Definition
An RNAV path and terminator leg type that defines a curved track flown along a constant-radius arc around a designated reference point (typically a DME navaid or a defined waypoint), terminating at a specified fix. The arc is defined by its center, its radius, the direction of turn, and the terminating fix.
Plain English
A curved segment of a flight procedure where the aircraft flies a circle of fixed distance around a chosen point until reaching a named fix where the segment ends.
Context Anchor
Seen in instrument procedure design and in navigation-system descriptions of how a published route segment is built.
Derivation
‘Arc’ comes from Latin arcus, meaning ‘bow’ or ‘curve’ — describing the curved path. ‘Leg’ is borrowed from everyday English, used in aviation to mean a defined segment of a route. So ‘arc to a fix’ literally describes a curved leg that ends at a named point.
Why Pilots Care
It enables precise, automated curved routing around obstacles or to intercept final courses without manual turn calculations.
Analogy
It is like drawing part of a circle with a compass: one point stays as the center, and the pencil traces a smooth curve until it reaches the marked endpoint.
Intuition Check
Do not read “fix” as “repair” here. In this term, a fix is a known navigation position, and the AF leg is the curved path that ends there.
Example Sentence 1
The approach begins with an AF leg that arcs the aircraft around the VOR at 12 DME until reaching the initial approach fix.
Example Sentence 2
After takeoff the procedure used an AF leg to route around a noise-sensitive area before proceeding direct.