DAVID KAMINSKI-MORROW / LONDON
European researchers are tentatively exploring the potential benefits of using automatic dependent surveillance - broadcast (ADS-B) to give pilots greater autonomy as they prepare to connect and broaden current ADS efforts through a large-scale implementation programme.
Handing responsibility for separation to pilots is contentious. But preliminary moves in this direction are contained within a European framework known as "Package I", which lists about a dozen potential near-term airborne and ground-based ADS-B applications that could be introduced over the next five to 10 years, and should become the platform for an ADS-B masterplan.
In setting out the Package I objectives, the European Joint Co-ordination Board, set up last year to oversee Europe's ADS-B efforts, deliberately focuses on "'airborne separation assistance", rather than the more controversial "airborne separation assurance" and stresses that Package I will not involve a transfer of separation responsibility from the ground.
Separation assistance is being examined under one of the central individual ADS-B efforts, the More Autonomous Aircraft in the Future ATM System (MA-AFAS) project, led by BAE Systems.
MA-AFAS programme co-ordinator Tony Henley says the sensitivity of the "airborne separation" issue has meant introducing the concept carefully during test-flight scenarios. Rather than delegating the task of self-separation to pilots, controllers are trained to use a new instruction - one which asks pilots to identify and confirm a target aircraft, using a cockpit display fed with ADS-B data, and to execute a manoeuvre to maintain a particular distance from it.
A series of test flights in Rome, using a BAC One-Eleven and a VFW614 research aircraft and similar tests combining an aircraft with simulated traffic at Braunschweig in Germany have shown that pilots are able to use such instructions to maintain spacing when passing behind a target aircraft. This process also has benefits when merging inbound aircraft into a sequenced approach stream. "In simulations we can have aircraft lined up earlier, there are fewer gaps and the sequencing goes more smoothly," says Henley. "There is an optimum flow into the airport for a very modest change in instructions or procedures."
Scepticism
International Federation of Air Line Pilots' Associations (IFALPA) air traffic services committee vice-chairman Heinz Frühwirth says technology has not advanced far enough to make large steps towards self-separation, and that IFALPA is sceptical about aircraft autonomy. "At the moment there are many things like [more autonomous] merging and spacing which show promising results," he says. "The problem we have is that several other factors have not yet been taken into account." These include the possibility that a crew might not be able to perform self-separation due to particularly heavy workload. Henley adds a further caution: "If the pilot is responsible [for separation] and you use this to push up capacity, you can't then [necessarily] give the task back to the controller."
Although a potential early benefit of ADS-B is the ability to reduce oceanic parallel track separation to pack more aircraft into the narrow optimum-wind corridor, he adds, giving pilots visual access to busier surrounding airspace via a cockpit display of traffic information (CDTI) is not necessarily a good idea, because it could increase workload for the crew. The MA-AFAS tests saw pilots presented with a single, identified target aircraft on an otherwise dark screen.
"Some people say that CDTI is valuable in its own right," he says. "I think that's a mistake. To the pilot you're saying: 'Here's 50 aircraft, but you're not allowed to do anything with that information'."
Trials by Dutch aerospace research laboratory NLR have shown that pilots with access to CDTI can theoretically handle self-separation even at airspace densities far higher than those normally experienced in Europe. But Henley remains cautious on the prospects for aircraft autonomy, saying: "In the near future there is a limit - but we can definitely see it going beyond where we are now."
Europe is trying to bring together its various ADS-B research programmes in a bid to converge its path with that of the USA and lay the groundwork for the longer-term "Package II" applications for the technology - which will probably look closely at airborne self-separation in low-density airspace - and "Package III", which will apply the concept to medium- and high-density areas.
Airborne spacing applications via ADS-B are set to feature as part of a new large-scale project which is awaiting funding approval under the European Union's Sixth Framework Programme. Designated the South European ADS Pre-Implementation Programme (SEAP), it will cover the Iberian peninsula and extend south west to the Azores, Canary Islands and Madeira - assisting the creation of an ADS corridor between Europe and Latin America. It will also complement the existing ADS infrastructure across Europe, connecting with the main programmes: the north European ADS-B Network Update Programme, the Mediterranean ADS Upgrade, and the Mediterranean Free Flight project as well as MA-AFAS.
Starting dates for SEAP will probably be fixed once European funding for the project is approved. European ADS-B Joint Co-ordination Board chairman Chris North says first-phase funding of SEAP is under consideration by controllers of the EU's Trans-European Network budget and that he is "relatively certain" that this will be granted. Funding of the main part of the programme, phase two, has yet to be decided on.
Source: Flight International
