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4 Is not substantial. Comply with §21.101. Develop the certification basis, per guidance in this order and AC-21-AA-2014-36. c. Samples of a design change that require a new TC are no longer listed in §21.19. These design changes are now evaluated case by case. d. §21.101 applies to all changes to type certificated products regardless of approval method: amended TC, STC, or amended STC, MDA or amended MDA. e. The certification basis can vary depending on the magnitude and scope of the change. See the tables in Appendix A of AC-21-AA-2014-36 for classifications of typical substantial, significant, and not significant design changes. Where the classification is not obvious for the proposed change, follow Paragraph

7 and Figure

1 of AC-21-AA-2014-36 to determine the appropriate certification basis for the changed product. f. A product level change is a change or combination of changes that makes the product distinct from the existing product (for example, range, payload, speed). Product level change is defined at the aircraft, aircraft engine, or propeller level and would result in an amended TC, STC, or amended STC, MDA or amended MDA. These changes typically, but not always, result in a model change that requires an amendment to the TC. However, a model change is not a prerequisite for a product level change. A system or component change can also rise to the product level. The product level change concept is directly related to the determination of significance, that is, the criteria used to determine significance. To assess if a change is significant, the applicant must consider the change and its effect on the overall aircraft, aircraft engine, or propeller at the product level. g. A significant change is a change to the type certificate to the extent that it changes one or more of the following: general configuration, principles of construction, or the assumptions used for certification, but not to the extent to be considered a substantial change. The significance of the change must be considered in the context of all previous relevant design changes and all related revisions to the applicable regulations. Not all changes or product level changes are significant. §21.101(b)

1 defines a significant change based on three automatic criteria: (1) Significant changes to the general configuration are changes likely to

5 require a new model designation to distinguish the product from other product models, for example, performance or interchangeability of major components. (2) Significant changes to the principles of construction are changes to the materials and/or construction methods that affect the overall product'

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