14 CFR 21.113 : Aeronautics And Space (§ 1.1 To Parts 1311-1399) — (§ 1.1 To Parts 50-59) — Federal Aviation Administration, Department Of Transportation (§ 1.1 To Parts 50-59) — Aircraft (§ 21.1 To Parts 50-59) — Certification Procedures For Products And Articles (§ 21.1 To § 21.700) — Supplemental Type Certificates (§ 21.111 To § 21.120) — Requirement for supplemental type certificate.

(a) 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 either apply to the appropriate aircraft certification office for an STC or apply to amend the original type certificate under subpart D of this part.

(b) 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 appropriate aircraft certification office for an STC.

(c) The application for an STC must be made in the form and manner prescribed by the FAA.