This would depend on what is written in your approved maintenance system manual (42M). If you have provision to adhere to manufacturers mandatory bulletins, you must comply.
I cannot see anything specific in the regs (1988 or 1998) that refers to this requirement if CASA have not issued an AD.
However, what date was the manufacturers mandatory bulletin issued? An AD may be still in formulation in Canberra, just not issued yet if it is a recent issue.
As a licensed engineer, I would bring it to the attention of your QA people per your approved maint system and let them take it up with CASA. It would not be the first time that CASA have missed something!
Please note, generally, CASA deem any Mandatory manufacturers SB as a Mandatory requirement under CASA. I just cannot find the reference to it yet!
------------------
When all else fails, read the manual!
[This message has been edited by Mice (edited 16 June 2000).]