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European defragmentation through a single, harmonised and interoperable surveillance framework

European multicultural and international context is its own signature. Europe benefits from a high-diversified pool of countries with different cultures, necessities and strengths, which overall constitutes a solid environment for development and research. These factors lead Europe to a unique position from an Air Traffic Management/Communication, Navigation and Surveillance (ATM/CNS), with a highly developed and busy air transport sector but also a fragmented system.

How the European airspace has evolved

The pan-European sociopolitical context when ATM/CNS systems were firstly deployed and the strategic capacity of controlling its own country’s airspace have driven to the development of a European sky based on fragmentation and, inevitably, duplication. The consequence of this fragmentation is no other than a multiple array of inefficiencies that translates to longer flights, larger security distances, higher emissions and ultimately higher costs.

The high complexity of the European airspace structure, controlled by almost 40 ANSPs (Air Navigation Service Providers) in the ECAC area, together with the severe growth in air travel witnessed in the las two decades are one of the main challenges in globalization.

Flight Information Regions in the lower airspace of EUROCONTROL Member States (February 2017)
Flight Information Regions in the lower airspace of EUROCONTROL Member States (February 2017)

This issue is not new; several studies have well identified the necessity to optimize European airspace. An IATA’s recent study (2016) estimates that flight trajectories in Europe are, on average, 50 kilometres longer than necessary and delays amount about 10 minutes per flight. Currently, these inefficiencies are costing Europe approximately €5 billion annually according to worldfootprints, but the scenario is going to worsen. IATA estimates a total annual cost of €245 billion by 2035 and a potential loss of one million jobs provided that no measures are taken.

How Europe is tackling this issue

Several global initiatives have been launched in the last years to overcome the defragmentation and globalise the European airspace. The EU Single European Sky (SES) initiative, launched in 1999, represents a legislative approach aimed to meet future capacity and safety needs at a global European level. Its main objectives are to restructure the European airspace as a function of air traffic flows, create additional capacity and increase the overall efficiency.

It is also important to highlight the benefits of improving European airspace. An efficient segmentation of the same could lead to savings of up to €43 per passenger. Furthermore, not only would it come with economic benefits, but also with a significant relieve on the environmental impact, as air traffic emissions could be reduced up to 10%.

However, modernization of European airspace shall be supported by a well-dimensioned ground infrastructure and complementary regulation. So is it that an outdated or inefficient regulation could diminish the whole effort towards reducing ATM costs, or even making unfeasible all the improvement programmes. This opens a two-fold discussion on infrastructure and regulation. For the scope of this article, we will tackle only surveillance infrastructure and regulation.

The pursuit of a harmonised surveillance infrastructure

Surveillance is a key pillar of this system, providing visibility for a safe and efficient use of Europe’s congested airspace. The fragmented growth of the European sky lead inevitably to a complex and national-level surveillance infrastructure deployment. Several surveillance initiatives are being held by international organizations to provide an interoperable and efficient surveillance infrastructure, which could lead to a significant rationalization in cost and spectrum while still delivering the required performance.

Within this context, EASA (the European Aviation Safety Agency) has been conducting a high-level and strategic study to assess the optimum surveillance infrastructure deployment in the ECAC area, on which we have actively participated. The outcome of this study consisted of a scenario where current surveillance deployment is disregarded, and a fully new configuration is proposed based on literature research on previous SESAR studies. This new configuration is driven only by efficiency and high-level safety and performance coverage.

With this scenario, it is obtained a full coverage and redundancy compliance of the ECAC area, by employing two layers of secondary surveillance. The first one consists of a dependent layer of surveillance systems (ADS-B stations), whilst the latter offers an independent surveillance combination of SSR Mode S and WAM.

European map of coverage of the new proposed surveillance infrastructure deployment. Secondary dependent ADS-B layer (red, left) and independent layer (right, orange for SSR Mode S and green for WAM systems)
European map of coverage of the new proposed surveillance infrastructure deployment. Secondary dependent ADS-B layer (red, left) and independent layer (right, orange for SSR Mode S and green for WAM systems)

The figures above gives an idea of how a more efficient infrastructure deployment would look like.  The results showed that a minimum of 150 surveillance systems would be required. Of course, this is a pre-feasibility analysis and, at this step, it is still at high strategic level. Therefore, it shall not be taken as an exact roadmap for deployment but rather as an acceptable estimate.

