Alternate Airport Selection Minimum

AggieMike88

AggieMike88

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The original "I don't know it all" of aviation.
In my study for the checkride, I think I've come across a nugget of information I wasn't sharp on before... And want to check with the CFII's here to make sure I got it down right.

For alternate airport selection, I'm good with knowing 600/2 for precision approach and 800/2 for non-precision, and that the approach must be one that I and the airplane are capable of doing.

I am also familiar with the the "Triangle A" in the briefing strip as a hint that there is additional details I need to know in the form of approach minimums. And for this, I go to Section L of the Terminal Procedures book and read up on the info.


What I just discovered was when the "N/A" appears there. From what I'm reading, am I correct that when this appears next to the "Triangle A", then this particular approach for that particular airport can not be selected as my alternate.

For an example. Look at the ILS 18 for Denton, KDTO and the RNAV (GPS) 18 for Denton.

The ILS approach has the N/A next to the Triangle A. So from this, I am saying that, as my alternate airport, I cannot use this approach.

However, the GPS approach does not have the N/A. So from this, I am saying that, as my alternate airport, I can use this approach, since my aircraft is equipped with an IFR certified GPS (CNX80/480).

Correct?

Applying this information further, if my aircraft was not equipped with an IFR certified GPS, Denton is totally out of the picture for an alternate airport. Correct?

--------------------------------

Man, so much to learn, but all of this does sort tickle the inner aviation geek.
 
To take it a step further, what are the rules on using a TSO C129 certified GPS receiver versus a TSO-C146 receiver? Hint, the latter is WAAS capable...
 
The only requirement for an alternate airport is the availability of on-airport rental cars ;) .
 
Mike look at page 4 of the Digital Terminal Procedures Supplement. The Triangle A n/a is Alternate Minimums are not authorized due to un monitored facility or absence of reporting service. It's my understanding that the airport is not allowed as an alternate. But I am not an expert.
 
You have to pick your alternate based on the availability of an approach that you are capable of flying (i.e., you are equipped for, it's not NOTAM'd out, and it's not N/A or below the published or standard alternate minimums).

As pointed out, not monitoring a navaid is one of the reasons that the approach may be NA. Obviously and ILS is sort of a local thing. VORs typically are monitored elsewhere. GPS approaches don't need external monitoring (though as already pointed out, if you're not using a WAAS unit, you can't use it for the alternate either).

The rules are specified in 3.4 of the TERPS (order 8260.3). It depends on weather availability, lighting, as well as monitoring.
 
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Yes, if you don't have GPS, Denton would be out as far as you are concerned for alternate planning purposes due to that A N/A on the ILS.

However, keep in mind that's only a planning function, once you get in the air, if you want to fly to Denton, that's perfectly fine.
 
RussR said:
Yes, if you don't have GPS, Denton would be out as far as you are concerned for alternate planning purposes due to that A N/A on the ILS.

However, keep in mind that's only a planning function, once you get in the air, if you want to fly to Denton, that's perfectly fine.
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As I understand it, the alternates are for planning. Once you decide to abandon your original destination and go to your alternate, the alternate becomes your destination and you can then look at plate minimums.
 
asgcpa said:
As I understand it, the alternates are for planning. Once you decide to abandon your original destination and go to your alternate, the alternate becomes your destination and you can then look at plate minimums.
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You have to use the alternate minimums if you decide to use that airport as an alternate. Otherwise, there would be no point of posting alternate minimums.
 
jordane93 said:
You have to use the alternate minimums if you decide to use that airport as an alternate. Otherwise, there would be no point of posting alternate minimums.
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No you don't. You fly the applicable minima as listed on the approach chart. Alternate mins 600-2, 800-2, or non-standard as identified by the triangle "A" are for planning purposes only.
 
tsts4 said:
No you don't. You fly the applicable minima as listed on the approach chart. Alternate mins 600-2, 800-2, or non-standard as identified by the triangle "A" are for planning purposes only.
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Yea that's correct. My fault, I need to brush up on some instrument stuff.
 
Plus you need to get to that legal alternate, shoot an approach and fly for another 45 min.

That may not be problem near most cities served by the airlines since an air carrier legal airport is usually by definition also a legal alternate.

