Definition
A section of Title 14 of the Code of Federal Regulations (14 CFR Part 91) that sets out the requirements for Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment and its use, including the airspace where ADS-B Out is required, the performance standards the equipment must meet, and the conditions under which deviations may be authorized.
Plain English
The federal rule that says where you must have working ADS-B Out equipment on your aircraft and what that equipment has to do.
Context Anchor
Seen in operating rules and equipment requirement discussions, especially when deciding whether an aircraft is legal to enter Class A, Class B, Class C, or other ADS-B-required airspace.
Derivation
In the U.S. regulations, '91' identifies Part 91 of Title 14 (General Operating and Flight Rules), and '.225' is the specific section number within that part. So 'section 91.225' is shorthand for one numbered rule inside the broader set of general flight rules.
Why Pilots Care
Compliance is mandatory; operating without approved ADS-B Out in Class A airspace violates federal regulations and can result in enforcement action.
Intuition Check
Do not read “section 91.225” as a physical section of airspace or an aircraft part. It is a numbered FAA regulation that tells pilots what equipment is required for certain operations.
Example Sentence 1
Before the flight, the pilot confirmed the ADS-B Out system was working so the aircraft would meet the requirements of section 91.225 in Class A airspace.
Example Sentence 2
Section 91.225 lists the specific ADS-B Out capabilities needed for flight above 18,000 feet MSL.