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Know Your Pros - Center Air Traffic Controllers (Part 1)

ZAN ARTCC Federal Aviation Administration

Aaron Merrick is a Certified Professional Controller (CPC) and the NATCA President at Kansas City Air Route Traffic Control Center (ZKC). In our next two articles, he gives us a look at the life of a Certified Professional Controller.

Air Traffic Control often seems ominous to pilots - especially to new pilots. The voice on the radio can sound intimidating, and often we have no idea what's happening in the background. Aaron Merrick, a Certified Professional Controller at the Kansas City Air Route Traffic Control Center, gives us a look at who's on the other side of the mic and how their world is a lot like ours.

ARTCC - What Is It?

We call them "Center," the en-route air traffic controllers who keep each of us in our own space. There are 20 Air Route Traffic Control Centers scattered throughout the United States, which manage en-route operations for IFR traffic and provide flight-following and other services for VFR operations. But their job doesn't end with en-route - they also provide approach and departure control for airports without a dedicated approach facility.

One Center, Many Areas

Each ARTCC facility breaks their airspace down into areas of specialization - blocks of airspace worked by a team of controllers. When controllers join the facility, they are assigned an area and certify on that area's airspace. If a controller moves to a new area, they must certify on the new airspace prior to working in that area.

Areas of specialization cover broad expanses of airspace - too much space to be worked by a single radar controller. To make the areas manageable, they're broken down into several high and low "sectors." At Kansas City Center, low sectors control airspace from the surface up to Flight Level 230, while high sectors cover airspace from Flight Level 240 and above. A radar controller works a single sector at a scope, possibly with the help of a "D-Side" controller and a "Tracker."

Kansas City Center has six areas of specialization, plus a traffic management unit. Each area includes seven to nine sectors, depending on traffic load. Around 240 controllers work at Kansas City Center and more than 100 controllers may be on duty at one time. So, while you only hear one voice, there's a lot going on behind the scenes.

It's A Complicated Process

You hear one voice on the radio, but up to four controllers may work together to manage your flight. "A-Side" controllers enter flight plans and disseminate flight progress strips for areas of low radar coverage. "D-Side" and "R-Side" controllers work a scope as a team to manage flight operations. Occasionally, during periods of more complex traffic, a "Tracker" may join the D and R-Side controllers on a sector to help manage the workload.

A-Side, D-Side, R-Side, Tracker - What's The Difference?

Looking at a controller's training and career progression is one of the best ways to understand what each specialty does.

The FAA hires controllers from a variety of sources, including the military, Air Traffic Collegiate Training Initiative schools like Embry Riddle and the University of North Dakota, and they sometimes hire off-the-street. While newly hired controllers may have had previous training and experience somewhere else, they all start from the beginning at the ARTCC.

Radar Training

Starting On The A-Side

Before hitting the center floor, new controllers hit the books. Each facility hosts its own training, and new controllers spend up to two months in the classroom learning every inch of the center's airspace. At the end, they know all of their area's maps and procedures and pass a written test.

Next, they head to the floor to work the A-Side. "Basically, the A-Side is where you put in flight plans and where flight progress strips are printed," says Merrick.

It's happened to most of us - during climb out, you call up center to pick up your flight plan, but nothing's on file. Maybe you were delayed, or maybe you mixed up your UTC conversion. After you relay your flight plan to center, an A-Side controller adds it into the system.

The A-Side also disseminates flight progress strips used by center controllers. "Each strip shows the call sign, type of aircraft, ground speed, true airspeed, altitude, route of flight - all that kind of stuff," says Merrick.

In the past, a flight progress strip accompanied each aircraft handled by the center. Now, center controllers use the User Resource Evaluation Tool, called "URET," which provides paperless strip information for most flights transiting the center's airspace. It also provides predictive traffic alerts for aircraft in the system. While URET has significantly reduced the A-Side's workload, they still create strips for aircraft in areas with little to no radar coverage. In additions, A-Side personnel help disseminate AIRMETs, SIGMETs, convective SIGMETs and PIREPs.

