pallets or bags into aircraft can result in them being outside of weight or centre of gravity operating limits, and this may influence aircraft controllability. Most high capacity aircraft loading occurrences are relatively minor, with cargo locks not being raised being the most common. More serious occurrences have involved shifting cargo and unlisted cargo being loaded onto aircraft. Aircraft performance has been affected in a small number of cases, and the result has been rejected takeoff, extra stabiliser trim, or aircraft control difficulties.

The study concluded that the following practices can help to guard against common loading errors:

  • Perform cross-checks between the mean aerodynamic chord and stabiliser trim setting, for all LIRs.
  • Perform a cross-check of the aircraft weight, as recorded in the aircraft manual –  with the load report weight, and ensure the aircraft registration details are correct on the loadsheet.
  • Flight crew should not accept a loadsheet while the aircraft is being loaded.
  • Incorporate rules within load  control software that stop incorrectly configured aircraft loadsheets from being generated.
  • Remove off-loaded/rejected containers or loads from next to the aircraft where they can potentially get reloaded in error.
  • Use on-board aircraft weight sensors as a cross-check against weight and centre of gravity calculations.

 


ATSB: Manufacturing problem potential factor in recent A380 engine failure

December 2, 2010

The ATSB has issued a safety recommendation about potential engine problems in some Airbus A380 aircraft.

The ATSB is investigating an occurrence involving a Qantas A380 aircraft that experienced engine failure over Batam Island, Indonesia on 4 November 2010. The aircraft landed safely in Singapore having returned with the aircraft’s No 2 engine shut down. There were no injuries.

The ATSB has now issued a safety recommendation (AO-2010-089-SR-012) about potential engine problems in some Airbus A380 aircraft.

The safety recommendation identifies a potential manufacturing defect with an oil tube connection to the high-pressure (HP)/intermediate-pressure (IP) bearing structure of the Trent 900 engine installed in some A380 aircraft.

The problem relates to the potential for misaligned oil pipe counter-boring, which could lead to fatigue cracking, oil leakage and potential engine failure from an oil fire within the HP/IP bearing buffer space.

In response to the recommendation Rolls Royce, affected airlines and safety regulators are taking action to ensure the continued safe operation of A380 aircraft. The action involves the close inspection of affected engines and the removal from service of any engine which displays the suspected counter-boring problem.

 

 


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: http://www.atsb.gov.au/publications/investigation_reports/2008/aair/ao-2008-053.aspx


Study: Steady increase in Australian birdstrikes

June 30, 2010

A new report released by the Australian Transport Safety Bureau (ATSB) highlights ways to manage the risks posed by aircraft hitting birds and reveals that the reported number of  birdstrikes in Australia has steadily increased over the past eight years.

The report, which provides aviation birdstrike and animal strike occurrence data between January 2002 and December 2009, shows that in 2009 alone there were 1,340 birdstrikes reported to the ATSB.

The increase in the number of birdstrikes, however, is consistent with the increase in the number of high capacity aircraft movements over the period as well as a greater willingness of people in aviation to report safety occurrences to the ATSB.

Most birdstrikes occur within the confines of aerodromes (less than 5 km). Major and regional towered aerodromes had significantly higher rates of reported birdstrikes than General Aviation Airport Procedures (GAAP) aerodromes, and had considerably increasing rates from 2002 to 2009. GAAP aerodrome birdstrike rates do not appear to have changed.

Engine ingestion makes up 11 per cent of all birdstrike occurrences in high capacity air transport for the 8- year period, and the highest number of damaging birdstrikes occurs in high capacity air transport. Birdstrikes causing multiple parts damaged were not common throughout the period. General aviation had the highest proportion of damaging birdstrikes, with almost 24 per cent of birdstrikes causing damage. Aeroplane wings and helicopter rotor blades are the most commonly damaged aircraft components across all operational types, particularly in general aviation. There have been eight occurrences from the period of 2002-2009 that have resulted in serious aircraft damage, and four that have resulted in injury.

The most common types of birds struck by aircraft were lapwings/plovers, bats/flying foxes, galahs, and kites. Not surprisingly, larger birds were more likely to result in aircraft damage.

Animal strikes were relatively rare. High capacity air transport had the highest average with 11.5 animal strikes per year, with general aviation having the second highest average with 9.3 animal strikes per year. The most common animals involved in strikes were hares/rabbits, kangaroos, wallabies, and foxes/dogs. Damaging strikes mostly involved kangaroos, wallabies and livestock.

Bird hazard control at aerodromes was found to be mostly related to the control of grass height (short or long) and growing specific plants or grass, and the daily or weekly use or auditory deterrents, especially car horns and shotguns.


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