August 28, 2014

Beyond the Tower: The Controllers That Guide You the Rest of the Way

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Written by: Eddie Trujillo
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Almost without fail, the question I get immediately following, “What do you do?” is, “Oh, so you work at the tower?” I’ve been a controller for nine years now, and no, I’ve never worked at a tower. I actually work in a big windowless building, nowhere near an airport. While the question irks some of us, it’s easy to see why it’s asked so often: The tower is one of the most recognizable landmarks of the flying experience. Of course the mainstream media almost never gets it right. Any time the news talks about ATC, we are referred to as the “controllers in the tower.” And the alternative misconception, that we are the crews on the ramp marshaling aircraft with the orange sticks, is no better. Let’s see if we can start clearing up just what we do as air traffic controllers.

ATC That You Can See

When you’re at an airport waiting for a flight, you can see all the hustle and bustle going on outside the windows – aircraft landing, departing and taxiing to and from the ramp. There are even other vehicles speeding about all the time. Every one of these is handled by people in the control tower. Even before your plane starts pushing back from the gate, the pilots are in contact with controllers, relaying information back and forth about their flight plan and taxi instructions to the runway.

Finally, with some patience, your pilots hear, “Cleared for takeoff.” The engines of your airplane roar to full power, you get pushed back in your seat, the rumble of the concrete suddenly becomes silky smooth and off you go. Everything beneath you becomes much smaller…and then what? It’s a big sky and the pilots have a flight plan, so they know where to go, right? Sixty years ago that may have been possible, but it is certainly not anymore. The airspace is far too busy and the airplanes far too fast for pilots to go it alone these days.

The National Airspace System (NAS)

Real-time air traffic map courtesy

On any average day, there are over 5,000 aircraft operating in the skies over the United States under Instrument Flight Rules (IFR). All of these flights are required to be controlled by ATC at all times in order to ensure proper separation with other aircraft. Flying IFR allows travel through clouds and adverse weather that can reduce visibility. There are countless more aircraft operating under Visual Flight Rules (VFR) that may or may not be getting ATC service. Visual rules puts separation responsibility solely on the pilots, so they are required to fly clear of weather and look outside the windows for other traffic.

Control facilities are divided up into three types (or environments): Tower, Terminal, and Enroute. All three come in different sizes and acronyms. An air traffic control tower (ATCT) can be anything from a small glass box on top of a mobile home to a dizzying three hundred foot obelisk at the center of a major international airport. Terminal Radar Approach Control (TRACON) facilities vary as well, from small single-screen operations that can be run within a tower cab to extremely complex “Large TRACONs,” which can encompass several busy airports. The third and biggest, the Air Route Traffic Control Center (ARTCC), can handle traffic across multiple states and even huge chunks of ocean.

You can almost envision the three by thinking of the Interstate highway system between crowded cities. The airports are the busy, crowded cities. Terminal Approach Control airspace would be the interchanges, on and off ramps, and smaller highways in close proximity to the city. Finally, Enroute would be the long expanses of highways themselves, stretching cross-country.

The On Ramp (Terminal Approach Control)



So, back to our original story. What happens after your airplane leaves terra firma? After a short climb and maybe a turn or two, pilots are told to contact departure, one of the primary functions of a Terminal Radar Approach Control (TRACON) facility. A TRACON typically encompasses an area of airspace within 40 miles of a primary airport, up to 10,000 feet or a little higher. Departure controllers climb and turn aircraft on their way out of the TRACON’s airspace towards the Enroute Center (more on that below). Approach control is very tactical, working with small airspace with many aircraft within. It takes a lot of rapid, yet accurate decision making to keep things safe, orderly, and expeditious.

Along with departure, TRACON controllers also work arrival and satellite traffic. Arrival is responsible for funneling and blending multiple streams of aircraft into single file lines in order to land. If you are near an airport and see a long line of lights off into the horizon, the “string of pearls,” you are seeing the result of an arrival controller’s work. Being able to guide aircraft from several different directions into a steady, consistent final approach takes expert timing and precision. “Pearls” are a source of pride for any approach controller.

While arrival is generally touted as the top of the food chain, satellite operations can often be even more difficult and complex. Satellite airports are scattered all around, and even though a TRACON usually only has one primary airport, these other fields also need air traffic control service. Chicago Midway, Dallas Love, and Fort Lauderdale are all satellite airports to their larger counterparts, but still have abundant traffic. With the bulk of the nearby airspace being dedicated to the primary airport, satellite is usually reduced to lower altitudes and smaller corridors of airspace, making things a bit tricky.

