Which statement about Service Bulletins (SBs) is true?

• A. SBs are legally mandatory actions.
• B. SBs are manufacturer recommendations that are not legally mandatory unless adopted.
• C. SBs apply only to engines.
• D. SBs are issued by aviation authorities.

Answer: (B)

Service Bulletins are notices issued by manufacturers to recommend actions addressing a potential safety issue. They are not laws by themselves; they become legally mandatory only if a regulator adopts them into an Airworthiness Directive or requires compliance through operator programs. SBs can cover a wide range of components, not just engines, and they are issued by manufacturers, not aviation authorities. That’s why the true statement is that SBs are manufacturer recommendations that are not legally mandatory unless adopted by the appropriate authority. When an authority adopts an SB into an AD, then compliance becomes mandatory.