Air traffic control consists of multiple services. Which ones and how do they collaborate?

Air traffic control as a service consists of several segments, the most basic division being operational and support services. The Air Traffic Control (ATC), Aviation Telecommunications Service (SLT), and Aviation Information Service (SLI) operate in the operational area. The support services employ personnel who are necessary for the normal operation of the company (HR, IT, financial services, etc.). All services operate independently and at the same time interdependently with others. Operational departments are closely intertwined, especially since they work 24 hours a day, 7 days a week, 365 days a year.


Can you describe your profession and everything that you do? “Air traffic control is the service that controls, directs, and coordinates air traffic with the invisible hand – every day, in all weathers and around the world,” says your brochure.

The job of an air traffic controller differs depending on which service they are in – “an airport” or “an area”. In the first one, they manage air traffic at the airport and its vicinity. In their work, they primarily use their eyes (and their extensions in the form of binoculars), and controllers in area control need a radar screen for their work. Only this one is a computer monitor with an atypical aspect ratio – it is a square with a resolution of 2000×2000 points (pixels). The position of the aircraft in space is shown in two dimensions, so the controllers must be skilled in spatial combinatorics and must have a good idea of ​​the three-dimensional space shown in two dimensions. 

It sounds very complicated, but with some practice and training (basically two to three years of training, practice, and training) it becomes completely normal and almost self-evident. Both of us control the flow of air traffic and ensure that aircraft do not approach obstacles on the ground and/or other aircraft in traffic. 

Here we use professional gibberish, which is called aviation phraseology and which is prescribed for the whole world by ICAO, the International Organization for Civil Aviation. All pilots and controllers in the world can understand each other, which was the basic goal. At its core, a profession is a kind of melange of various skills and knowledge, from the cognitive, motor, social and similar. 

If I describe what we do in general, I could say – to sum up – that tower and ground controllers make a lot of use of binoculars, radars, and other electronic aids,  where radar control (or control, since not only radars are used, but also other sensors, for example, Wide Area Multilateration, ADS-B, ADS-C and similar) uses various tools (for example, automatic measurement of the shortest distance between two or more aircraft, a safety net – Safety Net, which warns of a potential loss of separation between two or more aircraft, etc…).

For communication with airplanes, we use voice communication systems, and more and more so-called data link, or the data connection between the control and the pilots, which greatly reduced the saturation of the speech frequency, that is, we speak less into the microphone, more we send each other prescribed messages with instructions. 

In practice, this greatly reduced the phenomenon known as the deaf phone effect, i.e. incorrectly received and/or misunderstood instructions from both sides of the microphone. Most often, errors occur when handing over to the next control, when you tell the crew the channel or frequency on which they should report. If you just send it electronically and the crew reads it on the screen, the possibility of error is almost zero. 

The same is true with issuing and receiving instructions to fly towards the next point. In most cases, the names of only these are abstract five-letter “mash-ups” that cause a lot of problems for too many cultures, for example, the letter J in the middle of the name of a navigation point will confuse English speakers, while some other combination confuses some other speech group…

Air traffic controllers are also constantly trained. At least once, in practice mostly twice a year, we have exercises on the simulator, where we practice extraordinary procedures in a realistic environment or just maintain controller fitness. We also have theoretical training with each innovation (usually in the form of self-learning, but can also be in the classroom, if major changes are involved), and every day before starting the shift we have to familiarize ourselves with the meteorological situation, NOTAM messages and other relevant information for our work.


What is a typical controller’s week like?

There is no typical week. Every day, week, and month is different. In general, the only thing that applies here is that there is some difference between low and high seasons. The latter typically starts somewhere in mid-April and lasts until October and is of course linked to spring, summer, and autumn migrations to warm European and other seas, but in the low season this traffic is much less and only regular lines remain. 

Slovenia is of course tied to the traffic flows of large airports, as it is located exactly on the NW-SE and NE-SW axes. At the beginnings and ends of these axes are large European airports and tourist destinations. As a country, Slovenia is obliged to perform the service of air traffic control over its territory. 

According to the law, the normal work cycle for air traffic controllers is the 6-4 cycle, that is, six days on shift, four days off, and within this cycle, there are 13 different shifts (the earliest is, for example, the one that starts at 6:00 a.m., and the next one at 7:00 a.m., 8:00 a.m., 9:00 a.m., 10:00 a.m., etc….). 

We used to work exclusively on the system of two mornings, two afternoons, and two-night shifts, but the traffic pressure has grown so much in the last ten, or fifteen years that we have had to introduce many intermediate shifts to ensure as much traffic flow as possible through our airfield within one day space. 

