Which statement explains when a Service Bulletin becomes part of continuing airworthiness?

• A. A Service Bulletin is always voluntary and never mandatory.
• B. A Service Bulletin applies only to new aircraft.
• C. A Service Bulletin becomes part of continuing airworthiness actions when mandated by the manufacturer or regulator.
• D. A Service Bulletin replaces Airworthiness Directives.

Answer: (C)

Service Bulletins are notices from the manufacturer describing recommended inspections, modifications, or corrective actions to address safety concerns. They become part of continuing airworthiness when the regulator or the manufacturer mandates them as required actions. In practice, many SBs are voluntary, but they become enforceable once authorities or the OEM designate them as mandatory, such as by incorporating the SB into an Airworthiness Directive. They can apply to existing aircraft, not just new ones, and they do not replace Airworthiness Directives; an AD may require follow-on actions that align with an SB.