Incorporation by Reference means that a separate document is approved for Airworthiness Directive (AD) Incorporation by Reference by the Director of the Federal Register. The legal effect of Incorporation by Reference is that the material is treated as if it were published in full in the Federal Register (5 U.S.C. 552(a)).

Incorporation by Reference was established by statute and allows Federal agencies to meet the requirement to publish regulations in the Federal Register by referring to materials already published elsewhere. For an incorporation to be valid, the Director of the Federal Register must approve it.

What is a proper Incorporation by Reference?
The Director of the Federal Register will approve an "Incorporation by Reference" only when the requirements of 1 CFR part 51 are met.  Some of the elements on which approval is based are:

• The incorporation will substantially reduce the volume of material published in the Federal Register.
• The matter incorporated is in fact available to the extent necessary to afford fairness and uniformity in the administrative process.
• The incorporating document is drafted and submitted for publication in accordance with 1 CFR part 51.

When is Incorporation by Reference used?
The term "Incorporation by Reference" is used when it is recognized that referring to a service bulletin or other supplemental document in an AD may require that document to be "published" with the rule.  Publication is required if the AD mandates a method of compliance that is contained only in the supplemental material.

Reference material may include a manufacturer's service bulletin or repair manual, with which compliance is required as part of the AD.  If an AD states that a repair, modification, inspection, or other procedure must be accomplished in accordance with a specific service bulletin, the service bulletin instructions must either be included in the AD language (in which case it becomes part of the AD), or submitted for approval as referenced material.