Filing alternate on IFR.

Discussion in 'Cleared for the Approach' started by John777, Nov 26, 2016.

  1. John777

    John777 Pre-takeoff checklist

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    I read the text from IPH stating as follow:-

    'Because GPS is not authorized as a substitute means of navigation guidance when conducting a conventional approach at an alternate airport, if the approach required either DME or ADF, the aircraft must be equipped with the appropriate DME or ADF avionics in order to use the approach as an alternate...'

    Now, we know that GPS substitutes the DME, and here in the text says we actually need an actual DME equipment to fly approaches such as VORDME, ILSDME.

    I just wanted to verify if this text is outdated or applies to everyone equipped with WAAS capabilities.

    John.
     
  2. jordane93

    jordane93 Final Approach PoA Supporter

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    That's with non WAAS GPS. Your alternate has to have an approach other than a GPS approach. With WAAS units, your alternate can only have GPS approaches and you'd be fine.
     
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  3. John777

    John777 Pre-takeoff checklist

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    Ok. so even though I shoot VORDME approach or ILSDME at airport/Alternate, I can substitute DME with GPS correct?
     
  4. midlifeflyer

    midlifeflyer Final Approach

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    Perhaps this will help understand: the purpose of the rule is to make sure you have planned an option that relies on ground stations, not GPS.

    Just like we've discussed that you do not have to go to the alternate, there is no requirement to use the DME instead if the GPS in order to fly the approach.
     
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  5. pfking

    pfking Filing Flight Plan

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    The guidance in AIM 1-2-3(d) was updated a while back. If your non-WAAS GPS has fault detection and exclusion capability, and you perform a pre-flight RAIM check, then you may file based on a GPS-based IAP at either your destination or your alternate, but not both. If the above conditions can't be met, then the alternate airport must have an approach that does not require the use of GPS.

    If you have only GPS as a substitute for DME in your airplane, and no DME radio, then all approaches that require DME consequently require the use of GPS in that airplane.
     
  6. tsts4

    tsts4 Line Up and Wait

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    And don't forget the alternate selection rules apply only for filing purposes. Once in the air you can fly any approach you are equipped to fly (e.g. even with a non-WAAS GPS use GPS for DME, fly GPS at destination go missed and shoot a GPS at the alternate, etc) or divert to an airport that wasn't what you filed as your alternate.
     
    Last edited: Dec 30, 2016
  7. TheGolfPilot

    TheGolfPilot Pre-takeoff checklist

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    As long as the approach doesn't have a black triangle with a A in it followed by a NA next to it, you can use it. Gps or not. (Weather, notams, equipment, etc permitting of course.
     
  8. tsts4

    tsts4 Line Up and Wait

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    When you say "use" are referring to filing or flying?
     
  9. TheGolfPilot

    TheGolfPilot Pre-takeoff checklist

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    I should change that to filing. You need to have a fully (I hate the word but) compliant alternate approach. When it comes down to actually flying, whatever you want to do, but you need to be able to fly what you filed.
    I forget the exact situation but from one New Mexico airport to I forget where if the nearest alternate airport, which had an ils, had its ils system down, there wasn't another airport you could fly to legally despite other airports having non alternate approaches. With a fully loaded 172
    In most places it isn't really an issue but in the southwest it's something you have to think about.
     
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  10. tsts4

    tsts4 Line Up and Wait

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    Gotcha-- I just wanted to be sure we were on the same page, so to speak,