Ground work: ADS-B

Australia should now have ADS-B coverage above 30,000ft - but development issues have blown it off course. Can it get back on track?

Australia's automatic dependent surveillance - broadcast (ADS-B) programme has not been going to plan. Air traffic services provider Airservices Australia's original schedule called for a nationwide programme implementing ADS-B separation services above flight level 300 (30,000ft/9,000m) to be operational by now, while it hoped for approval to embark on extending the programme below FL300.

But a number of hurdles, including technical, operational and cost issues, have thwarted these ambitions. Airservices' commitment remains, however. "We are thoroughly committed to ADS-B," it says.

Airservices embarked on its upper airspace ADS-B programme in 2004, signing a contract with Thales for 57 ADS-B ground stations to be installed at 28 sites.

This is not Australia's first experience of ADS-B. Airservices launched an operational trial in the Burnett Basin region, north of Brisbane in Queensland in 2004 to evaluate the technology. That trial, which involved general aviation aircraft and airliners, provided valuable knowledge and experience of the technology and the ADS-B ground station used for the trial, in Bundaberg, continues to provide ADS-B service.

The upper airspace plan will see ADS-B provide radar-like surveillance services above FL300, providing air traffic controllers with GPS position, altitude and speed information via the Australian Advanced Air Traffic System (TAAATS). ADS-B promises safety and operational benefits, with much of the country - apart from the eastern seaboard and airspace over major cities - subject to procedural control services. ADS-B is expected to increase surveillance coverage from around 20% today to more than 99%, at a tenth of the cost of installing radars throughout the country.

The ADS-B sites were due to have been operational by the end of 2005, but problems in completing infrastructure at remote sites slipped that by around 12 months in late 2005.

The delay is related to the provision of duplicated communication links required to enable ADS-B to provide a 5nm (9km) separation service. That schedule slipped further with problems with the service provider's telecommunications infrastructure network replacement (TINR) programme, which will provide duplicated communication links from all of the ADS-B ground stations. The service provider expects all 28 ground station sites will take another 18 months to complete.

Meanwhile, the programme has been extended, with Airservices ordering 40 more ADS-B stations for 20 new sites. Five ADS-B ground stations are operational in areas where radar is not available - at the original Bundaberg station, Esperance in Western Australia, Woomera in South Australia, Bourke in New South Wales and Longreach in Queensland. The stations are providing air traffic controllers with position information via ADS-B, but apart from Bundaberg, are limited to procedural control and not separation service.

A further six sites in the outback are expected to come on line by mid-2007. These sites will "significantly increase surveillance", says Airservices.

The service provider concedes there are other "minor" problems remaining. "You always find small issues with every project this big, but they are small. The project team and technicians have completed an impressively large body of work," it says.

In the meantime, progress is being made elsewhere. The number of ADS-B-equipped aircraft flying through Australian airspace is continually increasing. The Civil Aviation Safety Authority (CASA) has now authorised more than 100 aircraft for ADS-B service, including Jetstar Airbus A320s, Virgin Blue Boeing 737s, Emirates Boeing 777s, Air New Zealand 777s and A320s, Qantas 737s and A330s.

CASA has published a manual of standards to include the ADS-B 5nm separation. In addition, the TAAATS has been upgraded to support ADS-B and a "substantial percentage" of Airservices' controllers have been trained. A revised aeronautical information publication and supplemental material have been produced detailing the operational procedures to be used for ADS-B, including new phraseology. National instructions on the new procedures have been issued to controllers. Technical training and formal commissioning of the infrastructure is under way and flightcrew training is being prepared, says Airservices.

Many of the ADS-B antennas are installed at ground station sites and once they have been connected to the terrestrial and satellite communication links to the air traffic control centres they will be commissioned and will start producing surveillance input. "When all sites are installed we plan to transition to stage three, which involves provision of a 5nm separation service," says Airservices. "

Lower airspace

The plan for Airservice's lower airspace ADS-B programme - referred to as ADS-B in lieu of en-route radar - is less clear. Airservices has held discussions about implementing ADS-B below FL300 in the 2009-10 timeframe, to replace the ageing en-route radar network. That programme would have required an ADS-B mandate and the country's general aviation fleet to be equipped for ADS-B to make it work.

Much work had been done. Airservices had issued a request for proposals (RFP) to avionics manufacturers for the purchase and installation of ADS-B avionics for 1,500 GA aircraft, and in 2005 CASA started work on the process that would have mandated it. Airservices has tested ADS-B units for GA aircraft, including systems from Australian manufacturer Microair Avionics and Germany's Eurotelematik. The Australian Strategic Air Traffic Management Group ASTRA had been discussing a lower airspace proposal for several years, including investigating subsidy options that would ensure industry compliance with the mandate.

But last June Airservices cancelled the RFP, acknowledging that "some elements of the aviation industry and government need more time to consider the costs, timeframe and implementation issues". Airservices chief executive Greg Russell said that introducing ADS-B in lieu of en- route radars is "a significantly more complex matter than upper-level airspace, and raises a number of operational and policy issues that require resolution before a decision to proceed can be made".

Meanwhile, Airservices is working with other countries in the Asia-Pacific region to allow them to exploit ADS-B. Early last year it teamed with Sita on ADS-B. The first product of the partnership is an ADS-B trial in Indonesia, which began late last year, with three ground stations - Denpasar in Bali, Kupang in Nusa Tenggara Timur and Natuna Island in the South China Sea.

The international ADS-B programme is likely to expand further, with Airservices discussing the potential benefits of a regional approach with Indonesia and other regional air navigation service providers at a conference late last year.

Source: Flight International