The idea of a continually up-to-date Pan-European air situation assessment is becoming real. To support European air traffic flow management EUROCONTROL has embarked on an Enhanced Tactical Flow Management System.

For close to ten years, a plan has been considered to combine the various sources of positional and flight plan data into one single air situation database of Europe. Requirements have come in particular from air traffic flow management (ATFM), which has been continually striving to improve the use of airspace capacity. Since 1988 the Central Flow Management Unit (CFMU) in Brussels has been assigned the task of balancing demand and capacity within air traffic management. This is particularly involved keeping delays to a minimum and avoiding congestion, bottlenecks and overload in the European Civil Aviation
Conference (ECAC) member states. It has been doing this with great success.

Up to now, however, the data on which the CFMU planning was based has been intrinsically incomplete. Based primarily on input from the EUROCONTROL Initial Flight Plan Processing System (IFPS), real positional data was missing - i.e. the assumed current air situation was only an estimate rather than a known quantity. This will change with the deployment of the Enhanced Tactical Flow Management System (ETFMS); its Data Collection System (DCS), was contracted to German COMSOFT in July 2000.

ETFMS will provide an overall representation of traffic over Europe and adjacent airspace based on current traffic data. This will largely improve accuracy of traffic prediction and facilitate additional functions such as statistical analysis and "what-if" extrapolation.ETFMS is a distributed system with close to thirty locations involved. At the current stage 23 ATC centres across Europe will feed their data into the system. ETFMS will process the data centrally and at a later stage will also distribute it to ATC service providers.

Objectives

The major objective of ETFMS is to increase the accuracy of the CFMU flight database which serves as a critical prerequisite for any decision-making by the Flow Management Operators. This applies to all flights in the CFMU-monitored airspace, and also to incoming out-of-area traffic exempt from ATFM. Flight plan data was often inaccurate particularly for the latter type of traffic, due to unknown flight delays and data arriving too late to be taken into account for any flow management actions. With ETFMS, positional information from the surveillance subsystems will always be available and provide realtime knowledge of the air situation.Increasing accuracy contributes both to safety and efficiency. In particular it avoids bunching effects or lulls in traffic, which occur when flow management decisions are based on incorrect or incomplete base data. Also the resilience of the ATFM system and procedures during unexpected or emergency situations is greatly improved. Rather than making a decision in such a case based on possibly incomplete input data, operators can work from a realtime picture on which they can rely.

Entry Nodes

Processing involves the conversion, correlation and filtering of a multitude of input data from various sources. This is done by so-called Entry Nodes (EN) located at the origin sites of the data - typically in the national ATC centres. The EN is a redundant communication front-end that has interfaces to the local surveillance and flight plan subsystems. It receives track and AFTN messages that it combines, correlates and converts to ASTERIX CAT 062, ETFMS's unique internal format.

As part of the process, the ENs implement a track/flight plan correlation algorithm and convert the positional data into a single coordinate system. They also filter data according to various user-defined criteria, for example disregarding sensitive flights and reports that cannot be used for ATFM planning. National radar data processing (RDP) systems as well as multinational track servers, such as ARTAS and MADAP servers will input their positional data to ETFMS ENs. On the flight plan processing side, interfaces to national flight data processing systems (FDPS) or message switches exist. Among others ADEXP messages like the first system activation (FSA) message, are processed.

Access Nodes

All EN nodes forward the preprocessed stream of target reports to a central Access Node (AN) located in the CFMU. The AN is supplied, like the EN, in a redundant hot standby configuration and has the task of interfacing to the ETFMS servers in the CFMU at Haren/Brussels.

The communication between EN and AN is via a multinational IP network. It uses on application level the ASTERIX Category 062, which is capable of expressing both the positional and flight plan elements required for ET-FMS. The format carries position, speed, heading, callsign, departure airport, destination airport, time of departure, and other information.

The AN is duplicated at a second site in Bretigny, France, to act as contingency in case of catastrophic failure. The AN nodes connect via LANs to the ETFMS servers and use TCP/IP over Ethernet for lower layer communication. At the application layer, ASTERIX is again used.

Eventually the AN node could also be responsible for distributing the cosolidated flight information held in the ETFMS central server's database. This will likely be done by Broadcast over a satellite (VSAT) network.

ETFMS Application

The ETFMS servers implement the flow management application. In fact, these are the second generation of the TACT system. The ETFMS server offers a user interface that enables the flow management position operator at the CFMU to retrieve, analyse, transform and present the collected data in order to make any kind of tactical decisions. For example, based on a predicted sector overloading the operator can propose alternative routes for individual flights or entire traffic flows.

With its always up-to data surveillance data basis ETFMS will be supporting enhanced tools and applications for air traffic flow management increasing the overall real-time knowledge of the current traffic situation:

• Enhanced load calculation, extrapolating loadings in the near future of sectors, routes and airports;
• Statistical presentation of data, e.g. histograms and graphical displays to support the operator;
• Alert and alarm triggers enabling a level of control and monitoring for ATFM data;
• Traffic comparisons for arrivals at and departures from an airport.
• What-If analysis support, starting with the current situtation and extrapolating data to show the results after modifications of the environment such as re-routings and closure or opening of sectors.
• All applications will run on a full graphical user interface connected to the centre LAN.

Dissemination of Information

In a later phase of the ETFMS implementation, the information collected at the CFMU can be optionally distributed to national air traffic service provider systems, for implementing regional or local services not provided throught the CFMU systems.

The dissemination of information will be carried out by broadcast from the AN node at the CFMU. Again ASTERIX Category 062 will be used as the common exchange format with the ATS systems. As a result of dissemination, tools for statistics, traffic prediction and planning could be developed to assist ATFM related operation, while using information consistent with that held at the CFMU.