![]() The investigation noted that in the weeks prior to the accident the maintenance company was experiencing a period of very high workload that likely exceeded the workforce’s capability and reduced the chief engineer's capacity to oversight maintenance activities. “Maintenance organisations are urged to consider the human factors elements associated with their practices, capture them in their documented quality control procedures, and ensure they are complied with.” “This investigation highlights the limitations of verbal communication as a method of explaining and understanding problems and their unreliability as a means for capturing essential tasks over an extended time period,” Dr Godley said. Instead, it had adopted a number of work practices that increased the risk of memory-related errors and omissions, including using abbreviated inspection checklists, not recording all flight control disturbances, and not progressively certifying for every inspection item as the work was completed. The investigation also found that the maintenance organisation had not recorded and tracked all maintenance activities for the overhaul as the work progressed over a period of almost four months. “Different scenarios were examined for the cause of the bolt separation however, as it was not possible for the helicopter to operate for any length of time without a nut attached to the bolt, it was likely that the nut was not reinstalled or inadequately torqued during the helicopter’s recent 2,200-hour overhaul,” Dr Godley said. After re-examining the helicopter wreckage, the bellcrank and a bolt, later confirmed to be from the missing fastener, were recovered from the wreckage site and examined by the ATSB.ĪTSB Director Transport Safety Dr Stuart Godley said the separation of the bolt would have resulted in the main rotor disc tilting back beyond its normal operating limits and striking the tailcone. The ATSB’s investigation subsequently identified that a fastener – a bolt and self-locking nut – which connected the helicopter’s cyclic assembly’s horizontal push-pull tube to a bellcrank, was missing. The wreckage of the R22 was subsequently located about 7 km to the north-north-west of the airport. About fourteen minutes after take-off witnesses observed a plume of smoke in the general direction of the helicopter’s path. The R22 had departed Cloncurry Airport, north-west Queensland, on 2 August 2017, on a ferry flight to reposition for aerial mustering after having undergone a major overhaul.
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