Keep in mind that in some of the more rural locations, if your destination is the air carrier airport - you may not have a legal reachable alternate after a long flight. . . .

So what I do [and this is in places like the northern plains, north west, and Southwest even] is if you need a legal alternate to file and accept an IFR clearance, you dispatch to one of the close by airports on your route of flight, using the legal alternate as your alternate even though it may be your destination. That airport does not require an IFR approach - but your alternate does. This way you simply change destination to your alternate and there you go - legal IFR.

This is a situation where legal is not always safe - because - if your real destination is below mins - where do you go?
 
murphey said:
me too. if not legal as an alternate for planning then why, all,of a suddedn, is it legal when in the air?
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Because in pre-flight planning, the process to plan for an alternate driven by the 1-2-3 rule (91.169) is really about fuel planning. In the air, you fly the approach as depicted on the plate to whatever minima the equipment and actual weather conditions dictate. For example say I listed an alternate with an ILS because based upon the forecast the weather there was at least 600-2. Once in the air I determined I had to divert to the alternate which was now reporting 400-1. However since the ILS mins are say 200-1/2 I can still shoot the approach, because I'm using the minimums listed for the straight in ILS vs. the planning mins of 600-2. In the end all the 600-2 does is establish reasonable criteria for the alternate selection so that I have planned for either adequate fuel or other options.
 
murphey said:
me too. if not legal as an alternate for planning then why, all,of a suddedn, is it legal when in the air?
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The intent is to have a conservative plan, with the assumption that a basic GPS may not have sufficient signal integrity to complete the approach (one of the reasons you do a RAIM check on your non-waas GPS prior to flight), and the weather worse than forecast.

Once you're in the air, you can use whatever approach you wish. You can fly the initial approach as well as the alternate now to the lowest mininums available.

This is one of the lesser advertised benefits of WAAS. In my home state (VA), every airport has a GPS approach of some type. Not all of them qualify as alternates, but it's handy to have.
 
AggieMike88 said:
The ILS approach has the N/A next to the Triangle A. So from this, I am saying that, as my alternate airport, I cannot use this approach.
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Correct.

However, the GPS approach does not have the N/A. So from this, I am saying that, as my alternate airport, I can use this approach, since my aircraft is equipped with an IFR certified GPS (CNX80/480).
Click to expand...
Correct.

Applying this information further, if my aircraft was not equipped with an IFR certified GPS, Denton is totally out of the picture for an alternate airport. Correct?
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Depends on the weather. You can still use Denton without a GPS if the forecast weather allows descent and landing under VFR from the MEA per 91.169(c)(2). Yes, I know the plain language says that applies for airports with no published approach, but it's OK to do that with no published approach you can use. Really. Just like it's not OK to use the published alternate mins for a published approach you can't fly. Common sense, all that, and you can ask your local FSDO if you don't believe me.
 
Todd got it right. The alternate you file is of little consequence other than assuring that in lesser whether conditions you have enough fuel reserve. As far as ATC or anybody else is concerned, you can (and should) have as many alternates for the case of not being able to complete the planned flight as you think practical. ATC doesn't know or care what your alternate is. Once you can't go to your destination, they only want to know where to next (and these days, why).

The altnernate/fuel reserve rules are somewhat inadequate. Let me give you an example.
My regular flight is CJR -> NC26 (which is a private strip 6 miles S of SVH).

To be LEGAL, since NC26 has no approaches, I have to file an alternate. Well SVH has an ILS and it takes less than a gallon to get there. So I don't have to add really any fuel over the 45 minute reserve on such a flight.

Now, let's say I actually WANTED to go to SVH. If I wanted to go to SVH on a day that 123 applies. Then the nearest legal alternate is really 20 miles more away.

So is it prudent that going into no approach, 2900' grass strip really should require less fuel than going into a 5500 strip with an ILS? No, I plan more.

In fact, I pick a "for fuel planning" alternate for NC26 that's equivalent to at least what I'd need if I was going to SVH. Further. If I have to miss out an ILS, I really want an airport with REALLY bright lights and longer runways. I'd blow away RUQ or HKY for CLT.
(Similarly I plan file IAD for CJR).

