Eurocontrol has begun work with the major aircraft manufacturers to enable the four-dimensional trajectory management of air traffic. This is one of the fundamental requirements for meeting Single European Sky and US Federal Aviation Administration's NextGen air traffic management performance objectives.

Airbus and Boeing have both told Eurocontrol they are ready with systems that can feed datalinked ATM clearances direct to aircraft flight management systems. Eurocontrol communication systems expert José Roca says that, up to this point, there has been no way to uplink ATM instructions to an aircraft FMS. Each uplinked instruction is subject to pilot acceptance before the crew routes it to the FMS. Eurocontrol, Roca says, expects to have drawn up the technical and operational standards for this system and procedure - which Eurocontrol calls "initial 4D link" - by 2011, and for it to be operational by about 2013. Part of the system-approval process will be providing an acceptable business case for the change.

As the project name implies, further into the future a more sophisticated datalink/FMS system will enable the advanced, highly accurate 4D trajectory control that will be required in Europe and the USA. Roca points out this is a joint project with the FAA, monitored by the respective European and US standards agencies, so the equipment and procedures will be globally accepted.

Roca explains there is no new airborne equipment needed for aircraft equipped with VHF datalink mark 2 (VDL-2) under Eurocontrol's Link 2000+ datalink programme, nor for new ground equipment in the area control centres already equipped for VDL-2 controller pilot datalink communications (CPDLC). The change is merely a software upgrade that would include additional clearance message options, he says. Airbus promises the necessary equipment will be retrofittable at low cost. At present, equipped aircraft in almost all of Europe can only receive datalinked ATM clearances in the enroute section of their trajectory.

Meanwhile trials at Brussels airport of datalinked departure clearances and other airport ATC messages have been ongoing since 2005, and this validation will enable aircraft, under the initial 4D link programme, to be able to receive routine CPDLC instructions throughout their journey from departure gate pushback to the destination gate. This will, however, require the airport towers to be equipped, as Brussels already is, with the necessary datalinking hardware.