IFR with certified Garmin G3X

Discussion in 'Instruments / Avionics / Electrical System' started by Scheny, Apr 5, 2019.

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  1. Apr 5, 2019 #1

    Scheny

    Scheny

    Scheny

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    Hi,
    a few days ago I saw on Youtube that the G3X can now also be bought in a certified version.

    I asked whether you could fly IFR by internal GPS on the old uncertified version of the G3X and got the answer, that you would need a GTN650 as you require a certified navigation device.

    Now, with the G3X certified I don't understand why you still need either a GTN650 or the new (GPS only) GNX375. In my understanding the GNX375 is doing nothing more than the internal GPS of the G3X. Or is the internal GPS of the certified G3X still uncertified?

    For our project we have huge space restrictions in the cockpit (glider sized) and it will make a big difference whether we have to use the GTN650. If we take it, the GTN would be located between the knees, pushing them more apart than in any glider I know and not leaving much space left... Without it, the leg room could be kept free.

    So what would you guys do?
     
  2. Apr 5, 2019 #2

    TFF

    TFF

    TFF

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    My guess is the GPS in the unit is really there to drive the screen; using for VFR navigation when there is no rules for VFR navigation made it easy to piggyback. Because the FAA requires certified GPS for IFR even in homebuilts, and Garmin rules the world in IFR GPSs, they probably decided to keep the unit VFR and require add ons for IFR. Could they have? Probably but the certification would have been another step up. They get to sell you two boxes, but they also save themselves money certifying. I bet the FAA does not like all the eggs in one basket either, really making certification undoable.
     
  3. Apr 6, 2019 #3

    gtae07

    gtae07

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    The GPS (as in, the antenna/chip that receives the satellite transmissions and calculates position) isn't the issue here, really (though there are still some specific requirements for the GPS hardware/software you have to meet). What the FAA is really concerned about with regarding IFR GPS is the database. The G3X itself doesn't have the IFR procedure database inside it, nor does it have all the "magic stuff" to guarantee the "integrity" of that database.

    By keeping all the IFR stuff to a separate box, it eases the certification (as TFF notes) and it also makes it a lot easier to maintain configuration control and ensure that the right nav signals are being output. There's a lot more "stuff" inside a G3X unrelated to navigation so it's easier to keep it all separated, and that way you don't have to make all of it meet the IFR GPS standards.


    There's also the commercial aspect; Garmin knows that a standalone IFR box can sell to a really wide market (especially if it's TSOed and can go in certified airplanes). Why spend all the extra money incorporating the IFR stuff into a different product if they can just sell more 375s?
     
  4. Apr 6, 2019 #4

    Marc Zeitlin

    Marc Zeitlin

    Marc Zeitlin

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    Yes it most certainly does. As does the Dynon Skyview, and other VFR only EFIS's. All you have to do is take a look at the pilot manual to see that. For the G3X, see page 176 of revision H of the Pilot Guide to see how to load and use an approach when an external navigator is not available. Of course, they are VERY clear that:

    WARNING: Do not use the approach information provided by the VFR navigation database residing within the G3X as a means of navigating any instrument approach. The G3X VFR navigation database is limited to present only the waypoints for the final approach leg of a published procedure. These waypoints and associated course line are made available for monitoring purposes only.​

    But it's there, and it does work. What I tell my customers, when they ask if they should install a an approved GPS navigator, is that _IF_ they're instrument rated, and _IF_ the plane is equipped for flight into IMC, and _IF_ they plan on flying approaches, THEN they should get an approved navigator for the legality. IF, however, any of those things aren't the case, then in an emergency where they HAVE to shoot an approach to land safely, the G3X/Skyview/etc. will certainly allow them to do it.

    And for enroute operations, since it's legal to fly enroute IFR via dead reckoning and/or pilotage, no "approved" GPS is required. Use your iPad/handheld as a "backup" to your primary means of navigation, which is one of the above.

    I think you're conflating the accuracy of the database, which it most certainly does have, with the "integrity" of the GPS signal:


    These EFIS's don't have RAIM, but the approved, TSO's receivers do. As far as I can tell, that's about the only difference. There are most probably a number of more subtle differences too, possibly in the software and hardware, but I'm not aware of them.

    Garmin DID just release their GPS 175 approved GPS enroute/approach box. For $4200 (retail) it makes one IFR legal for enroute and GPS approaches - far cheaper than the IFD-440 (which I was GOING to install in my panel) or the 650 or 750.
     
    delta likes this.
  5. Apr 9, 2019 #5

    Scheny

    Scheny

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    OK, thank you very much for the input!

    Means we have to make a study if potential customers would prefer IFR capability in an otherwise not so cross-country flying friendly airplane or rather have better ergonomics (more legroom).

    Another huge point will be whether VOR antenna can be incorporated into the plane or if place is too small for it. Idea was to have COM and transponder antennae in the rudder leading edge and COM in the elevator leading edge. Outside hull should stay clean.
     

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