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Awareness of the potential for nut failure

Issue number: AO-2011-135-SI-02
Who it affects: All owners and operators of aircraft using MS21042 and related nuts
Issue owner: Manufacturers of aircraft using MS21042 and related nuts, and relevant regulatory agencies
Operation affected: Aviation: Air transport
Background: Investigation Report AO-2011-135
Date: 22 January 2014

Safety issue description

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.

Proactive Action

Action organisation: Australian Civil Aviation Safety Authority
Date: 22 January 2014
Action status: Closed

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.

Proactive Action

Action organisation: New Zealand Civil Aviation Authority
Date: 22 January 2014
Action status: Closed

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.

Proactive Action

Action organisation: Transport Canada
Date: 22 January 2014
Action status: Closed

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).

Proactive Action

Action organisation: European Aviation Safety Agency
Date: 22 January 2014
Action status: Closed

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.

Proactive Action

Action organisation: Federal Aviation Administration U.S.A.
Date: 22 January 2014
Action status: Closed

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.

ATSB response:

The ATSB is satisfied that the actions taken by the above organisations will adequately address the safety issue.

   
Current issue status: Adequately addressed
Status justification:

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.

 
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Last update 22 January 2014