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#1
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Alternate airports
OK I picked this topic after reading through the 'flying to hamvention''
thread. Being a non-instrument rated private pilot, not sure what constitutes a 'legal' alternate airport. If VFR, weather minimums must be met just to get there. If IFR, I assume there is visibility minimum (decision height?) that could cause a plane to not be able to land using ILS or whatever. So what is the process for choosing an alternate? |
#2
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"Mike W." wrote in message
... [...] So what is the process for choosing an alternate? It can be quite complex, especially for Part 91 because so much is left to pilot discretion. Basically, an alternate needs to be forecast to meet the requirements given for that airport (its "alternate airport minima" specified for a given instrument approach at the airport). One is not even required to have an alternate if the intended destination meets some basic weather forecast requirements. See FAR 91.169 for the nitty-gritty. However, in reality what you're trying to do when selecting an alternate is to provide for a genuine Plan B. This means you need to consider the weather that is causing you to want an alternate in the first place, and to pick an airport that will not be similarly affected. This may mean picking one that's not in the same valley, on the same side of a mountain range, near the ocean shore, etc. Of course, you also need to pick an airport that is suitable for your airplane and your piloting skills. A person could write a whole chapter in an IFR training manual on the topic. Between this post and many others you'll get, maybe you'll get an inkling of what's actually involved. Pete |
#3
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If the destination does not have an instrument approach you must pick an
alternate. If the destination has an instrument approach, then you don't need an alternate unless the the weather is worse than 2000' ceiling or 3SM vis +/1hr of the ETA. (ie if the forecast is worse than VFR then you need an alternate). You can't pick any airports as an alternate. Only a few airports qualify as an alternate. "Mike W." wrote in : OK I picked this topic after reading through the 'flying to hamvention'' thread. Being a non-instrument rated private pilot, not sure what constitutes a 'legal' alternate airport. If VFR, weather minimums must be met just to get there. If IFR, I assume there is visibility minimum (decision height?) that could cause a plane to not be able to land using ILS or whatever. So what is the process for choosing an alternate? |
#4
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"Andrew Sarangan" wrote in message
1... If the destination does not have an instrument approach you must pick an alternate. If the destination has an instrument approach, then you don't need an alternate unless the the weather is worse than 2000' ceiling or 3SM vis +/1hr of the ETA. (ie if the forecast is worse than VFR then you need an alternate). The above is not "the process for choosing an alternate". It's the process for deciding whether you NEED an alternate. You can't pick any airports as an alternate. Only a few airports qualify as an alternate. Wrong. Any airport qualifies, as long as the forecast is for VFR conditions from the descent from MEA all the way to the ground. Beyond that, lots of airports have instrument approaches and thus qualify as an alternate under lower forecast conditions. Even in IFR conditions, it's far from true that "only a few airports qualify as an alternate". Pete |
#5
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"Peter Duniho" wrote in
: "Andrew Sarangan" wrote in message 1... If the destination does not have an instrument approach you must pick an alternate. If the destination has an instrument approach, then you don't need an alternate unless the the weather is worse than 2000' ceiling or 3SM vis +/1hr of the ETA. (ie if the forecast is worse than VFR then you need an alternate). The above is not "the process for choosing an alternate". It's the process for deciding whether you NEED an alternate. But you have to first decide whether you need an alternate before going to the trouble of picking one. You can't pick any airports as an alternate. Only a few airports qualify as an alternate. Wrong. Any airport qualifies, as long as the forecast is for VFR conditions from the descent from MEA all the way to the ground. Beyond that, lots of airports have instrument approaches and thus qualify as an alternate under lower forecast conditions. Even in IFR conditions, it's far from true that "only a few airports qualify as an alternate". Pete Any airport does not qualify. Most of those airports have "A-NA" on the chart, which stands for "Alternate - Not Authorized". The thread was a follow-up to 'flying to hamvention' thread. If you look at the Dayton area, there aren't any airports within a short distance of DAY that does not have an "A-NA" on it. |
#6
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"Andrew Sarangan" wrote in message
1... But you have to first decide whether you need an alternate before going to the trouble of picking one. So? Any airport does not qualify. Most of those airports have "A-NA" on the chart, which stands for "Alternate - Not Authorized". FAR 91.169 doesn't say anything about whether an alternate is authorized or not. ANY airport is authorized, as long as VFR conditions from MEA to landing are forecast. The thread was a follow-up to 'flying to hamvention' thread. If you look at the Dayton area, there aren't any airports within a short distance of DAY that does not have an "A-NA" on it. Ideally, an alternate would not be a short distance from your destination anyway. After all, if the weather's too poor for landing at your destination, often it will be at a nearby airport as well. In any case, while something in that thread brought this to the original poster's attention, the fact that he posted in a new thread implies to me that he intended the question as a general one, not specific to that particular destination. Pete |
#7
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Ideally, an alternate would not be a short distance from your destination
anyway. After all, if the weather's too poor for landing at your destination, often it will be at a nearby airport as well. Not necessarily, IMHO. If the airport you are aiming for has high minima (such as an NDB approach into the hills), and right nearby there is an airport with low minima (such as an ILS), then under many weather circumstances it is quite reasonable to use the neighboring airport as an alternate. OTOH, if the weather system is wide and threatens to possibly go low (probably all over), then such a choice is... er... less optimal. You'd want an airport (and the gas to get there) that is outside the weather system. The excercise of choosing a "legal" alternate has more to do with gas than anything else. You need the gas to get there, and still fly almost an hour at full cruise. Once you're in the air, and you actually =need= an alternatative landing site, you can use any airport as that alternative landing site, no matter what you filed in your flight plan as a legal alternate, and no matter whether or not the airport is A-NA on the charts. It just becomes an ordinary destination (albeit an unplanned one) Jose -- Get high on gasoline: fly an airplane. for Email, make the obvious change in the address. |
#8
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"Jose" wrote in message
. com... Ideally, an alternate would not be a short distance from your destination anyway. After all, if the weather's too poor for landing at your destination, often it will be at a nearby airport as well. Not necessarily, IMHO. "Often" is not the same as "always". I already pointed out in my initial reply that choosing an alternate is a complex exercise. It is pointless of you to take me to task for a comment that was obviously not meant to cover all the bases. Pete |
#9
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"Peter Duniho" wrote in message ... However, in reality what you're trying to do when selecting an alternate is to provide for a genuine Plan B. This means you need to consider the weather that is causing you to want an alternate in the first place, and to pick an airport that will not be similarly affected. Pete I think Pete has a bit of key advice here. I favor picking one along my route of flight but prior to my destination. That way if things are going south at the destination you can just land at the alternate and take a look at alternatives. |
#10
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"Often" is not the same as "always". I already pointed out in my initial
reply that choosing an alternate is a complex exercise. It is pointless of you to take me to task for a comment that was obviously not meant to cover all the bases. Well, I wasn't "taking you to task". And my reply was not so much to =you= as to the idea, often repeated as a mantra, that an alternate should be outside the weather system to be really useful. Jose -- Get high on gasoline: fly an airplane. for Email, make the obvious change in the address. |
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