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:

Modern GPS approaches utilize "radius to fix" (RF) legs to create precise curved paths, evolving from older DME arcs and offering greater flexibility for instrument procedures.
Although many General Aviation (GA) navigators are technically capable of flying RF legs, public databases for certified GA aircraft currently do not include these segments, making initial "RF Required" portions of approaches inaccessible to most GA pilots.
The legality of bypassing "RF Required" segments by accepting radar vectors past them is somewhat ambiguous, but the article suggests it's a reasonable and safe workaround, similar to how other "required" equipment can be managed.
While current limitations exist, RF legs are anticipated to become standard in GA cockpits in the future, providing more accurate and efficient curved approach capabilities.

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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.