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If I were to redo my avionics to only include a WAAS GPS unit and two comm radios, would anything prevent me from operating IFR? 14 CFR 91.205(d) only states that my airplane must have:

(2) Two-way radio communication and navigation equipment suitable for the route to be flown.

I'm aware that this is not the most bulletproof way to fly hard IFR. In this case, assume that the aircraft is primarily used for currency/proficiency and the occasional light IFR flight.

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Keep in mind that GPS is not available everywhere or at any time, due to, in bulk: air-segment failure, poor DoP, DoD shutting down or jamming GPS signal in war area, obstruction, solar pulse...). Also WAAS is only available in North America. Galileo/EGNOS still to be made operational for Europe, as well as GAGAN for India. –  mins Nov 16 at 9:59

1 Answer 1

up vote 6 down vote accepted

The AIM contains the information required to operate under IFR using GPS1.

To summarize the requirements, WAAS (but not "traditional" GPS) may be used stand-alone without an alternate means of navigation provided:

  • Installation requirements:
    • The WAAS navigation equipment is approved in accordance with TSOC145 or TSOC146
    • The installation is done in accordance with AC 20-138
  • Operational Requirements:
    • The WAAS AFM procedures are followed
    • It is not be used by a commercial operator
  • Preflight Requirements:
    • The GPS database is current
    • The GPS database provider does not have any notices prohibiting the use of any fix or procedure that you are going to use
    • GPS NOTAMs/Aeronautical Information is reviewed prior to each flight
    • A RAIM prediction for the time and route is done that shows no loss of RAIM
    • The flight plan navigation equipment is listed as RNAV

Note that commercial operators are required to have redundant systems or ground based backups in order to use it, and while not required for you, it's a pretty good idea.


1 More specifically, see:

AIM Chapter 1, Section 1 - Navigation Aids

  • 1-1-18. Global Positioning System (GPS)
    • d. General Requirements
    • e. Use of GPS for IFR Oceanic, Domestic En Route, Terminal Area, and Approach Operations
    • f. General Database Requirements
  • 1-1-19. Wide Area Augmentation System (WAAS)
    • c. General Requirements
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You're not allowed to substitute GPS for a ground-based navaid for lateral guidance on the final approach course, i.e. you cannot legally fly ILS, localizer, VOR or NDB approaches with GPS alone. Also, you may not plan to fly GPS approaches at both your intended and alternate destinations. That means with GPS only you can only fly RNAV approaches and you can't plan IFR flights that require an alternate. That might still be OK, but it's quite limiting. –  Pondlife Sep 12 at 14:32

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