The Parenthetical Fix

Like many of our clinics, this one started with a readers letter. This particular fellow was a flight instructor who had to go old-school with a Private student in a Diamond DA20 equipped with a Garmin GNS 430 GPS. They were following V86-365 from the Bozeman VOR to the Livingston VOR at night through the mountains. Happily motoring along on GPS, they ran into a snag with the bend in the airway.

jwanwest

Tuesday, December 02, 2014 at 12:00 AM ET

Verified

Key Takeaways:

VFR pilots using GPS on airways may encounter unmarked bends, known as Computer Navigation Fixes (CNFs), which are not depicted on sectional charts but are crucial for accurate navigation, especially at night.
CNFs are found on IFR low-altitude en-route charts; pilots should consult these to incorporate CNFs into their GPS flight plans for accurate airway navigation.
In-flight strategies, such as using GPS "Nearest" functions or combining VOR/GPS navigation, can help locate and navigate these fixes if not pre-planned, highlighting a gap in VFR chart information.

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Like many of our clinics, this one started with a reader’s letter. This particular fellow was a flight instructor who had to go “old-school” with a Private student in a Diamond DA20 equipped with a Garmin GNS 430 GPS. They were following V86-365 from the Bozeman VOR to the Livingston VOR at night through the mountains. Happily motoring along on GPS, they ran into a snag with the bend in the airway.

With two VORs, this is a no brainer: Track R-110 from BZN on one Nav and dial up R-246 to LVM on the other. When the second Nav needle centers, turn left and continue. It’s a bit tougher with one GPS/Nav. You can’t load the airway on a GNS 430 and the bend had no fix name associated with it on the VFR chart. They ended up flying the right distance outbound from BZN via the VOR part of the GPS and then using GPS direct for the leg to LVM.