Alternate required?

Discussion in 'Cleared for the Approach' started by FlatPiglet, Jan 25, 2021.

  1. FlatPiglet

    FlatPiglet Filing Flight Plan

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    So here's a TAF for a proposed destination:

    FM261500 36005KT P6SM OVC050
    PROB30 2616/2618 2SM -SN BR OVC020

    Is an alternate required? The base forecast says no, but there's a 30% chance of less than 3 mile visibility. Does that 30% create the requirement for an alternate?

    I know it's not a big deal to add one, and it's a good idea to have in mind..I'm asking purely from a regulatory POV, not an ADM POV.
     
  2. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    My understanding is that the 30% probability of 2SM visibility means that you do have to file an alternate.
     
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  3. EdFred

    EdFred Taxi to Parking

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    That's not answered in 14CFR91.

    Gonna need a CC interpretation, and I didn't see one addressing that specifically in the first 5 pages I looked through.

    I did however see a question of "can my destination be my alternate also? I think it can."

    W. T. F.

    BTW, the answer was no.
     
  4. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Yes.
     
  5. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Sure it is.

    Unless otherwise authorized by the Administrator, no person may include an alternate airport in an IFR flight plan unless appropriate weather reports or weather forecasts, or a combination of them, indicate that, at the estimated time of arrival at the alternate airport, the ceiling and visibility at that airport will be at or above the following weather minima:​

    A forecast saying there's a 30% probability it won't be is not a forecast saying it will be. As I recall from the olden times, this iis/was a question on the knowledge test.

    The problem with alternate requirement is that they are often taught backwards — "we only need an alternate when..." — when the regulation actually tells us "we always need and alternate unless..."
     
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  6. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Also:

    Paragraph (a)(2) of this section does not apply if : ... For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the estimated time of arrival, the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.​

    Which also says "will be."

    The OP's example TAF tells us, in effect, that there is a 70% chance that the visibility will be greater than 3SM, not that it "will be" greater than 3SM.
     
    Last edited: Jan 25, 2021
  7. cowman

    cowman En-Route PoA Supporter

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    Just file an alternate and don't worry about it if in doubt. It's not like you HAVE to go there.
     
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  8. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    Yep, PROB and TEMPO are count like they were sure things.
     
    Last edited: Jan 25, 2021
  9. Tantalum

    Tantalum Final Approach

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    Is there any reason you would not file an alternate for standard practice?

    there could be a whole host of reasons why at the last minute you can't go to your originally planned destination.. might as well have a backup planned and briefed

    Right??
     
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  10. wayne

    wayne Pattern Altitude

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    And if you can't get into your destination you can go to an airport that is NOT your filed alternate.
     
  11. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    I guess it doesn't hurt to file an alternate even if one is not required, but you still need to know whether the alternate is required or not, because that determines whether your fuel planning must account for flying from your destination to your alternate, and that can affect whether you're going to have to make a fuel stop or not.
     
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  12. Salty

    Salty Final Approach

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    Not if you assume you need the fuel and plan accordingly.
     
  13. Tantalum

    Tantalum Final Approach

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    Personally speaking as I slowly get older I find my flying style has shifted towards the more careful side. There's nothing wrong with having an alternate on a clear VFR day and enough fuel to get there. You never totally know what might happen. Maybe you're going somewhere with a single runway and a plane gets disabled there? Now what? Rather than scramble it's easy to just automatically switch to option 2

    But I agree, one should still know the rules

    For what's it's worth, in the case of the OP, to me a "30% chance" of it being below the requirement means I need an alternate as I cannot definitely say that it WILL be within the required limits
     
  14. midwestpa24

    midwestpa24 En-Route

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    I have to say, I've never seen PROB in a TAF.
     
  15. jordane93

    jordane93 Final Approach

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    JFK TAF today. It’s definitely not uncommon.

    [​IMG]
     
  16. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    I fly into fields with no approaches, so I file alternates all the time anyhow.
     
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  17. EdFred

    EdFred Taxi to Parking

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    But that's for the alternate. The OP showed the weather for the destination. That quoted reg doesn't apply.
     
  18. EdFred

    EdFred Taxi to Parking

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    Where's the source for that?
     
  19. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    The destination is covered by:

    (2) Appropriate weather reports or weather forecasts, or a combination of them, indicate the following:

    (i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the estimated time of arrival, the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.


    So it's even broader there. IF anytime during the two hour window around the ETA, it could possibly or temporarily be worse, then you need the alternate. As I said, PROB or TEMPO as as good as the sure thng.

    If there's a probability or temporarily lower the two hours, it's no longer the case that the ceiling and visibility will be above the limits mentioned. While I don't think you will find a hard reference for GA, the sense of the FAA's application of these conditional blocks to things like Part 121 supports this interpretation.
     
