Definition
To navigate a curved flight path that maintains a constant distance from a navigation aid, where that distance is measured by Distance Measuring Equipment (DME) or, when permitted, by an equivalent GPS-derived distance. The pilot flies the arc by making small heading adjustments to keep the displayed distance from the station within a narrow tolerance, typically while transitioning from an enroute structure to a final approach course.
Plain English
It means flying a curved path that stays the same distance from a ground station the whole way around. The pilot watches the distance readout and gently turns to keep that number steady, so the aircraft traces a portion of a circle around the station.
Context Anchor
Seen on instrument approach procedures and training tasks, including procedures where GPS is used in place of traditional DME distance information.
Derivation
An 'arc' is a portion of a circle, from the Latin arcus meaning 'bow' or 'curve.' Flying a DME arc means flying along the curved edge of an imaginary circle drawn around the navigation station.
Why Pilots Care
Provides a precise way to maneuver around terrain or traffic while setting up for an approach without flying directly to or from the station.
Analogy
Imagine walking around a flagpole while holding a rope tied to its base. As long as the rope stays the same length, you trace a perfect circle. Flying a DME arc is the same idea, with the distance readout playing the role of the rope.
Intuition Check
Do not read “fly a DME arc” as simply flying to the DME station. The key idea is holding a set distance while moving around the station or point.
Example Sentence 1
Cleared for the approach, the pilot intercepted the 15 DME arc and began making small right turns to keep the distance steady at 15 miles.
Example Sentence 2
Using GPS to substitute for DME, I maintain the arc by adjusting heading every few degrees to stay at the published distance.