STC Privileges

FAR 21.119 — STC Privileges

FAR 21.119 explains what a Supplemental Type Certificate (STC) holder can do: get airworthiness certificates, install changes, and obtain production certificates.

In Plain English

FAR 21.119 lists the privileges granted to the holder of a Supplemental Type Certificate (STC). An STC is FAA approval for a major change to an aircraft's type design — think a new avionics package, an engine swap, or a cargo conversion — that isn't significant enough to require a brand-new type certificate.

Under this section, an STC holder may:

Obtain airworthiness certificates when the STC is for a complete aircraft.
Obtain approval for installation of the modified product (such as an engine, propeller, or appliance) on already-certificated aircraft.
Obtain a production certificate under subpart G of Part 21 to manufacture the change covered by the STC.

Why it matters operationally: As a pilot, you'll regularly fly aircraft that have been modified under STCs. Knowing this rule helps you understand where the legal authority for those modifications comes from, why STC paperwork must stay with the aircraft records, and how an installer's approval traces back to the FAA.

Regulation Text

14 CFR § 21.119

§ 21.119 Privileges. The holder of a supplemental type certificate may— (a) In the case of aircraft, obtain airworthiness certificates; (b) In the case of other products, obtain approval for installation on certificated aircraft; and (c) 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. [Doc. No. 5085, 29 FR 14568, Oct. 24, 1964, as amended by Amdt. 21-92, 74 FR 53387, Oct. 16, 2009]

Oral Exam Questions a DPE Might Ask

Q1What privileges does the holder of a Supplemental Type Certificate have?

Per FAR 21.119, the STC holder may obtain airworthiness certificates for aircraft, get approval to install the modified product on certificated aircraft, and obtain a production certificate for the design change.

Q2If an STC covers a new engine installation rather than a complete aircraft, what can the STC holder do with it?

Under FAR 21.119(b), the holder may obtain approval for installation of that product on certificated aircraft, allowing the modification to be added to existing airframes.

Q3Can an STC holder manufacture the modification covered by their STC?

Yes. FAR 21.119(c) allows the STC holder to obtain a production certificate under subpart G of Part 21 for the design change approved by the STC.

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Related Sections in Part 21

§ 21.1

Certification Procedures