    Last edited: Jan 26, 2021
  20. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Oops. Bad copy/paste. How about (b)(2)? Same "will be" language for when you don't need a filed alternate.

    (b)(2) Appropriate weather reports or weather forecasts, or a combination of them, indicate the following:
    (i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the estimated time of arrival, the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.​
    Probability it "won't be" is still not "will be."
     
    Last edited: Jan 26, 2021
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  21. kgruber

    kgruber En-Route

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    Out here in the west we just filed Lewiston Idaho as an alternate. It is always (never use that word) a good choice.
     
  22. MauleSkinner

    MauleSkinner Final Approach

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    So you’re saying the reg says exactly what it means?!?
     
  23. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    I love it when a plan comes together.
     
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  24. eman1200

    eman1200 Touchdown! Greaser!

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    Cancel IFR and go wherever the F you want? I would think as part of GOOD pre flight planning you’ve considered alternates whether you filed one or not. But yeah, doesn’t hurt to actually file it.
     
  25. EdFred

    EdFred Taxi to Parking

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    But we all know forecasts aren't 100% either. They aren't a will be, just better than 70% chance of will be. Just like as I look outside today. This forecast was wrong. Every forecast is a probability, and not a guarantee. The regulation you quoted said "will be" as in guaranteed. Iron clad. 0 chance of it not being. But that's never the case. So where's the regulation that says 70% probability is unacceptable but an unlisted probability is acceptable? That's all I'm asking.

    All this said, I'd file alternate, but the question wasn't "would you."
     
  26. MauleSkinner

    MauleSkinner Final Approach

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    The reg says weather reports/forecasts indicate that the weather “will be”, not the weather “will be”.

    Reports and forecasts can be wrong, but the reg says they’re what you need to use.
     
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  27. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    I think there's a bit of regulitis at work here :rolleyes:
     
  28. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    And it's even plain English!
     
  29. EdFred

    EdFred Taxi to Parking

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    So, if it can be demonstrated that over a given time period the forecasts for a certain area are historically wrong a given percentage of the time, say 40% of the time, are we now required to file an alternate because history indicates that forecasts only have a 60% accuracy? I mean, I am using "all available information" for that flight, am I not?

    If we want to let the regs be open for interpretation, then let's open them up for interpretation.
     
  30. MauleSkinner

    MauleSkinner Final Approach

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    The reg doesn’t provide a means to determine the statistical accuracy of the forecast, nor do I believe an advisory circular exists on the subject. If the forecast is wrong, hopefully the reports will reflect that, and you can make your determination legally. If both are wrong, you might plan and file an alternate that you don’t need, don’t plan and file an alternate that you don’t need, or don’t plan and file an alternate that you do need.

    in any case, you keep up with the weather enroute, and divert if necessary.

    Why open them for interpretation when reading them works?
     
    Last edited: Jan 26, 2021
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  31. Arnold

    Arnold Cleared for Takeoff

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    Related question: Now that textual area forecasts are gone, is it permissible to use the graphic forecast if your destination or alternate do not have a TAF?
     
  32. midlifeflyer

    midlifeflyer Touchdown! Greaser!

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    Yes. Again its in the plain English words of the regulation: "Appropriate weather reports or weather forecasts, or a combination of them, indicate the following..." It doesn't say "A textual area forecast or TAF indicates the following..."

    I'm sure someone can play around with what are considered "appropriate" reports and forecasts, but it's basically a recognition that technology changes and some things just aren't' conducive to super detailed regulation.
     
  33. Arnold

    Arnold Cleared for Takeoff

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    I am in complete agreement.
     
  34. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    Taking the reg literally, it says that the alternate requirement is to be based on what the forecasts "indicate," which in the OP's example is that there is only a 70% chance of the visibility being better than 3SM. The purpose of the requirement to file and carry fuel for an alternate is to protect ourselves from the consequences of the known inaccuracy of forecasts. Treating a 70% chance as equivalent to "will be" and therefore sufficient to avoid the alternate requirement would defeat that purpose.

    On the other hand, using the known inaccuracy of forecasts as a requirement to ALWAYS file an alternate would render 91.169(b)(2) meaningless. My understanding is that courts tend to reject interpretations that render the regulation being interpreted meaningless.
     
    Last edited: Jan 26, 2021
  35. Arnold

    Arnold Cleared for Takeoff

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    Yes, but ambiguous regulations are usually left to the interpretation of the agency.
     
  36. Palmpilot

    Palmpilot Touchdown! Greaser! PoA Supporter

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    My understanding is that ALL regulations are left to the interpretation of the agency. :(
     
  37. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    The fact that forecasts aren't accurate is why the alternate require is pretty broad: 2 hours, 2000-3. If they were dead on accurate, the alternate would only be required if the weather at the destination was close to the minima for the approach.
     
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