For TC holders for the affected aeroplanes, EWIS ICA requirements are applicable to any changes to TC.
For STC applicants for the affected aeroplanes, due to the nature of the tool used (Special Conditions levied on STC applications received), applicability of EWIS ICA requirements will be limited to new STCs or major changes to STCs. This is applicable to the transition period until the TCDS of the affected aeroplane is updated.
It also means for an STC applicant, that when the SC regarding EWIS ICA is in the TCDS, all changes (major/minor) need review on necessity of revision of EWIS ICA.
(see also Question “Will we need to amend the TC basis for each type to include this CS-25 requirement and publish in amended TCDSs?” which gives further guidance on the TCDS.