The night shift ends at 7:00 a.m. the next day, so basically there are just over three and a half days off. 


Work is organized by sectors? 

Yes. Shift work is organized by so-called sectors, i.e. volumes of air space controlled by a pair of controllers. Due to the relatively small size of the country, it is laterally almost identical to the outline of our country, but it is cut vertically as needed. 

In one sector, two people work in this way, during the day it is usually the case that there are three people designated for each sector, who rotate. On the left sits the executive controller – who communicates with the aircraft and directs air traffic, on the right is the assistant who coordinates work with neighboring controls, whether within our entire sector, with airports, or with other similar units in the neighborhood.

Depending on the amount of traffic, this sector can then be divided into two, three, four, or at most five levels (as many as we can open here). What are the vertical boundaries between them depend on the amount of traffic for each segment, so they are determined by the shift manager on the recommendation of the flow manager, who constantly monitors what traffic is expected in the next two hours. 

For each particular day, it is known quite precisely how many planes will fly over certain airspace, as flight plans are usually submitted at least one day in advance, and there is a lot of traffic anyway on regular and other lines, which are announced half a year in advance. 

If an individual sector threatens to be overloaded, the shift leader changes the vertical boundaries of the individual sectors so that the load is redistributed as evenly as possible.

foto: Jože Kovačič

Do you earn the operating funds yourself?

In the vast majority of countries, this is done by a company owned by the state, which has been authorized by the state to perform the service on its behalf. 

Almost everywhere, it is a similar organization to ours – i.e. a company that was granted a monopoly by the state and tasked with performing the task of providing navigation services in the airspace. 

It, therefore, does not need funds from the state budget for its operation, but rather earns it through its operation, and since it is a monopoly, almost all companies (at least within the European area) are heavily regulated and obliged to measurably reduce costs and increase the quality of work (both in the amount of turnover which the individual unit can process per given unit of time, as well as technical capabilities).

In our country, the work of Air Traffic Control is regulated by the Aviation Act. I must say that it is for historical reasons – we controllers actively participated in the construction of the entire system and the service itself, since in 1991 air traffic control did not exist as a service, there were only individual units, which until then were part of the Federal Air Traffic Control – that we are now perfectly taken care of. 

It wasn’t always like that, at the beginning of my career, the country didn’t care much about radars, control, and air traffic, and only after a few successful strikes did we manage to bring the job and conditions to the level where they are today.

foto: Jože Kovačič

Is the controller’s job stressful? 

The amount of pressure, i.e. traffic, depends on the workplace. The amount of pressure that is reflected in the time crunch (traffic situation unfolds mercilessly, and there is no time for long reflection) of course additionally depends on what and which airspace is controlled by the individual airspace controller. 

Arrival control at a large airport works at the same pace almost all day, because many airlines fly there with different planes, and the amount of traffic alone makes the work complex, although it is usually not complicated. Every air traffic control service tries to ensure that operatives are as well prepared and trained as possible and that they have as many aids as possible to facilitate their work.

How much a controller can work in the sector is also specified in the Aviation Act and amounts to two consecutive hours, a maximum of three in case of emergency. Then there is an hour of break and then another two hours of work. Usually, the work is organized in such a way that three rotate in each sector so that the third replaces the assistant, and only the latter replaces the executive, and so on in a circle. 

It is stressful in the summer season, Slovenia is the crossroads of the shortest connections between NW and SE, and NE and SW, but at the same time we are also close to large airports such as Venice, Zagreb, Vienna, Munich, Frankfurt, and of course traffic for them also comes through us. 

But the most stressful is in the summer when there are storms… then all the planes try to avoid them and fly across… then it’s tense and both controllers on the sector are busy. Adrenaline jumps into the sky even when something goes wrong, either with our equipment (which is extremely rare) or with the plane (various cancellations, errors, problems with the health of passengers, etc.). 

According to Murphy’s Law, such things usually happen when they are least needed, when there are already enough other adventures in the sky anyway. Some of my colleagues have witnessed tragedies when the planes they were guiding crashed and took the crew and passengers to their deaths… I can’t imagine what kind of stress it is when you helplessly watch the plane fly on its own, the crew doesn’t respond or announces a catastrophic cancellation… and you can’t do anything…

Of course, you need to come to work rested, otherwise, concentration and focus quickly drop. If the sky is crowded, it can quickly happen that something approaching is overlooked…

Fortunately, we maintain and develop the systems we work with ourselves by creating tools and accessories that help us detect potentially conflicting situations in time and resolve them before they become too dangerous. 

