Mandatory Bulletins and Service Bulletins vs. ADs, Limitations, and TCDs

A current controversy over the scope of mandatory service bulletins has been caused by a decision of the NTSB involving the field overhaul of a Lycoming engine.


Here's what the Board said that raised so much fuss….

"While compliance with service instructions, or service bulletins may not be mandatory in the absence of an Airworthiness Directive, a manufacturer may legitimately incorporate such service publications into a manual by reference. The Lycoming overhaul manual incorporates all future service instructions by reference."

Thus the Board concludes (many fear) that this Part 91 mechanic must follow the mandate of all the Lycoming service instructions, service bulletins, and letters of instruction since they are included by reference in the manual. This is just not industry practice today nor is it FAA opinion and policy.

More importantly, since when can future unknown and unstated service bulletins be incorporated by reference into overhaul manuals? This statement by the Board is just a little off the wall in the opinion of this writer.

Many observers feel that the Board's language is in conflict with current rules and policy as described in the FAA's own opinions on the subject. The FAA's position on the subject has frequently and unequivocally been stated in the past. Some of its comments on the subject follow below. There is a fear that FAA inspectors and mechanics could misinterpret this decision to mean that mechanics have to comply with all manufacturers' service bulletins, instructions, and other repair operations referenced to their manuals. This is not the rule nor is it required by any FAR for Part 91 aircraft operations.

FAA Statements on the Subject

This subject is not something new and the Board should have discussed FAA's clear position on the matter, before deciding this case. The Board is in error in this writer's opinion based on current practice and opinion of the FAA.

For example, in a position statement in April 2001 the FAA Small Aircraft Directorate stated: "Mandatory service bulletins … are to be considered advisory only."

Earlier in April of 1987 they said: "Small airplane design approval holders cannot unilaterally impose mandatory compliance with manufacturer's service bulletins. A statement that bulletin compliance is mandatory must be FAA approved to be included in the Airworthiness Limitations Section of Instructions for Continued Airworthiness. FAA policy does not permit this approval to be delegated to organizations or individuals.

"FAA policy does not permit a predetermination that compliance with some future document is mandatory. Thus, service bulletins issued after the Airworthiness Limitations section is FAA-approved cannot be made mandatory without FAA involvement."

In February 2004 the Aircraft Maintenance Division cited FAR 91.403(c) as the controling rule for following manufacturer's maintenance recommendations …

"No person may operate an aircraft for which a manufacturer's maintenance manual or instructions for continued airworthiness has been issued that contains an airworthiness limitations section unless the mandatory replacement times, inspection intervals, and related procedures specified in that section or alternative inspections intervals and related procedures set forth in an operations specification approved by the Administrator under Part 121 or 135 of this chapter or in accordance with an inspection program approved under FAR 91.409(e) have been complied with." (Emphasis added.)

In addition, the FAA has stated that for most general aviation aircraft, mandatory retirement times or life limits are the only approved airworthiness limitations. Airworthiness limitations are found in few other places: Type Certificate Data Sheets, Instructions for Continued Airworthiness, and more commonly in ADs. If a limitation is placed against an aircraft, engine, propeller, or accessory in a Type Certificate Data Sheet or an AD, the limitation is mandatory under the law.

Consider for example, time between overhaul for piston engines. Manufacturers recommend specific times in service where they should be removed and overhauled. These times are not set out in the approved limitations section of their manuals and therefore are not mandatory. Likewise the same rule should apply to service bulletins unless they are set out in an AD.

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