Page 65 - UK Regulation Part 21 Initial Airworthiness Annex I (consolidated) March 2022

PART 21 - INITIAL AIRWORTHINESS (ANNEX I)

21.A.101 APPD to GM Appendix D to GM 21.A.101 Other guidance for affected areas
D.1 Sample Questions in Determining Affected Areas.
Below are sample questions to assist in determining whether an area is affected by the
change. If the answer to any of these questions is yes, then the area is considered to be
affected.
1. Is the area changed from the identified baseline product?
2. Is the area impacted by a significant product-level change?
3. Is there a functional effect on the unchanged area by a change to the system or
system function that it is a part of?
4. Does the unchanged area need to comply with a system or product-level
certification specification that is part of the change?
5. Are the product-level characteristics affected by the change?
6. Is the existing compliance for the area invalidated?
D.2 Sub-Areas within an Affected Area.
Within areas affected by a change, there may be ‘subareas’ of the area that are not
affected. For those subareas, the amendment levels at the existing certification basis
remain valid, along with the previous compliance findings. For example, if a passenger
seat fitting is changed as part of a significant change, then the structure of the seat is
affected. Thus, the amendment level for CS 25.561 and CS 25.562, along with other
applicable structural certification specifications, would be at the amendment level on the
date of application (unless an exception is granted). However, the seat fabric is not
affected, so the amendment level for CS 25.853 (flammability) may remain at the existing
certification basis, and a new compliance finding would not be required.
21.A.101 APPE to GM Appendix E to GM 21.A.101 Procedure for evaluating material contribution to safety or impracticality of
applying latest certification specifications to a changed product
E.1 Introduction.
E.1.1 The basic principle of enhancing the level of safety of changed aeronautical
products is to apply the latest certification specifications for significant changes to
the greatest extent practical. In certain cases, the cost of complying fully with a later
certification specification may not be commensurate with the small safety benefit
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