In the last instance, we also have a safety net, which is called that (Safety Net), that immediately recognizes an approaching aircraft, that will lead to a loss of separation within a maximum of two minutes, that is, two planes (or several of them) will be at the same height (or less than the prescribed distance of 1000 feet or just over 300 m), or less than 5 (in lower airspace 3) nautical miles apart (which is just over 8 or 6 km). An alarm is triggered, which graphically warns the controller that he must take action to prevent this from happening.

8, or 6 km sounds like a lot, but you have to understand that it also represents a strong psychological limit that must not be broken. 

If two planes pass each other at two kilometers, or even less, that is still more than enough separation from a layman’s perspective, but it is a serious offense in the air traffic control system. 

I must also add that Slovenia was one of the pioneers of the non-punitive culture, i.e. a culture of non-punishment for transgressions that did not end in a disaster or were of such a nature that they are punishable under other laws. This, of course, does not mean that there are no consequences for controllers who commit such an offense. Any deviation from the safety minimums must be recorded in the form of an electronic form, in certain cases, a committee is also formed to examine all aspects of the event and, if necessary, prescribe additional training and/or other actions for the “culprit”, which will alert the other controllers to certain errors, practices or tendencies that are not good for safety and that must be eliminated or eliminate with the help of simulator or classroom training. 

Anonymized examples are available to the entire professional public in terms of collecting and sharing examples and data, which should ultimately help others learn from mistakes already made. 

When such a security event, as we call it, occurs, the controller is usually in considerable shock and it is often necessary to withdraw him from his working position at that moment, as he is often no longer capable of satisfactory focus and concentration. 

We are trained and used to holding back stress until an unusual or urgent situation is underway, because we simply cannot afford to just put down the microphone and go on a break. When the situation passes, the stress hits with full force. Some colleagues are more stubborn, others less so, just like in everyday life. Some need more pause, others come together faster. I don’t know anyone who hasn’t experienced such stress in their air traffic control career for one reason or another.

Foto: Jože Kovačič

What are the most important qualities that a controller should have?

It is not so much about individual qualities or predispositions, it is about their combination. A single quality or characteristic is not enough. Roughly speaking – a person must not be afraid of unusual situations, or constantly changing situations, he must have a good spatial and temporal orientation (especially the control controllers, who monitor the three-dimensional situation on a two-dimensional screen and must have a good idea of ​​which planes are separated by height and which are not, and which planes are approaching each other and which are not), mental stability is almost an inevitable necessary attribute, then the ability to quickly adapt and solve three-dimensional puzzles that move across the screen at speeds of up to a thousand km/h, a good knowledge of English is required, and of course, the ability to tactically maintain concentration and its ever-changing intensity.  Good hearing it is also important. 

Most of the qualities of new, future colleagues are measured with the help of tests, that are a combination of cognitive, psychological, and motor skills. They are also checked by psychologists and psychiatrists, and general health is also a matter of careful examination. 

I must admit that in the entire history of modern air traffic control in our country, all of the above has been extremely well taken care of, as we have had minimal dropout of candidates during the training itself, which until a few years ago took place abroad, according to international standards. 

In the last years, when the training takes place at home, of course, these have not decreased at all, at most they are even higher. As older controllers, we sometimes bitterly admit as a joke that many of us would probably not pass the entrance tests as they are today. Which, of course, does not mean that we are any worse than younger colleagues. We all went through similar, strict, and precise training, which takes a good year and a half for each permit.

foto: Jože Kovačič

Is training different depending on the sector?

Each job and each branch (tower, control controller) has its training system and its permits. In general, a job permit (e.g. tower controller, area controller…) is obtained first, followed by a so-called unit authorization. So someone who has just completed training for a tower controller cannot just go to the airport tower and start working. He must also obtain authorization for each unit, as each airport, and each workplace (sector) is specific, so in the final phase, the candidate must be trained in a specific position. 

In the past, we had tower, area procedural, and area radar permits (separately in the approach sector and at area control). I started my career as a tower controller in Brnik and then trained for all the permits that were valid at the time, which means that I first completed the theoretical and practical part (simulator) in Great Britain, then trained in Ljubljana to become a tower controller for Brnik, then for procedural approach, control approach, procedural area and finally control area. Each step included at least two months of lectures, two to three months of simulators, up to half a year of training in live traffic (job training), and then a final exam.


How do people most often misperceive your profession?

When people who don’t know it firsthand talk about our profession, they tend to shoot too high and describe it as more complex and complicated than it is. Of course, they cannot know that the amount of traffic at Heathrow, i.e. one of the busiest airports in the world, is not comparable to Ljubljana, so you may not hear so much talking at the arrival control, but there are other challenges, for example, the high mountains nearby, mixed traffic (from a small propeller, military, helicopters to large passenger planes), etc. Every job has its challenges. 

