Definition
The section of the Federal Aviation Regulations that lists the minimum instruments and equipment required for flight under instrument flight rules (IFR) in a powered civil aircraft. It builds on the day and night VFR equipment lists in 91.205(b) and 91.205(c) and adds items needed for instrument flight, including a two-way radio and navigation equipment appropriate to the ground facilities used, a gyroscopic rate-of-turn indicator, a slip-skid indicator, a sensitive altimeter adjustable for barometric pressure, a clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation, a generator or alternator of adequate capacity, a gyroscopic pitch and bank indicator (attitude indicator), and a gyroscopic direction indicator (heading indicator or equivalent).
Plain English
It is the rule that lists the instruments and equipment an aircraft must have on board to legally fly in the clouds or under instrument flight rules.
Context Anchor
Seen in airplane equipment discussions, preflight planning, aircraft airworthiness checks, and training for instrument flying.
Derivation
14 CFR means Title 14 of the Code of Federal Regulations, which is the section of U.S. federal law dealing with aeronautics and space. Part 91 covers general operating and flight rules. Section 91.205 is the specific rule on required instruments and equipment, and paragraph (d) is the subsection covering IFR.
Why Pilots Care
A pilot must confirm the aircraft meets these requirements before any night flight to remain in legal compliance and to have the lights and instruments needed for safe visual reference and collision avoidance after dark.
Analogy
A regulation citation works like an address. “14 CFR part 91” gets you to the right neighborhood, “section 91.205” gets you to the right building, and “(d)” gets you to the exact room.
Intuition Check
Do not read this as the name of a piece of equipment. It is a legal citation that points to the exact rule covering required equipment for instrument flight.
Example Sentence 1
Before the IFR cross-country, the pilot ran through 14 CFR part 91, section 91.205(d) to confirm the airplane had every required instrument working.
Example Sentence 2
During the preflight inspection the instructor pointed out the position lights and landing light required by 14 CFR part 91, section 91.205(d).