Test flights confirm ADS-B self-separation potential

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Researchers investigating techniques by which pilots could provide airborne separation assurance have successfully demonstrated that automatic dependent surveillance broadcast (ADS-B) can be used for specific aerial co-ordination manoeuvres.

Test flights were conducted under the More Autonomous Aircraft in the Future Air Traffic Management System (MA-AFAS) programme – a joint European Union effort between avionics providers and air traffic control specialists.

MA-AFAS is focused on three main components – taxi management, cockpit display of traffic information, and four-dimensional trajectory operations – as part of a larger overall programme aimed at examining complete gate-to-gate advanced flight management concepts.

The self-separation trials fall under the ‘cockpit display’ section of the project; pilots would use ADS-B displays to monitor surrounding airborne traffic. This section of the project envisaged the use of specially-equipped BAC One-Eleven aircraft from UK research group QinetiQ and a twin-engined VFW614 test-bed aircraft from the German DLR aerospace research facility.

Five flights in the vicinity of Rome demonstrated that ADS-B could be used for key sequencing and conflict-avoidance manoeuvres such as ‘merge behind’ and ‘pass behind’ in which one aircraft maintains a fixed separation distance from the other – in this case, 6nm (11km) – while operating at the same flight level.

The ‘merge behind’ technique involves aligning an aircraft’s flight path with that of a target aircraft over a fixed waypoint, such that the two emerge in train, while a ‘pass behind’ instruction requires one aircraft to deviate from its track to pass behind a crossing aircraft, before re-joining its original flight-path.

This concept, says the MA-AFAS project team, could be extended to vertical crossing, overtaking and other similar movements involving pilots’ adjusting flight paths in relation to other traffic.

Although still a controversial subject, autonomous separation by pilots is seen as a way of reducing controller workload while increasing pilots’ situational awareness and providing greater airspace flexibility.

BAE Systems’ avionics division is participating in, and part-funding, the MA-AFAS programme alongside 18 other contributors including air traffic control systems manufacturers, research groups and air traffic services providers.