If a manufacturer wants an owner to do something with his aircraft, the FAA has to approve it -- that's the bottom line, AOPA said on Monday. A manufacturer's Service Bulletin doesn't carry the same weight as an Airworthiness Directive, which has gone through a complex, public rulemaking procedure. AOPA has always held that position, but sought clarification recently after an NTSB judge issued a ruling a couple of months ago that clouded the issue. Now, the FAA says AOPA is right. FAA Assistant Chief Counsel for Regulations Rebecca MacPherson issued an interpretation of the regulations to answer a question raised by Cessna Pilot Association's Mike Busch almost a year ago. MacPherson said that if manufacturers could make SBs mandatory, it would, "effectively authorize manufacturers to issue 'substantive rules,' as that term is used in the Administrative Procedures Act." But only the FAA has that authority. For most of the aircraft flown by AOPA members in noncommercial operations, all you have to do is comply with the FAA's regulations and any applicable airworthiness directives (ADs), AOPA said. But complying with an SB still might be a good idea -- check with your mechanic. SBs sometimes become mandatory ADs after they've gone through the rulemaking process. And, if your aircraft is used in commercial operations, you probably do have to comply with SBs. Also, AOPA said, for newer aircraft certificated under Part 23 (rather than CAR 3), SBs can be made mandatory if approved by the FAA and incorporated into the airworthiness limitations section of the aircraft's maintenance manual or instructions for continued airworthiness.