Definition
A path and terminator leg type used in RNAV procedure coding that defines a specified course the aircraft flies until it intercepts the next leg in the procedure. The leg has no fixed endpoint of its own; it terminates when the aircraft captures the following leg, which is typically a course or track to a fix.
Plain English
A flight path that tells the aircraft to fly along a set heading or course until it runs into the next part of the procedure, then turn onto that next part.
Context Anchor
Seen in instrument procedure coding, especially when a departure, arrival, or approach segment is built for a navigation system to follow automatically.
Derivation
The two-letter codes used for procedure legs come from ARINC 424, the industry standard for navigation database coding. 'C' stands for Course and 'I' stands for Intercept, so CI literally describes a course flown to an intercept of the next leg.
Why Pilots Care
Ensures the aircraft follows the correct path to join the approach or airway without deviation.
Intuition Check
Do not read “course” here as a class of study or a general plan. In this context, it means a direction to fly. “Intercept” does not mean stop; it means meet and join another path.
Example Sentence 1
After the runway heading climb, the departure procedure coded a CI leg that flew the aircraft outbound until it intercepted the next course toward the en route fix.
Example Sentence 2
After takeoff the procedure uses a CI leg to reach and join the assigned airway.