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Aviation History
1990
1990 - 0099.PDF
conflict alert function that is already installed at some European centres will continue to warn the controller independently. ASTA is also to be used with simulations of the experimental flight management system (EFMS). These will be carried out before the airborne trials at Royal Aerospace Establish ment Bedford (Flight, 23 September, 1989, P 55). The two scenarios being considered are the automatic ATC environment of the year 2000 and the fully automatic ground/air system of the year 2015. An electronic flight instrumentation system (EFMS)-equipped basic simulator has been evaluated by RAE pilots and others. The simulator is based on a model of the perfor mance of the Fokker F.28 provided by the Dutch national aerospace laboratory (NLR) and is run on Bretigny's Siemens computer. Initially the pilot will input EFMS-derived data manually, but automatic transfer, under Mode S simulation, is expected to in a few months. New standard arrival and departure procedures will be assessed, using a range of general pilot opinion. Other aircraft types, including the 747, will be simulated later. The extent of the work going on at Bre- tigny shows that the need for a total air traffic system concept in Europe is wisely being extended beyond its borders. The fluctuating flow of traffic to and from the north Atlantic has a significant effect on the continental flows. SATELLITE ATC Work on satellite data transmissions from aircraft under the European PRODAT pro gramme started in 1987. Bretigny first simu lated a single sector of Portuguese airspace from the Lisbon upper airspace flight infor mation region to the east of Santa Maria Oceanic. The work is aimed primarily at automatic dependent surveillance (ADS) (where aircraft positional data is transmitted by satellite to ground control), and at full- colour graphic, radar-like displays for the controllers. The first flight to be "controlled" by a civil ATC centre (Madrid) by satellite datalink was made more than a year ago, by a BAe Jetstream owned by Racal Avionics. UK RAE British Aerospace One-Elevens and Civil Aviation Authority (CAA) BAe 748s took part in other practical trials. Trials are made in co-ordination with the European Space Agency, using the MARECS B2 Inmar sat satellite. In the longer term, the load on satellites and integration of communications management will have to be examined. Bretigny is preparing for the start of airline participation. Sabena, Saudia and Air France are having aircraft equipped for satellite communications, for the exchange of ATC and weather messages and for ADS reporting. TAP and Varig aircraft will be equipped initially only for message exchange. The first two airlines should continue trials of ADS operation through 1990. Satellite coverage will extend from the bottom of Satellite-based oceanic ATC is being evaluated at Bretigny Greenland down to Africa, and westward from the Urals to the east coast of America. This should be adquate for monitoring flights in the eastern mid-Atlantic. A two-sector simulation exercise—over airspace extending up to Shannon Oceanic— is under way at Bretigny. The UK CAA and the Irish and French authorities are partici pating. Evaluation of a radar-type oceanic display will be made first, using past samples of north Atlantic traffic taken from records at centres. It will then be reconstructed auto matically into continuous targets. AUTOMATIC SURVEILLANCE In actual operation, ADS reports will be initiated automatically by the aircraft system. It will also be possible to interrogate the aircraft from the ground, or to request keying of data by the crew. A simple keyboard action could be used, like the "ident" function with secondary surveillance radar equipment, when increased positional certainty is re quired—for crossing traffic (north/south At lantic traffic, say) or in emergencies. The overall frequency of reports needed for all purposes will need assessment. The exercise will run ATC solely on ADS data from 30°W to 15°W. A 5min polling interval might be used eastbound to 18°W, reducing to a 2min interval to 16°W and 30s interval until entering Shannon Oceanic airspace. A polling interval as low as 10s might be set up on the aircraft by a signal from the ground, where nearby traffic needs to be manoeuvred. An increase in the polling rate could be introduced automatically for a period when a route-change clearance is issued and continuing throughout its execution. The basic ADS system could operate on a continuous display of extrapolated positions, which would look like those on a radar monitor. There could be colour conventions for planned, active and handover flight rout ing and operational situations. ADS will pose questions on message han dling and it could change the work of controllers with the new format of flight progress display. Eurocontrol believes it will change oceanic control style. Some authorities may still be reluctant to introduce such an area display, however; they could favour instead the retention of the recently developed electronic strip displays, with automatic update of system-calculated position. If an area display technique is used, then the question of the uncertainty of ADS position arises; inertial navigation system position drifts with time, and Omega or Loran is dependent on geography accuracy. Bretigny is considering displaying position by a circle of variable size; its radius could be based on the accuracy of data already present in an FMS, or it could be time-related to the most recent accurate update. This format, for display of positional "confidence", might be shown full-time or it might be called up automatically in the event of traffic conflict or need for manoeuvre. Data on positional accuracy would have to be used in any conflict-alert function for oceanic areas. The work of such research centres as Bretigny should open the industry's eyes to the great potential for extending a uniform air traffic control environment over ever- increasing areas. It is possible that the trend towards satel lite navigation and communication will open up new opportunities for world-wide com patibility of air traffic control and flow man agement. The interface problems generated by national differences in policy, equipment and capacity may merely move further afield, thereby losing much of the potential for efficiency. Q FLIGHT INTERNATIONAL 17-23 January 1990 41
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