Monthly nr 0

December 2004

Skycontrol Home

Service Providers

Content of December issue

Safety first !


Recently, the air traffic controllers of Liege have a new instrument at their disposal:

the approach radar of Liege.

In the past, they used the information provided by the « en-route » radars of St.-Hubert and Bertem, which was transferred by the CANAC centre (Computer Assisted National Air Traffic Control Centre)

of Belgocontrol. Nevertheless, its coverage was not sufficiently low and the renewal frequency

of the radar image was not sufficient to render an optimal approach service.

Because of the high density of the air traffic, it is important for the air traffic controllers to receive

on their radar screens a clear image of aircraft in the approach zone around the airport and down

to almost on the landing strip. The new radar allows a higher image frequency, so that the situation

of the traffic displayed on screen will be more truthful. Contrary to the "en-route"-radar

of Bertem or Saint-Hubert, of which the antennae executes five rotations per minute, the rotational

speed of the antennae of the new approach radar of Liege is three times higher:

it performs fifteen rotations per minute. In this way, the new position of the aircraft

is displayed every four seconds on the air traffic controller’s screen.

    The antennae of the primary and secondary

    radar at Voroux-Goreu

Because of obvious safety precautions, the system is entirely doubled. There are three operational positions, two of which are installed in the visual control room of the control tower. Moreover, there is a double recording and play back system. The radar data are displayed on colour screens, which are much more « readable » than the old monochrome screens. The air traffic controller can choose from 75 background charts. The positions of the aircraft are represented by different symbols that indicate whether the aircraft is being controlled by the Liege approach or by adjacent sectors.

Multiple high-tech functionalities were built into the new radar system, which contribute to the improvement of safety, the priority of Belgocontrol: the STCA, the MSAW and the DAIW:

  • The STCA (Short Time/Term Conflict Alert) sends a warning signal to the air traffic controller when the separation distances between aircraft threatens to drop under the previously determined safety margins. In the case of horizontal separations, these margins should minimally be 5 nm (about 8 km) for cruising flights, and minimum 3 nm (about 5.5 km) in the approach phase; and 1,000 ft (about 300 m) for vertical separation.
  • The MSAW (Minimum Safe Altitude Warning) warns the air traffic controller when an aircraft threatens to descend under a minimum level.
  • The DAIW (Danger Area Infringement Warning) gives a warning signal when an aircraft threatens to enter a « forbidden » zone.


The introduction of such a powerful and high-tech instrument requires, besides detailed and intensive tests, a thorough training of the technical and operational personnel. 13 air traffic controllers received a training that lasted two times five days, and the whole team receive an 18-day training on the spot.

Belgocontrol’s technical staff took a theoretical course in two sessions of two weeks, followed by a practical training of 26 days.

The period of operational validation started in February 2004 and the operational use by day on June 7th 2004. By the end of the year, the new radar will also be operational at night.


The control tower of the airport of Liège


E-mail : [email protected]

Website :

Text and illustrations : Copyright©2004. Belgocontrol. All rights reserved.

Back to top



Liège gets a new approach radar


The project for the installation of approach radar in Liege was started

at the explicit request of the Walloon Region in order to cope with

the air traffic growth in Liège. The approach zone of Liège was covered

by the « en-route » radars of Belgocontrol located in Saint-Hubert and Bertem.

After a technical study and a strict selection, Belgocontrol has ordered

the whole system from Thales on March 2nd 2000 (including the installations

that process radar signals and display them on the screen).The total amount

of the investment is about 8 million euro.

Screen of the approach radar of Liège.


Sowaer, which is responsible for the public infrastructure and equipment investments necessary to the activity of Liege Airport, has put a lot of effort into this project. This project enables to make a progress in traffic management and as what regards safety and environment. Sowaer has invested some 10.6 million euro by mostly financing the radar and the corresponding infrastructure: optical fibres, foundation, building, and access road…

Finally for SAB, the new radar represents an additional element to global equipment that has to come up to the expectations of the airlines and other operators.

The radar is situated in Voroux-Goreux, two kilometres north-west of the airport. The civil engineering works (the building and the road) were executed by the Walloon Region between March and December 2001, according to Belgocontrol specifications. From the initial request until the operational commissioning, there was an absolute perfect co-operation between Belgocontrol and the Walloon Region.

