A320 carries out initial four-dimensional trajectory test

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Airbus's A320 test-bed has carried out the first flight for an operational concept which aims to increase predictability of traffic flows into airports, by using four-dimensional trajectory calculations.

The initial four-dimensional (I-4D) concept - which could be tentatively deployed in Europe from 2018 - uses airborne computed predictions to determine an arrival sequence for aircraft converging on a point in congested airspace.

Each aircraft flying towards this point, known as the merging point, exchanges trajectory information via automatic dependent surveillance-contract datalink with air traffic centres and negotiates a time constraint for arrival. The aircraft is then permitted to operate its optimum flight profile until it reaches this point, without the need for air traffic control vectors.

By adding a time constraint to three-dimensional positional navigation, the traffic situation at a future point in time and space becomes better-defined. This allows traffic flow to be managed more efficiently, and eases the use of other concepts such as continuous descent approaches.

Under the Single European Sky initiative to modernise airspace control, airlines and air navigation services will eventually agree 4D trajectories before a flight takes place - a trajectory which could be amended in real-time during flight if necessary.

Airbus's A320 flew from Toulouse to Copenhagen and Stockholm, and back to Toulouse, for the 10 February test. It secured an initial time constraint, while under Maastricht upper area control, for a merging point near Copenhagen before entering Danish airspace to perform an optimised descent.

Having reached the merging point, it returned to cruise altitude and exchanged data to secure a second time constraint for a merging point at Stockholm. The flight proceeded to land at Stockholm Arlanda airport.

"This flight test offers a concrete solution towards improving the existing European system which is reaching its capacity limit," said Airbus, which is participating in the I-4D initiative alongside several Single European Sky partners.

These include Honeywell and Thales, who modified their flight-management systems to handle the operations under 4D constraints - meeting a required time of arrival at a specific waypoint, and swapping data with ground systems supported by Thales and Indra. The partnership also involved several northern European air navigation providers.

Organisers of the project said the flight "successfully verified" the datalink exchange of 4D data between the aircraft and ground-based systems.

Further flight tests and validation efforts are intended towards the end of this year, and the processes and procedures will then be sharpened in 2013.