(The simple explanation is straightforward. If you have an IFR-approved GPS, and absent restrictions in the AFM supplement for that GPS, you can use it instead of a VOR, DME, or NDB indicator, even when a charted navaid is out of service or noted as ?required? on an approach chart.

Under FAA regulations in 2026, a pilot can substitute a TSO-certified GPS (such as one with WAAS) for a VOR in several specific scenarios to enhance safety and efficiency. You can use GPS as a primary means of navigation for "En Route" and "Terminal" phases of flight, even if the underlying route is defined by VOR radials. GPS can also be used for "DME substitution" or to identify "fixes" like intersections that were originally based on VOR crosses. However, there are critical limitations: you cannot use GPS to substitute for a VOR that is specifically required for an "ILS" or "Localizer" final approach segment unless the approach is explicitly titled "GPS" or "RNAV." Additionally, for non-WAAS aircraft, the VOR equipment must be operational and tuned to the required frequency as a backup. This substitution is part of the FAA's "NextGen" initiative, moving the National Airspace System toward a satellite-based infrastructure while maintaining a "Minimum Operational Network" of ground-based VORs for resiliency.