Definition
The section of the Federal Aviation Regulations that establishes maximum aircraft speed limits in specified airspace and operating environments. It sets a 250-knot limit below 10,000 feet MSL, a 200-knot limit at or below 2,500 feet AGL within 4 nautical miles of the primary airport in Class C or D airspace, and a 200-knot limit in airspace underlying Class B or in a VFR corridor through Class B.
Plain English
This is the rule that tells pilots how fast they're allowed to fly in different parts of the airspace, especially near airports and at lower altitudes. The main numbers to remember are 250 knots below 10,000 feet, and 200 knots when you're close to busy airports.
Context Anchor
You may see this citation in traffic pattern, approach, departure, and airspace discussions when speed control is required by regulation.
Derivation
14 CFR means Title 14 of the Code of Federal Regulations, which is the section of U.S. federal law covering aeronautics. Part 91 contains the general operating rules for all civil aircraft. Section 91.117 is the specific paragraph within Part 91 that addresses aircraft speed.
Why Pilots Care
Compliance prevents excessive speed in the traffic pattern, reduces the risk of overtaking other aircraft, and supports safe spacing during arrivals and departures.
Analogy
It works like a speed-limit law on a road: the limit depends on where you are, not just on what your aircraft can do.
Intuition Check
Do not read this as a page number in the handbook. It is a legal citation to a federal aviation rule. Also, “part” does not mean an airplane component here; it means a numbered division of the regulations.
Example Sentence 1
Approaching the Class D airport at 2,000 feet AGL, the pilot reduced speed to comply with 14 CFR part 91, section 91.117.
Example Sentence 2
Above 10,000 feet the aircraft accelerated beyond 250 knots because that altitude is outside the restrictions of 14 CFR part 91, section 91.117.