Saturday, June 13, 2009

Filing IFR

You probably follow one or more online forums. They can be a good source of information, and they can be a good source of mis-information. I skip any post that starts with "I'm not instrument-rated but..." or "I'm not an instructor but..." or "I'm not a doctor but...". At least they are honest.

Today's discussion began in a website newsletter and in an online forum, so use some judgment. The Aeronautical Information Manual may or may not change based on it. But the final advice is so compelling that I am sure it worthwhile. It's about one of my pet peeves,

Filing Direct


Look back this post about lost communications. One of the many big puzzles is what to do when the clearance limit is the destination airport, for example, "You are cleared to the Boise airport via as filed, climb and maintain 12 thousand, departure with Salt Lake Center... ."

Boise airport is not an initial approach fix (IAF), so what do you do? The rule (14CFR91.185) is almost clear: you should go to the Boise airport, then fly to and hold at an initial approach fix (IAF) until the appointed time. Strictly speaking, you are supposed to go to the clearance limit, and then go to the IAF. In principle, you can go to the clearance limit by following the approach path at the lowest of the 91.185 altitudes (that is, not descending at all). But then what? How do you get the to the IAF without compromising your safety (don't hit anything) or someone else's airspace?

The punch line: some people now recommend that you include an IAF in your flight plan route. This makes a lot of sense to me.

The alternative is to just file "direct" to the destination; one wag justified this particular bit of laziness by saying that "filing direct tells ATC that they can put you wherever they like." This is fallacious in two ways. First, ATC puts you wherever they like no matter what, so they gain nothing. Second, if your destination airport is in a different center's airspace, the computer may not know where it is, so a controller will have to go look it up and enter your flight plan by hand. Filing direct doesn't save ATC from work; it gives them more!

Let's pin this down by considering an IFR flight to Scottsdale, AZ from the north. In a non-GPS aircraft, the basic route must be V257 to Phoenix: V257 takes you down the PHX 336 radial. The only - the only - IAF for Scottsdale is the PHX VORTAC, so the proper route to file ends with V257 PHX. If you are lost comm then you hold at PHX until it's time to start down.

(One of the automated online routers uses V257 BANYO; BANYO is a fix on the PHX 336 radial, but it is not an IAF. Their route leaves you scrambling if you lose radio contact.)

The IAF route takes you well south of the airport, but that's the way things go in the IFR world. Unless you can get vectored for a visual approach, you are going to go to PHX anyway. If you want to stay north of Scottsdale, you have to invest in an IFR GPS, and include POURS in your route.

Picking an IFR route is work, but it is artful work. Enjoy the journey; the destination becomes that much sweeter. This applies to finding the route as much as it applies to flying it.

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At June 14, 2009 at 9:28 AM , Anonymous John said...

Great post. Luckily for me, this is how I was always taught to file IFR. Always file ti an IAF.

I've also heard from multiple sources that filing DIRECT sucks for ATC unless you are staying in the same sector.


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