Service Bulletin (SB)

Service Bulletin – a technical document issued by the manufacturer (type certificate holder) of an aircraft or by a Part 21 design organization. An SB contains information on how to modify an aircraft or aircraft maintenance schedule. The modification can be safety related, but it may also be for the purpose of fixing a known, but not safety related problem or simply to satisfy the need of an airline to make a modification to their fleet (such as change of livery). A service bulletin is not mandatory. Those SBs which are safety related are often called up by an airworthiness directive, therefore becoming mandatory for a given fleet