Originally Posted by
GlobalNav
The new wiring rules may have been part of amendments that were issued after the NG certification, but prior to the application date of the MAX.
My understanding was the same bundles were used on the MAX as the NG. No changes. Since they didn't change the wiring there was no reason to treat it as a new part of the deign. The point of grandfathering is that unchanged items stay unchanged. So as far a Boeing was concerned it didn't need to be evaluated under new rules. There are 100s (1000s?) of places on the NG and the MAX that wouldn't have meet the changed rules at the time of certification but were allowed because is wasn't a new part of the design.
Now the FAA is retroactively deciding that the old grandfathering rules don't apply to a certain case (the wire separation) and wants to make that unchanged item meet the new standards.