Outsmarting the *!#@% ATC Computer

Tired of getting circuitous IFR routes that bear no resemblance to what you filed? Upset with those clearances that take you over the mountains or way out to sea? You can probably wangle the IFR route you want...provided you're willing to resort to deviousness and skulduggery.


"Preferred routes.” Hah! Preferred by whom? Not us general aviation pilots, that’s for darn sure.

A lot of the IFR routes that we get from ATC are positively obscene. Either they add 50% to the total trip mileage, or they take us over the most hostile possible terrain with MEAs above the freezing level, or they send us so far overwater that a Grumman Widgeon pilot would need a change of underwear. And it doesn’t seem to matter one whit what route we file, or what pleas we put in the remarks box of the flight plan form.

Sometimes it seems like a big FAA conspiracy designed to coax General Aviation pilots to keep out of the IFR system. Do we have to accept this kind of treatment, or what?

Know thine enemy

First of all, it’s important to know who the enemy is. Don’t get mad at the FSS specialist who copied your flight plan, or the center flight data person who tore off your strip and reviewed it, or the clearance delivery controller who read you that horrendous route. It’s not the fault of any of these guys…and it’s considered bad form to shoot the messenger.

Your adversary isn’t human. It’s the ATC computer. To be precise, it’s the computer system in the ARTCC where your flight originates. Automation of the flight data function has purged all traces of flexibility, judgement, compassion and humanity from the system, replaced by the heartless predictability of a computer program.

The computer looks at your airports of origin and destination and checks them against its database of “canned” routes: Preferential Departure and Arrival Route (PDARs), Preferential Departure Routes (PDRs), and Preferential Arrival Routes (PARs). It almost always finds an applicable P-route of some sort, and that’s what you’ll get from clearance delivery…guaranteed.

The route you filed is often ignored altogether. Only your origin and destination airports really matter. The FAA automation people haven’t yet found a way to change those.

Man vs. computer

I first became aware of the degree to which computers have taken over and human judgement has been eliminated one day a few years ago when I was at Oakland Center (near San Francisco), visiting a close G.A.-pilot friend of mine who was an air traffic controller at the center. I’d spent a few hours plugged-in on position watching my buddy shepherd targets across his radar screen.

Finally it was time for me to leave and fly home. The weather was moderately crummy. I asked whether my friend could save me a call to Flight Service by putting an IFR flight plan into the system for me. He said sure, led me over to a nearby FDIO (a computer terminal with a strip printer attached) and entered my flight plan from Hayward (HWD) to Santa Maria (SMX).

HWD is right in the heart of the congested Bay Area airspace. SMX is 180 nm southeast of Hayward, out in the boondocks. About an hour’s flying time in my C310 as the crow flies. (But then crows don’t require IFR clearances.)

My friend instructed the computer to print out my flight strip. The strip came out with the standard route: HWD..OAK.V244.ECA.V113.MQO..SMX. In case you don’t have a chart handy, I can tell you that this route goes 6 miles northwest to Oakland (OAK), then 50 miles northeast to Manteca (ECA), before finally turning southeast toward SMX. The route adds 60 nm to the great-circle distance of 180 nm for a total of 240 nm as-flown. Yuck!

I joked with my controller-friend about what a terrible route this was, and he said, “Hang on, we ought to be able to do better than that.” He proceeded to try to convince the computer to issue an alternative routing that was more direct. Each time, he would type in some undecipherable computer command, hit the “Enter” key with a flourish, and exclaim “There! That should do it.”

And each time, the computer printed a strip with precisely the same circuitous route as before. He kept this up for about 10 minutes, trying every trick he knew to override the computer’s route assignment. Nothing worked.

“That’s okay,” I sighed, “I’ll just have to live with the Manteca tour as usual.”

“Don’t give up so easily,” he said. “I know one sure-fire way to get a decent route.” His scowl transformed into an evil grin. “We’ll cheat.”

When all else fails…cheat!

He took a deep breath, cracked his knuckles, and attacked the FDIO keyboard once again. This time, he entered an IFR flight plan from Hayward to Salinas (SNS). SNS is about 65 nm southeast of HWD and almost precisely on the great-circle route from HWD to SMX. The printer generated yet another flight strip, this time with a virtually direct IFR routing from HWD to SNS.

