14 CFR §21.319

1. (a)Classification of design changes.
   1. (1)A “minor change” to the design of an article produced under a PMA is one that has no appreciable effect on the approval basis.
   2. (2)A “major change” to the design of an article produced under a PMA is any change that is not minor.
2. (b)Approval of design changes.
   1. (1)Minor changes to the basic design of a PMA may be approved using a method acceptable to the FAA.
   2. (2)The PMA holder must obtain FAA approval of any major change before including it in the design of an article produced under a PMA.