Aviation glossary · Continuing airworthinessWhat is SB?
Service Bulletin
A notice from the manufacturer describing a modification, inspection or repair. Unlike a directive it is not mandatory by itself, though an authority can make one mandatory by issuing a directive that references it.
Why it matters
Bulletins accumulate quietly. Whether a given one was embodied, and on which serial number, is a question that surfaces years later during a sale or a lease return.
In AerSynx
Embodiment is recorded against the aircraft or component with the evidence attached, so the answer is in the record rather than in somebody's recollection. Technical Records →