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11 Answers

Why are IFR “Alternate Mins” runway or approach specific

Asked by: 18841 views ,
Commercial Pilot, FAA Regulations, General Aviation, Instrument Rating

There are several specifics around an airport being legal as an alternate. I am confused why there are different criteria for different approaches for that airport to be filed as an alternate. For example, KBJC as an alternate, it says VOR/DME Rwy 29L/R “NA when local weather not available”. 

But when you file KBJC as an alternate you are not specifying an approach. And if you miss your destination and go to your alternate KBJC, wouldn’t you be able to do the VOR/DME approach normally using normal mins and it’s a valid usable approach under those conditions? 

So I am confused why the Alternate Mins are approach or runway specific.

11 Answers



  1. Sam Dawson on Mar 20, 2014

    An IFR alternate is for flight planning only. Yes, you are filing an airport- KBJC in this case. But to use it as an alternate there must be a valid approach.
    Once you are in the air the alternate only really applies in a lost communication situation. Otherwise you can go to any airport you want and shoot any approach you want.

    As an example, I once had a flight to KPHF, Williamsburg VA. The closest legal alternate was KBWI- 123 miles away. KORF (Norfolk), 20 miles away, was below alternate minimums.
    I got to KPHF and the glideslope was out. I could not get in on the localizer. Went missed and entered the hold where I coordinated with dispatch. Weather at KORF was 200-1- within the limits for the ILS. I had enough fuel to conduct the ILS, get to KBWI and still have a 1 hour reserve. Did the ILS into KORF and landed. Perfectly legal.

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  2. John D Collins on Mar 20, 2014

    We specify the alternate airport when filing an IFR flightplan and an alternate is required. However, the aircraft must be equipped appropriately to fly a specific approach to a specific runway. There are two issues that must be satisfied in order for an approach to qualify for use as a planned alternate. First, the primary navigation needed to fly the approach must be monitored and second, there must be weather reporting available at the airport. Particularly at non towered airports or those whose tower is not open 24-7 may not be able to meet these criteria. If an aircraft can’t meet the equipment requirements for an approach that is suitable for use as an alternate, then the airport can’t be chosen as an alternate. Another possibility is that the required weather minimums for use of the approach for an alternate may not be satisfactory, An example that occurs often, many ILS are not monitored, but the VOR is. That would mean that for planning purposes, the ILS can’t be used. If the weather is not good enough to satisfy the use of the VOR approach alternate minimums, the airport can’t be used as a flight plan alternate and another alternate airport that does meet the criteria needs to be chosen.

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  3. Matthew Beyer on Mar 20, 2014

    Thanks. Not to change my question. But what about if the alternate wx is forecast to be above VFR mins to allow descent from MEA to airport… That is a legal alternate regardless correct? Even if it has “Alternate mins” posted that say “NA if….tower closed or …”?

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  4. Sam Dawson on Mar 20, 2014

    No. In order to use the rule permitting a descent from MEA… etc, it must be an airport without an instrument approach.
    91.169
    “(2) If no instrument approach procedure has been published in part 97 of this chapter and no special instrument approach procedure has been issued by the Administrator to the operator, for the alternate airport, the ceiling and visibility minima are those allowing descent from the MEA, approach, and landing under basic VFR.”

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  5. Matthew Beyer on Mar 20, 2014

    When I read it that way, I see what you are saying. But help me with the logic. You mean a nice fancy airport that has approaches, if the weather is forecast to be perfect (allowing VFR descent from MEA to…), it CANT be listed as an alternate? In reality wouldnt that be a perfect alternate? Or am I missing some logic here? Thanks

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  6. Sam Dawson on Mar 20, 2014

    Please, we’re talking about the FAA and the federal government… and you want logic?

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  7. Matthew Beyer on Mar 22, 2014

    One more related item: I read references to “if the airport has only a GPS approach, it cannot be listed as an alternate”. Where in the part 91 is that written, I dont see it (but have read it somewhere). thanks

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  8. John D Collins on Mar 22, 2014

    Matthew,

    The regulations specify in 91.205 that the aircraft must be suitable for the route flown. FAR section 23 requires that an AFM or AFMS must be provided with the aircraft that defines any limitations of the aircraft or its systems. The AFMS for an IFR GPS will describe the applicable alternate filing requirements in the limitations section. FAR 91.9 requires a pilot to comply with any AFM or AFMS limitations, which makes the GPS AFMS Limitations section binding on the pilot. So to answer your question, see the GPS AFMS and follow its limitations regarding the use of an alternate.

    The current guidance on use of an alternate can be found in the AIM, 1−1−18. Global Positioning System (GPS) and it is quoted below for your convenience:

    1. For flight planning purposes, TSO-C129() and TSO-C196() equipped users (GPS users) whose navigation systems have fault detection and exclusion (FDE) capability, who perform a preflight RAIM prediction at the airport where the RNAV (GPS) approach will be flown, and have proper knowledge and any required training and/or approval to conduct a GPS-based IAP, may file based on a GPS-based IAP at either the destination or the alternate airport, but not at both locations. At the alternate airport, pilots may plan for applicable alternate airport weather minimums using:
    (a) Lateral navigation (LNAV) or circling minimum descent altitude (MDA);
    (b) LNAV/vertical navigation (LNAV/VNAV) DA, if equipped with and using approved barometric vertical navigation (baro-VNAV) equipment;
    (c) RNP 0.3 DA on an RNAV (RNP) IAP, if they are specifically authorized users using approved baro-VNAV equipment and the pilot has verified required navigation performance (RNP) availability through an approved prediction program.

    2. If the above conditions cannot be met, any required alternate airport must have an approved instrument approach procedure other than GPS that is anticipated to be operational and available at the estimated time of arrival, and which the aircraft is equipped to fly.

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  9. Matthew Beyer on Mar 22, 2014

    Ok thanks. And asking a previous again….evev if the Weather is forecast to be oh so nice that allows for descent in vfr……This airport with only a GPS IAP….still cant be filed as an alternate. Thanks, I am almost fully there 🙂

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  10. Sam Dawson on Mar 22, 2014

    That is correct. The VFR rule only applies to airports without approaches.

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  11. John D Collins on Mar 23, 2014

    It depends. If your GPS is a legacy non WAAS GPS GNS430, it meets the requirements below and may be used at the destination or the alternate, but not both. So assume the destination has an ILS and the alternate has an RNAV (GPS) approach that is suitable for use as an alternate, then it can be used, even though the GNS430 is not WAAS capable. Change the assumption that both the destination only have RNAV (GPS) approach options, then the answer is no,

    “For flight planning purposes, TSO-C129() and TSO-C196() equipped users (GPS users) whose navigation systems have fault detection and exclusion (FDE) capability, who perform a preflight RAIM prediction at the airport where the RNAV (GPS) approach will be flown, … may file based on a GPS-based IAP at either the destination or the alternate airport, but not at both locations.”

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