The provision Air Traffic Services (ATS) is a safety-critical business, whose basic capabilities and models are currently dramatically evolving thanks to digital technologies. In particular control towers are rapidly evolving into digital towers, augmenting air traffic control capabilities at an aerodrome through fully digital means, making airports around the world safer, more flexible and efficient.
The most organic way for a conventional tower to evolve into a digital tower is by investing into specific digital features aimed at enhancing situational awareness for air traffic controllers, such as cameras to cover blind spots of an apron, or night view of the traffic through infrared. When these features are implemented into the current control tower, we talk about a “digital tower” or an “enhanced conventional tower”.
Technology however allows to recreate the full out-of-the-window (OTW) view through 360 degrees screens mounted in a control room, whose physical location become then independent from the location of the airport. This enables the possibility to have remote positions (RP) staffed by air traffic controllers in a control room which can be located anywhere, at a dedicated facility at the airport itself or at a remote tower centre (RTC) hundreds of kilometres away, which can host dozens of different RPs to provide services at different airports. This is what we call the “remote tower”, a specific category within the digital towers family.
Depending on the traffic demand at the airport, the same RP can be devoted to control just one airport (single mode) or allow more airports to be controlled simultaneously by one controller, thanks to advanced automation. This is known as the “multiple mode”, which is currently not yet operationally but undergoing validations in SESAR.
The remote tower can serve as primary facility for ATS provision or as a contingency solution. A full set of different solutions is available to air traffic control, depending on the specific needs, existing infrastructure and operational requirements.
Figure 1. Different solutions for digital remote towers
How does a remote tower work?
Remote Towers are based on two main components: the sensors at the airport and the controller working positions located at the remote control centre, which can be located right on site or at thousands of kilometres away, relying on a secure data communication network connecting them.
Since air traffic control remains a human-centred business, the challenge is to recreate a natural, real-time 360-degree panoramic view of the aerodrome at the remote facilities for air traffic controllers to provide services. This requires recreating the out-of-the-window (OTW) view by cameras, monitors and dedicated software. To achieve near real time presentation, the image of the remote aerodrome has to be captured by cameras and displayed on the monitors of ATCOs with a latency under 1 second in the worst case.
Figure 2. High level architecture for remote towers
The video feed is retrieved from a set of cameras installed in a convenient point at the aerodrome, usually on a top of a mast. Other data such as airfield lighting, or periodic meteorological reports, are transferred by the respective aerodrome systems or by dedicated sensors. The RTC itself has a typical control room setting, hosting the necessary hardware for humans to staff remote position in a quiet environment. Each module has a set of screens (usually following a curved layout) in front of one or more controllers’ working positions, presenting not the live video-feed from the cameras on-site, but also complementary information such as aircraft identifiers, systems status alerts, runway and taxiway borders or zoom-ins from the cameras, among others.
Figure 3. Remote positions in a remote tower centre (source Indra Company)
What opportunities and challenges appear?
Digital and remote towers bring about opportunities regarding safety, cost optimisation, service provision and scalability.
The main advantage is the increased safety based on advanced capabilities to detect risky situations, thanks to advanced visualisation capabilities: infrared cameras improving low-visibility operations; artificial intelligence algorithms detecting objects in order to prevent runway incursions or wildlife collisions; or all controllers having an identical view of the entire airport. This also allows for a higher technological scalability, since digital tower capabilities can be expanded based on the latest technology advancements.
From the cost perspective, remote towers represent a more compelling business case than their conventional counterparts. On one hand, an RTC is in general cheaper to build, even taking into account the additional infrastructure required for the aerodrome-RTC connection. On the other, economies of scale appear in multi-airport RTCs: airports that previously could not bear the full cost of ATS provision can now afford it, since all needed resources (physical, digital, human) are shared among the different airports, thus maximising their use and enabling roster optimisation.
Regarding service provision, delinking the control centre location from that of the aerodrome allows for more convenient sites to be chosen, both concerning the accessibility and the land cost. This allows an easier attraction and retention of specialised workforce at a generally lower cost while allowing more flexibility in the co-location of the RTC with existing air traffic control facilities.
In terms of scalability, remote towers allow for ATS provision to grow in capacity based on traffic demand, given that additional RPs can be installed when required. This stands in contrast to conventional control towers, which are naturally bounded by their physical dimensions, thus being inevitably oversized during the first years of operations, and having limited growth possibilities afterwards.
Obviously many challenges arise during the implementation of remote towers related to human factors, infrastructure and certification.
Not only the initial implementation of remote tower operations demands for careful planning, but also the transition requires long validation and training to ensure a smooth change of operations.
New system requirements appear, related to the network and infrastructure used in the connection between the airports to be controlled and the RTC: there must be sufficient redundancy, very high availability, very high quality of service (high throughput, low latency and low bit error rate), relying on cutting-edge technology with the highest cybersecurity standards.
From a certification perspective, safety concerns make the associated procedures longer, given that these work as a combination of two processes: the standard certification that a conventional control tower has to go through; and the certification of the new procedures supporting remote tower operations.
Where have remote towers been implemented?
Nine countries have fully-operational and certified digital remote towers: Sweden (pioneer in 2015), Brazil, Germany, Norway, United Kingdom, France, Malta, Hungary and Canada.
The Netherlands will have an operational RTC in the coming months, while Estonia, Singapore and the United States are on their path to implementing an RTC in the near future. Australia, Ireland and Italy have also conducted tests on RTCs, but have not announced any plan to operationalise them yet.
The first major international airport in the world to be fully controlled by a remote digital air traffic control tower is London City, which is serviced 115km away at NATS’ air traffic control centre in Swanwick, Hampshire (UK).
Figure 4. Existing digital remote towers around the world (As of Abril 2021)
Where should remote towers be considered?
There is no one-size fits all model for digital and remote towers. Based on ALG recent experience, we recommend looking into a digital remote tower business case in one of these six circumstances:
- Whenever a conventional tower needs to be renewed or refurbished, given obsolescence or operational limitations, entailing a large investment
- Whenever airports that have low traffic volumes, or exhibit traffic volatility or heightened seasonality
- Whenever airports located are in remote regions, limiting access to qualified personnel or even hindering the service continuity of conventional towers
- In multi-airport contexts when direct coordination among nearby airports is desirable
- Whenever it is desirable to bring geographically scattered assets closer to the ANSP-HQ and facilitate its internal coordination
- Whenever adverse climatic or environmental conditions have an impact on operations, that can be curbed with the additional visualisation capabilities that remote towers do not have
To learn more about how remote towers can improve the safety and efficiency of ATS provision at your airport, please contact the authors of this article.
About the authors
Andrea Ranieri is Ph.D. in Operations Research and Principal at ALG. firstname.lastname@example.org
Mario Cano is MSc. in Aeronautical Engineering and Team Leader at ALG. email@example.com
Davide Marchesan is Aeronautical Engineering and Senior Consultant at ALG. firstname.lastname@example.org
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