How long does a new controller spend on the A-Side? "You can be in the position anywhere from a couple of weeks to four or five months, depending on where you fall in the training program," says Merrick.

"When it's slow, new controllers spend that time studying the maps and learning frequencies. They'll plug in with controllers to learn the intricacies of each sector."

I ask Merrick what's the toughest part about learning the A-Side. "The A-Side is knowledge," says Merrick. "It's memorizing the frequencies, maps, and VORs. You're cramming for a test every single day, trying to get these procedures down, while you're also learning the letters of agreement, phraseology, military procedures, special use airspace, MEAs, airports, approach plates. That's tough."

High Altitude Enroute Chart

Moving On Up To The D-Side

With A-Side experience under their belt, controllers head to Stage 3 training. They learn to work the Radar Assistant position, called the "D-Side."

"With every single radar scope, there's also an assistant position. Generally when traffic in a given sector gets busy, or is predicted to get busy, and the radar controller or manager realizes that the complexity warrants additional help, they'll put an assistant with them. That's the D-Side position," explains Merrick.

Radar Scope - ZSE

We're familiar with center's communication with pilots - you can imagine the focus and attention needed to separate flight paths and altitudes. But, at the same time, radar controllers are coordinating flights with other facilities. "We have numerous written letters of agreement and procedures with other facilities. Anytime we're going to do something that's against what's written in our agreements, then we have to get approval. We call it 'APPREQ,' which means 'approval request,'" explains Merrick.

Prior to working the floor as a qualified radar assistant, controllers must certify on each sector in their assigned area. The first week focuses on classroom training, where they "re-draw maps, re-draw approach plates, and take an area knowledge test on VORS, airports, procedures, letters of agreement with approach controls and military airspace. You have to test out of all of that stuff again," explains Merrick.

With the classroom training complete, controllers head back to the floor for on-the-job training. They'll perform all of the D-Side's duties under the supervision of an instructor, from maintaining information in the URET to coordinating with other ATC facilities.

"There's target hours, training hours, monthly skills checks and things like that," he continues. A controller usually trains on two to three sectors at a time. They get a pay raise after qualifying on two sectors, which is a significant benchmark in the training process. "Then they work those positions on their own - we call it seasoning time," explains Merrick. "They're able to work there without a trainer, without someone else watching over their shoulder. Once you get those, that's the time you start to cut your teeth as a controller. You're liable for the decisions you make."

"You can make every command and control decision that the person sitting at the radar can make," explains Merrick, "with the exception that you're not actually talking to the aircraft. You're talking to other controllers, whether down the hall, in another area in your building, or to another facility."

I ask Merrick what's the toughest part about learning the D-Side. "The hardest part of D-Side, aside from 'seeing' traffic, is learning to work with the radar controller. Now you're working with a controller who might have been here for 25 years. They may already see traffic, without the URET telling them to do anything. You're a young, green guy doing what he's trained to do, who has to turn to this experienced controller and say, 'Hey, those two 35's are going to be a problem. If you give this guy direct to Kirksville, it'll fix it. And the radar controller may say, 'OK thanks - I appreciate that.' Occasionally, they'll say 'Oh, I didn't see that.' Getting that rapport, figuring out what the radar controller needs to know and what he doesn't need to know, that's tough." As Merrick's describing the D-Side and it's challenges, I keep thinking back to CRM - and considering how similar the experience is to a new first officer's.

With experience in the first two positions, new controllers continue certifying in sectors, two to three at a time. Once they've qualified in the entire area, they're scheduled for Stage 4 training - radar qualification.

Click here to read part two of this two-part series on Center Air Traffic Controllers.

Aleks Udris

Aleks is a Boldmethod co-founder and technical director. He's worked in safety and operations in the airline industry, and was a flight instructor and course manager for the University of North Dakota. You can reach him at

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