EMMA KELLY / PERTH
ADS-B technology is inexpensive and could be ideal for countries such as Australia where vast tracts of land lack radar coverage
Automatic dependent surveillance - broadcast (ADS-B) is nothing new. It has been tested in its various forms for several years, but only now is the technology's potential being realised and there are pockets of activity around the world where it is making the leap from testing to operational implementation.
Although Australia is only at the trial stage, it has had ambitious plans for implementation since the start. Australia's air traffic services provider Airservices Australia hopes its ADS-B trial could lead to national implementation in just a few years.
The service provider took its first steps on the road to ADS-B in 2001 when it issued a tender for the provision of equipment for a trial in the Burnett Basin around Bundaberg, Queensland, in 2002. The Burnett Basin was selected as it lacks radar coverage below 9,000ft (2,745m). The original plan was to equip 17 regional and general aviation aircraft ahead of a decision on whether to deploy the technology across the rest of the country. The trial would involve one ADS-B ground station connected to the Australian Advanced Air Traffic System (TAAATS).
At that time Airservices had not selected the ADS-B link technology to be used - either VDL Mode 4, Mode S squitter or universal access transceiver (UAT). "The call for tender was link-agnostic," says Greg Dunstone, Airservices' technology development and ADS-B project director. In the end, Airservices selected Mode S extended squitter as the datalink, based on it being the one most capable of doing the job it wanted at the lowest cost, says Dunstone. There were no technical or political reasons for the choice, he says, adding that if UAT proves a better link it will be considered for national deployment. "Our strong preference is for one system," he says.
Two years later and the service provider has established one ADS-B ground station at Bundaberg and by mid-July two Royal Flying Doctor Service Raytheon Beech King Airs, four Bombardier Dash 8s operated by Qantas regional carrier Sunstate Airlines and two Energex community rescue helicopters had been equipped with Honeywell-Bendix King KT 73 transponders.
Eventually, 15 GA and regional aircraft that regularly operate in the Bundaberg region will participate in the programme, automatically transmitting position and altitude information to air traffic control every half second using ADS 1090MHz Mode S squitter datalink rather than conventional radar.
Delays
Data collection is expected to begin in August - slightly later than originally planned following delays related to upgrading the country's national air traffic management system, TAAATS, with ADS-B processing and display capabilities. By mid-July site acceptance of the ADS-B software for TAAATS had been completed, but it was waiting in line behind other upgrades for release on to the platform.
Airservices has approval from the Civil Aviation Safety Authority to start the trial, which is "a major tick in the box", and Dunstone is hopeful that ADS-B will be on the operational TAAATS platform next month. He concedes, however, that the delay is a setback, with it "playing havoc with training air traffic controllers" who must also undergo training for the new National Airspace System around the same time.
Despite the delay, the service provider has made progress in several areas. It has already identified problems with international ADS-B standards, says Dunstone. For example, the ADS-B algorithms for data transmission on the ground when the aircraft is still in range of the ground station do not work, says Dunstone, adding that Airservices is seeking to get them changed. "This is what the trial is all about," he says.
The service provider also recently demonstrated that its ground station is compatible with ADS-B avionics other than the type it is using in its trial. A UPS Boeing 767 equipped with UPS Aviation Technologies' ADS-B became the first international aircraft to be tracked by Australia's ADS-B ground station when it flew through the Queensland coverage area in June. The aircraft, flying at 38,000ft from Sydney to the Philippines, was tracked 435km (235nm) from the ground station.
There are four aspects to Australia's ADS-B programme, says Dunstone - the Burnett Basin trial; research and development; national deployment through a network of 20 ground stations and widescale deployment through the equipage of the GA fleet. Airservices has high hopes for ADS-B, believing that in particular it will provide operational and safety benefits in remote parts of the vast country that now have procedural separation services. The benefits of ADS-B are much clearer in Australia - with its large areas of non-radar airspace - compared to Europe or the USA, says Dunstone.
ADS-B would also be a much cheaper alternative to radar infrastructure, Airservices argues. The service provider estimates that it would cost $12-$13 million to provide ADS-B coverage across the whole country, compared with 10 times that figure for traditional radars.
Airservices believes that with the country's ageing radar network approaching its 15-year end of life in 2006, now is the time to commit to an ADS-B solution. "ADS-B has the potential to provide surveillance over the whole continent at a fraction of the cost of installing and maintaining conventional radar sensors," says Dunstone.
Seeking input
Airservices has already sought the input of the country's airlines and aircraft operators, sending a proposal to its customers suggesting the deployment of 20 ADS-B ground stations throughout the country replacing the radar network. Airlines were due to respond to the proposal by 15 July and Dunstone says that so far responses have been favourable, although issues of who should pay and for what need to be resolved.
The service provider is hoping to issue a call for tender for 20 ground stations as soon as board approval is obtained in the next few months, which could lead to national deployment from late 2005.
The GA sector is key to getting national implementation to work, Airservices says. For this sector the costs involved in any avionics upgrade is a vital consideration. "If we don't solve the issues for GA, it [national implementation] won't work," says Dunstone. As a result, Airservices is considering several innovative financing options to make GA equipage more attractive. These include the possibility of a rent-to-buy programme whereby Airservices would subsidise mandatory equipment for GA users and after a set period they would own it.
In a bid to make ADS-B avionics more affordable to GA operators, Airservices recently teamed up with Australian avionics manufacturer Microair Avionics, which will design and develop low-cost ADS-B avionics. The kit will be based on Microair's T2000SFL mode A/C transponder and will transmit a reply to conventional radar interrogations, as well as broadcasting ADS-B position and altitude information via digital datalink. The avionics manufacturer has initially been contracted to develop two prototype systems by mid-2004. The price target for production systems for the GA sector is under $10,000, says Dunstone.
Watching
Australia's ADS-B programme has significance for the whole region, with other service providers watching Airservices' ADS-B experience with interest. The technology has potential particularly in countries that lack radar coverage and cannot afford costly ground infrastructure.
The Asia-Pacific region has already agreed to the progressive implementation of ADS-B for ground-based surveillance services on major traffic flows from January 2006. Earlier this year the ADS-B Study and Implementation Task Force of the International Civil Aviation Organisation's Asia/Pacific Air Navigation Planning and Implementation Regional Group selected Mode S extended squitter datalink for air transport category aircraft.
The group says that ADS-B will provide many benefits, including giving operators increased access to optimum routes and altitudes through separation reduction, resulting in reduced block times and fuel burn, plus improved aircraft utilisation. Service providers, meanwhile, will experience more efficient operations through the optimisation of sectorisation, increased controller capacity and efficiency and reduced air-ground voice communication traffic.
With an ADS-B ground station costing a tenth of that of a secondary surveillance radar, the ICAO group says the technology has potential in countries like Fiji, Indonesia, Papua New Guinea, the Philippines and Pacific islands, which cannot justify the expense of ground infrastructure.
Source: Flight International
