When is compliance with a manufacturer's service bulletin considered mandatory?

Compliance with a manufacturer's service bulletin is considered mandatory when it is incorporated into an Airworthiness Directive (AD). An AD is a legally enforceable regulation issued by the FAA that requires the owner or operator of an aircraft to take specific actions to correct an unsafe condition. When a service bulletin is referenced in an AD, it signifies that the FAA has determined that the information or instructions in the bulletin address a safety issue that must be rectified to ensure continued airworthiness of the aircraft. As such, non-compliance with an AD can lead to serious repercussions, including penalties and potential safety risks, making adherence to these directives crucial for maintaining fleet safety and regulatory compliance.

The other scenarios do not establish a mandatory requirement, as simply a request from an aircraft owner or technician’s personal judgment do not have the same regulatory weight as an AD. Similarly, while the FAA does issue directives that can alter compliance requirements, it is the specific incorporation of the bulletin into an AD that elevates its status to mandatory.