EASA Investigates Cracking Standard Hardware

The European Aviation Safety Agency (EASA) has published a bulletin concerning defective hardware, known as EASA Safety Information Bulletin No. 2012-06.

The bulletin concerns defective standard hardware identified as

  • MS21042 Self-Locking Nuts
  • NAS1291 Self-Locking Nuts
  • LN9338 Self-Locking Nuts, and
  • NAS626 Bolts

EASA explains that they have received reports of defective standard hardware installed on aircraft.

In particular, many self-locking nuts have been found cracked, parallel to the nut axis, in some instances only a short time after installation. Broken bolts have also been found.

Certain countries have already issued ADs in relation to this issue.  In 2010, Israel issued an AD that applied to the Israel Aircraft Industries Models GALAXY and Gulfstream 200 because cracked nuts were found in the aircraft production line.  In October 2011 CASA (Australia) issued an Airworthiness Bulletin concerning nuts that had been identified as compromised as a consequence of hydrogen embrittlement which appeared to have been caused by improper heat treatment.

EASA has explained that their investigation is ongoing, and insufficient evidence is currently available to determine whether an unsafe condition exists that would warrant the issuance of an Airworthiness Directive.  EASA will continue to investigate the reported occurrences to determine whether (and if so, what) further action is necessary.  An EASA source revealed to us that the investigation has revealed “several issues with the suppliers of this hardware, such as CoC not matching the supplied batch, CoC not identifying the manufacturer, hardware supplied with obvious damage.”

While the investigation is pending, EASA has recommended that those who use parts meeting the standards described above to perform a close visual inspection for surface irregularities, such as gouges or cracks, of all such parts before being installed on a product.

EASA has asked that suspect parts be quarantined until conformity to the manufacturing standard can be verified.  They have also asked that suspect parts be reported to the appropriate government body (e.g. UK-CAA in the United Kingdom, FAA in the United States, etc.).


About Jason Dickstein
Mr. Dickstein is the President of the Washington Aviation Group, a Washington, DC-based aviation law firm. He represents several aviation trade associations, including the Aviation Suppliers Association, the Aircraft Electronics Association, the Aircraft Fleet Recycling Association and the Modification and Replacement Parts Association.

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