Sitting around and talking with pilot friends, you hear nonstop talk about aircraft and equipment. Eventually, someone always brings up ATC in conversation. Pilots argue among themselves more intensely than Socrates debating Plato. One question that new and even veteran pilots bring up is why, when they file an IFR flight plan, that their clearance is usually never “as filed” but includes a route change of some sort.
Since I’m a working controller, they all look at me, while I briefly state a possible reason. After the assembled pilots all nod their heads and let out an “ohhh,” some will walk away still uncertain of what was explained. Overall, it is simple, there are about eight topics, within three areas, which determine whether or not you get “cleared as filed” or if ATC re-routes you before you take off.
Tower Enroute
Tower Enroute Control (TEC) routes first became widely known in the immediate aftermath of the 1981 Patco strike, when thousands of FAA controllers walked off their jobs, leaving the nation’s air transportation system in a lurch. The TEC routes were published to allow flights not needing to enter the overlying air route traffic control center (ARTCC) airspace to conduct an IFR flight by remaining at altitudes and on routes handled by terminal radar approach control (Tracon) facilities. While towers and Tracons had (barely) adequate staffing, the ARTCCs were chronically understaffed at the time. Using TEC routes eased their burden and kept slower, short-range traffic moving.
A TEC route should not be confused with Preferred IFR Routes. Descriptions of both types can be found in the back of the Chart Supplement (ne Airport/Facility Directory, or A/FD). As the name implies, preferred routes are what ATC would like for the pilot to file, since that’s likely the route the flight will be cleared for, and getting it right the first time saves everybody time and energy down the road.
A preferred route can be from LAX to JFK, or just LAX to SFO. A TEC route, on the other hand and as its name implies, does not exit the airspace overseen by the appropriate Tracons. Not every airport may have a TEC route. Some may just have an arrival; some may have a route going into busy or congested airspace and some have to or from routes. The ultimate purpose of these routes is to eliminate congestion and to put IFR traffic on predetermined routes, which increases efficiency in the Tracon’s airspace.
Controllers at the towers have the ability to clear you on TEC routes because the towers are connected to their appropriate Tracon system that oversee them. As the pilot, you should do your homework and file the appropriate TEC route for short-range, lower altitude flights, or preferred routes for the flight levels. In any event, pay attention to the notes for each route, as some are only for specific aircraft types: (J) turbojet, (M) turboprop aircraft, (P) propeller aircraft with a cruise speed of 190 knots or greater and (Q) propeller aircraft cruising at 189 knots or less.
Clearance Elements
An IFR clearance contains at least four main elements:
- Clearance Limit: A clearance issued prior to departure will normally authorize flight to the airport of intended landing. Under certain conditions, a clearance limit may be a navaid or other fix.
- Departure Procedure: Headings to fly and altitude restrictions may be issued to separate a departure from other traffic. Where the volume of traffic warrants, various departure procedures have been published, including obstacle departure procedures.
- Route of Flight: Clearances are normally issued for the altitude or flight level and route filed by the pilot, but traffic or other operational considerations may result in an altitude or route different from that requested.
- Altitude Data: Instructions in an ATC clearance normally require that a pilot maintain the cleared altitude. If the altitude assigned is different from the altitude requested, ATC normally will inform the pilot when to expect a climb or descent clearance, or when to request an altitude change from another facility.
The Chart Supplement for the southwest U.S. includes published TEC routes for the locations shown in the two maps at right, one for the NorCal Tracon and one for SoCal. Refer to the Chart Supplement covering your geographic area for similar maps and detailed route information between facilities and the Tracons serving them.
Air Traffic Reroute
Hearing something like “Skysmasher 12345, I have an amendment to your clearance; advise when ready to copy” always sets off something of a scramble in the cockpit as we fumble for the pencil to write down the new clearance. Among the various thoughts that run through our minds—”How long will this delay me?” or, “What did I do to anger this controller?”—we may also wonder exactly why we’re getting an amended clearance.
Controllers have something we call a “bad route.” This means that the route that was originally filed will require extra attention somewhere, perhaps many miles down the line, or may require extra internal coordination. Rerouting prevents any conflicts down the line which would put the pilot in a conflict with airspace, internal coordination and agreements between facilities.
Higher level terminal facilities such as the SoCal and NorCal Tracons have what they call “enter and exit gates.” One of the jobs approach control has is getting IFR aircraft safely out of the airspace and providing a smooth handoff to the next sector or adjacent approach control. The purpose of these gates is to reduce workload and allow the next controller positive control of entering and exiting IFR traffic. Think of these gates as the transition ramps of a freeway. Could you imagine the chaos if you were allowed to enter a busy freeway at any point? Entry and exit gates are an air traffic tool, and their identity and location are easy enough to figure out. If you regularly get re-routed to a certain fix and want to know the best route in or out of certain airspace, call your Tracon and ask what the best route would be given a specific direction of flight and aircraft type.
