LP turbine support bearings (part numbers LK30313 and UL29651) showed increased susceptibility to breakdown and collapse under vibratory stress conditions associated with LP turbine blade release.
High service time stage-2 LP turbine blades were susceptible to a reduction in fatigue endurance as a result of vibratory stresses sustained during operation at speeds close to the maximum.
The Australian Transport Safety Bureau encourages all operators and owners of R44 helicopters that are fitted with all-aluminium fuel tanks to note the circumstances of this accident as detailed in this preliminary report. It is suggested that those operators and owners actively consider replacing these tanks with bladder-type fuel tanks as detailed in the manufacturer's Service Bulletin (SB) 78A as soon as possible.
The Williamtown air traffic control procedures did not clearly define the separation responsibilities and coordination requirements between the Approach sectors for departing aircraft.
The Department of Defence’s air traffic controllers had not received training in compromised separation recovery techniques.
An important alerting function within the Australian Defence Air Traffic System had been disabled at Williamtown to prevent nuisance alerts.
The aircraft operator’s flight crews were probably not adequately equipped to manage the vertical profile of non-precision approaches in other than autopilot managed mode.
The operators recurrent simulator training did not address the recovery from a stall or stick shaker activation such that the ongoing competency of their flight crew was not assured.
The operators procedures did not include a validation check of the landing weight generated by the flight management system which resulted in lack of assurance that the approach and landing speeds were valid.
The operator's procedure for confirming the validity of the flight management system generated take-off weight did not place sufficient emphasis on the check against the load sheet.
The presentation on the aircraft load sheet of the zero fuel weight immediately below the operating weight, increased the risk of selecting the inapropriate figure for flight management system data entry.
The available Cross Crew Qualification and Mixed Fleet Flying guidance did not address how flight crew might form an expectation, or conduct a ‘reasonableness' check, of the speed/weight relationship for their aircraft during takeoff.
When developing the A330/A340 flight control primary computer software in the early 1990s, the aircraft manufacturer’s system safety assessment and other development processes did not fully consider the potential effects of frequent spikes in the data from an air data inertial reference unit.
The LTN-101 air data inertial reference unit (ADIRU) model had a demonstrated susceptibility to single event effects (SEE). The consideration of SEE during the design process was consistent with industry practice at the time the unit was developed, and the overall fault rates of the ADIRU were within the relevant design objectives.
Although passengers are routinely reminded to keep their seat belts fastened during flight whenever they are seated, a significant number of passengers have not followed this advice. At the time of the first in-flight upset, more than 60 of the 303 passengers were seated without their seat belts fastened.
There has been very little research conducted into the factors influencing passengers’ use of seat belts when the seat-belt sign is not illuminated, and the effectiveness of different techniques to increase the use of seat belts.
Industry practices for tracking faults or performance problems with line-replaceable units are limited, unless the units are removed for examination. Consequently, the manufacturers of aircraft equipment have incomplete information for identifying patterns or trends that can be used to improve the safety, availability or reliability of the units.
There was a limitation in the algorithm used by the A330/A340 flight control primary computers (FCPCs) for processing angle of attack (AOA) data. This limitation meant that, in a very specific situation, multiple spikes in AOA from only one of the three ADIRUs could result in a nose-down elevator command.
In recent years there have been developments in guidance materials for system development processes and research into new approaches for system safety assessments. However, there has been limited research that has systematically evaluated how design engineers and safety analysts conduct their evaluations of systems, and how the design of their tasks, tools, training and guidance material can be improved so that the likelihood of design errors is minimised.
One of the aircraft’s three air data inertial reference units (ADIRU 1) exhibited a data-spike failure mode, during which it transmitted a significant amount of incorrect data on air data parameters to other aircraft systems, without flagging that this data was invalid. The invalid data included frequent spikes in angle of attack data. Including the 7 October 2008 occurrence, there have been three occurrences of the same failure mode on LTN-101 ADIRUs, all on A330 aircraft.
