If a person holds the TC for a product and alters that product by introducing a major change in type design that does not require an application for a new TC under § 21.19, that person must apply to the FAA either for an STC, or to amend the original type certificate under subpart D of this part.
If a person does not hold the TC for a product and alters that product by introducing a major change in type design that does not require an application for a new TC under § 21.19, that person must apply to the FAA for an STC.
The application for an STC must be made in the form and manner prescribed by the FAA.