Which statement is true about the enforceability of Service Bulletins (SB) relative to rules or Airworthiness Directives (AD)?

Which statement is true about the enforceability of Service Bulletins (SB) relative to rules or Airworthiness Directives (AD)?

• A. A Service Bulletin is always mandatory.
• B. A Service Bulletin never becomes mandatory.
• C. A Service Bulletin becomes mandatory if adopted by rule or AD.
• D. An AD is always optional.

Answer: (C)

Service Bulletins are notices from the manufacturer describing recommended inspections or fixes. They aren’t legally enforceable by themselves. The only time a Service Bulletin becomes mandatory is if the aviation authority adopts it into a rule or issues an Airworthiness Directive that requires the actions described in the bulletin. An Airworthiness Directive is a legally enforceable rule with a specified compliance time, so following the SB becomes mandatory only in that regulatory context. That’s why the statement about mandatory status when adopted by rule or AD is the correct one. If no AD or rule references the SB, it remains a recommendation rather than a legal requirement.

Service Bulletins are notices from the manufacturer describing recommended inspections or fixes. They aren’t legally enforceable by themselves. The only time a Service Bulletin becomes mandatory is if the aviation authority adopts it into a rule or issues an Airworthiness Directive that requires the actions described in the bulletin. An Airworthiness Directive is a legally enforceable rule with a specified compliance time, so following the SB becomes mandatory only in that regulatory context. That’s why the statement about mandatory status when adopted by rule or AD is the correct one. If no AD or rule references the SB, it remains a recommendation rather than a legal requirement.