Definition
A coding system used in RNAV and RNP procedures that defines each segment of a flight path by two elements: the path the aircraft must fly (such as a course, heading, or arc) and the terminator that ends that path (such as a fix, altitude, or distance). Each leg in a procedure is assigned a two-letter code (for example, TF for Track to Fix, CA for Course to Altitude, or RF for Radius to Fix) that tells the flight management system exactly how to fly the segment and when to transition to the next.
Plain English
A standard way of describing each piece of an instrument procedure by saying two things: how to fly it, and what ends it. The flight computer reads these codes and flies the procedure accordingly.
Context Anchor
Seen in instrument procedure coding, flight management system behavior, GPS navigation, and discussions of how departures, arrivals, and approaches are built in the database.
Derivation
‘Path’ describes the route through the air; ‘terminator’ comes from the Latin terminare, meaning ‘to end or set a limit.’ Together they answer two questions for every segment: what path do I fly, and what ends it?
Why Pilots Care
These legs allow procedures to be flown with precision and repeatability, which is essential for safety in low-visibility conditions and for meeting required navigation performance standards.
Analogy
It is like written driving directions that say, “Drive north on this road until the bridge.” The path is “drive north on this road,” and the terminator is “until the bridge.”
Grounding Statement
Each leg answers two practical questions: what should the aircraft fly, and what tells the system that this part is complete?
Intuition Check
Do not read “path” here as just the visible line on the screen, and do not read “terminator” as a person or object. In this FAA context, the path is the coded route to fly, and the terminator is the coded condition that ends that route segment.
Example Sentence 1
The missed approach begins with a CA leg — a course flown until reaching a specified altitude — followed by a DF leg direct to the holding fix.
Example Sentence 2
During missed approach coding, the procedure designer selects path and terminator legs that ensure the aircraft climbs to a safe altitude before turning.