Ya Gotta Fly a DME Arc

A DME arc is a curved track at a constant distance around a facility that offers omnidirectional course information and DME, such as a VORTAC, VOR/DME or NDB/DME. This eliminates ILS or LOC DMEs. An arcs radius is 7- 30 NM and is 5-15 NM long, with 10 NM preferred. Thus, arcs can be lengthy and inefficient. The primary area required obstacle clearance is 1000 feet within four NM of the arc along the initial segment, with a 500-foot secondary clearance extending another two NM. In the intermediate segment, the clearance drops to 500 feet.

Fred Simonds

Wednesday, August 15, 2018 at 12:00 AM ET

Verified

Key Takeaways:

DME arcs are a challenging but essential IFR skill, representing a curved flight path at a constant distance around a navigation facility, typically as an initial approach segment.
Pilots execute DME arcs by leading turns to join and exit, and continuously monitoring distance using DME, VOR CDI, or RMI to make constant wind corrections.
Modern IFR GPS navigators can simplify flying DME arcs, but for approaches using a localizer, traditional localizer guidance is still required for the final approach segment.

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Most IPC tasks are routine. But, flying DME arcs is not and it’s no surprise that IPC applicants have more difficulty with them than any other. Perhaps this is why seldom-used skills like DME arcs remain on the books.

The Airman Certification Standards (ACS) does not require that a DME-arc approach be flown: “While the applicant is expected to be able to fly DME arcs, they may be selected for testing only if they are charted and available.” Since the nearest arc approach where I fly is some 50 miles away, flying an arc not on an approach will suffice. On approach or not, the skill is the same.