AerostarDriver Posted March 1, 2021 Report Share Posted March 1, 2021 Working with a friend who is trying to go GPS only in her Arrow. After talking with her avionics shop of choice, they claimed that the GPS175/GNC355/GNX375 cannot be used as the primary source of IFR navigation and requires a nav radio like an SL30 or something like a GPS400, GNS 430, or GTN 650. I cannot remember where I heard it but I also remember seeing it in text on one of the forms fairly recently. Has anyone run in to this or heard similar? Quote Link to comment Share on other sites More sharing options...
Davidv Posted March 1, 2021 Report Share Posted March 1, 2021 I've heard the same. When I did my upgrade I put in a Garmin GNC255A ($4k). I did it because I wanted a ground based navigation system but it also satisfies the legal requirement. Quote Link to comment Share on other sites More sharing options...
kortopates Posted March 1, 2021 Report Share Posted March 1, 2021 (edited) That doesn't appear to be true for any Single Engine piston under 6000 lbs, only for all others - from the AFMS below. However, IMO as a CFI-II I wouldn't ever be caught out doing training in actual IMC with only GPS on-board - that's nuts given how easily they're jammed and with almost daily GPS interefence testing NOTAMs putting it at risk of losing coverage. That said, all I ever use to navigate is GPS. But I have lost GPS from jamming 3 times now, including being IMC, (although not yet in US airspace) and each time I was abe to fall back on VOR navigation. So for me, not even two TSO GPS navigators (which I do have) are sufficient without a Nav radio backup The Arrow came with 2 nav-com radios, personally I'd want both for an IFR Arrow. Edited March 1, 2021 by kortopates 1 1 Quote Link to comment Share on other sites More sharing options...
Skates97 Posted March 1, 2021 Report Share Posted March 1, 2021 The GNC355 can be used as primary NAV in our planes for IFR, as long as you have a second COM at a minimum. Whether you want to have only GPS in your plane or retain ground based NAV is another discussion and Paul brings up some very good points. Here is a post in a different thread which may be the one you were thinking of. I included the information from the GNC355 Installation manual for the GNC355 along with links to an FAA notice from 2013 and the current AIM. Quote Link to comment Share on other sites More sharing options...
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