USA campaigns for universal access transceiver standards to be drawn up by ICAO

The US Federal Aviation Administration has announced its choice of datalinks for automatic dependent surveillance-broadcast (ADS-B), although the system is not due to be deployed nationally before 2012.

As expected, the FAA has selected 1,090MHz Mode S extended squitter (1090ES) for airliners and business jets, and the lower-cost 978MHz universal access transceiver (UAT) for general aviation. Regional airlines that use high-altitude airspace but serve non-radar airports may need to fit both links.

The FAA says its decision was co-ordinated with Eurocontrol, which has focused its ADS-B link evaluation on 1090ES and VHF datalink Mode 4 (VDL-4). While the USA will propose 1090ES as the initial global ADS-B link, it is pushing the International Civil Aviation Organisation to publish standards for UAT so that it can be a candidate.

The FAA has concluded that 1090ES can provide a 75km (40nm) air-to-air range in high-density airspace, increasing to 165km where there is less interference from other transponders. Due to lingering doubts over whether 1090ES can meet long-term capacity and range needs, the FAA is recommending that avionics manufacturers adopt flexible architectures that are able to accommodate a second link, either UAT or VDL-4.

The FAA plans to deploy the ADS-B ground infrastructure between 2007 and 2012. ADS-B will provide improved surveillance data to air traffic controllers, while traffic and weather information will be broadcast to aircraft via the same links.

Because air transport aircraft will mostly have 1090ES and general aviation aircraft will get UAT, the FAA plans to provide interoperability using a multilink gateway service.

Eurocontrol plans to deploy ADS-B by 2007, with 1090ES as the preferred link because of the expected wide equipage with Mode S. However, the deadline for all instrument-rules flights in European airspace to be Mode S-equipped is expected to be pushed back to March 2005. Currently, all visual-rules flights must be Mode S-equipped by 2008.

Source: Flight International