Does point 21.A.90C(c) imply that we may encounter non-ALS changes which can be minor with/without additional work to demonstrate compliance and major? Should a TCH process start with the identification of the affected requirements, to determine, for non-ALS ICA changes, if they can take benefit of point 21.A.90C(c)?
Answer
In general, type certificate changes can be minor without showing of compliance, minor with showing of compliance and major.
For non-ALS ICA changes, the GM1 21.A.90C is proposing a different perspective on how the stand-alone changes have to be considered:
'[...] Stand-alone changes are usually straightforward changes, and are not considered to require additional work in order to show compliance. However, they must be managed in accordance with a process accepted by EASA under point 21.A.239 or point 21.A.14(b), for discharging the obligation to keep the ICA up to date and to cover aspects like preparation/verification/release in accordance with their respective AMC/GM material.
Examples of changes that may require additional activities in order to show compliance are changes to the CDCCL, and EWIS ICA.'
Also, App. A to GM 21.A.91, section 10, is listing cases where compliance needs to be demonstrated (in this respect, the section contains examples of major changes).
The TCH process may document this kind of approach - i.e. a list of examples of stand-alone changes which require additional compliance demonstration as either major or minor. When a change is within the list, a classification on airworthiness criteria should be performed (with the identification of applicable requirements).