There are more factors that should also be added to the equation such as ATM policies, national security, or other operational issues. Nonetheless, this proposal may set the ground for defining the roadmap for surveillance systems optimisation: decommissioning those that are not required, deploying only the ones that are really needed and integrating the rest into a collaborative scheme.

What about regulation?

On the other hand, according to Croatian Airlines’ CEO, current regulation in EU is limiting the capacity of airspace optimization. Regulation shall be effective and straight forward, but more important, shall be aligned with the changes in the airspace.

Additionally, it should also be supported by an impact assessment and stakeholders consultation. Otherwise, for instance, a new surveillance fee for deploying new infrastructure could dismiss small players. Furthermore, regulation shall also be simple and easy in order to avoid inefficiencies emerging from amendments of ill-conceived laws.

Thus, regulation shall be assessed prior entering into force. Strong stakeholder’s consultation and exhaustive cost-benefit analysis are recommended to ensure that new regulations are not counter-productive. In this regard, EASA is executing an excellent job. Currently, EASA is updating its economic scale for its regulatory impact assessments (RIA) which is now on the stakeholder validation and consultation phase.

The objective of this update is to identify the impact on the industry of the measures taken and determine the feasibility of the same. The new scale will consider each of the players within the air transportation industry, and their capacity to make front regulatory fees or investments.

To put everything in a nutshell

Briefly, if we want a unified airspace in Europe, infrastructure shall be sized according to the user needs. Collaboration and synergies are a must for the optimization of the airspace and reducing cost and the environmental footprint. Additionally, the regulation shall be updated accordingly and consider its impact on all the stakeholders.

The EU is convinced of the necessity to improve European airspace and it is self-conscious of the gaps to solve and just the time will tell how the European SES will be. The modernization and defragmentation of the European airspace is long-term and delicate process that has to be implemented in close collaboration with the entire chain of aviation stakeholders.


This analysis has been possible thanks to an in-house developed tool that has permitted us to model the suitable locations of the surveillance stations, ensuring coverage and redundancy requirements.

The surveillance deployment assessment tool is an interactive and user-friendly software that provides support to the assessment of ground surveillance equipment. It allows the user to construct user-defined surveillance deployment scenarios through interactive maps, providing visual representation of the surveillance equipment location and aggregated coverage, as well as presenting redundancy and coverage analysis regarding surveillance stations.

Screenshots from the surveillance deployment assessment tool regarding location of equipment, redundancy indicators and interaction with terrain elevation
Screenshots from the surveillance deployment assessment tool regarding location of equipment, redundancy indicators and interaction with terrain elevation

Secondary surveillance is cooperative by definition, since it relies on the collaboration of the aircraft through its on-board transponder. The different secondary surveillance technologies employed in our analysis are:

  • Secondary Surveillance Radar (SSR), an independent surveillance system that actively interrogates the aircraft’s on-board transponder, which replies to each interrogation signal by transmitting a response containing encoded data from which the position is determined.
  • WAM (Wide Area Multilateration), also an independent surveillance system which employs an array of ground stations that determine the position of the aircraft by triangulating the response signals from the transponder.
  • ADS-B (Automatic Dependent Surveillance – Broadcast), which is dependent by definition since it passively receives the position from the aircraft, who derives its position from global navigation satellite systems (GNSS) data and broadcasts it through datalink without the need of interrogation.

About the authors
This article was motivated and based on the participation of ALG, in consortium with APAC and SENASA, in EASA’s Regulatory Impact Assessment (RIA) to support the RMT.0679 – Revision of Surveillance Performance and Interoperability.
Within the scope of this project, the consortium:
  • Performed the surveillance assessment and the optimum and current ground surveillance deployment.
  • Proposed standard economic values to measure the impact of new surveillance infrastructure deployment in areas previously not provided with such coverage.
  • Proposed the new economic scale for EASA, based on stakeholders consultation and financial results.
Rubén Martínez is MSc in Aeronautical Engineering, PMP and Director at ALG
Vladimir Coca is MSc in Aeronautical Engineering, Project Manager at ALG
Laia Garrigó is MSc in Aeronautical Engineering, Consultant at ALG
Mario Cano is MSc in Aeronautical Engineering, Consultant at ALG
For more insights, please check www.alg-global.com or contact:
rmartinez@alg-global.com
vcoca@alg-global.com
lgarrigo@alg-gobal.com
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