So here we are, climbing above 10,000 feet. Departure has vectored your flight through the web of arrival traffic flows, and on course to your destination. The departure controller instructs you to “contact center.”

Highways and Byways (Enroute Center)

Image courtesy Federal Aviation Administration

Image courtesy Federal Aviation Administration

The network of enroute centers is the backbone of the National Airspace System. There are twenty two ARTCC facilities in the United States, responsible for air traffic control service up to 60,000 feet over huge expanses of area. Some even handle oceanic operations over the Pacific and Atlantic. Each facility is staffed by roughly 250-350 controllers, weather specialists, traffic management coordinators, technical support staff, and many others.

The center is the grand master of all airspace and, ironically, is the least visible to the flying public. As your flight reaches its cruising altitude of 38,000 feet, you look outside and it feels like you’re all alone in a sea of blue. Appearances can be quite deceiving, however. Watch outside long enough and you can see other aircraft zip by, only 1,000 feet above or below you. Contrails can stretch for hundreds of miles in any direction. The sky can be very busy.

The enroute controller, in contrast to approach, works in a “strategic” or “big picture” method. The aircraft travel much faster at altitude, but since the airspace is so much broader, the traffic picture appears to move more slowly. Traffic separation is often maintained with small moves over longer distances, for example, instead of more drastic turns that are quite common in the Terminal environment.

Centers also get to handle a lot of extracurricular activity, including air refueling, large military aircraft movements, training areas, search and rescue, research flights, and so on. As you fly along, you could pass over a group of Air Force fighter jets refueling from a KC-135 Stratotanker. Beneath them could lie a stack of holding airliners, waiting to get into Atlanta. It all blends together with the horizon out your window, but it’s all clearly visible to the Center’s radar.

The Off Ramp to Town

After passing through a few ARTCCs, it’s time to descend. The center controller clears your aircraft for a lower altitude. They place you into one of four or more arrival streams for your destination. “Contact approach,” and the process begins to reverse. Arrival blends your stream with the others, gets everyone in line, and clears the planes for their final approaches. Nearing the end of your voyage, after a couple thousand miles and a few dozen skilled controllers, your airliner is a shining pearl in the sky. One after another, with two and a half miles of in-trail spacing between them, they contact the tower, where the last few controllers will guide them the final few miles.

“Cleared to land.” The main gear screeches on the concrete below, the engines roar again with reverse thrust to slow down your craft enough to exit the runway. As soon as the plane clears, another is touching down within seconds. The local controller constantly ensures that only one aircraft is coming or going at all times. Now you can see a swarm of airplanes outside the window. The delicate choreography between controllers in the tower and the pilots below keep everything moving swiftly. Before long, you see the jetway attach and your voyage has been completed safely. One voyage out of thousands that have occurred that day.

Welcome home.

Eddie Trujillo has been an FAA Air Traffic Controller for nearly a decade. He has been at Chicago TRACON since 2010, and prior to that spent five years at Memphis ARTCC. He is a loving husband, a father to three girls, and a proud #AvGeek. Follow Eddie on Twitter @trujilloea.

About the Author

Eddie Trujillo



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  • Sahir Siddiqui

    Hey – great article! Thank you very much for this interesting insight into your job!

  • Daveabbey

    Eddie, Thanks for the thorough article. ATC is my favorite part about aviation and listen to the ATC feeds just about as much as I do regular radio.

  • No Fly Zone

    Great article, thanks!!

    • Mike Smith

      Yeah, but are you down there ’cause I’m up here or am I up here ’cause you’re down there ?

  • TexanInExile

    Great article explaining the different types of facilities.

  • jheath

    Good article. Though I don’t know how they convinced everyone to let them turn the lights up high enough for that picture up top. I’ve never seen any area in our facility anywhere near that bright.

    • Jbeke

      I’m sure this is the simulator lab.

      • CrankyOne

        Nope, that’s the normal control room… ARTCC’s are much, much brighter than approach control radar rooms. Oh, and “en route” is TWO words

    • Guest

      I worked at ZJX and the lights were almost that bright after they made the equipment changover to the new screens.

    • Charlene Richard

      our lights would change from off to full bright depending on who was working – if we couldn’t all agree, they were halfway….

  • Disqususer8675309

    I have gotten the orange wands question before. This is going on my FB page!

  • Iain Parsons

    Great article Eddie! I retired from ZSE four years ago, and have had to explain this concept to folks my entire career. This article needs to be put out there on other blogs though. After the ZAU debacle, it is an easy, informative and fun read that just might educate some “Main Stream Media” folks

    Keep up the great writing and get out there and share it!

  • Mark Linsdell

    Amazingly insightful article

  • stephen ramsden

    Nice job Eddie.