Garmin 430 Approach Activation question

Discussion in 'Cleared for the Approach' started by sarangan, Oct 13, 2020.

  1. aterpster

    aterpster En-Route

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    Nitpick: It is within 30 miles of the airport reference point. Lots of RNAV criteria are predicated on this 30 mile point from the ARP.
     
  2. Arrow76R

    Arrow76R Pre-takeoff checklist

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    And RAIM (Receiver Autonomous Integrity Monitoring) can be calculated for a specific airport at a specific time based on a minimum of 5 GPS satellites being received with appropriate geometry.
     
  3. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Why the heck not?!!!!

    :D
     
  4. MauleSkinner

    MauleSkinner Final Approach

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    Because that’s the angle “they” determined Shouldn’t be exceeded.

    yes, I know...but you weren’t specific. ;)
     
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  5. David Megginson

    David Megginson Pre-takeoff checklist

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    This is slightly different — the diagram shows where the GTN 650 will autoswitch the CDI to VLOC on an ILS approach — but the boundaries may be similar for activating an approach. For this case, you have to be within 1.2 nm on either side of the approach course, and between 2 nm and 15 nm before the FAF for the switch to happen.
    upload_2020-10-16_15-21-6.png
     
  6. John Collins

    John Collins Pattern Altitude

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    When you load an approach into the GNS, it inserts it as a flight plan section after the enroute section. You can edit the approach section or leave it as is. If you subsequently activate the approach, the effect is identical (except in the case of VTF) to selecting the first fix in the flight plan section and providing navigation via a direct-to the first fix. If you don't edit the approach section, it will always be direct to the original first fix in the approach section. If you edit the approach section, the first fix in the resulting approach sequence will be where the GNS will proceed direct-to. You can manually select any fix before the FAF in the approach section and use direct-to and the GNS will proceed direct and fully activate the approach sequence from that point. You can't go direct to the FAF as that will generate an error message to the affect that the approach has been cancelled. You can activate the leg ending at the FAF or you can activate the leg beginning at the FAF to the MAP. Either of those actions will end up providing you with vertical guidance for a GNS/W. Now on the GTN series, we have a visual approach option. You can get the equivalent on a GNS/W if you activate the leg between the FAF and the MAP (usually the runway) and I find this useful to obtain vertical guidance on a visual approach when you intercept the final approach course inside the FAF.
     
  7. chemgeek

    chemgeek Pattern Altitude

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    I both love and hate the fact that the GNS boxes have eleventy-seven ways to do the same task. It is sometimes the most challenging part of flying IFR!
     
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  8. David Megginson

    David Megginson Pre-takeoff checklist

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    If you upgrade to the GTN, you'll have eleventy-nine ways.
     
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  9. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Same as most computer programs.
     
  10. David Megginson

    David Megginson Pre-takeoff checklist

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    Extra data point -- today I tested going direct to the FAF (more specifically, the FAWP) in an RNAV approach several times in the Garmin GTN trainer, and every time, the GPS switched into LNAV mode (even when I was further out than the IAF/IAWP and fairly far off track). That doesn't mean the same would happen with the GNC 430, of course, since it's much-older software.
     
  11. aterpster

    aterpster En-Route

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    I was just reading up on the G-1000Nxi. For that "FMS" it is 45 degrees. :p

    That may very well be the TSO limit.
     
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  12. John Collins

    John Collins Pattern Altitude

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    It is similar for a GNS530W. You can't use direct-to the FAWP, even if you are dead center on the final approach course. The approach indication won't be there and at 2 NM to the FAF you get the error message Approach Not Active, but at the FAF, the LPV annunciation comes on and vertical guidance is available. You can activate the leg of the approach that ends at the FAF or at the RWT and LPV plus vertical guidance will be available.

    Direct to FAF approach not active GNS530W.jpg At FAF approach goes active and LPV annunciated.jpg
     
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  13. David Megginson

    David Megginson Pre-takeoff checklist

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    Interesting. I don't get the "Approach is not active" warning with the GTN trainer, just the switch to LNAV/LPV.