Now if I'm still in the soup at the 1000' (or I'm expecting to be) going into NC26, where am I going to divert? Well, barring reported weather below ILS mins at SVH, I'm going there. It's a short amount of flying. I've got a good chance of getting in, and it's a short drive in the courtesy car or one of my buddies to come retrieve me.

Yes, I know there are caveats on using SVH as an alternate but usually it's OK.
 
Brad Z said:
To take it a step further, what are the rules on using a TSO C129 certified GPS receiver versus a TSO-C146 receiver? Hint, the latter is WAAS capable...
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For a c129 GPS (basically, non-WAAS units), you cannot be using approaches at both your destination and your alternate to meet these requirements unless you have an approach at one of them you can fly without your GPS. So, if your destination approaches all require GPS, then you must have an alternate, and your alternate must have either an alternate-approved approach you can fly without the GPS, or VFR-from-the-MEA weather. OTOH, if your destination has an approach you can fly without GPS, you can use GPS-required approaches at your alternate to meet your alternate filing requirements.

With a c146 WAAS GPS, you can use GPS-required approaches at both destination and filed alternate to meet the alternate filing requirements.

Also, note that it's possible you may need your GPS to fly a non-GPS approach. For example, if you're considering Easton MD (KESN), the only non-GPS approach is the ILS or LOC/DME 4, which is marked DME REQUIRED -- and that includes the ILS version. If you don't have a DME, and are using your GPS to substitute, you cannot use that as your alternate unless either you have a c146 WAAS GPS or you have an approach at your destination you can fly without your GPS. Likewise, if Easton is your destination, and you don't have a either a DME or a c146 WAAS GPS, you must have an alternate regardless of the forecast weather at Easton.
 
jordane93 said:
You have to use the alternate minimums if you decide to use that airport as an alternate. Otherwise, there would be no point of posting alternate minimums.
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Only for the purposes of flight planning. Alternates are paperwork exercises.

When you file the IFR flight plan, your alternate airports weather must be above alternate minimums (and forecast to remain so) at the time of your planned arrival at the time you filed.

If you launch and the forecast was wrong and your alternate is at published minimums when you divert to it thats no biggie. You can use the published (not alternate) minimums. You can also divert to any other field of your choosing and land there as well, even if they are not authorized to be filed as alternates in your flight plan.
 
You guys are talking about two different things.

jordane93 said:
You have to use the alternate minimums if you decide to use that airport as an alternate. Otherwise, there would be no point of posting alternate minimums.
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This is discussing the requirements to FILE the airport as an alternate (with all the attendant fuel requirements.)

tsts4 said:
No you don't. You fly the applicable minima as listed on the approach chart. Alternate mins 600-2, 800-2, or non-standard as identified by the triangle "A" are for planning purposes only.
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This is referring to what a pilot is allowed to do once airborne and possessed of actual weather reports.
 
Doggtyred said:
Only for the purposes of flight planning. Alternates are paperwork exercises.
..................................................................
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Yes, ....actually the main purpose of the filed alternate is to assure (hopfully) that if you can't get in at your intended destination that you'll have enough fuel aboard to get to someplace where it's a good bet that you can get in.
 
Doggtyred said:
Only for the purposes of flight planning. Alternates are paperwork exercises.

When you file the IFR flight plan, your alternate airports weather must be above alternate minimums (and forecast to remain so) at the time of your planned arrival at the time you filed.

.
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Isn't it the 1 hr before/after; 2,000 ceiling; 3 mile vis rule that you need an alternate?
 
asgcpa said:
Isn't it the 1 hr before/after; 2,000 ceiling; 3 mile vis rule that you need an alternate?
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That's correct. But that just tells you whether you need to PLAN an alternate or not. And, as a(n intended) side effect, how much fuel you need to carry.

