Chris Yates/BERLIN
The first live trial of the prototype Airborne Separation Assurance System (ASAS), jointly developed by the Eurocontrol Experimental Centre as part of the Free Route Experimental Encounter Resolution programme, and Carmenta of Sweden, has been successfully completed.
Initial results were demonstrated at the Global Navcom 98 conference in Berlin, Germany, on 13-15 October, and seem to indicate that the ASAS has moved from the conceptual to the practical stage of development.
The success of the trial is a key development in the drive towards free flight in European airspace. Under the ATM2000+ Strategy, which is being developed by Eurocontrol and expected to be endorsed by European Civil Aviation Conference transport ministers in 1999, there is limited transfer of air traffic control functionality. This includes separation assurance under certain conditions, in the timeframe 2005-10, and extended transfer, including autonomous aircraft operations from 2015.
The ASAS makes use of VHF datalink Mode 4/self organised time division multiple access ADS-B transponders. In addition to providing situational awareness based on position reports, trajectory broadcasts allow the display of intentions and on-board detection of potential conflicts, which are displayed in the form of conflict zones on the Carmenta-developed traffic situation display.
The trial involved a Fairchild Dornier Metro turboprop of Ostfriesiche Lufttransport (OLT) and an in-service Lufthansa Boeing 747-200. Both aircraft were ASAS-equipped and flew opposite tracks to one another. A potential conflict was indicated 10min before loss of separation on the traffic situation displays aboard each aircraft. The OLT crew constructed a new trajectory to avoid separation loss and, after obtaining clearance, activated and flew the new route.
All manoeuvres and intentions were clearly visible to the crews of both aircraft on the traffic situation display and also on the ground monitoring system. To ensure safety, both aircraft were separated vertically at all times, but with the ASAS configured to ignore the vertical separation. Further trial flights involving commercial aircraft are under way.
Source: Flight International
