An FAA AD is considered mandatory
only for USA operators (enough abbreviations in that sentence?
). Similarly, an EASA AD is only mandatory for EASA operators.
However, it is pretty standard practice for other countries airworthiness agencies to automatically mandate EASA/FAA ADs for their own operators. Usually the only change might be an adjustment to the compliance dates.
Note that the airframer can't mandate anything - that needs to be done by the airworthiness authorities.
At Boeing, we had three levels of Service Bullitens - 'normal', unusually significant (I don't think that was the terminology we used but I don't recall the exact words), and "Alert". We pretty much assumed that any SB classified as "Alert" would result in an AD (painful lesson, as a DER/AR, I could normally approve normal and significant SBs without getting the FAA involved - but anything that would result in an AD I couldn't 'approve', I could only "Recommend Approve" - it then had to go to the FAA for final approval. First time I had an Alert SB, I didn't know that and went ahead and approved it. Got my hand slapped pretty hard by the FAA for that one - I protested that when I approved it, it
wasn't AD'ed, to which my FAA Advisory responded 'You should have known it would be AD'ed."
). Sadly, this meant that it took longer (roughly a month) to get an important Alert SB released to the field than it did for a routine SB.
BTW, years ago I saw some statistics on operator compliance with SBs - and it was shockingly low. I don't recall exact numbers but it was something like: Normal - ~50%, significant ~65%, Alert (the rare ones that didn't get AD'ed) ~80%, AD'ed, and most shockingly, those that were AD'ed were not much over 90%
. I think those numbers got somewhat better over the years (In the early days of ETOPS, I recall Boeing putting together a presentation to the operators stressing the importance of incorporating engine related SBs to avert engine shutdowns (pointing out just how much a shutdown and the associated diversion and AOG actually cost the operator, compared to a relatively inexpensive SB that would have prevented the shutdown) - prior to that there were a lot of major operators who simply ignored non-AD'ed engine bulletins, accepting the odd shutdown as just a part of doing business. But shockingly I don't AD compliance has ever made it to 100%. Perhaps in the western world, but there are always a few shady operators out there that find a well placed bribe to be cheaper than compliance.