In the control tower of Liège, the screen of the approach radar

is positioned ideally right in front of the air traffic controller

The installation of the equipment was carried out in two phases. The first phase consisted of the setting up of the radar and antennae (first half of 2002). The second one comprises:

  • The installation of the computer systems and the screens in the tower (from March until October 2002)
  • The technical and operational tests (from November 2002 until September 2003)
  • The period of operational validation (from February 2004 on).

The priority given to safety explains the phased implementation of this radar. It was necessary to test the reliability of the equipment and systems and to accustom air traffic controllers to handling with confidence their new tool after an appropriate training. The setting up of new radar requires detailed and intensive tests as well as a thorough training of the technical and operational staff.

The radar system

The radar system is composed of 2 main elements:

  • the radar components comprising a primary radar (emitting electromagnetic impulses that are reflected by the metal of the aircraft and receiving echoes in return) that enables to determine the aircraft position, and secondary radar that also determines the aircraft position but also its identity                          (via a « transponder » code) and its altitude.
  • the central system for visualisation and radar data processing transmitted by the site, which is situated in the building of the control tower.

Advantages of the new radar

Thanks to its rotation frequency and its nearness, the new radar improves accuracy and thus also aircraft guidance controls

  • it enables to give up approach by day or “double loop”: aircraft had to make a loop around the north zone of the airport in order to line up                          for the landing procedure.
  • it also enables to suppress a horizontal level off between 2500 and 3000 feet with power increase in order to perform the approach loop.

So, it improves:

  • the safety, with a better traffic flow and accuracy
  • the environment: the overflight of the zone is reduced and the approach is “smoother” without power increase. So, there is less noise on the ground and less greenhouse gas emissions
  • the costs: saving for the companies
  • the accuracy of information to the people living in the neighbourhood of the airports.


E-mail : [email protected]

Website :

Text and illustrations : Copyright©2004. Belgocontrol. All rights reserved.

Back to top


EUROCONTROL celebrates 40th anniversary

of official decision to set up the first multinational

air traffic control centre at Maastricht


Maastricht, the Netherlands – On the occasion of the 40th anniversary of the decision to build the first European air traffic control centre at Maastricht, Wolf Liedhegener (D), President of the Maastricht Coordination Group, declared yesterday: “The decision on 19 October 1964 made by the Permanent Commission of EUROCONTROL to build the Maastricht Upper Area Control (UAC) Centre was one of the most significant milestones in the European airspace consolidation process. Since 1972, when the UAC first became operational, the four participating States have, through their tangible political commitment, been able to see all the benefits of this regional air traffic management integration project.”

On 28 February 1964 the Permanent Commission decided to set up the first EUROCONTROL international air traffic control centre on the territory of the Netherlands. From 3 March of the same year, the upper airspace over the Brussels Upper Information Region (comprising Belgium and Luxembourg) was placed under the responsibility of EUROCONTROL. It was on 19 October 1964 that the Permanent Commission decided to locate the UAC at Beek, near Maastricht. Roughly two years later, on 4 October 1966, the first foundation stone of the UAC building was laid and it became fully operational on 29 February 1972.

“This was an important development in Europe at the time, and we are quite proud that the four States gave EUROCONTROL the mandate to fulfil this important mission. Recently, the ATM Cost-Effectiveness (ACE) 2002 Benchmarking Report commissioned by the Performance Review Commission confirmed that the Maastricht UAC is tangible demonstration of a cost-efficient border-crossing ATM system in the core area of Europe. On behalf of the Organisation and the Maastricht staff in particular, I want to thank the four States for their long-lasting confidence and support,” said Víctor M. Aguado, Director General of EUROCONTROL.

The Maastricht UAC provides air traffic services in the upper airspace (as of 24 500 feet, roughly 7.5 km) of the Benelux and north-western Germany. Its international area of responsibility represents an efficient solution to simplifying airspace management in one of the most complex and congested air traffic areas of the continent.

The Maastricht Coordination Group is the executive body responsible for determining a common position for Belgium, Luxembourg, the Netherlands and Germany with regard to the operation of air traffic services by the Maastricht UAC. The competencies of the Maastricht Coordination Group include a wide range of management issues such as airspace organisation, operational/technical concept, daily operations, staff management, budgetary and financial issues or contingency planning.

The members of the Maastricht Coordination Group

meeting at Maastricht UAC on 19 October 2004


For further information, please contact:
Kyla Evans or Mireille Roman
Tel.: +32 2 729 50 95 / +31 43 366 1352
E-mail: [email protected]
Web site: [email protected]

Back to top