If you get to your planned destination and can't get in, you can go anywhere you want as an alternate (provided you can remain legal airspace and fuel wise). You don't have to go to your planned alternate and wherever you do go doesn't need to meet the 1-2-3 rule, but the minimums for whatever approach you intend to fly at the time. (Including a visual approach in VFR conditions from the MEA down to landing.)
 
asgcpa said:
Isn't it the 1 hr before/after; 2,000 ceiling; 3 mile vis rule that you need an alternate?
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Actually, the rule is you always need an alternate on your IFR flight plan unless:

  1. Destination weather is forecast for +/- 1 hour of ETA better than 2000-3, and
  2. Destination has an approach you can fly
See 91.169 for full verbiage.
 
peerlesscowboy said:
Where does it say you need to consider fuel required to "shoot an approach" in your alternate calculations?
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It doesn't, John. The Chief Counsel misinterprets the rule (yet again) because they don't know aircraft operations and don't understand those who do and try to explain it to them. Here's the interp: http://www.faa.gov/about/office_org...6/gallagher - (2006) legal interpretation.pdf

When applied to, say, an old fuel-guzzling Learjet, this means the pilot needs to carry enough fuel for three climbs to altitude, once for the original takeoff, once again for the missed approach and trip to an alternate, then again as part of the 45 minutes of normal cruising flight after landing at the alternate.

The rule actually only requires two climbs, since flying "to" the alternate only means "over" it--it is, after all, a radius of action fuel planning requirement.

Of course, climbs burn much more fuel than cruising in turbojets and descents burn much less, so what you save during the descent offsets the extra you need for an approach. The Chief Counsel blew it again and we're stuck with it.

Note: Part 121 rules for alternates are more carefully worded and don't require three climbs, IIRC.

dtuuri
 
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AggieMike88 said:
In my study for the checkride, I think I've come across a nugget of information I wasn't sharp on before... And want to check with the CFII's here to make sure I got it down right.

For alternate airport selection, I'm good with knowing 600/2 for precision approach and 800/2 for non-precision, and that the approach must be one that I and the airplane are capable of doing.

I am also familiar with the the "Triangle A" in the briefing strip as a hint that there is additional details I need to know in the form of approach minimums. And for this, I go to Section L of the Terminal Procedures book and read up on the info.


What I just discovered was when the "N/A" appears there. From what I'm reading, am I correct that when this appears next to the "Triangle A", then this particular approach for that particular airport can not be selected as my alternate.

For an example. Look at the ILS 18 for Denton, KDTO and the RNAV (GPS) 18 for Denton.

The ILS approach has the N/A next to the Triangle A. So from this, I am saying that, as my alternate airport, I cannot use this approach.

However, the GPS approach does not have the N/A. So from this, I am saying that, as my alternate airport, I can use this approach, since my aircraft is equipped with an IFR certified GPS (CNX80/480).

Correct?

Applying this information further, if my aircraft was not equipped with an IFR certified GPS, Denton is totally out of the picture for an alternate airport. Correct?

--------------------------------

Man, so much to learn, but all of this does sort tickle the inner aviation geek.
Click to expand...

Correct. The reason for this is that in order for an approach to be usable as an alternate, there are two main considerations that must be satisfied. There must be local weather reporting so you can get your altimeter setting. The approach must be monitored. At a towered airport, the equipment is available for the ILS to be monitored, but at a non towered airport it most often is not. The WAAS system is monitored at the national level. There are other criteria as well.
 
Note that the 800-2/600-2 (or alternate minimums) has to be forecast met *AT* the ETA. Not +/- hour of the ETA.
 
If you are wondering why the 600-2 and 800-2 are the standard alternate weather forecast, this is to allow the approach to be completed assuming the weather holds under the most adverse outage conditions for the approach that might develop during the flight, yet still permit the approach to be flown. So for example if it is an ILS with a 200 foot DH, but along the route the ALS, PAPI, and GS all fail, yet the approach may still be conducted using the localizer only minimums and they require an MDH of 600 feet or less, then the standards will apply. But if the MDH was 700 feet, a higher non standard of 700-2 would end up being required.
 
This post has been very helpful. Hopefully I am understanding this correctly.

I fly an IFR Certified Non-WAAS G1000.

If I am planning an IFR flight and my destination has an active instrument approach my airplane is capable of flying legally and is forecasting +&- 1hr, 2000'+ ceilings and 3+ miles Vis, I dont need to even file an alternate.

If the Destination weather is below the "123" rule, then I will need an alternate.

I cannot plan on flying to an alternate if all of thier approaches have the "N/A" or if the only remaining approach is the same type of approach as my initial destination.

The alternate must have a forecast of 600' cielings and 2mi Vis if using a precision approach (ILS). or.. 800' ceilings and 2mi Vis if using a non-precision approach (RNAV).