When they visit us at the center, they are usually also surprised that we don’t wear headphones – the way we work is such that both controllers in the sector actively cooperate, so headphones would be an obstacle. 

What also surprises them is that our control is not some dark room, crammed with consoles full of screens and buttons… as I explained before it is for historical reasons we were always on the front lines and developed many things ourselves. 

So we also designed our new center, which we moved to ten years ago, at least its operational part, ourselves, including the consoles. So we were lucky to make the work environment ourselves. This is extremely rare in the world, not only in Europe.


Controllers are a connected community.

There is a huge difference between most controls in the developed world and some less developed countries. Some time ago, I was in contact with colleagues from other parts of the world, and many times I listened with horror to the miserable conditions in which they work. And yet, they do their work with as much, if not more, love and passion than everyone else. Controllers are a close-knit community because the nature of the work is such that we are all connected in a single global system. Not only as a profession but also operationally. With a bit of luck, we could get a colleague from Japan on the line through our cascaded telephone systems. Only each next neighbor would have to connect me to their next neighbor. How cool is that?!


How many planes do you monitor per day? 

It depends on the season. In the low season, around 600 per day, and in the high, regularly over 1,300-1,400 per day. For example, this July we had 43,043 flights, which means an average of around 1,300 per day. The daily numbers of course fluctuate, the current record if I remember correctly is 1569 flights per day. I don’t have exact data for the other units, but their traffic is different from ours in the area.


What do emergencies usually look like? 

Huh… they are different. Most of the time, it is a medical emergency, that is, the health condition of the passenger on the plane deteriorates so much that the crew decides to land at the nearest suitable airport. The next most common is completely banal – the plane does not check out from the previous control and does not check in to the next one. In such cases, when after several unsuccessful attempts to call the plane into contact, the process is taken over by the military, sometimes they also send interceptors (if they are nearby) to check what is happening with the plane. Then there are in-flight system failures and things like that when they require a little more attention and coordination work.


Why do people most often choose to work as a controller, what drives you?

I don’t know, I’m from an aviation family, and also a pilot. In the mid-1990s, there were not many opportunities for an aviation career. So I grabbed the opportunity I got with both hands. It was similar for many of my colleagues from the beginning of my career. Later, the profile of controllers changed considerably, the youngest generations hardly have any special affinity for aviation. So the motives for this profession are different.


Who has the higher rank, you or the army?

Everyone performs their work within the framework of legal and other requirements. In aviation, no one is above the other. We all work together.


Air traffic control attitude towards “Sunday pilots” and sailplane pilots? 

There are only different airspace users for air traffic control. We help those who have problems with this due to ignorance, just as we help everyone else in various ways. In short, we do not distinguish between Sunday and daily pilots. For everyone, we assume that they have completed all the necessary training, that they are driven by positive motivation when flying, and that no one causes problems on purpose.

Attitude toward glider pilots is the same as the one toward “Sunday” pilots. With that, I admit that we, who have roots in aviation and/or are still active pilots, offer glider pilots more than we should, especially when the weather conditions for sailing at high altitudes are more than favorable. We try to accommodate everyone as much as possible, that is, as far as the weather and traffic situation allows.


The difference between a pilot and a non-pilot controller?

The first will do everything possible to accommodate the pilots and provide a nice and safe experience, while the second will do it only if he or she feels like it.


What is the hardest part of this job?

When you hear that there has been a disaster, the loss of human life. I was in a similar situation where it was already looking like a small turboprop plane was going to hit the mountains in a minute or two at most, the pilots were not responding to my calls, and their radar response on the screen was in a downward spiral approaching altitudes where the possibilities, that they hit the mountain was getting bigger every second, and when they finally came online, I learned on top of everything that they were in the cloud, below all the minimum altitudes in that part. 

As I successfully brought them to a safe height, out of harm’s way, it struck me like lightning out of the blue…all tension was instantly released after a minute or two of helplessly watching their descent into increasingly certain disaster. 

This feeling of helplessness, after you have done everything necessary and invented all other possible solutions and passed them on – then it is no longer up to you how it will unfold… and you see, this is the hardest part of the job. 

Doctors and other medical personnel probably feel the same way, when they do everything they know and it doesn’t end well…


What advice would you give to someone considering this career?

If you are interested in something, then jump. There is always water in the pool, no one will be hurt. If you are not for the profession, it will quickly become clear during the selection process, if not during the training. But if the only motive is to make money, then don´t do it!

foto: source
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