The step-by-step, “how-to” instructions for accomplishing maintenance, preventive maintenance, and alterations. These instructions are considered “acceptable to the Administrator” if the certificate holder shows that the instructions will return the aircraft, engine, or other article to its original or properly altered condition. (Reference sections 21.50(b), and 43.13(a).)
AC 120-77
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METHODS, TECHNIQUES, AND PRACTICES VERSUS TECHNICAL DATA.
a. The terms “methods, techniques, and practices” and “technical data” have often been confused. While the concepts are related, each has a distinct meaning in 14 CFR.
(1) The methods, techniques, and practices referenced in section 43.13(a) are the step-by-step instructions for performing maintenance (including inspections), preventive maintenance, and alterations. These “how-to” instructions are normally contained in manufacturers’ maintenance manuals and other service documents, and are usually based on approved technical data developed by the approval holder.
(2) Technical data consists primarily of engineering information. It includes drawings and specifications that define the configuration and design characteristics of an article, and information on materials, dimensions, and processes necessary to define structural strength. Substantiating data is technical data used to establish that the aircraft or other article, if repaired or altered using the instructions that the substantiating data supports, would be returned to its original or properly altered condition in accordance with section 43.13(b). The operator is responsible for showing that any substantiating data is directly related to the change that is being evaluated. This is especially important when it is necessary to substantiate a change using service experience, maintenance and alteration experience, and reliability data. Accordingly, the technical data, when substantiated, is considered acceptable to the Administrator even in cases when it does not require the FAA’s explicit approval.
b. Maintenance manuals and/or restoration/overhaul manuals may contain technical data. For example, if the manual specifies the required materials, dimensions, or other design information, this represents technical data.
c. An allowable damage limit in an SRM represents an acceptable method for accomplishing a repair or authorizing a continue-in-service condition. The TC holder’s damage “limit” is based on approved substantiating data—i.e., an engineering analysis showing that even with such damage, the airplane would then still meet the appropriate airworthiness standards. In many cases a higher limit can also be shown to comply with those standards.