A few years ago, the SoCal airspace was redesigned per the FAA’s Metroplex concept. The purpose of this is to maximize the usage of airspace while increasing the capacity of IFR aircraft. Aircraft are encouraged to use standard instrument departures (SIDs) and standard terminal arrival routes (STARs), but if unable to do so, the pilot should advise ATC immediately. In general aviation, low-performance aircraft are allowed to use these routes if they have the proper equipment to comply with the routing. Just understand that you will be mixed in with the heavier metal of the airliners and corporate jets. As pilot in command, use your best judgment. Just because it’s legal to do something does not always make it a good idea to actually do it.
Amended Clearances
Amendments to an ATC clearance will be issued when a controller deems such action necessary “to avoid possible confliction between aircraft,” according to the Aeronautical Information Manual (AIM). Amended clearances also are handed out for other reasons, including weather. An amended clearance may require a hold, a different route or a change in altitude, or—if you’re having a really bad day—perhaps all three.
Again according to the AIM, “Some pilots have questioned this action and requested ‘traffic information’ and were at a loss when the reply indicated ‘no traffic report.’ In such cases, the controller has taken action to prevent a traffic confliction which would have occurred at a distant point.
“A pilot may wish an explanation of the handling of the flight at the time of occurrence; however, controllers are not able to take time from their immediate control duties nor can they afford to overload the ATC communications channels to furnish explanations. Pilots may obtain an explanation by directing a letter or telephone call to the chief controller of the facility involved.
“Pilots have the privilege of requesting a different clearance from that which has been issued by ATC if they feel that they have information which would make another course of action more practicable or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued.”
Traffic Management Unit
There is a traffic management unit at each ARTCC, Tracon, and some high-volume airports. Who are these people? Most are prior controllers, now furthering their careers. They specialize in managing traffic to ensure a more efficient flow. How does this affect a reroute?
First, all IFR flight plans can be seen by the TMU. The most common reason for them to issue a reroute is weather. They will reroute you on an alternate path coordinated between facilities. This minimizes the amount of aircraft deviating, for weather, from their routes. You will usually get this while still on the ground. If conditions worsen during a flight, make sure to have a pen handy.
What TMU may also do instead of a reroute is what we call flow times. If you have ever been asked by a controller, “What’s your wheels-up time?” then more than likely you have a release time within the IFR system. So, how is this part of the reroute clearance? The idea behind this is to reduce a controller’s workload in their sector of airspace. The TMU gives you a time for departure, which acts like a reservation for a slot of airspace. In turn, you may be scheduled 10 or 20 miles in trail for departure, or even while en route. It is an alternative for rerouting, which allows an aircraft to keep its filed route because conditions don’t warrant a route change. An expected departure clearance time (EDCT) is used during periods of high arrival volumes. Instead of having you fly all over the sky to put you on an arrival, TMU may just delay you with this program. This is used for volume control, runway closures or severe weather conditions lingering around the arrival airport.
- Record It: Make a written record of your clearance, since the clearance may be different than what was included in your flight plan.
- Clearance/Instruction Readbacks: Pilots of airborne aircraft should read back those parts of clearances and instructions containing altitude assignments, vectors, or runway assignments as a means of mutual verification.
- Include Aircraft Identification: Include your call sign in all readbacks and acknowledgments to help controllers ensure the correct aircraft received it.
- Sequence: Read back altitudes, altitude restrictions, and vectors in the same sequence as they are given in the clearance or instruction. It’s the pilot’s responsibility to accept or refuse the clearance.
Routed as Expected
All in all, a reroute is nothing mysterious. It is put in place not to add extra complexity as you fly, but rather to keep a safe and efficient flow of aircraft moving. Being proficient aviators, pilots should do their homework and research the route before the flight.
Pilots should avoid special use airspace (SUA) like restricted areas and MOAs, and try to avoid transitioning through Class B airspace. When you file your flight plan, file the most direct route. This means low-performance aircraft should stay on Victor or Tango airways, at least near terminal areas. High-performance aircraft planning to cruise in the flight levels are able to plot more directly. Asking for a more direct route should be done airborne, in real time. This makes it easier on the controller.
Pilots should think efficiently when filing a proposed route. What grinds controllers’ gears is when a professional pilot files direct from departure to destination airport, which we view as being extremely lazy—not to mention a bad practice. Controllers have more to do and watch out for, but now must take time and do the pilot’s job of putting in a full route clearance for them. A word of advice for pilots beginning or even those who have been flying for a while: If you have a hard time pronouncing some of the fixes in the clearance, do not mumble them or say it really fast in hopes that the controller will not catch your bad readback. If you have a hard time with the pronunciation, do not feel embarrassed to ask the controller to spell out the VOR or intersection identifier phonetically.
Lastly, if you have any IFR routing questions, do not hesitate to ask. Time permitting, controllers will be more than happy to answer any questions. A pilot that is in the know is safer, better off and requires less supervision than a pilot who is not current, not proficient and wants others to do all the work for them.
Safe flying!
Eric Lyn is a private pilot who works as an air traffic controller in Southern California.
