Definition
An RNAV path-and-terminator leg type that begins at a defined fix and ends when the aircraft reaches a specified altitude. The ground track is along a published course from the fix, and the leg terminates the moment the altitude is achieved, regardless of distance flown.
Plain English
A coded segment of an instrument procedure that says 'starting at this point, fly this course until you climb (or descend) to this altitude — then the leg is finished.'
Context Anchor
Seen in RNAV instrument departures, arrivals, and approach procedure coding when the FAA describes path and terminator legs.
Derivation
The naming convention comes from the ARINC 424 path-terminator system used to code instrument procedures. The first letter ('F') indicates the leg starts at a fix; the second letter ('A') indicates it ends at an altitude. So 'FA' literally reads as 'Fix-to-Altitude.'
Why Pilots Care
Knowing an FA leg ends at altitude rather than at a fix prevents the autopilot or FMS from continuing past the intended point and helps maintain proper vertical guidance during approaches.
Grounding Statement
Picture crossing a named point after takeoff and continuing on the shown path until the altimeter reaches 3,000 feet; reaching that altitude ends the FA leg.
Intuition Check
Do not read fix as repair or leg as a body part; here, fix means a named navigation point, and leg means one coded segment of an instrument route. Do not assume the segment ends at another map point; on an FA leg, it ends when the specified altitude is reached.
Example Sentence 1
The departure begins with an FA leg from the runway end fix, climbing on runway heading until reaching 800 feet before turning on course.
Example Sentence 2
After crossing the fix the autopilot continued on the same heading until the altitude constraint was met and the FA leg terminated.