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Alternate Thinking

The most important back-up plan you may ever have involves the IFR Alternate airport.The most important back-up plan you may ever have involves the IFR Alternate airport. But selecting an alternate that is both safe and legal requires real detective skills.

Getting Down or Getting Out
There are many airplanes today that have advanced auto-land systems that can make an approach and lightly touch down on the runway, even in the blind. I don't fly one of those airplanes. I fly IFR the old-fashioned way -- I need to see the runway to land on it. If I shoot an instrument approach down to the minimum altitude and even then cannot see the runway, I'll be forced to make a Missed Approach when I arrive at the Missed Approach Point (MAP). When you make a Missed Approach, the controllers will want to know what you're going to do next. You will be right in the middle of one of the highest work-load periods in your life and the controller will interrupt you with: 'What are your intentions?'

Your choices are:

  1. try another approach to the destination airport, or
  2. fly to the alternate airport.
The decision you make will be one of the most important you'll ever face. The weather at the destination may not be improving and another approach attempt could be a critical waste of fuel. At this point, you must rely on your preflight preparations -- and they had better be good -- because the alternate airport is now your way 'out' ... or not.

The 1 – 2 – 3 Rule ... It's Not Quite That Easy
When you plan an IFR flight you are not always required to list an alternate airport on your flight plan (block 13). FAR 91.169 (a.k.a. the 1 – 2 – 3 rule) is the rule to use in determining if you do or if you do not require an alternate. The regulation says that you need an alternate if:

from 1 hour before until 1 hour after your estimated time of arrival
the ceiling is less than 2,000 feet
and the visibility is less than 3 miles.

Translation: VFR weather conditions. If the weather is forecast to be VFR when you arrive, then there is little risk that you will need to fly to an alternate.

Good WX Gone Bad
Even though your preflight preparation must include a look at the forecast weather for a two hour block of time (1 before to 1 hour after your arrival time), and this is a very conservative rule, forecasts are not always correct. The rule is telling us that if the weather is less than 2,000 and 3, the possibility exists that the weather could drastically deteriorate to a condition much worse than forecast while we are enroute to the destination. The weather could get so bad that we might be forced to execute a Missed Approach instead of landing as planned. The weather forecasters probably don't miss it that badly that often, so actually being forced to the alternate is rare. But, if it happens, you must be prepared.

DIVERSIONS
If the forecast weather at the destination airport violates any part of the 1 – 2 – 3 rule then you must become a detective. You must now select an airport that is within your fuel range and meets an altogether different set of rules. The rule for choosing the alternate is 91.169(c)(1). For an airport to be used as an alternate, the weather at the estimated time of arrival at that alternate must have at least a 600-foot ceiling and 2 miles visibility if the airport has an operating precision approach (ILS). If no ILS, then an 800-foot ceiling and 2 miles visibility provided the airport has a non-precision approach. So, now you must look at several weather forecasts from several possible airports in order to find the combination of weather that is good enough and operating instrument approaches, all within the distance your airplane can fly with its fuel load ... plus 45 minutes. I fly a slow, trainer-type instrument airplane, so my choices are very limited. How are yours?

What The Regs Don't Say
The regulation tells us the rule -- it does not help us understand our predicament if we must fly to an alternate. First of all, most airports cannot be used as an alternate even if the weather is good. The only airports that are eligible are those that have human weather observers on duty at the time that you would arrive at the alternate -- and this is just common sense. If I am asked, 'what are your intentions' after being forced to make a missed approach, I want to get first hand weather information from somebody who is already at the alternate. I want that observer to be able to say either, 'the weather is good enough for you to land here, so come on!' or 'the weather is even worse here, so go somewhere else!' Now, I probably will not speak to that weather observer directly, but I want direct information. If there is no weather observer present at the alternate I will not know for sure and I might be wasting my fuel flying there. So, when selecting an alternate I must consult the Airport Facilities Directory to discover where and when the weather observer will be present.

Note: A weather observer can be an air traffic controller, a Flight Service Station briefer ... even an airline ticket agent. But whoever it is, that person must be an 'official' weather observer, which simply means they've passed a written and practical test given by the National Weather Service. (I became a weather observer in 1995.)

Darkness And Dark Skies
An IFR flight in the middle of the night will have many fewer alternate airport possibilities since many weather observing stations are not staffed 24 hours a day. You can tell which airports do and which don't by consulting the approach charts. The NOS charts indicate the lack of weather observers by using the symbol of the letter 'A' inside a triangle followed by the letters 'NA.' This translates to mean 'Alternate Not Applicable.' Jeppessen Charts spell out the same information on the back of the approach chart.

One Way Out
You can only file a single alternate airport when you file an IFR alternate. Note: The Flight Plan form at Block 13 does indicate that more than one alternate airport is possible when it prints 'Alternate Airport(s)' in the block. But the same form is used for both IFR and VFR flight plans and that '(s)' indicates the possibility of plural airports for VFR only. Except in some Air Carrier (Part 121) operations, there can be only one alternate. Why? Because if you were to experience two-way radio communications failure and then were forced to fly to the alternate, the controllers would have to know in advance where you were going. If you had more than one alternate choice they would not know which airspace to clear. Of course, if your safety is in question, you should take whatever measures necessary to ensure it -- regardless of your flight plan.

Of course, if you were forced to an alternate and your radio is operating properly, then you could ask to try other airports even if they were not the 'legal' alternate that was filed on the flight plan. You can do anything that you can work out with the controllers, but your radio must be working in order to make those arrangements.

BOTTOM LINE: If pilots do a poor job of preflight IFR alternate planning, they could find themselves in real trouble. Don't just write down any airport as the alternate because you used it last time or someone told you it would work. Do your preparation and always leave yourself an 'out.'

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About This Author:
Paul A. Craig is a Gold Seal Multiengine and Instrument Flight Instructor. He currently holds a total of 11 Flight Certificates including his ATP. Craig is a previous winner of the North Carolina and Tennessee Flight Instructor of the Year award, the NCVT Outstanding Teacher award and has served as the regional representative of the National Air and Space Museum. Craig is an FAA Aviation Safety Counselor and the author of eight books, including Pilot In Command, The Killing Zone: How and Why Pilots Die, and Controlling Pilot Error: Situational Awareness (all from McGraw Hill).
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