Differences in the traffic alert phraseology between the Manual of Air Traffic Services and Aeronautical Information Publication increased the risk of non-standard advice being provided by the controller to the pilot of the G-IV during the compromised separation recovery.
The aircraft's centre of gravity varied significantly with hopper weight and could exceed both the forward and aft limits at different times during a flight.
The Auto Release procedures at Melbourne Airport allowed for aircraft to be departed at or close to the separation minima, with no controls in place to ensure aircraft would maintain a minimum speed and flight crews would advise air traffic control if the speed could not be achieved.
A significant number of R44 helicopters, including VH-HFH, were not fitted with bladder-type fuel tanks and the other modifications detailed in the manufacturer's service bulletin 78 that were designed to provide improved resistance to post-impact fuel leaks.
A number of self-locking nuts from other aircraft, of the same specification as that used to secure safety-critical fasteners in VH-HFH, were identified to have cracked due to hydrogen embrittlement.
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.
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.
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.
An important alerting function within the Australian Defence Air Traffic System had been disabled at Williamtown to prevent nuisance alerts.
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.
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 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 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 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 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 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.
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.
For the data-spike failure mode, the built-in test equipment of the LTN 101 air data inertial reference unit was not effective, for air data parameters, in detecting the problem, communicating appropriate fault information, and flagging affected data as invalid.
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.
