Air/Ground Negotiation

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Trajectory Negotiation (TN) was the heart of the air / ground integration in PHARE. It was the mechanism by which air and ground systems interchanged detailed information about their requirements and came to an agreed contract for the execution of (the next part of) a flight.

Overview

The Trajectory Negotiation process was intended to allow detailed agreement between air and ground about the future progress of a flight with the minimum necessary complexity for either end. It is expected that in any particular case there will be an agreement reached as a result of Trajectory Negotiation in a very small number of air / ground exchanges.

The overall process is that the aircraft down links full details of its preferred trajectory while the ground assesses this for possible conflict and responds with any necessary time or altitude constraints to prevent loss of separation. The initial down link of a proposed trajectory by the aircraft is important in the process of arriving at an agreed solution which is as optimal as possible for the aircraft. The initial down link without constraints informs the ground of the aircraft’s preferred operating regime. Constraints are then applied from this preferred regime leaving the final agreement as close as possible to it.

Three versions of Trajectory Negotiation, Standard Negotiation, Formalised Clearance and Pre-emptive Down link, were available within PHARE Demonstration 3 to be used at the discretion of the ATC operator or the pilot.

The Trajectory Negotiation process can be carried out in advance and that the trajectory being agreed may not start for some considerable time.

Standard Negotiation

Standard Negotiation (SN) is the basic Trajectory Negotiation process, which was expected to be used whenever time allowed. The overall process from the airborne point of view is outlined in the figure below.
The standard negotiation cycle
Standard Negotiation can either be started by an Air Proposal initiated by the aircraft or a Ground Proposal from ATC.

Trajectory Down-link

Standard Negotiation begins with the aircraft down-linking to ATC a detailed trajectory, which is the proposal for a forthcoming flight. There may be profile constraints at the start and at the end for terrain avoidance or noise abatement but otherwise the proposal reflects an optimum flight profile.

The aircraft then awaits a response from the ground; this may be in one of two forms, a Constraints Up-link or an Acceptance.

Constraints up-link

It is the responsibility of ATC to ensure that an agreed trajectory is not in conflict with other trajectories, thus maintaining separation between aircraft at all times. ATC makes its requirements known by uplinking a set of constraints which need to be applied to the proposal before it is resubmitted. The pilot will review the constraints and the process continues from the Trajectory Down-link stage again.

Approval and Acceptance

When ATC receives a down-linked trajectory which has no conflicts an approval is up-linked. The pilot will respond with an acceptance.

Formalised Clearance

Formalised Clearance (FC) is a shortened version of the air / ground dialogue. It allows the ground to propose a set of constraints on the flight and at the same time grant approval for any trajectory, which is compliant with those constraints.

The required response from the pilot is to accept the Formalised Clearance if the resultant trajectory is acceptable and to perform a Trajectory Down-link (as above) to confirm to ATC the trajectory the aircraft is following.

Pre-Emptive Down-Link

The Pre-Emptive Down-link is a way in which an aircraft that does not have a contract for the trajectory that it is currently following can inform the ground in detail of its intentions. It consists of a single Trajectory Down-link. It is expected that whenever such a down-link is made the ATC will respond either with a Formalised Clearance or a Ground Proposal.

For more information

The Trajectory Negotiation process is fully documented in:
  Acrobat 97-70-14 Trajectory Negotiation in a Multi-Sector Environment131 Kb
  Acrobat 98-70-19 Airborne Report2,588 Kb
There are further significant mentions of trajectory negotiation, in some cases in conjunction with the PHARE Advanced Tools Negotiation Manager, in the following documents:
  Acrobat 94-70-28 PD/1 Operational Scenarios101 Kb
  Acrobat 95-70-02 PD/3 Demonstration Operational Specification175 Kb
  Acrobat 95-70-03 PHARE: Air-Ground Data Exchange Study, S3190 Kb
  Acrobat 95-70-11 PD/2 Operational Scenarios171 Kb
  Acrobat 97-70-04 PD/3 Operational Scenarios Document (Volume 1)279 Kb
  Acrobat 97-70-08 PD/3 Operational Scenarios Document (Volume 2)303 Kb
  Acrobat 97-70-13 PD/2 Final Report Volume 1912 Kb
  Acrobat 97-70-13 PD/2 Final Report Volume 2 Annex F Airborne Aspects of PD/2198 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 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 Report1,189 Kb
  Acrobat 99-70-01 Volume 2 of PD/3 Final Report - CENA PD/3 Final Report Annex E Airborne Aspects886 Kb
  Acrobat 99-70-01 Volume 4 of PD/3 Final Report - NLR PHARE Demonstration 3 Final Report528 Kb
  Acrobat 99-70-02 PHARE Ground Human Machine Interface (GHMI) project: summary report2,196 Kb
  Acrobat 99-70-09 PHARE Final Report1,412 Kb