EASA SIB 2012-06R2
Defective Standard Hardware — MS21042, NAS1291 and LN9338 Self-Locking Nuts, and NAS626 Bolts
Summary
EASA Safety Information Bulletin 2012-06R2 addresses defective standard hardware, specifically MS21042, NAS1291, and LN9338 self-locking nuts, as well as NAS626 bolts. These defective parts have been installed on various rotorcraft, aeroplanes, appliances, and engines, including Gulfstream 200, GALAXY (Israel Aircraft Industries), and AgustaWestland A109 helicopters. The bulletin provides information on reported occurrences of cracked nuts and broken bolts and highlights ongoing investigations by EASA and other aviation authorities.
What Changed
This revision 2 of EASA SIB 2012-06 includes references to additional relevant documents such as Transport Canada CASA-2013-04 and updates information regarding defective nuts manufactured by Airfasco. It expands the scope to note that other lots and manufacturers might be affected beyond those initially identified. The bulletin also incorporates findings from various investigations and service bulletins from multiple manufacturers.
Why It Matters
The bulletin is important for aviation professionals because defective self-locking nuts and bolts can compromise the structural integrity and safety of aircraft components. Operators, maintenance organizations, and manufacturers need to be aware of potential hardware failures to prevent in-service incidents. Early detection and proper inspection protocols help maintain airworthiness and compliance with safety standards.
What To Do
Stakeholders are recommended to visually inspect the affected hardware for surface irregularities such as cracks or gouges before installation. Incoming lots of self-locking nuts should undergo a torque check by applying specified torque values for one week and then be inspected for cracks. Suspect parts must be quarantined until conformity to manufacturing standards is confirmed. Occurrences of cracked nuts or bolts should be reported through established channels and to EASA's Occurrence Reporting System.