GNC 355 vs GTN 635

Discussion in 'Avionics and Upgrades' started by AA5Bman, Nov 4, 2019.

  1. AA5Bman

    AA5Bman Pre-takeoff checklist

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    I’m comparing these two WAAS GPS/Comm units, and as far as I can tell the only real difference between the two is the screen size. Not having used either of them, however, I don’t really know.

    Does anyone know if there is a difference between these units other than screen size?
     
  2. Jesse Saint

    Jesse Saint Pre-takeoff checklist

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    The GTN has more serial and arinc ports/options. Price is different too. Besides that, screen size.
     
  3. Sinistar

    Sinistar En-Route

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    The GTN does not have a NAV radio (for VOR)?
     
  4. Jesse Saint

    Jesse Saint Pre-takeoff checklist

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    The 650 does. The 635 doesn’t.
     
  5. AA5Bman

    AA5Bman Pre-takeoff checklist

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    Neither of these units have the Nav function.

    Can you translate this as to how it might affect the user / owner? I’m guessing it would limit how many different things you can talk to, but I’m wondering if it would limit, for instance, a dual G5 + future GFC500 panel?
     
  6. Jesse Saint

    Jesse Saint Pre-takeoff checklist

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    For the average user, especially going with G5’s and a GFC500, the difference is screen size. I think the GTN May have some more VNAV functions, but don’t know much about that.
     
  7. asicer

    asicer En-Route

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    Ah yes, VCALC vs VNAV. I believe @flyingcheesehead can probably explain it better than me.
     
  8. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    I'm not sure what functions the newer more economical boxes have, but here's the difference.

    VCALC lets you manually set a distance before the destination, an altitude above the destination, and a descent rate and it will alert you when to start your descent.

    VNAV lets you enter altitudes for any point in your flight plan, including multiple points and along-track offsets. If you have any glass to go with it (G5, G3X, G500, etc) you'll actually get a glideslope indication, and if you have a Garmin autopilot it'll automatically initiate the descent if you press the VNAV button and set the bug to the lowest target altitude you've been cleared to.

    With a GTN, VNAV requires an altitude source to be interfaced with the GTN. Right now I have relatively "dumb" steam gauges - My altimeter provides the baro setting to the autopilot but that's about it, so I would have to hook it up through an air data computer. As a result, VCALC is all I can do. If I added a G5, I could do VNAV.

    I'm not sure whether the newer, cheaper units (355, 375) will do VNAV right now or not, and if not, whether they'll get software updates to add it in the future. The GTN didn't have VNAV until last year (v6.50 of the software) so even if the 355/375 don't do it now, they may in the future.
     
    Last edited: Nov 8, 2019
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  9. joeb2300

    joeb2300 Filing Flight Plan

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    Looks good. I have a similar situation.
     
  10. N1120A

    N1120A Cleared for Takeoff

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    If you are hooking up to a G5, you really should get a 650.
     
  11. WannFly

    WannFly En-Route

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    speaking of 650... are there any differences between 650 and the latest and greatest XI or whatever its called apart from a faster processor? i am guessing a lot of used 650 will hit the market soon enough
     
  12. bnt83

    bnt83 Final Approach PoA Supporter

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  13. bnt83

    bnt83 Final Approach PoA Supporter

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    My brother is working on a GPS 175 now, it cannot do anything but HSDB (aka eternet) traffic & weather interface, it cannot input fuel flow data and display range rings and I'm sure there are other things I have yet to discover.

    It cannot do TAWS/HTAWS, display on board aircraft weather radar, etc.
     
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