15 July 1999
An SDR submitter reported cracking under the nutplates on the passenger seat bulkhead frame P/N 206-033-107-049. The cause was due to AN525 washer-head screws having been replaced by AN3 bolts and AN970 washers. The extra length of the unauthorized substitution meant that the bolt indented the frame, initiating the fatigue cracking.
If left uncorrected, the integrity of the frame is compromised and the damage spreads to surrounding structures. Cracks were also reported on the inner skin and these could migrate up to the frame.
This cracking can only be found after removal of the interior. Therefore, Transport Canada strongly recommends an immediate inspection for the proper use of AN525 washer-head screws. If an AN3 bolt is found instead, the removal of the interior and close inspection of the frame for cracking is required.
The following Bell Illustrated Parts Breakdowns refer:
For further information contact a Transport Canada Centre, or call Mr. Bogdan Gajewski, Continuing Airworthiness, Ottawa, telephone (613) 952-4450, facsimile (613) 996-9178 or e-mail firstname.lastname@example.org.
For Director, National Aircraft Certification
Chief, Continuing Airworthiness