You Cant Fly that Curve

When I learned IFR, the oddball technique for GA pilots was the DME Arc. These were the days of turn 10, twist 10, which was the best we had for approximating a curve using the straight-line navigation of VORs and slant-range distance. When GPS came on the scene, the box simply drew the magenta line in an arc and we, or George, followed it. An era was over.

jwanwest

Friday, November 06, 2015 at 12:00 AM ET

Verified

Key Takeaways:

GPS-enabled "radius to fix" (RF) legs are the modern evolution of DME arcs, providing flexible curved paths now appearing in some general aviation (GA) GPS approaches.
Despite some GA navigators having RF capability, public databases for certified GA aircraft do not yet include these RF legs, preventing pilots from flying the full RF segment.
Pilots can often bypass "RF Required" segments by requesting ATC vectors to a later fix, a practical workaround that highlights how aviation regulations often lag behind technological advancements.

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When I learned IFR, the oddball technique for GA pilots was the DME Arc. These were the days of “turn 10, twist 10,” which was the best we had for approximating a curve using the straight-line navigation of VORs and slant-range distance. When GPS came on the scene, the box simply drew the magenta line in an arc and we, or George, followed it. An era was over.

The progeny of DME arcs are the graceful curves of RNAV Required Navigation Performance (RNP) approaches that thread airliners down to socked-in runways set in rocky chasms that defy any kind of a straight-in approach.