I can hear you say: “A what?!”. An ARTCC or fully extended: an Air Route Traffic Control Center. To make it short and easy, it is the centers that are handling all the routing of the planes under IFR while in flight. 

There are a total of 21 centers on the main land and a 3 outside the main land. The Minneapolis Center happens to be one of the largest.

And today I had the chance to have a tour organized specifically for me. My tour guide would be one of the ATC in function there.

As I’m approaching the gates of the center, I’m not sure what to expect but I can feel the excitement of entering a place that few had the chance to get in…

Serendipity of an MBA class

As I’ve explained in a previous post, one of the main reason I’m in Minneapolis these days is to continue my MBA. The ceremonial around the first day of a given class is almost always the same and include not only a presentation of how the class will take place, what would be the assignments but also the professors like to know what type of students they have. By what type, what profession they are practicing. As it is a part time program we all have real day job! Being in the major urban area with several headquarters, we are usually finding people from the same companies but from different position! We have the Target guys, the Best Buy guys and usually a smaller mix of 3M, Cargill and General Mills!

I’m usually pretty attentive at the description because I usually like to talk to the students that have connection to my interests or are in areas that I might be looking for! Yes! It’s called networking! But this time, I was surprised to hear a voice from the other side of the room claiming working as an ATC for the Minneapolis area. I realized immediately that I would need to talk to that person and see if it would be possible to get a visit of an actual ATC. Her name? Anna!

2 classes later, during a break, I’ve finally managed to get to talk to her. After some basic introductory discussion, she explained to me that it should be possible but that authorization would be required. Not a problem I have been cleared by the government, the FAA and TSA several time, I’m pretty sure it should go without a problem but still, I’m really hoping to get the approval. As a justification, we put: “Pilot wanted to increase his knowledge of the ATC processes”. This is something that pilots are encouraged to do so that should give me a good chance to get the permission granted.

Anna went on explaining also the type of centers that she is working at. At first, I thought she might be working in an airport tower or for the Minneapolis Approach but no, in fact, she is working at a larger level by handling en route flight or as mentioned above in one of the 21 ARTCC in the country. We closed our discussion and class break with the promise of more email communication to turn my request into an happening!

TSA: We meet again!

Of course, a few days later, I do hear about Anna. She is mentioning in her email that since I’m not a citizen, there are extra paper work to fill and an approval process through … TSA! I can decidedly not escape TSA these days! After dealing with them at each trip on a commercial airline, dealing with them for getting my student pilot license, they show up again with another approval for this visit! Oh well! I’m glad to oblige them if it is allowing me to visit the site. After submitting all the information and waiting for a couple of weeks, Anna announces me the good news: I have been approved!

Entering the site

The day before the visit, I meet Anna again in class and we set up the last details for the next day. I’m becoming impatient because there is another interesting detail about Anna. She is not only an ATC but happens to be also a CFI (flight instructor)! This means that she perfectly understands both sides of the business making her explanation even more valuable.

So here we are, I have now been driving for about an hour from the office to get to the site. It is raining pretty bad and I’m actually missing a turn. TomTom caught my mistake and immediately reroute me! Unfortunately, TomTom did not make the difference between paved road and a dirt road. And a dirt road with rains = mud + lots of sliding! My Cadillac being a propulsion, needless to say that the tail of the car was all over the road! But after a good 5 minutes on the road, I’m back on asphalt but not without changed the car color from dark blue to light brown! A few more turns, a couple of long stretch and I’m finally there. The site is fairly inconspicuous. There are no marking visible and a couple of antennas with a big hangar/warehouse style building! As you approach the security booth, you start to realize that these guys means business and that you are not entering just a simple plant or something like that! Metal detector and X-Ray machine, no camera’s allowed. By the time, they have checked my identity and my credential, Anna has arrived to pick me up at the booth. The tour can now starts! From now on, my ears and eyes would be working 110% and try to grab as much detail as possible.

Overview of the system

After going through the common areas where I could drop my coat, Anna brought me to a big map to offer me some explanation of the extent of the work getting performed in this center. The map is similar to the picture on the side and shows the Minneapolis Center. As you can see this is a fairly wide area. To facilitate the management of the traffic, each area is divided into 3 layers covering a range of altitude. Each layers is then divided in self into sectors. The sectors delimitation are not matching from one layer to the next, they are usually different. The map that Anna showed me at also some extra information like the approach zone. It is now making sense and the delimitation between Approach and the ARTCC becomes really clear. Anna is mentioning that part of the role of controllers from the ARTCC is to bring IFR flight to a certain position, altitude and speed to hand off the planes to Approach that can then take the plane and bring the plane to the tower for a landing.

The map was interesting also because it was highlighting part of the infrastructure used by the center. They are including not only the antennas but also all the wiring that was used to make the system work. I was under the impression that ATC were distributed a little bit everywhere but it seems that I was totally wrong and that only 1 center is enough to monitor such a large area!

Real Mission

I was looking at the 2010 AIM for the definition of an ARTCC and it said the following:

Centers are established primarily to provide air traffic service to aircraft operating on IFR flight plans within controlled airspace, and principally during the en-route phase of the flight.

Well, the least we can say is that it is pretty simple and they are pretty sure to not miss anything with something like that! The question then becomes, how does it translate and what are some of the operations that they are really performing? What does it really mean to “provide air traffic service”?

