As I understand the regulations the aircraft has to be maintained IAW the aircraft maintenance manual.this is the starting point and AD's are in addition to the MM requirements.
Not necessarily correct; on N-reg the only mandatory maintenance is
- ADs
- lifed items listed in the Airworthiness section of the aircraft MM (which includes the Annual, etc)
Everything else can be done "on condition".
That is how Part 91 maintenance has been operated in the US GA fleet which is far bigger than all the rest of GA put together, and their safety record is the best.
Aircraft MMs have subsequently been written with that in mind i.e. most of what is in them are recommendations.
Unfortunately JAA and then EASA came along and decided to take the MM literally. Very good for revenue generation!