Definition
An ARINC 424 path-and-terminator leg type that requires the aircraft to fly a specified course (a magnetic heading or track) until it reaches a specified altitude, at which point the leg terminates and the next leg begins. The leg has no defined endpoint in space — only an altitude that must be reached.
Plain English
A piece of a procedure that tells the aircraft to fly in a particular direction until it climbs (or descends) to a certain altitude, then move on to the next instruction. The leg ends when the altitude is hit, not at any specific point on the map.
Context Anchor
Seen in instrument departure, arrival, and missed approach procedure coding, especially where the instruction is to follow a course until reaching an altitude.
Derivation
In ARINC 424 leg coding, each two-letter code names the path first and the terminator second. CA is Course-to-Altitude: the path flown is a course, and the thing that ends the leg is reaching an altitude.
Why Pilots Care
It ensures the aircraft reaches a safe altitude before turning or joining the next course, protecting terrain clearance and procedure compliance.
Grounding Statement
On a CA leg, the aircraft keeps going in the assigned direction until the altimeter reaches the specified altitude.
Intuition Check
Do not assume a CA leg ends over a charted point. It ends when the specified altitude is reached.
Example Sentence 1
The departure procedure starts with a CA leg: fly runway heading until reaching 1,500 feet, then turn on course.
Example Sentence 2
The CA leg terminates automatically once the aircraft levels at the published altitude, allowing the autopilot to sequence to the next waypoint.