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

1. (a) Under a PMA;
2. (b) Under a TSO;
3. (c) In conjunction with type certification procedures for a product; or
4. (d) In any other manner approved by the FAA.

[Doc. No. FAA-2006-5877, Amdt. 21-92, 74 FR 53385, Oct. 16, 2009]