Thorp Air Command - T18.net

Transport Canada has issued a Civil Aviation Alert for:
DEFECTIVE STANDARD AIRCRAFT HARDWARE - SELF-LOCKING NUTS - MS21042
Nuts manufactured by Airfasco Industries (Canton, Ohio, USA).

Analysis of the failed nuts was conducted and it was determined that the nuts failed due to hydrogen embrittlement. This condition was likely introduced during the manufacturing process.
The defective nuts originated from Airfasco lots 17147 and 17559 for MS21042-4 nuts and lot 18621 for MS21042-06 nuts.

http://www.tc.gc.ca/media/documents/ca- ... 013-04.pdf

The photo's inside the document show failure on the nuts on the side where stamping identification occurred. I received this information thru 245 Ottawa EAA chapter, FYI.

_________________
Victor J Thompson
C-GIRQ
In memory of Dad

It is interesting a week ago we where discussing self locking nuts and quality control.

The lots are specific and from a USA supplier which may not affect your aircraft however, I put it out there for your information.

Cheers.

_________________
Victor J Thompson
C-GIRQ
In memory of Dad

Embrittlement, sadly enough, anything that is plated is probably acid dipped before the plating process to remove scale and such, it is in this acid dipping process that the Embrittlement occurs. These fractures are so small they most generally cannot be detected with the eye, the surface of the material can be fractured profusely and not be seen. This same acid cleaning is also used sometimes where powder coat is going to be used and sometimes surfaces to be anodized are cleaned this way. It is the fastest way to get the surfaces clean but when left in the acid or caustic too long then Embrittlement most generally will occur. When we have something coated(engine mounts,windscreen frames,canopy frames, landing gear and such) we need to be aware that this can happen without being easily detected. You would think something a critical as Aviation grade hardware would be processed with a very high degree of quality control and process management, but this now is a world of profits,cheaper process and production so quality can suffer. Been in Manufacturing for 38 years, I have seen this happen in every way shape and form, heads up everybody, keep a close eye on your components and goodies purchased for your Bird, Slick pulled a stunt like this not long ago and suffered massive failures, but did manage to get their parts cheaper.....Dan