 §§ 21.137 (quality system requirements for production certificates), 21.307 (requiring PMA holders to establish a quality system that meets the requirements of § 21.137), 21.607 (requiring TSOA holders to establish a quality system that meets the requirements of § 21.137).The FAA is also working on new policies concerning parts fabricated in the course of repair.This practice has historically been confused with PMA manufacturing, although the two are actually quite different practices supported by different FAA regulations.