SB643B-Bendix mags *mandatory* overhaul every 4 years now?

I was recently talking with my A&P/IA friend about my upcoming annual on my PA-28-180. He said
that there's some particularly disturbing news regarding manufacturer's service bulletins that can
*require* compliance even for Part 91 operators.

The one that brought is up is SB643B from TCM regarding Bendix mags. Basically, it's a the
normal 100-hour inspections, impulse coupling inspections, etc. The kicker is that it also says mags
must be overhauled every 5 years from previous overhaul, or 4 years from the date put in service.

Normally, a Part 91 guy would say, "Service Bulletins aren't mandatory, so I don't need to do
it." TCM added the magic phrase at the beginning of the SB which says: "The following information
constitutes the manufacturer's Instructions for Continued Airworthiness..." Those magic words appear to
make it a mandatory legal requirement as per the FARs.

Has anyone run into this already? The mandatory 4-year overhaul of mags seem excessive for most
owners. The precidence it sets essentially allows a manufacturer to issue an "AD" without oversight by
the FAA and public comments, etc.

-Cory

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* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
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