By David Kaminski-Morrow in London
Studies into the potential effectiveness of downlinking resolution advisory data from airborne collision-avoidance systems (ACAS) indicate that it could prevent more than 90% of unintentional air traffic controller intervention incidents.
Eurocontrol has been assessing the value of downlinking such information to prevent controllers, during an airborne conflict, inadvertently relaying instructions that contradict ACAS commands to pilots. Contradictory instructions between the controller and ACAS equipment were a contributing element to the mid-air collision between a Tupolev Tu-154 and a Boeing 757 over Lake Constance four years ago.
Following the collision, Eurocontrol began examining the potential of transmitting ACAS data, under the Feasibility of ACAS Resolution Advisory Downlink Study (FARADS) programme, and presented its latest findings at a Brussels workshop on 31 May.
Part of the study, conducted by UK-based Qinetiq, has assessed the critical issue of whether an ACAS downlink would increase controllers’ situational awareness enough to prevent a possible inappropriate intervention.
Researchers examined both candidate datalinks for performing the task – Mode-S and 1090MHz extended squitter – and looked at scenarios in both en route and terminal airspace.
Fewer than 40% of documented cases result in controllers becoming aware of ACAS resolution advisories before an aircraft has noticeably deviated from its course.
But the study has found that downlinking ACAS data would allow controllers to detect 95% of resolution advisories within 8.1s of their being issued – a large improvement over the present figure of 28s. “The downlink of resolution advisory information virtually doubles the chances that the controller will be aware of the [advisory] before any significant deviation occurs,” says the study. “[This] indicates that the downlink of resolution advisory information by either of the technologies… is sufficiently timely to allow a significant increase of the situational awareness of controllers in ACAS encounters.”
Source: Flight International
