I've been sorting through the publications outlining the proper use of GPS in IFR scenarios. Looking at AIM 1-2-3 (dated 10/12/17), it appears that there is some regulatory language in (b) and (c). To me it seems this information belongs in Part 91 somewhere between 91.167 and 91.299, along with VOR checks, ELT's and ADS-B.

  • Why isn't this information in the regulations rather than in the AIM?
  • $\begingroup$ See Also AIM 1-1-17 $\endgroup$ May 4, 2018 at 20:03
  • $\begingroup$ I should also note that the FAA publications I am looking at are citing GPS specifically rather than GPS. I presume that is because the FAA has no stake in non-US GNSS systems. $\endgroup$ May 4, 2018 at 20:05

1 Answer 1


There are formal rules required to make new federal regulations and it would be incredibly difficult and time-consuming to put every detailed point through committees, public feedback etc. (Some people might actually see that as a good thing, but that's a discussion for another site.)

As for your specific example, 14 CFR 1.1 defines "suitable RNAV system" as (emphasis mine):

an RNAV system that meets the required performance established for a type of operation, e.g. IFR; and is suitable for operation over the route to be flown in terms of any performance criteria (including accuracy) established by the air navigation service provider for certain routes (e.g. oceanic, ATS routes, and IAPs). An RNAV system's suitability is dependent upon the availability of ground and/or satellite navigation aids that are needed to meet any route performance criteria that may be prescribed in route specifications to navigate the aircraft along the route to be flown. Information on suitable RNAV systems is published in FAA guidance material.

In other words, "there's far too much detail here to make this a regulation, and technology keeps changing anyway. So just go read our dedicated documentation on it".

  • 5
    $\begingroup$ The key words are in the first line of your quote; "system that meets the required performance". The FAA has approved standards (RTCA DO-236 and DO-283) that specify the required nav performance of RNAV systems. The FAA is rightly concerned with performance, not the means by which the performance is attained. In other words, the rules cover what the system must do, not how it does it. $\endgroup$
    – Gerry
    May 4, 2018 at 22:23

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