FAR 21.138 — Quality Manual

FAR 21.138 applies to anyone applying for or holding a production certificate under Part 21 — typically manufacturers of aircraft, engines, or propellers. The rule requires the applicant or holder to give the FAA a quality manual that describes their quality system, and the FAA must approve it.

Two specific format requirements apply:

• The manual must be written in the English language.
• It must be retrievable in a form acceptable to the FAA (for example, a paper copy or an approved electronic format the FAA inspector can readily access).

Why it matters operationally: the quality manual is the master document the FAA uses to verify that a manufacturer consistently produces conforming, airworthy products. Without an approved quality manual, a production certificate cannot be issued or remain valid. While most pilot students won't author one, understanding this requirement helps explain how the airworthiness chain begins at the factory — long before a pilot performs a preflight inspection.