CFR /  Title 14  /  Part 21  /  Sec. 21.8 Approval of articles.

If an article is required to be approved under this chapter, it may be approved--

(a) Under a PMA;

(b) Under a TSO;

(c) In conjunction with type certification procedures for a product; or

(d) In any other manner approved by the FAA. [Doc. No. FAA-2006-25877, Amdt. 21-92, 74 FR 53385, Oct. 16, 2009]