Service Directive Bulletins
A Service Directive Bulletin (SDB) is used to direct the owner/operator and/or maintenance personnel to make mandatory changes, improvements, or inspections to the aircraft.
The information provided in the Service Directive Bulletins will be incorporated into the maintenance manual as needed at a later date. At the time of incorporation, the SDB is superseded by the maintenance manual, and accomplishment or sign-off of the SDB in the maintenance records book is no longer required. A detailed entry should be made in the maintenance records to indicate that the SDB is superseded by the maintenance manual.
Enstrom Helicopter has Service Directive Bulletins for its piston and turbine models.