14 CFR § 21.319 - Design changes.

(a) Classification of design changes.

(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) A “major change” to the design of an article produced under a PMA is any change that is not minor.

(b) Approval of design changes.

(1) Minor changes to the basic design of a PMA may be approved using a method acceptable to the FAA.

(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.