My alternate must offer an active approach with a different method than my destination. ie. if the destination has only an ILS, my alternate will need to be GPS or vise versa. however, I am not required to fly that unless required due to instrument failure.
 
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There's no requirement for the approach to be of a different type. It's just that non-WAAS units can't use a GPS for both the destination and the alternate. So you can fly to an airport served by an ILS and use an airport with only a GPS as an alternate or vice versa. However, you can chose destinations and alternates that both have only an ILS (or any other ground based navaid).

Your'e never REQUIRED to go to your alternate. Once the flight begins, you make the best decision for the situation.
 
JasonM said:
This post has been very helpful. Hopefully I am understanding this correctly.
..............................................................
I cannot plan on flying to an alternate if ..................... or if the only remaining approach is the same type of approach as my initial destination.
.......................................................
My alternate must offer an active approach with a different method than my destination. ie. if the destination has only an ILS, my alternate will need to be GPS or vise versa. ...............
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That's not correct.
 
JasonM said:
This post has been very helpful. Hopefully I am understanding this correctly.
Click to expand...
Very close.
I cannot plan on flying to an alternate if all of thier approaches have the "N/A" or if the only remaining approach is the same type of approach as my initial destination.
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As noted above, it need not be a different type, but with a non-WAAS GPS, you cannot need the GPS at both destination and alternate.

The alternate must have a forecast of 600' cielings and 2mi Vis if using a precision approach (ILS). or.. 800' ceilings and 2mi Vis if using a non-precision approach (RNAV).
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...or have weather forecast to be good enough to descend under VFR from the MEA to landing, in which case your alternate doesn't need any approach at all.
 
Thanks. I modified my current understanding. Is this correct?


I fly an IFR Certified Non-WAAS G1000.

If I am planning an IFR flight and my destination has an active instrument approach my airplane is capable of flying legally and is forecasting +&- 1hr, 2000'+ ceilings and 3+ miles Vis, I dont need to even file an alternate.

If the Destination weather is below the "123" rule, then I will need an alternate.

I cannot plan on flying to an alternate if all of thier approaches have the "N/A"

I cannot plan on flying to an alternate if my initial destination and the Alternate only offer non-ground based nav aid approaches (GPS).

I can plan on the Destination and the Alternate both using ground based nav aids if available

The alternate must have a forecast of 600' cielings and 2mi Vis if using a precision approach (ILS). or.. 800' ceilings and 2mi Vis if using a non-precision approach (RNAV). or be forecast to allow VFR decent from the MEA.
 
JasonM said:
Thanks. I modified my current understanding. Is this correct?


I fly an IFR Certified Non-WAAS G1000.

If I am planning an IFR flight and my destination has an active instrument approach my airplane is capable of flying legally and is forecasting +&- 1hr, 2000'+ ceilings and 3+ miles Vis, I dont need to even file an alternate.

If the Destination weather is below the "123" rule, then I will need an alternate.

I cannot plan on flying to an alternate if all of thier approaches have the "N/A"

I cannot plan on flying to an alternate if my initial destination and the Alternate only offer non-ground based nav aid approaches (GPS).

I can plan on the Destination and the Alternate both using ground based nav aids if available

The alternate must have a forecast of 600' cielings and 2mi Vis if using a precision approach (ILS). or.. 800' ceilings and 2mi Vis if using a non-precision approach (RNAV). or be forecast to allow VFR decent from the MEA.
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It looks correct to me with the exception of the last statement. The 600-2 or the 800-2 are the standard requirements, but a particular approach may require other than the standard.
 
John Collins said:
It looks correct to me with the exception of the last statement. The 600-2 or the 800-2 are the standard requirements, but a particular approach may require other than the standard.
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Great. So basically modifying that to say: "600-2/800-2 or meeting any non standard approach minimum weather requirements for the approach planned at the alternate airport"

I have not seen one yet, but I assume there is airports that will have approach requirements for greater ceilings and/or vis than the standards?
 
JasonM said:
Great. So basically modifying that to say: "600-2/800-2 or meeting any non standard approach minimum weather requirements for the approach planned at the alternate airport"

I have not seen one yet, but I assume there is airports that will have approach requirements for greater ceilings and/or vis than the standards?
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Yes, see the ILS approaches at KRNO for an example.
 
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