“Ha! Even the computer isn’t cold-hearted enough to send you to Manteca if you’re only going as far as Salinas,” my friend said excitedly. “It would be nearly triple the distance.”

“Hey, wait a minute,” I protested, “I don’t _want_ to land at SNS. I’m going to SMX!”

“Not to worry,” he said. “As soon as Bay TRACON hands you off to Oakland Center, simply tell the controller that you want to amend your destination to SMX via SNS.V25.PRB..SMX, which is virtually a straight shot.”

“Won’t the Center controller be upset if I throw him a curve like that?”

“Not at all. Happens all the time. It’s no sweat for the controller…just a few keystrokes. Trust me.”

“Bu-bu-but th-th-that’s ch-ch-CHEATING,” I stammered.

“Sure it is,” my controller-friend replied brightly. “It’ll save you 20 minutes of flying time and fuel, and won’t inconvenience anybody. It’s a win-win situation. Ain’t life wonderful?”


“Try it, you’ll like it!”

Flying the Salinas subterfuge

A half-hour later I was starting engines on the ramp at HWD and calling for my IFR clearance to, er, Salinas. Cleared as filed, of course. I read back the clearance nervously, feeling like some sort of white-collar criminal. Try as I might, I couldn’t think of any way that I could get my ticket punched for filing HWD-SNS instead of HWD-SMX.

I launched into actual IMC. Bay Departure gave me a few vectors to thread me between the SFO and OAK arrivals, then turned me loose to fly direct SNS when able. When Bay told me to contact Oakland Center, I knew my moment of truth was near.

“Oakland Center, twin Cessna 2638X, seven thousand, request.”

“Twin Cessna 2638X, Oakland Center, say request.”

“Aaah, Oakland…twin Cessna 38X needs to amend our destination. Ahh…the…uh…boss just decided he wants to go to Santa Maria instead.” I looked back at the totally empty cabin and verified that I was the sole occupant of the aircraft. “After Salinas, request Victor 25, Paso Robles, direct Santa Maria.”

“Twin Cessna 2638X, cleared as requested, maintain seven thousand.”


And that was all there was to it!

To make a long story short, I started using the “Salinas subterfuge” scheme on a regular basis, and extrapolated the technique to a variety of similar situations. It invariably works like a charm. Nowadays, I even leave out all the stammering and the reference to my fictitious fickle boss.

Bait-and-switch, basic and advanced

Let’s review the basic technique. You want to fly from AAA to BBB, but you know from past experience that the ATC computer insists on issuing a circuitous or otherwise objectionable preferred route. So you find an intermediate airport XXX such that the preferred routes from AAA to XXX and from XXX to BBB are both acceptable. Then you file from AAA to XXX, and as you get close to XXX you amend your destination in-the-air to BBB.

If XXX is in an area of known-hostile controllers (the Northeast U.S., for example) and you’re worried that ATC might hassle you about switching destinations with no warning, here’s an advanced variation on the basic subterfuge. Pre-file _two_ IFR flight plans, one from AAA to XXX and the other (with an appropriately delayed P-time) from XXX to BBB. Launch from AAA toward XXX. As you approach XXX, advise ATC that you won’t need to land at XXX after all, and that you’d like to pick up your pre-filed second-leg IFR from XXX to BBB. Even the most hard-hearted controller won’t have the nerve to tell you that you have to land at XXX anyway.

Of course, the key to the successful application of this technique lies in artfully choosing your bogus destination airport XXX such that you can get an efficient IFR routing from AAA to XXX and from XXX to BBB. To do this consistently well, it helps a lot to have a pretty good idea of what preferred routes are in the center computer.

If you fly in the Northeast U.S., this is not a big problem…there are a huge number of preferred routes published in the AFD or Jeppesen service. And if you’re flying in Southern California, the entire PDAR system is published in the form of “SoCal Golf Routes” (previously in a memo from the FSDO, now in the AFD). But if your stomping grounds are somewhere else, you may have to do a little research.

Obtaining the key to the kingdom

For example, the PDARs for Northern California are not published anywhere. Officially, that is. But they are available if you’re enterprising enough.

I called Oakland Center to ask for a computer listing of Northern California PDARs and was eventually connected with the Center’s training department. It turns out that most ARTCC training departments are staffed by non-FAA civilian contractors (almost all of whom are retired controllers), and they are the most helpful folks you ever care to meet. The training folks at Oakland Center sent me a 28-page printout showing the PDAR between every conceivable pair of Northern California airports. They also provided me with a set of gorgeous blueprints (suitable for wall-mounting) that show exactly how all the airspace in Northern California is parcelled up amongst Center sectors and TRACONs.

