• Diversionary Tales


    Diversionary Tales

    By Tony Vallillo

    One thing that pilots deal with all of the time, something that virtual pilots can skip lightly over (since there is always the option to disable fuel burn, to say nothing of changing the weather instantly!), is the selection and possible use of alternate airports in our flying. All flights, VFR and IFR and big airplane as well as small airplane, require that consideration be given to the successful completion of the flight when conditions change from the original plan.

    Usually this involves changes in weather; since of all the factors that affect flight, weather is indeed the most fickle. The regulations guide us both as to the need to consider an alternate and the conditions that make an airport suitable as an alternate. In purely meteorological terms, an alternate airport must be planned whenever the forecast weather at destination is below certain limits, which differ for VFR and IFR flights, and can be found in the FAR's. In the case of IFR flights, there are additional weather limits which bear on the suitability of an airport as an alternate. So if the destination forecast is below the specified ceiling and visibility when you are planned to arrive, you will search, in the flight planning process, for another suitable airport where the weather is forecast to be better than a different set of ceilings and visibilities. And you will plan on carrying sufficient fuel to proceed from your destination to your alternate, fly an approach, and then hold for 45 minutes. That is the minimum legal requirement for fuel. If you want to give yourself more options, carry more fuel; and if that is not possible, plan a series of shorter flights so that your available fuel can provide you with these extra options, such as holding at destination or choosing a more suitable alternate farther away.

    All of this planning is just that - planning. Once you take off, the choices, and the consequences, are yours. You may change your designated alternate while you are enroute, if reports and new forecasts make for a better choice. You may also consider the fuel onboard to be your own possession - to use as you see fit. But in all things a conservative approach is warranted -- it would be foolish to use your "holding fuel" (the legal amount of which is intended for use at the alternate) at your destination, since you would be robbing yourself of options later on in the flight where they might be important.

    There are other factors that might require the selection of an alternate airport for a given flight. Extended overwater flights always require an alternate airport in the overwater portion, typically within 180 minutes for most jets, and a few more minutes for others. This requirement protects against certain mechanical malfunctions overwater and allows for a landing on terra firma. Of course weather is a consideration here as well, not so much in the requirement for the alternate but in the requirement that the alternate be viable - obviously bad weather at an airport along the way might preclude a safe approach.

    Flights in some mountainous areas, such as the Andes and possibly the Himalayas, require careful selection of alternate airports with respect to drift down over high terrain, especially in twin engine airplanes. This is to cover the loss of an engine over the middle of the mountain area. Terrain in these areas is sometimes in excess of the single engine ceiling of the airplane at its current weight, so an immediate turn toward lower terrain and a specific alternate airport is mandated.

    There are many things that play into the selection of alternate airports. Other than weather, and thinking of the part 121 environment, things like runway weight bearing capability, approach aids, taxiway dimensions and weight bearing considerations, availability of suitable egress equipment like passenger stairs, jetways, baggage handling equipment, Customs, and of course ARFF, as well as more mundane considerations like does your company have a contract in place for fuel and services! And don't forget availability of hotels and such for accommodating crew and pax. Also maintenance, considering that a common reason for a diversion, particularly on the Oceanic segments, is a mechanical malfunction. And of course availability of fuel; although at any airport capable of handling a transport category jet, fuel is pretty much a given unless some disaster has precluded deliveries, particularly to island locations...

    And thereby lies a tale or two, or three:

    JFK-Rome in a 767-300. We had very little holding fuel, against a fine forecast and two alternates (Ciampino and Genoa). Two alternates is a common practice at the airline, at least when I was working. One will usually be close in, like EWR for JFK, and be intended for use if traffic backups at destination are the only stumbling block. They are obviously in the same weather pattern, and hence the second and more distant alternate. (An aside - often, in the part 121 world, the fuel requirements for a close-in alternate like EWR for JFK are actually less than the requirements for a no-alternate flight plan. This is the other reason you often see EWR or JFK as alternates for LGA and vice versa. Note, however, that LGA might not be a suitable alternate for the other two in the case of a widebody.)

    Upon arrival in the greater Rome area, we discovered that the weather earlier that morning had been actually below CAT III minimums (yes, that is possible!). Although things had "cleared up" to around RVR 1200, there were several score of airplanes in various holding patterns all around the thigh of the boot. Upon arrival at our assigned hold, I determined that we had fuel for about 2 turns, using the Genoa alternate. Ciampino would have been out of the question for both weather and traffic reasons.

    Once you get into the situation where you will probably go to an alternate, along with a bunch of other airplanes, an important consideration becomes beating the other guy to the fuel pump! So I immediately requested clearance to Genoa upon holding pattern entry. While the good controllers at Roma were figuring out how to get us up there, my compatriot on the ORD-FCO flight apparently took my hint and decided that Genoa (also his alternate - same dispatcher!) would be just fine for him as well. This is a phenomenon that is often seen in the airline world - everyone follows the last guy through the maelstrom like elephants in a circus parade, until one guy or gal decides that valor is NOT the better part of discretion and demands to go another way. I've seen it many times in my career; and on that day, as it turned out, the ORD flight got cleared to Genoa first, presumably because he was at a lower altitude in the stack. Damn and Hellmnation! The first of my best-laid plans began to go astray.

    Genoa after landing
    Just after landing at Genoa. There is a considerable bay behind the runway.


    5 Comments
    1. dswanson's Avatar
      dswanson -
      Tony,

      I love your stories, keep them coming !!!!
    1. graaant's Avatar
      graaant -
      Fine case studies, superbly written, thanks, Tony.
    1. allanj12's Avatar
      allanj12 -
      Thanks Tony, for sharing great first-hand experiences. The mention of Genoa brought a smile; I once found myself sitting next to a woman passenger with a different diversionary experience. She had flown into Munich from SFO to change aircraft en route to GOA. Delicately (I thought) I advised her that our plane, now on the taxiway, was actually going to GVA. The shriek brought the Lufthansa attendant hurrying down the aisle…
    1. darrenvox's Avatar
      darrenvox -
      I never knew about that you were real world pilot...
    1. avallillo's Avatar
      avallillo -
      Hmmm.....I would have thought that it was pretty much self-evident! But then again, there are plenty of simmers around here with near-real-world levels of knowledge about aviation and I can see that it might not be so clear.

      But for the record, I have flown professionally for over 40 years, including 17 years in the USAF and 31 years with American Airlines. In case you notice that those numbers don't add up correctly, a certain amount of that was concurrent while I was both with AA and in the AF reserves.
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