Definition
The portion of an instrument approach where the final approach course is flown along a DME arc rather than a straight-in track to the runway. The aircraft maintains a constant distance from a navigation aid (typically a VOR/DME) while descending toward the missed approach point, with course guidance provided by the arc itself rather than an inbound radial.
Plain English
The last leg of the approach is flown as a curved path that stays a fixed distance from a ground station, instead of as a straight line pointing at the runway.
Context Anchor
Seen on some VOR or VOR/DME approach charts when the final approach path is drawn as a curved arc instead of a straight final course.
Derivation
Arc' comes from the Latin arcus, meaning 'bow' or 'curve.' It describes the shape of the path: a section of a circle drawn around the navigation aid. 'Final approach segment' is the last segment of the approach, ending at the missed approach point.
Why Pilots Care
It allows safe lateral guidance on approaches where terrain or airspace prevents a straight-in final, reducing the risk of losing course alignment.
Analogy
It is like walking around a pole while keeping the same length of rope stretched between you and the pole. Your direction keeps changing, but your distance from the center stays the same.
Grounding Statement
In the airplane, this feels like a controlled shallow turn while the distance from the navigation facility stays nearly constant.
Intuition Check
Do not read “final” as simply the last visual turn toward the runway. Here it means a specific published instrument-approach segment with protected airspace and altitude rules. Do not read “arc” as just any curve; here it means a curved path built around a fixed navigation point at a set distance.
Example Sentence 1
The approach plate showed an arc final approach segment, so the pilot briefed flying the 10 DME arc inbound rather than tracking a radial.
Example Sentence 2
On the published VOR approach the arc final approach segment replaced the usual straight final and led directly to the missed approach point.