Thanks to John Collins, an avionics expert and colleague of mine, I recently learned about feature that Garmin seems to have added to the GTN Xi series navigators and the G500/600 TXi flight displays.
Update: This feature is now documented in the latest GTN 750Xi Pilot Guide (190-02327-03 Rev. D). VOR+V Approaches (p. 3-135) explains that:
Per guidance provided in AC 90-108 regarding the use of GPS as an alternate means of navigation, VOR and NDB approaches may be treated as LNAV+V approaches (i.e., LNAV with advisory vertical guidance) as long as the pilot monitors the VOR.
During approach selection, “+V” displays for VOR and NDB approaches when advisory guidance is available. Approach strings remain unmodified when no vertical guidance is available.
If the approach indicates “VOR+V,” then advisory vertical guidance may be removed without indication. This is due to the vertical guidance not being within tolerances. This does not constitute a downgrade. You may still fly the approach to VOR minimums. Flying a VOR approach with advisory vertical guidance (VOR+V) does not change how the approach should be flown. The pilot is still responsible for descending to the correct altitude at each step down. The result is still an MDA and missed approach point.
FAA updated the AIM and other guidance a few years ago to allow you to “fly the magenta line” along the final approach course of a VOR or NDB approach, if the navaid is working and you can monitor the course with a CDI or bearing pointer.
Note that with GTN Xi software version 20.30 and later, descriptions of VOR/DME, VOR, NDB/DME, NDB, and TACAN approaches with advisory vertical guidance now show “+V” instead of “LNAV+V.”
I’ve explained the details and shown examples of this technique in several posts here at my blog and in a video presentation and a webinar about using GPS while flying conventional procedures and routes:
But now the Garmin GTN Xi units, and I assume their siblings, the GTX and latest GPS navigators, have added advisory vertical guidance, even to VOR approaches. To my knowledge, this feature hasn’t been documented in Garmin manuals or other sources, and it’s not clear to me which minimum hardware and software combinations support this feature.
To test the feature on a fine VFR day in an airplane, I hopped from Boeing Field (KBFI) in Seattle to nearly Olympia, WA (KOLM) to fly the VOR RWY 35 approach.
Ride along with me in this video to see this feature in action.
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