Definition
An RNAV path-and-terminator leg type that defines a specified course flown until it intercepts the next leg in the procedure. The leg has no fixed endpoint of its own; it terminates wherever it crosses the following leg.
Plain English
A flight path that follows a set heading direction until it runs into the next part of the route, then transitions onto that next part.
Context Anchor
Seen in RNAV and instrument procedure coding, especially when describing how the aircraft moves from one segment of a procedure to the next.
Derivation
In ARINC 424 procedure coding, each leg type is named by two letters: the first describes how the path is defined, the second describes how it ends (the terminator). 'C' stands for Course and 'I' stands for Intercept. So a CI leg is a Course-defined path that ends when it Intercepts the next leg.
Why Pilots Care
Correct execution keeps the aircraft on the protected path and ensures timely capture of the next segment without overshooting or undershooting the intercept.
Grounding Statement
Picture flying a straight line until it crosses the next line you are supposed to follow.
Intuition Check
Do not read “leg” as just any loose part of the flight; here it means a defined procedure segment. A CI leg is not a turn by itself—it is a course flown until it intercepts the next path.
Example Sentence 1
After takeoff, the departure procedure used a CI leg to fly runway heading until intercepting the outbound course from the VOR.
Example Sentence 2
After the hold, a CI leg rejoined the airway at the next fix.