My experience with the folks at Oakland Center was not a fluke. I’ve dealt with the training department at Los Angeles Center and found them to be equally helpful.

Call the training people at the ARTCC where you do most of your flying…or better yet, pay them a visit. You’ll be amazed at the useful information that you can pry out of these folks.

A complete listing of PDARs is the key to the IFR kingdom. Armed with that list and a devious imagination, it’s amazing how effectively you can subvert the PDAR system to your advantage.

Beware of flow control

I hasten to add one note of caution: Don’t try to use the “Salinas subterfuge” or any of its variants if your _real_ destination is a major jetport for which flow control is in effect. If you’re flying to a flow-controlled destination, you’re probably wise to accept the standard route, even if it isn’t as direct as you might like.

Flow control means that the ARTCC’s Traffic Management Unit has instituted a ground delay program in order to limit arrivals into the airport to a pre-determined acceptance rate. The TMU folks don’t cotton much to pilots who try to cut into line. If you try to pick up an IFR clearance to a flow-controlled airport while you are airborne, you’ll probably be told “no” (and sometimes not all that politely).

All is not lost for the pilot-cum-grifter, however. There’s a slightly devious way to beat flow control delays…and it works most of the time. The key is understanding how flow control is administered. Flow control is done largely by computer. Which means you can cheat.

Suppose your destination is SFO. The TMU specialist at Oakland Center declares an official “acceptance rate” for SFO, based on weather, runway closures, and so forth. If all runways are open and the weather is good enough to permit visual approaches, SFO’s acceptance rate is about 60 landings per hour (or one landing per minute). When the stratus rolls in and instrument approaches are necessary, the acceptance rate drops to just 28 per hour.

The TMU specialist monitors a computer-generated “metering list” of IFR flight plans destined for SFO, sequenced by ETA. For aircraft that aren’t yet in the air, the ETAs are based on the proposed departure time and estimated time enroute that was filed in the IFR flight plan. If the computer-projected SFO arrivals during a particular period of time don’t exceed SFO’s acceptance rate, no flow delays are necessary. But if the projected arrivals exceed the acceptance rate, the computer calculates an appropriate delay for each not-yet-airborne inbound flight that will reduce the arrival rate to the required figure.

Beating flow delays

So how do you beat the system? Easy. Lie about your proposed departure time!

Say you plan to depart for SFO at 1600Z to drop off a passenger departing SFO on an air carrier flight. By listening on your air-band scanner at home, you learn that flow control is in effect for SFO, and ground delays are running about 30 minutes. A 30 minute delay would mean that your passenger may miss his connection. What do you do?

If you were an honest and upstanding citizen-pilot, you’d file your IFR flight plan for 1530Z, leave for the airport 30 minutes early to ensure you arrive by 1500Z, make sure your pre-flight and pre-start checklists are complete in time for your 1530Z P-time, and spend a half hour sitting in the runup area waiting for your flow window.

But since you’re out to beat the system, you file your P-time as 1530Z but leave for the airport in time for a 1600Z departure as originally intended. As you pull into the parking lot around 1530Z, you call clearance delivery on your handheld and copy your clearance and your Estimated Departure Clearance Time (EDCT) of 1600-ish. You then do a relaxed pre-flight, load the luggage, make a final potty stop, light the fires, call for taxi at 1555Z, and finish your run-up just as your flow window arrives.

This technique isn’t foolproof, because you can’t always pre-guess how much of a flow delay you will receive. If it turns out that the TMU assigns you an actual flow delay of 45 minutes (from your P-time), you’ll have shaved off 30 minutes of that and will sit in the aircraft for 15 minutes (still a good deal). On the other hand, if your actual flow delay is 20 minutes and you aren’t ready to depart in time, you run the risk of going all the way back to the end of the line.

Consequently, it doesn’t pay to cut things too close when backing up your P-time to beat an anticipated flow control delay. If you guess that you’ll have a 30-minute delay, maybe you should file for a P-time that’s only 20 minutes earlier than the time you actually expect to be ready to depart. No point in trying to be too greedy.

After all, the seasoned cheater is content to beat the system. He doesn’t insist on pulverizing it.