IFR-Choosing an alternate

Baronman

Baronman

Well-Known Member
I'm a little confused....

I have no problem determining if I need to file an alternate when planning an IFR flight, my problem is with determining if an airport is a suitable alternate based on its forecast weather.

I know the whole 600-2(precision) and 800-2 (non-precision) at time of arrival standards. But if the airport I want to file as an alternate has no TAF, how can I see that the weather will meet the requirement? The Area Forecast?
 
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The Area Forecast?

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Thats what I've always used (thats the way I was taught), and thats what I teach (on the rare occasion I get an instrument student).

Speaking of alternates, here's another one that I was pondering the other day. Why exactly is it that some airports cannot be filed as an alternate? I'm sure I knew at one point, but a guy asked me that other day, and all I could tell him was that sometimes it has to do with weather reporting capability (or lack thereof). But what are some other reasons why you can't use some airports as alternates? Weather can't be the only reason, because some airports that aren't available as alternates have both wx reporting capability, AND an IAP. (Kissimmee, FL, for example).
 
There are two reaons why they can't be used as an alternate. You are right about one, the lack of weather reporting capability, the second is having an unmonitored navigation system (VOR, ILS). (KFPR is a good example)
 
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[Why exactly is it that some airports cannot be filed as an alternate? I'm sure I knew at one point, but a guy asked me that other day, and all I could tell him was that sometimes it has to do with weather reporting capability (or lack thereof). But what are some other reasons why you can't use some airports as alternates? Weather can't be the only reason, because some airports that aren't available as alternates have both wx reporting capability, AND an IAP. (Kissimmee, FL, for example).



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Correct on FA, it's the next best WX to TAF.

Airports that have A-NA, or can't be filed as an alternate is:

1. Primarily for no WX reporting capability. If the airport is a part-time tower and WX is normally given on the ATIS, then there's no ATIS with the hourly WX when the tower is closed, only the ATIS saying the tower is closed and when it will reopen. If there's an AWOS/ASOS, then this might not be a problem.

2. If the approach is a GPS-only approach. Take a look at an IAP book and find an airport that has both GPS-only approaches and the standard ILS/VOR/TACAN approaches. If you look at the remarks box, the airport might be able to be filed as an alternate for the ILS approach plate, but if you look at the GPS-only approach plate for the same airport, it will say A-NA. This is because........

3............the NAVAID is unmonitored. Any airport with a NAVAID that is unmonitored, or a GPS-only IAP is unusable as an alternate.
 
Cool...thanks guys!
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(I should have known that though...oh well, now I do!)
 
Thanks guys...I guess there was some brain cell back in my head that had learned once upon a time that it was the Area Forecast. Good thing to know...I'll sleep better tonight
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3............the NAVAID is unmonitored. Any airport with a NAVAID that is unmonitored, or a GPS-only IAP is unusable as an alternate.


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What does that mean? A low powered VOR not on a victor airway? Because my airport has a VOR approach from a VOR not on a victor airway and it can't be used as an alternate.

Thanks for the help

Surf
 
Remember that an alternate is ALWAYS required UNLESS certain conditions are present. So an airport with no weather would always require an alternate.
 
An airport with no IAP would always require an alternate. Having wx reporting capability has no bearing on whether an alternate is required, just whether you can use a certain airport AS an alternate.

An alternate is only not required when: The airport has an approved IAP (besides GPS) and the weather is above the 1-2-3 rule.
 
One thing that not many people realize is that if you use GPS in lieu of DME, you cannot file an airport as an alternate if the approach you need would require DME.

For example: You check the weather reports at your destination and realize you need an alternate. You check a nearby airport that has an ILS and standard alternate minimums. The weather is forcast to be 700-2 so you decide to file this as an alternate. You notice that the ILS plate has a note that DME is required. If you are using GPS for your DME information (your aircraft has an IFR certified GPS, but does not have DME) you cannot file this as your alternate.

The same rule applies if you are using GPS as a substitute for an ADF.
 
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