Definition
A type of RNAV path segment defined as a curved track of fixed radius between two waypoints, centered on a defined turn center, ending at a named fix. Unlike a standard fly-by turn, an RF leg specifies the exact ground track of the turn, allowing flight management systems to fly a precise, repeatable arc rather than approximating the curve.
Plain English
A curved part of an RNAV route that follows a precise arc of a set distance from a center point, ending at a specific waypoint. The aircraft flies the same exact curved path every time, instead of cutting the corner.
Context Anchor
Seen on RNAV instrument departures, arrivals, and approaches when the published route includes a curved track between fixes.
Derivation
The name describes the shape: a constant radius (unchanging distance from a center point) leading to a fix (a named waypoint). The path is geometrically a portion of a circle, which is why the radius stays the same throughout the turn.
Why Pilots Care
Enables precise routing around terrain, obstacles, or noise areas while maintaining a predictable turn radius for the aircraft.
Analogy
Think of drawing part of a circle with a compass. The pencil follows a smooth curve at the same distance from the center; an RF leg works the same way in the sky.
Intuition Check
RF does not mean “turn however you need to until you reach the fix.” It means “follow this specific published curved path to the fix.” Also, “fix” here means a defined navigation point, not a repair.
Example Sentence 1
The departure procedure included an RF leg that curved the aircraft around rising terrain before joining the next straight segment.
Example Sentence 2
On the approach, the aircraft flew a 2-mile-radius RF segment to align with the final approach course.