Which statement correctly distinguishes Airworthiness Directives from Service Bulletins?

Which statement correctly distinguishes Airworthiness Directives from Service Bulletins?

• A. ADs are manufacturer-issued and optional; SBs are FAA-issued and mandatory
• B. ADs are FAA-issued and mandatory; SBs are manufacturer-issued and not mandatory but recommended
• C. ADs are issued by NTSB; SBs are optional
• D. ADs and SBs are the same

Answer: (B)

Airworthiness Directives target an identified unsafe condition and carry legal force. They are issued by the FAA and must be complied with by a specified deadline, applying to affected aircraft, engines, or parts. Service Bulletins, on the other hand, are issued by the manufacturer as recommended maintenance actions to address issues. They are not mandatory by themselves; compliance becomes required only if the FAA adopts the bulletin into an AD or otherwise mandates it through regulation. For example, an AD might require an inspection and possible repair within a set number of flight hours, while a Service Bulletin might advise performing a routine inspection or modification but isn’t enforceable unless tied to an AD. The other options misstate who issues ADs and SBs or treat them as the same.

Airworthiness Directives target an identified unsafe condition and carry legal force. They are issued by the FAA and must be complied with by a specified deadline, applying to affected aircraft, engines, or parts. Service Bulletins, on the other hand, are issued by the manufacturer as recommended maintenance actions to address issues. They are not mandatory by themselves; compliance becomes required only if the FAA adopts the bulletin into an AD or otherwise mandates it through regulation. For example, an AD might require an inspection and possible repair within a set number of flight hours, while a Service Bulletin might advise performing a routine inspection or modification but isn’t enforceable unless tied to an AD. The other options misstate who issues ADs and SBs or treat them as the same.