Part 107 aircraft are not subject to Part 21.
§ 21.1 Applicability and definitions.
(a) Except for aircraft subject to the provisions of part 107 of this chapter, this part prescribes—
(1) Procedural requirements for issuing and changing—
(i) Design approvals;
(ii) Production approvals;
(iii) Airworthiness certificates; and
(iv) Airworthiness approvals;
(2) Rules governing applicants for, and holders of, any approval or certificate specified in paragraph (a)(1) of this section; and
(3) Procedural requirements for the approval of articles.
(b) For the purposes of this part—
(1) Airworthiness approval means a document, issued by the FAA for an aircraft, aircraft engine, propeller, or article, which certifies that the aircraft, aircraft engine, propeller, or article conforms to its approved design and is in a condition for safe operation, unless otherwise specified;
(2) Article means a material, part, component, process, or appliance;
(3) Commercial part means an article that is listed on an FAA-approved Commercial Parts List included in a design approval holder’s Instructions for Continued Airworthiness required by §21.50;
(4) Design approval means a type certificate (including amended and supplemental type certificates) or the approved design under a PMA, TSO authorization, letter of TSO design approval, or other approved design;
(5) Interface component means an article that serves as a functional interface between an aircraft and an aircraft engine, an aircraft engine and a propeller, or an aircraft and a propeller. An interface component is designated by the holder of the type certificate or the supplemental type certificate who controls the approved design data for that article;
(6) Product means an aircraft, aircraft engine, or propeller;
(7) Production approval means a document issued by the FAA to a person that allows the production of a product or article in accordance with its approved design and approved quality system, and can take the form of a production certificate, a PMA, or a TSO authorization;
(8) State of Design means the country or jurisdiction having regulatory authority over the organization responsible for the design and continued airworthiness of a civil aeronautical product or article;
(9) State of Manufacture means the country or jurisdiction having regulatory authority over the organization responsible for the production and airworthiness of a civil aeronautical product or article.
(10) Supplier means a person at any tier in the supply chain who provides a product, article, or service that is used or consumed in the design or manufacture of, or installed on, a product or article.