Definition
A subsection of Title 14 of the Code of Federal Regulations that prohibits any person from operating an aircraft below 10,000 feet MSL at an indicated airspeed greater than 250 knots (288 mph).
Plain English
An FAA rule that says when you are flying below 10,000 feet above sea level, you cannot go faster than 250 knots indicated.
Context Anchor
Seen in takeoff, climb, descent, and general operating discussions when speed limits below 10,000 feet are being referenced.
Derivation
Section 91.117' refers to Part 91 of the Federal Aviation Regulations (general operating and flight rules), section 117 (speed limits). The '(a)' identifies the first paragraph of that section, which sets the general 250-knot limit below 10,000 feet.
Why Pilots Care
Keeps the aircraft within safe speed margins in the terminal area and prevents airspace violations.
Intuition Check
Do not read “section 91.117(a)” as a section of an airplane or a handbook chapter. Here it is a legal citation pointing to one specific paragraph in the federal aviation rules.
Example Sentence 1
During the initial climb, the pilot leveled the airspeed at 240 knots indicated to remain compliant with section 91.117(a) until passing through 10,000 feet MSL.
Example Sentence 2
The instructor reminded the student that section 91.117(a) applies throughout the initial climb until reaching 10,000 feet.