FAA defining technical requirements for ADS-B on ground vehicles

The Federal Aviation Administration is gearing up to define Automatic Dependent Surveillance-Broadcast (ADS-B) technical requirements for ground airport vehicles, according to a draft advisory circular (.doc).

ADS-B is a Global Positioning System-derived location system already headed for deployment on most aircraft within American airspace by 2020; it forms part of the FAA's $40 billion air traffic control modernization effort known as NextGen.

Ground traffic visibility, even that of airplanes on the tarmac, has been a historical weakness of air traffic control. Since 2000, the FAA has been rolling out a ground traffic surveillance system Airport Surface Detection Equipment, Model X (ASDE-X). However, while ASDE-X makes use of multiple sources of information such as ground surface radar and a multilateration radio system that fixes vehicle position based on the difference in the time of arrival of a signal from targets to receiving towers, it has limitations that integration of ADS-B information into the ASDE-X display could overcome.

ADS-B "can provide a more accurate and timely position report that includes identity and other information," the draft notice states. Multilateration as a technique doesn't work well on fast-moving vehicles while precipitation can disrupt radar detection. The FAA's preferred frequency for the ADS-B ground vehicle transponders is 978 megahertz/universal access transceiver (978 MHz/UAT).

"Fused data, combining data from the [radar], [multilateration] and ADS-B, would provide controllers with the aircraft's size, its identification, and position whereas each data source alone could only provide a piece of the information," the draft circular states.

According to the FAA roll-out schedule, ASDE-X should be operational already in 26 U.S. airports, including Dulles International Airport. The draft advisory circular proposes the international airports of Boston, Philadelphia and Louisville, Ky., as sites for early vehicle ADS-B implementation. Philadelphia and Louisville are already key sites for ADS-B-based air traffic control implementation.  

The FAA awarded ITT Corp. in 2007 a $1.86 billion contract to build, install and maintain a national ADS-B network of ground towers. All towers should be in place by the end of 2013, according to the company.

For more:
- read the draft advisory circular (.doc) (comments were due by July 30)
- go to the FAA's ADS-B webpage
- go to ITT's ADS-B webpage
- watch this video of a Dec. 6, 1999 United Flight 1448 runway incursion at the T.F. Green, R.I., airport

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