G5 vs SI 275

Discussion in 'Avionics and Upgrades' started by murphey, Feb 15, 2020.

  1. murphey

    murphey Final Approach PoA Supporter

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    Dithering. Do I want the G5 HSI or the GI-275 HSI?
    Considerations:
    • $1300 retail difference (G5 cheaper)
    • Already have the G5 AI installed
    • G5 has 4 hr battery backup, GI 275 only 1 hour backup (according to Garmin website)
    • Don't need the Enhanced HSI option on the GI 275, will have GPS 355 and the iPad for redundancy
    • [another update] GI 275 has bigger and brighter display
    • [update] No plans for AP
    I'm dithering. Plan is for Aug or Sept for install along with the GPS
     
    Last edited: Feb 15, 2020
  2. chemgeek

    chemgeek Pattern Altitude

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    I'd get the matched set of G5s. The GI 275 has a nice screen, but won't make you fly better. There are lots of G5s in service, and if you have a legacy rate-based AP, a G5 will work well, and someone has figured out the proper configuration already.

    On the Grumman Gang, a pilot reported the consequences of a total electrical failure in flight with dual G5s, and it was indeed comforting to see an emergency countdown timer showing in excess of 4 hours of backup power. If flying IFR, this is important indeed.

    The biggest installation challenge is finding a good spot for the GMU-11.
     
    Last edited: Feb 15, 2020
  3. asicer

    asicer Final Approach

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    The GI-275 is easier to install if it's going into a round hole. Will it save you 10-12 hours of labor?

    BTW, it's "GI-275", not "SI-275". It's a Garmin product, not a Sandel product. ;)

    If I suffer an electrical failure flying IFR and put myself in a position where I'm going to need more than 1 hour of backup then I need to plan better.
     
    Last edited: Feb 15, 2020
  4. murphey

    murphey Final Approach PoA Supporter

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    Not sure. Original quote is for the round thingy. I'm not devoted to round or square.
    snorf.
    Very true
     
  5. NordicDave

    NordicDave Cleared for Takeoff

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    Get the 2nd G5, you will not be sorry. My opinion, the 275 is trying to do too many things in a small space.
     
  6. murphey

    murphey Final Approach PoA Supporter

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    But then there's also the highly anticipated AV-30 HSI at considerably less money.
     
  7. asicer

    asicer Final Approach

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    Technically the AV-30 is not a true HSI but rather just a DG, at least initially but this may change in the near (or far off) future.
     
  8. chemgeek

    chemgeek Pattern Altitude

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    Why would you want to mix and match a Frankenglass panel and make the gyros even more difficult to communicate with each other? The G5s interconnect, allowing display of certain nav information on both instruments, and provide instant AI redundancy should the need arise. The AV30 does not include a remote magnetometer.

    What are your current or future nav and AP plans? Having different AI and HSI devices will likely make a hash out of interconnecting these devices to them. Or anyone else who will own the plane in the future.
     
  9. chemgeek

    chemgeek Pattern Altitude

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    This assumes your batteries maintain 100% of their original capacity over time, or are fully charged on startup. If I haven't flown in a while, the G5 batteries will not register 100% on startup. So your 1 hour of reserve might be considerably less than an hour as batteries age. If the G5 batteries lose half their capacity over time, they are still generous in an emergency.
     
  10. chartbundle

    chartbundle Cleared for Takeoff

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    Although it's not required for many types of operations I know the ICA for most of these devices with battery backups have a test procedure or a replacement requirement. I think even if not required it's probably a really good idea if you use them for IFR. My RC Allen battery requires replacement every 3 years. The GI-275 requires a test every 12 months with a minimum rundown time of at least 30 minutes for aircraft approved for flights at 25,000 or less.

    Obviously until they're out in the field there's no way to know if the average time when new is 61 minutes or 3 hours.
     
  11. murphey

    murphey Final Approach PoA Supporter

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    [update] No plans for AP.
     
  12. David Megginson

    David Megginson Pre-takeoff checklist

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    Unfortunately, it turns out the AV-30 in HSI mode isn't certified as the primary CDI (unlike a G5 or GI-275), so it's not comparable. The HSI display is "advisory only", and works only for RNAV, not for VNAV.

    It's too bad. I was excited about the AV-30 at first--because of the round form-factor--but it turns out the certified version will be almost as expensive as a G5, but will do a lot less (no GPSS, no CDI, no heading output to the A/P, no magnetometer option, etc). As it stands now, it's just an expensive toy rather than a cheap HSI.
     
  13. David Megginson

    David Megginson Pre-takeoff checklist

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    The much-higher resolution and round form factor for the GI 275 look nice. The downside (besides shorter backup batter, higher price, and lack of GFC-500 compatibility) is that it locks you into buying database subscriptions from Garmin for some features, while the G5 itself doesn't.

    But I still can't imagine myself ruining my panel with the ugly square G5 displays (much less an even-uglier E5 rectangle), so I don't know what I'll do when my mechanical AI and DG wear out. Let's hope they keep running for a while.
     
  14. bnt83

    bnt83 Final Approach PoA Supporter

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    Imho G5 all the way, the standby batteries cost half and the units themselves are almost half.

    also, front mounted they are easier to service despite the possibility of being more work to install initially.

    unless you have compatible interfaces like WAAS GPS and ADS-B in and/or pay for options the GI275 is gonna be a blank looking thing similar to the G5 anyway, at double the cost
     
    Last edited: Feb 15, 2020
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