The PHARE concept was based on an environment in which all existing and planned aircraft trajectories were known to both airborne and ground systems in 4 dimensions (i.e. including time). Datalink was used for the exchange of data to ensure consistency.
Picture of the BAC1-11 
The DERA BAC1-11  
The PHARE Demonstration 1 experimental system included: advanced computer assistance tools; a live aircraft; simulated and real 4-D flight management systems (FMS); and an air-ground datalink. The aim was to explore, in en-route flight, the effectiveness of the negotiation of conflict-free trajectories and the reduction of the workload primarily of the Tactical Controller, but also of the Planning Controller, and thus increase airspace capacity. PHARE Demonstration 1 used the enhanced capabilities of Mode S (ground initiated comm. B messages) as the datalink.

PHARE Demonstration 2 designed, implemented, and demonstrated the PHARE prototype air and ground computer assistance tools for air traffic management in the extended terminal area (ETMA). The PHARE Demonstration 2 system was run on DLR’s real-time simulator ATMOS (Air Traffic Management and Operations Simulator). The system incorporated advanced controller assistance tools with an associated Ground Human Machine Interface (GHMI).
 Picture of the Citation
  The NLR Citation
Originally, it was planned to integrate a fully working arrival management system with advanced arrival management tools performing arrival time prediction, sequencing, approach problem solving and 4D descent management during the whole arrival phase. However, due to system limitations, no trajectory renegotiations were possible once the aircraft was in the TMA. This limitation was overcome in the NLR PHARE Demonstration 3 trials, however, many recent simulations still suffer from this limitation.

The airborne component of the PHARE Demonstration 2 experiment was evaluated by integrating the DLR Advanced Technologies Testing Aircraft System (ATTAS) Experimental Cockpit, simulating air-ground datalink and 4D EFMS. PHARE Demonstration 2 used a high-speed VHF datalink.

For PHARE Demonstration 3 it was decided to use the experimental PHARE Aeronautical Telecommunications Network (PATN) with the SATCOM subnetwork.


The PHARE Demonstration 1 airborne demonstration programme, with the participation of the NATS funded Defence Research Agency BAC 1-11, was extremely successful. It confirmed the ability of an aircraft to agree conflict-free trajectories with ATC, and to fly these trajectories while operating within continuous 4-D constraints. The flights also provided a convincing demonstration to the aviation community of the ‘silent cockpit’.
Picture of the Attas 
The DLR Attas  
PHARE Demonstration 2 was a successful demonstration of the integration of advanced tools, 4D Flight Management System and datalink into an air-ground air traffic management system in an extended terminal area airspace. Experimental evidence suggested that the PHARE concept of trajectory-based traffic guidance provided by the advanced tools and human/machine interfaces was approved by the controllers and pilots, and that it provided the potential for improving traffic throughput and quality of service, at acceptable or reduced levels of controller workload.

At the end of PHARE datalink performance remained a cause for concern. Trajectory negotiation was successfully demonstrated in both PHARE Demonstration 1 and PHARE Demonstration 2. The introduction of the PHARE Aeronautical Telecommunications Network (PATN) in PHARE Demonstration 3, with its complex data structures and protocols, increased the volume of data transmitted considerably. The SATCOM subnetwork could not handle such volumes of data quickly and so in PHARE Demonstration 3 the trajectory negotiation process with real aircraft took, on average, between 4 and 6 minutes to complete.

The large real-time simulations performed demonstrated, but did not prove, the PHARE operational concept of a known trajectory environment using exchange of ground and 4D Flight Management System information over datalink. Due to the limitations of real-time simulations in the number of exercises and lack of exception-handling ability, it could not be stated that PHARE proved that airspace capacity could be increased. However, where the operational procedures and working methods were adapted to make full use of the tools, it was shown that the concept is feasible in an environment with twice the amount of traffic of today, with acceptable controller workload.

For further information

The datalink activity is not specifically documented, however there are significant mentions of datalink in the following:
  Acrobat 95-70-03 PHARE: Air-Ground Data Exchange Study, S3190 Kb
  Acrobat 96-70-20 PD/3 Demonstration Facility Intersite Simulation Requirements Specification224 Kb
  Acrobat 96-70-24 PD1 Final Report Volume 1291 Kb
  Acrobat 96-70-24 PD1 Final Report Volume 2 Annex E Airborne Aspects of PD/11,514 Kb
  Acrobat 97-70-13 PD/2 Final Report Volume 1912 Kb
  Acrobat 97-70-13 PD/2 Final Report Volume 2 Annex C Analysis of Traffic Throughput / Quality of Service171 Kb
  Acrobat 97-70-13 PD/2 Final Report Volume 2 Annex F Airborne Aspects of PD/2800 Kb
  Acrobat 97-70-14 Trajectory Negotiation in a Multi-sector Environment Trajectory Negotiation in a Multi-sector Environment131 Kb
  Acrobat 98-70-05 PD/3 AHMI Design Document CDU and Navigation Display for use with EFMS Phase II369 Kb
  Acrobat 98-70-13 PD/3 Airborne Evaluation Pilot Briefing Guide816 Kb
  Acrobat 98-70-18 PATs Project Final Report Volume 1880 Kb
  Acrobat 98-70-18 PATs Project Final Report Volume 7 Negotiation Manager203 Kb
  Acrobat 98-70-18 PATs Project Final Report Volume 10 Trajectory Predictor160 Kb
  Acrobat 98-70-19 Airborne report2,558 Kb
  Acrobat 99-70-01 Volume 1 of PD/3 Final Report - PHARE Demonstration 3 (PD/3) Synthesis Report204 Kb
  Acrobat 99-70-01 Volume 2 of PD/3 Final Report - CENA PD/3 Final Report Annex E Airborne Aspects886 Kb
  Acrobat 99-70-02 PHARE Ground Human Machine Interface (GHMI) project: summary report2,196 Kb
  Acrobat 99-70-09 PHARE Final Report1,482 Kb
The use of datalink within the various PHARE Demonstrations is described in the following:
  Acrobat 94-70-02 PD/1 Operational Specification142 Kb
  Acrobat 94-70-28 PD/1 Operational Scenarios101 Kb
  Acrobat 95-70-02 PD/3 Demonstration Operational Specification175 Kb
  Acrobat 95-70-11 PD/2 Operational Scenarios171 Kb