What Is the Best Source for GPS Overlay on IFR Approaches?

Pilots must navigate rules for using GPS info as a substitute means of navigation to stay legal.

Meg Godlewski

Wednesday, August 19, 2026 at 09:00 AM ET

Verified

Edited By:

Travis Tingle

Most private pilot candidates usually don’t learn about the IFR approaches until they begin their instrument training. [Credit: Meg Godlewski]

Key Takeaways:

The FAA's Instrument Procedures Handbook and Advisory Circular 90-108 are the best sources for understanding GPS overlay approaches, confirming RNAV (GPS) systems can substitute for conventional navigation when facilities are out of service.
Using GPS for a non-precision approach is legal only with an approved GPS receiver and if the approach plate explicitly includes "or GPS" in its title.
Conventional non-precision approaches, especially NDBs, are rapidly declining in number (76 remaining) and are expected to be phased out by 2030, making dedicated RNAV approaches (over 6,900) the predominant type.

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Question: I am getting back into instrument flying after a 15-year break, and I’m a little confused about flying a non-precision approach with a GPS overlay. I’m getting conflicting information from the instructors at the flight school. Some say I don’t need to know it since there are always RNAV approaches at airports. It seems like GPS overlay means GPS can be used to fly any approach, but then I hear there are all sorts of caveats. What is the best source of reliable information?

Answer: Your best bet is to go to the agency that makes the rules and establishes the procedures, and by that I mean of course the FAA. Get your hands on the most recent version of the agency’s Instrument Procedures Handbook (FAA-H-8083-16) and read Chapter 4, which explains an RNAV system (GPS) may be used as a substitute means of navigation when a VOR, DME, TACAN, VORTAC, VOR/DME, NDB, or compass locator facility are out of service.