The common understanding of the Air Traffic Controller’s job is that they are providing flight separation, meaning that they are maintaining the safety distance between all the planes. While this is totally true, and probably the one that we should be the most thankful for, this is in fact a very small aspect (in quantity) of their mission.

There are multiple others services that they are providing:

• Military Activity Following
• Flight optimization
• Delivering airplanes to Approach Centers
• Plane spacing and streaming

Military Activity Following

Anyone who has looked over a sectional has seen signs of military activities: MOAs, military routes… The ARTCCs are actually tracking all the military flights and keep track of status of the all the MOAs. They have a dedicated team to track all the flights and make sure their needs are satisfied.

Flight Optimization

While routing the planes, they are aware of the winds and the weather and are therefore in position to recommend alternatives routes to help the planes to save time and gas but more importantly, stays on track for arrival time. As you can see they are one of the important hidden actor of what makes a good flight for millions of passengers.

Delivering airplanes to Approach/Departure Controls

En Route Centers,the other name of the ARTCCs, have agreements with the different Approach Controls. These agreements are usually specifying a certain number of gates for a plane to handed over. A gate is specified by a certain number of information: First, the geographical location. Planes are expected to enter in certain areas and a certain altitude. But this is not enough! Plane have also have a certain heading and a certain speed to make sure that they can enter smoothly into airspace. There is also another element called spacing but we will see that in the next section…

So why is it important for the ARTCC to respect these agreements? After all, they can simply just bring the plane, hand them over and let Approach Control deal with the plane… Well, beyond a matter of courtesy, you have to think that approach controls have fairly confined area to deal with and there role is to make sure that all the planes that are in bound for landing can land safely and swiftly! So if too many unruly planes are entering the approach airspace at the same time, approach control will spend a large amount of time just trying to select, coordinate and make sure that the airport is operating at optimum capacity. This would be a nightmare for them! Remember that approach is usually dealing with large airports (B & C airspace!) and that their mission is to bring airplanes down to the runway but they have to deal with departure, over flight and all VFR flight with flight following requests…

Thankfully for them and, unfortunately for the ARTCC, they have one weapon that they can use, it’s closing the airspace when the workload is becoming too large! If an Approach Control is closing the airspace then no plane is allowed to enter, which means that the ARTCC is left with the planes to handle. It is therefore the interest of the ARTCC to make sure that the agreements are respected to avoid having to deal with a bunch of airplanes with no where to go!

Plane spacing and streaming

The most impressive and unknown aspect of an ARTCC is the plane spacing and streaming. What is it about? When you think about it, it is obvious but the scale at which this is happening is just plain unbelievable! Let’s start at the airport. Let’s suppose that we are on a large airport but we have only one runway available (having two would make the discussion more complex but would not help the understanding! ).

This runway is able to accept all size of aircraft. Then we need to start thinking about capacity. How many plane can I land per hour!? I know it depends on a lot of parameters but the most important parameters is plane separation. After all if we could land a plane every 5 seconds that would be perfect but we all know this is not possible. Let’s assume that we have to wait a plane every minute. This means that the capacity of the airport is 60 planes an hour.

This capacity is well known for an airport and for weather condition so they can inform the ARTCC of what they can receive in terms of plane. But now comes the real trick. Giving a number is not enough, the plane have to come to the airport at a steady rate. If all 60 planes are at the airport ready to land in the first 15 minutes of the hour, then there is an issue because we have too many planes on hand and obviously, no place to put all of them! So it is important that the plane are getting space accordingly.  This means that the 60 planes will be put a long a line. But a 60 plane spaced exactly one minute apart is quite a long line and that would extend beyond the airspace of the tower, beyond the airspace of approach control right into … ARTCC’s airspace! This is actually where it is starting!

This means that the ARTCC is actually pacing all the planes. How do you pace a plane? By playing on its speed. The centers have complex computer systems that are capable of highlighting the planes positions and to know if a plane is at the right position or not. If they are not, the computer is capable of telling how many minutes ahead or behind the planes is compared to the expected position. The information is then passed back down the line to the controller in charge of the plane. The controller would then instruct the plane with a speed that would allow him to gain or loose speed. The benefit are enormous because the plane is more or less guaranteed to not have to go into an holding pattern.

But there is another trick. You can only imagine how long a 59 planes line can be, depending where the 60th plane is coming from, it might have to cover a lot of extra ground to get on the line. Not exactly a good plan to stay on time and minimizing fuel consumption. In other to avoid that, there is a simple solution: you can create several lines. One for each of the main direction the planes are coming. These multiples lines have to be merged into a single line since we have only one runway. So how do you merge two lines into one. The strategy is to divide the capacity. For example, if we can land 60 planes an hour and we split the stream into 2 sub streams then the capacity of each stream is 30 planes per hour. In other words, you have to separate the plane by two minutes before the merge point and they will be nicely merged into a 1 minute separation. Of course, you can use different strategy based on the relative volume but the idea remains the same…

So back to the ARTCC, their role is then to manage the multiple streams of the airports that they have in their areas. I think Minneapolis has 3 main streams but that needs to be confirmed but they also have to manage the streams from other airport from other area. As an example, they told me that at some point in the year, the Minneapolis ARTCC is managing a stream for … JFK! Yes! JFK as John F. Kennedy International Airport, New York City!!! That’s a 893 nautical miles (1,000+ miles) lines! I’m glad to not see such a line at the supermarket!