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Thread: Gnc 355

  1. #1
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    Default Gnc 355

    Did anyone install the new GNC 355? Any thoughts?
    I was offered to install it instead of the GTR200 and get full IFR approach capability via the G3X and autopilot.


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  2. #2
    Senior Member Andy's Avatar
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    Post Re: Gnc 355

    Quote Originally Posted by Schwbo View Post
    Did anyone install the new GNC 355? Any thoughts?
    This configuration was fitted to an FX-3 delivered about the same time as mine. I studied it but decided it was not the way I would give my FX-3 IFR approach capability. Note that I was considering a post delivery retrofit, not a factory installation.

    Advantages of GNC 355 are
    * includes the radio so GTR 200 not needed

    Disadvantages of the GNC 355 are:
    * Forces use of a remote intercom
    * More expensive than GPS 175
    * A single point failure could result in loss of NAV and COMS

    If a GPS 175 is used instead of the GNC 355 the disadvantages are:
    * No room for GMC 305 (options may include LVL button and use of AFCS GUI, or mounting a GMC 305 or GMC 507 somewhere else)

    The advantages are:
    * Lower cost
    * No need for a remote intercom
    * NAV and COM are independent with reduced risk of single point failure

    GPS 175 and GNC 355 have identical NAV capability. The only difference is the addition of the radio. You have to decide what's important to you. You will also need to consider the total height required and whether a change from the standard panel is needed.

    (Edited to correct GPS 155 to GPS 175)
    Last edited by Andy; 01-08-2021 at 06:40 PM.

  3. #3
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    Default Re: Gnc 355

    Andy, I think you're talking about GPS 175. I've been looking at this as Trent with his FX-3 got the GNC 355 setup. It's mounted over top of the GMC 305, a Garmin G5 left of the G3X. Here is the breakdown as you probably know.

    GPS 175 is WAAS GPS for the IFR use
    GNC 355 is a GPS 175 with a radio, no intercom
    GNX 375 is a 175 with Transponder

    In Trent's setup he has a remote intercom mounted on the ceiling after of the rear seat. I'm not a fan of that. The setup is nearly $30K I believe.

    My personal alternate plans IF I want IFR is to see if a different intercom can be used that goes behind the panel. Other options are to use the 175 over the GTR-200 with a blue level flight button that puts autopilot into level flight mode, all other features are done from the G3X for autopilot.

    I'll attach Trent's cockpit setup, it's pretty sweet, I just don't like the intercom situation.
    Attached Images Attached Images

  4. #4
    Senior Member Andy's Avatar
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    Default Re: Gnc 355

    Quote Originally Posted by hawgdrvr View Post
    Andy, I think you're talking about GPS 175.
    Yes, I have edited my post. Thanks.
    Last edited by Andy; 01-08-2021 at 06:51 PM.

  5. #5
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    Default Re: Gnc 355

    Quote Originally Posted by hawgdrvr View Post
    Andy, I think you're talking about GPS 175. I've been looking at this as Trent with his FX-3 got the GNC 355 setup. It's mounted over top of the GMC 305, a Garmin G5 left of the G3X. Here is the breakdown as you probably know.

    GPS 175 is WAAS GPS for the IFR use
    GNC 355 is a GPS 175 with a radio, no intercom
    GNX 375 is a 175 with Transponder

    In Trent's setup he has a remote intercom mounted on the ceiling after of the rear seat. I'm not a fan of that. The setup is nearly $30K I believe.

    My personal alternate plans IF I want IFR is to see if a different intercom can be used that goes behind the panel. Other options are to use the 175 over the GTR-200 with a blue level flight button that puts autopilot into level flight mode, all other features are done from the G3X for autopilot.

    I'll attach Trent's cockpit setup, it's pretty sweet, I just don't like the intercom situation.
    I agree itís really nice and adds welcome functionality. However, I donít think Iíd spend $20k on this upgrade. If it were priced at $12k I would do it. The equipment delta is circa $8k.


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  6. #6
    Senior Member Andy's Avatar
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    Default Re: Gnc 355

    Quote Originally Posted by Schwbo View Post
    The equipment delta is circa $8k.
    My preliminary estimate is about $5k for similar functionality (keep GTR 200, add GPS 175 and GAD 29, re-locate GMC 305). I'm retired and my labor comes cheap now.

    Until I get round to the mod I have programmed the RNAV approaches for my base airport as saved G3X routes. I should be able to fly practice approaches to RNAV minimums fully coupled. Days when it's IMC and safe to fly are few and far between in Arizona. (Note - this takes more effort than simply selecting "final approach". I strung all the approach waypoints and all the missed approach waypoints. In some cases the MAP had to be user defined.)

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