FYI

Neither the manufacturer, IAI, nor its product support division (Worthington Aviation) can mandate the compliance of any service bulletin regardless of its designation (either “optional”, “recommended” or “mandatory”) with these exceptions:
1. Service Letters or bulletins, which are incorporated into the current manufacturer’s maintenance manual and /or assure continuous airworthiness. Example: SB1124 -55-020, found in the 1124 AMM, 5-20-06.
2. Service Letters or bulletins which are referenced in current FAA Airworthiness Directives
3. Service Letters or bulletins which are incorporated as part of the type certificate data sheets for the aircraft, engines, etc. The classification of service data by manufacturers with words such as ”optional”,” recommended “or “ mandatory” Should be perceived only as a measure of importance placed on the publication for the operators benefit. Please note that Worthington Aviation does not utilize the “mandatory” classification on any service publications.

In summary, 1121, 1123, 1124 and 1124A operators are obligated by FAA regulations to comply with a manufacturers service publication only if it is presented in one of the above three categories