Instrument Pilot IFR Tips – Using GPS on a VOR or ILS approach, Foreflight + GA News


Last week we talked about briefing the approach and said one of the first things you should do is check to see whether GPS is in the title of the approach. For example, you might look to see whether the title is just VOR 21 approach or if it’s VOR 21 OR GPS. If it’s the latter, it’s obvious you can use GPS in lieu of a VOR signal for the entire approach. But what’s less clear is when you can use GPS for a portion of the approach if it says just VOR 21 and doesn’t have GPS in the title of the approach.

Although GPS receivers have been around for over 20 years, pilots are still unclear as to when they can use GPS on non-GPS approaches such as ILS and VOR approaches. As Max explains, the rules are different for VOR and ILS approaches. The regulatory basis can be found in FAA Advisory Circular AC 90-108, dated March 3, 2011, and in the AIM, the Aeronautical Information Manual, in section 1-2-3, sub-paragraphs c4 and c-5, updated May 26, 2016.

These tell us that for a VOR or NDB approach, you can now use GPS for the entire approach, even if GPS is not listed in the title of the approach. So in our example, if the title of the approach is VOR 21, and GPS is not in the title, you can still now use GPS for the entire approach, but with one caveat. The VOR or NDB signal MUST be in service, and you MUST monitor that signal for the final approach course.

But for an ILS or Localizer approach, as soon as you turn onto a localizer or ILS, you need to display course guidance from the Nav radio. On the Garmin 430/530, that means as soon as you turn onto the localizer, you must push the CDI button so VLOC is displayed. You can, if you wish, monitor RNAV (GPS) data as you fly along a localizer, but GPS cannot be used for primary guidance at any time while on a localizer.

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