November 2, 2009
By Ian J. Twombly
Determining the route to file on an IFR flight plan shouldn’t be difficult. But experienced instrument pilots, instrument students, and even CFIIs can get tripped up on this supposedly pedestrian process. And no wonder. There are so many options, from GPS-direct to a full airway routing and everything in between. The correct choice is not always clear, unfortunately. The FAA’s guidance tells pilots one thing, while the part that really matters—actually flying within the system—works another way.
If you begin the search for answers in the federal aviation regulations, you’re going to be disappointed. The FARs say only that we must have a proposed route, not what is supposed to define it. Obviously, the Aeronautical Information Manual is the next place to turn.
The AIM gives us a bit more information, albeit buried and written for attorneys. Chapters 4 and 5 go into some detail about what to file in the route portion of the flight plan and why. In the most basic terms, the routing of an IFR flight plan is set by long stretches of straight lines and transitions between those lines. Which route to choose is partially based on the navigation capabilities of the airplane in question.
Traditionally, the routes are made up of various Victor airways and jet routes, and the transitions are intersections or fixes. But routes can be defined by NDBs, GPS in the form of T-routes, and more. And intersections can be predefined points where VOR radials cross, points based upon GPS, a pilot-defined latitude and longitude, or any other identifiable fix.
To define the route, most pilots have historically looked at a low-altitude en route chart, found the straightest line between here and there, and listed that in the route block. So a flight from Craig Municipal Airport in Jacksonville, Florida, to Gainesville, Florida, might be V198 MONIA V441 KGNV. In plain language, that means the pilot will take off from Craig, head northwest on Victor 198 to the MONIA intersection, then follow V441 to Gainesville. Some pilots will tell you that you must file an initial approach fix for the expected approach into Gainesville—more on that later.
One thing we should always do is file a preferred route. If a commercial flight is going between Chicago O’Hare and Newark, that’s obvious. But with our flight between Jacksonville and Gainesville, where we’re flying lower altitudes between two non-hub airports, the situation isn’t quite as clear. There are some Internet resources and software programs that recognize this and will suggest a routing close to the preferred. In most cases, however, it’s very difficult to look through the preferred routes in the Airport/Facility Directory only to find that one doesn’t exist between your departure and destination, and the one at the hub airport 50 miles away is unrealistic to use. So what happens when a preferred route doesn’t exist? It’s up to the pilot to decide how he wants to get there. To aid in that decision, it helps to know what happens after the flight plan is filed.
Around 30 minutes prior to departure a strip will automatically print out in the tower if you’re departing from a towered airport, or in the approach control or center if you’re not. Whether filed through flight service, DUATS, or another provider, the FAA’s computers look at the request, decide if it’s possible based upon preferred routing, and then send it to the appropriate facility. Traffic is taken into account only when there’s a traffic management program in effect.
On that strip is the N number, aircraft type, and other pertinent information. Also included is the cleared route and the requested (filed) route. We’ve all heard the one about having to file an initial fix within a certain distance from the airport, say 10 miles. And then there’s the one about having to file an initial approach fix into the destination. Oh, and of course, everyone knows you can’t file GPS-direct more than 100 miles away, right? Wrong on all three counts.
When it comes to flying within the system, you might as well file direct every time. It doesn’t matter if the clearance limit is 10 miles away or 800, filing direct is fine, doesn’t hurt the controller’s feelings, and won’t get you in trouble with the FAA. There’s really no human intervention here. But the computer is going to give you what it’s going to give you regardless of the request, and the controller is simply going to read that as a clearance.
The issue of filing certain points in the flight plan, such as an IAF, is related to lost communications, not ATC needs. The argument goes that if you file direct and are cleared as such, there’s no way to comply with FAR Part 91.185, which says that in the case of radio failure where a pilot cannot land in VMC, the pilot is to go the clearance limit and begin the approach, if it’s a place where that’s possible—in other words, if it’s an IAF. The regulation further states that if it’s not an IAF, you are to go to the clearance limit and then go to a place where an approach can be started. Since the clearance limit is usually an airport anyway, that means the regulations require you to fly to the airport and then somehow navigate to an IAF, then fly the approach to land. So why not just file direct and fly to the airport anyway?
The issue of filing direct remains controversial among pilots, but controllers seem to be in agreement—just do it. In fact, the AIM not only tells us how to file direct, it says we don’t even need to be GPS-equipped. The AIM says to file preferred routes, but then gives guidance on how to file direct even without a GPS.
If the airplane is GPS-equipped, it says to define the route by points within 200 nautical miles of the preceding center’s boundary. It’s easier just to file direct from one VOR to the next, choosing points around 100 miles apart. If the airplane isn’t GPS-equipped, the AIM says it’s best not to make the VORs more than 80 nautical miles apart if flying below Flight Level 180. ATC is so comfortable with direct routing, the AIM even says that ATC may assign a direct routing outside a VOR’s service volume, and the inference is that it’s regardless of equipment suffix.
The AIM says you can file direct, and controllers don’t mind, so why would you ever file anything different? For one thing, it’s good practice to plan a flight well and fly the plan. Living in the Northeast, for example, you’re rarely going to get direct for the entire route, so it helps to know ahead of time what to expect. If you’re familiar with the route, you can even have it loaded in the GPS or noted on the preflight paperwork before receiving the clearance. There’s just something satisfying about hearing, “Cleared as filed.”
Knowing that you can file any route you wish, the question then becomes how to arrive at the magic “cleared as filed.” First, check the preferred routes for more dense traffic areas, and then review some of the online resources that list the most recent ATC-assigned routes (see “Help Along the Way,” page 99). These are like cheat sheets that give the most recent cleared routes between two airports. And if you don’t get the route you want? Just ask the controller for an amendment, either in flight or before departure. This is especially true if you’re cleared on a long, circuitous route for no apparent reason.
Finally, take the time to visit your local ATC facilities, which are more approachable now that we’re years removed from September 11, 2001. Sitting down with a controller can help as he or she explains the routing process. The airlines used to have a program in which controllers could ride the cockpit jump seat for familiarization trips. Those have ended, but GA pilots can offer rides to controllers. So the next time you don’t get the route you want, don’t grumble to the controller about it—just ask if he’d like a ride.
With modern tools and a little know-how, filing an IFR flight plan routing is easier than ever. Pilots have an immense amount of control over their route—if they only know how to use it.
E-mail the author at firstname.lastname@example.org.
www.aopa.org/aifp—AOPA’s Internet Flight Planner uses a high-resolution map with weather overlays to help visualize your route.
www.fltplan.com—Check the most recent ATC-assigned routes and file a flight plan.
www.duats.com or www.duat.com— Both DUATS services automatically select waypoints within 200 miles of the preceding center’s boundary using the various “direct” options. Preferred routes are automatically checked and assigned in the airway routing selection.
www.flightaware.com—Find the most efficient route in an easy-to-read matrix with winds and route taken into account.
www.navmonster.com—Quick and easy planning for direct routes, as well as weather in a user-friendly format.
Flight Training Editor Ian J. Twombly joined AOPA in 2003 and is an instrument flight instructor.
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