Definition
A type of RNAV path segment defined as a curved track of fixed radius between two waypoints, centered on a defined turn center. The aircraft flies a precise arc of a specified radius to the terminating fix, allowing repeatable, predictable curved flight paths in RNAV departure, arrival, and approach procedures.
Plain English
A curved leg of a flight path where the aircraft flies along an arc of a set distance from a center point, ending at a specific waypoint. Instead of flying straight between points, the aircraft follows a precisely shaped curve.
Context Anchor
Seen in area navigation departure and approach procedures, especially where the published path needs the aircraft to follow a precise curved track.
Derivation
The name describes exactly what the leg is: a constant radius (an unchanging distance from a center point) flown to a fix (a named waypoint). The phrase comes straight from the geometry -- a circle has a constant radius, so flying along part of one produces a smooth, predictable curve.
Why Pilots Care
Allows precise navigation around obstacles or to meet airspace requirements during departures.
Analogy
It is like drawing part of a circle with a compass: the pencil moves around the center while staying the same distance from it, then stops at the planned endpoint.
Grounding Statement
Picture the airplane following part of a circle in the sky, staying the same distance from an invisible center point until it reaches the named fix.
Intuition Check
Fix does not mean repair here, and leg does not mean a body part. A fix is a named point in space, and a leg is one segment of a route. Constant radius means the curve keeps the same distance from a center point, not that the bank angle or speed must stay constant.
Example Sentence 1
The departure procedure included a constant radius to a fix leg that curved the aircraft around rising terrain before joining the outbound course.
Example Sentence 2
Pilots must maintain the specified radius during the constant radius to a fix leg to stay on the protected path.