14 CFR Part 21eCFR Sep 29, 2026
Subpart E
Supplemental Type Certificates
6 Sections§§ 21.111–21.120
§ 21.111 Applicability.
This subpart prescribes procedural requirements for the issue of supplemental type certificates.
§ 21.113 Requirement for supplemental type certificate.
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.
§ 21.115 Applicable requirements.
Each applicant for a supplemental type certificate must show that the altered product meets applicable requirements specified in § 21.101 and—
In the case of an acoustical change described in § 21.93(b), show compliance with the applicable noise requirements of part 36 of this chapter;
In the case of an emissions change described in § 21.93(c), show compliance with the applicable fuel venting and exhaust emissions requirements of part 34 of this chapter; and
In the case of a fuel efficiency change described in § 21.93(d), show compliance with the applicable fuel efficiency requirements of part 38 of this chapter.
Each applicant for a supplemental type certificate must meet §§ 21.33 and 21.53 with respect to each change in the type design.
§ 21.117 Issue of supplemental type certificates.
An applicant is entitled to a supplemental type certificate if the FAA finds that the applicant meets the requirements of §§ 21.113 and 21.115.
A supplemental type certificate consists of—
The approval by the FAA of a change in the type design of the product; and
The type certificate previously issued for the product.
§ 21.119 Privileges.
The holder of a supplemental type certificate may—
In the case of aircraft, obtain airworthiness certificates;
In the case of other products, obtain approval for installation on certificated aircraft; and
Obtain a production certificate in accordance with the requirements of subpart G of this part for the change in the type design approved by the supplemental type certificate.
§ 21.120 Responsibility of supplemental type certificate holders to provide written permission for alterations.
A supplemental type certificate holder who allows a person to use the supplemental type certificate to alter an aircraft, aircraft engine, or propeller must provide that person with written permission acceptable to the FAA.