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 official sources for understanding GPS overlays on conventional instrument procedures.
Using GPS to fly a conventional non-precision approach is permissible only if an approved GPS receiver is used and the approach plate explicitly includes "or GPS" in its title (e.g., "Runway 24 NDB or GPS").
Conventional non-precision approaches, such as NDBs, are rapidly diminishing in number (only 76 left in the U.S.) and are expected to be removed from the National Airspace System by 2030, while RNAV approaches are far more common.

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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.