FAQ n.19433

Can an applicant use FAA’s AC 25-27A, notably Appendix B for the handling of design changes?


The FAA has published a new issue of the AC 25-27 (rev.A) on the development of EWIS ICA using the EZAP analysis. The revised AC intends, among others, to provide more clarity for applicants seeking approval of a design change when one has no access to the TC holder’s EZAP analyses. It means the availability of TC holder’s EWIS ICA is sufficient for the STC applicants to assess/develop EWIS ICA for their change. EASA recognises the use of this AC as an acceptable method of compliance for the assessment of design changes.

The Appendix B in the AC 25-27A contains new flowcharts, leading through the process of determining EWIS ICA step by step. First, the applicant must determine if revised or new EWIS ICA are potentially necessary. If this is the case, the applicant has two ways to continue in the flowchart, depending whether the TC holder’s EZAP analysis in the affected zone is available to him or not. Detailed questions in the flowchart help the applicant in the creation of tasks specific to the design change. 
The STC applicant has always to make sure he has the latest (current) TC holder’s EWIS ICA for the affected zone.

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