Definition
The section of U.S. federal aviation regulations that sets out the rules and procedures the FAA uses to certify aircraft, aircraft engines, propellers, and other aeronautical products and parts. It covers type certificates, production certificates, airworthiness certificates, and the approval of changes to certified designs.
Plain English
It is the rulebook the FAA uses to decide whether an aircraft design and the parts that go into it are approved for flight. If a manufacturer wants to build and sell a new airplane in the United States, this is the part of the regulations that tells them how to get it approved.
Context Anchor
Pilots encounter 14 CFR part 21 when reading about FAA aircraft certification, airworthiness certificates, and how an aircraft becomes legally approved for flight.
Derivation
‘CFR’ stands for Code of Federal Regulations, the official collection of U.S. government rules. ‘Title 14’ is the volume covering ‘Aeronautics and Space.’ ‘Part 21’ is one numbered section within that volume. So ‘14 CFR part 21’ is simply a precise address: Volume 14, Section 21 of the federal rulebook.
Why Pilots Care
Every airplane a pilot flies was built and approved under the rules in this part, which directly affects airworthiness and legal operation.
Intuition Check
Do not read part here as a physical aircraft part. In 14 CFR part 21, part means a numbered section of the federal aviation rules.
Example Sentence 1
The new airplane model received its type certificate under 14 CFR part 21 after completing flight testing.
Example Sentence 2
Before an aircraft can receive an airworthiness certificate, inspectors verify that it was produced in accordance with 14 CFR part 21.