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After reading both AD's it seems clear enough that the new AD only applies to those Lycoming 540 models listed and that our Continental 360's no longer require inspection. The AD goes on to say that compliance with SB643b and MSB645 is still highly recommended. Which then begs the questions: What service life is actually being experienced with our engine/mag combination and is there a significant difference between the riveted and snap ring couplings? From those operators who have inspected their mags since the '96 AD, what percentage have failed the 645 tolerences? SB643 goes on to say that all mags, regardless of application, must be replaced or overhauled every five years regardless of hours in service, which I suspect nearly no Part 91 operator is complying with. Its hard to know if this is a real problem or a Continental CYA bulletin. Obviously the FAA must have felt the 500 hr. interval was overkill for engine/mag combinations other than the Lyc. 540 to have recinded the applicability yet they say they expect that all operators will voluntarily comply with the manufacturer's SB. I'd be interested to hear about any real world in service experience anyone else can share.
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