The German Remote Tower Control Concept

Photo by DFS

zby Philippe Domogala, SENIOR CORRESPONDENT, IFATCA

Since December 2018, the aerodrome control of Saarbrucken airport (EDDR) has been done remotely nearly 500 km away from Leipzig (EDDP). Does it work well? I flew VFR into Leipzig/Halle Airport last August to see for myself.

First, let me give some context for this remote tower. Saarbrucken is a small regional airport that before COVID-19 had 15,000 movements per year or around 40 per day. The old control tower needed replacement, which would have meant a major investment. Instead, DFS, the German air navigation service provider, decided to introduce a remote tower control concept. In a bidding process, Frequentis offered a suitable remote tower control (RTC) technology solution, and the European Commission agreed to co-finance the project. The development started in 2010. It took a few years to find a suitable technology and validate it.

I met RTC supervisor Andreas Willmann at the tower in Leipzig. He has been involved since the initial development and described the challenges and his experiences with the remote tower control.

Willmann first talked about challenges related to selecting the screens. “We immediately disregarded the 360-degree vision,” he said. “While the cameras were able to depict such a view, why should the controller move around the room? Then, we tried two huge 65-inch screens, but the separation of the two screens, the bar right in the middle of the field of vision, was extremely disturbing. It became obvious that we needed an odd number of screens. The next set up was three big screens, but the view didn’t seem real. It was like sitting on the front row of the cinema. We finally decided on five smaller screens, and that was universally accepted.” He continued, “The top screens give a large 215-degree panorama vision. The view can be turned into any direction and even moved to a complete 360-degree view using a mouse device. The lower screens are used for the directional cameras called pan-tilt-zoom cameras (PTZ), which act as electronic binoculars with zoom possibilities from 2x to 24x. We also have two fixed cameras to monitor the apron.”

Willmann next described challenges related to the interface. “The next. We first would all have preferred only one mouse and one keyboard, but it soon became impracticable as there were too many functions, so that we now have three mouse devices and two keyboards per position.”

He then described the challenges related to selecting the options of the display. “The system can show a lot of information on the screens – such as wind information or labels about the aircraft,” he said. “But if it is all displayed, you would lose the picture. So it was decided for a more basic set up because too much information is confusing.”

In talking further with Willmann, he made an interesting point: “You cannot replace the human eye with a camera. And a remote tower is not ATC with a camera. It is a different concept.

He then discussed plans to implement it at additional airports. “We started with Saarbrucken, because it was a relatively small airport where the old tower needed to be replaced,” he said. “We are located here at Leipzig Airport because there was a large room available at the base of the control tower. The next airport to be added to the RTC Centre will be Erfurt (EDDE). We planned to do it this year, but it is now planned for 2021. After Erfurt, we plan to add Dresden airport (EDDC). Saarbrucken and Erfurt are roughly the same size; however, Dresden is much larger (roughly 100 movements per day) and will need a different configuration of the system.”

Dresden will be the final airport to be added as part of this initial project. When completed, the RTC Centre will contain three sectors – one for each airport. Each will be staffed by a single controller. In the room, there will be a fourth position – the clearance delivery – staffed by a single controller, who will do this task for the three sectors.

Ground movement control is done by DFS at the airports on tower frequency in coordination with Apron Control. In Saarbrucken, Apron Control does not use a dedicated frequency. When the aircraft has landed, it remains on the TWR frequency. When the aircraft is on the apron area, it is taken over by a marshaller.

Staff wise, the concept offers savings. Each of the three local airport towers is manned by two controllers, one active and one clearance delivery/ground control. This means that six controllers are needed for the three airports. With RTC, you will still have three controllers but a single clearance delivery, which means

that four people are on duty at the same time instead of six. In addition, the concept allows for more flexibility in staff planning. It is planned to have the controllers crosstrained for the three airports, However, with this project, the concept is clear: It is one controller per airport, not one controller controlling multiple airports at the same time, as some other ANSPs are considering.

Supervisor Andreas said, “It is the same operations, same rules, same communications and same procedures. Nothing changes, we also do visual separation as before. The R/T call sign is still ‘Saarbrucken Tower’ and it is transparent to the pilot. We do not tell every aircraft coming in where we are located.”

Willmann highlighted some advantages of the RTC system: “There is a nice feature,” he said. “ If you lock the electronic binoculars (PTZ) on a target, it follows it automatically. Even if, for instance, an obstacle, like a lamp post appears between a PTZ camera and the aircraft that it is following. The system compensates for the temporary loss of the visual contact and continues tracking the object.”

He continued, “We also have an infrared (IR) camera, which is very good at night. Unfortunately, it is not working well when there is fog or clouds. The high humidity of the air disturbs it. But at night it is perfect, you can see an aircraft like in daylight. Without it, you can only see the navigation lights.”

Another advantage of the system is that it detects targets on its own. Willmann continued, “Any certain number of pixels that start to move will create a red box on the screen and direct your attention to it. You may switch off that function, if there is something unimportant, like a flock of birds, which would create a huge number of boxes on the screen. It is an excellent feature to detect vehicles moving without clearance or a drone entering the aerodrome vicinity, for instance.”

The system also has shortcut buttons like predefined hot spots. Willmann said, “The camera then moves rapidly to these hot spots. You can temporarily define two of them yourself, for example, during work in progress, grass mowing, tug movements, etc.”

He then stated, “There is also an Aldis lamp feature mounted on the cameras and some pre-set buttons like ‘clear to land.’”

The camera will paint the aircraft and issue powerful green flashes to the aircraft on final. That is a nice feature that, as a pilot, I intend to verify myself when flying there next time!

Photo by DP

Photo by DP

Photo by DFS

z Photos: (top) Saarbrucken remote TWR (center) ALDIS Red light and (bottom) One of the zoom PTZ remote cameras

The out-of-the-window-view is made of 12 HD cameras stitched together for a 360-degree panorama vision. It has overlay possibilities to show areas, taxiways, etc. “It has another very interesting feature which allows visual tracking based on radar tracks. It is basically a touch screen where you can follow aircraft tracks on radar. You just touch the track, and a camera will automatically lock on it, and you can track it visually. It is very useful to track an aircraft on the circuit pattern, for instance.”

About the training, Willmann stated, “Out of the 12 TWR controllers of the old tower of Saarbrucken, 10 accepted to move to Leipzig. (One retired, and one went to the Academy.) We did shadow training that lasted 4-8 months with staff at an RTC-working position in Saarbrücken, and the remaining training was completed in the old tower. We also used our simulator, where we are able to simulate very high levels of traffic, far beyond what it actually will be, to determine the personal limitations for each controller. We also recruited two new trainees. We currently have 10 controllers, working shifts from 06:00 to 22:00 local.

For Willmann the answer is yes. He stated, “It is a paradigm shift, a new concept, a completely new technology, and it has got its bugs.”

He says that it isn’t a question of whether it is better than a real-life control tower. Rather, does it perform the job safely? For him, again the answer is yes.

When asked if he thinks this technology is the future. He stated, “Oh, yes! You bet it is. Iit is only a question of time.” One has to note that in this concept, DFS chose to keep the principle of one controller, one airport, and not a single controller controlling multiple airports.

Regarding regulatory oversight, Willmann stated, “On the regulatory side, our remote tower concept has been approved by our regulator. It is just a new endorsement on your existing licence saying ‘remote.’”

It looks like the business case here is made by combining the clearance delivery positions, having a standard equipment and procedures for all towers, and allowing staff to swap around towers easily. Not having to rent space, build, and maintain various buildings and facilities in airports is also a contributing factor.