Definition
A federal regulation under Title 14 of the Code of Federal Regulations, Part 91 (General Operating and Flight Rules), Section 91.213(a), which prohibits operating an aircraft with inoperative instruments or equipment unless the operator complies with an approved Minimum Equipment List (MEL) that has been issued for that specific aircraft by the FAA. It establishes the conditions under which an aircraft with one or more inoperative items may be legally flown.
Plain English
It is the rule that says you cannot fly an aircraft that has broken or missing equipment unless you are following an FAA-approved list that spells out exactly what can be inoperative and under what conditions.
Context Anchor
Seen when deciding whether an aircraft, especially a complex or jet aircraft, may be flown after a required instrument or piece of equipment is found not working.
Derivation
CFR' stands for Code of Federal Regulations, the official compilation of U.S. federal rules. Title 14 covers Aeronautics and Space. Part 91 contains the basic operating rules every U.S. civil aircraft must follow. The number after the decimal (.213) identifies the specific section, and (a) is the first paragraph within it. Knowing this structure helps decode any FAR citation you see.
Why Pilots Care
Knowing this rule determines whether a pilot can legally depart with certain equipment inoperative or must ground the aircraft until repairs are made.
Intuition Check
Part does not mean an aircraft component here; it means a major division of the federal aviation rules. Section does not mean a physical section of the airplane; it means a specific numbered rule within those regulations.
Example Sentence 1
Before dispatch, the captain checked 14 CFR part 91, section 91.213(a) and the MEL to confirm the inoperative cabin light could be deferred for the flight.
Example Sentence 2
Maintenance confirmed the inoperative item met the requirements of 14 CFR part 91, section 91.213(a) so the flight could proceed without an approved MEL.