At the time of the occurrence there was limited advisory material available to owners, operators and maintenance personnel to alert them to the possibility of MS21042 nut failure and to assist with appropriately detailed inspections aimed at identifying affected items.
Many civil aviation regulatory agencies and original equipment manufacturers have now produced and disseminated advisory material on this issue, providing appropriate background information and guidance on the identification of defective components.
On 12 October 2011, the Australian Civil Aviation Safety Authority (CASA) issued Airworthiness Bulletin 14-002, recommending that pilots and maintenance personnel closely monitor aircraft hardware (such as nuts) during installation and thereafter at pre-flight and periodic inspections. Any cracked MS21042 and related nuts were to be reported to CASA via their Service Difficulty Reporting (SDR) system.
On 20 September 2013, EASA issued Emergency Airworthiness Directive AD 2013-0225-E, to visually inspect for cracked MS21042L4 nuts on Agusta Westland helicopter tail rotor drive shafts before the next flight. Cracked nuts are to be replaced before the next flight and all MS21042 nuts on the drive shafts are to be replaced with a different part number within ten flight hours or 30 days. The AD applies to particular helicopter models and serial numbers.
On 3 October 2013, the FAA issued Airworthiness Directive AD 2013-20-51 to visually inspect for cracked MS21042L4 nuts on Agusta Westland helicopter tail rotor drive shafts before the next flight. Cracked nuts are to be replaced before the next flight. Within ten flight hours or 30 days, all such MS nuts on the drive shafts are to be replaced with a different part number. The AD applies to particular helicopter models and serial numbers.
The ATSB is satisfied that the actions taken by the above organisations will adequately address the safety issue.
On 2 December 2011, the New Zealand Civil Aviation Authority (CAA) issued Continuing Airworthiness Notice 14-001 requiring operators and maintainers to inspect all standard aircraft hardware, including MS 21042 nuts, after installation and thereafter at every daily/pre-flight inspection and every periodic inspection.
On 24 September 2013, Transport Canada issued Civil Aviation Safety Alert CASA 2013-04, advising the aviation community of the potential hazard resulting from the potential failure of MS21042 series nuts manufactured by Airfasco Industries (Canton, Ohio, USA).
