ADS-B: Next step toward the Next Generation air transport system

Yesterday the FAA announced a formal proposal to require "all aircraft flying in the nation’s busiest airspace to have satellite-based avionics by 2020, enabling air traffic controllers to track aircraft by satellites using a system known as Automatic Dependent Surveillance Broadcast (ADS-B)." The proposed requirements for equipping aircraft with ADS-B systems is designed to enable the transition to the Next Generation satellite-based air transportation system.

The ADS-B system is said to be ten times more accurate than current radar technology. As explained in an FAA Fact Sheet about ADS-B issued earlier this year:

ADS-B works by having aircraft transponders receive satellite signals and using transponder transmissions to determine the precise locations of aircraft in the sky.

The system converts that position into a unique digital code and combines it with other data from the aircraft’s flight monitoring system — such as the type of aircraft, its speed, its flight number, and whether it is turning, climbing, or descending.

The code containing all of this data is automatically broadcast from the aircraft’s transponder once a second.

Aircraft equipped to receive the data and ADS-B ground stations up to 200 miles away receive these broadcasts. ADS-B ground stations add radar-based targets for non-ADS-B-equipped aircraft to the mix and send all of the information back up to equipped aircraft — this function is called Traffic Information Service-Broadcast (TIS-B). ADS-B ground stations also send out graphical information from the National Weather Service and flight information, such as temporary flight restrictions — this is called Flight Information Service-Broadcast (FIS-B).

Pilots see this information in their cockpit traffic display screens. Air traffic controllers will see the information on displays they are already using, so little additional training will be needed. ADS-B signals are transmitted once per second, providing a more accurate tracking system for pilots and controllers.

One of the advantages of the ADS-B system over current radar-based systems is that both pilots and controllers will be able to see the same real-time displays of air traffic.

• Pilots will have much better situational awareness because they will know where their own aircraft are with greater accuracy, and their displays will show them all the aircraft in the air around them.
• Pilots will be able to maintain safe separation from other aircraft with fewer instructions from ground-based controllers.
• At night and in poor visual conditions, pilots will also be able to see where they are in relation to the ground using on-board avionics and terrain maps.

ADS-B also should help to reduce the risk of runway incursions since "both pilots and controllers will see the precise location on runway maps of each aircraft and even equipped ground vehicles, along with data that shows where they are moving," according to the FAA.

The proposed compliance date for equipping aircraft with ADS-B technology is 2020.

UPDATE October 17, 2007: Here is some interesting follow-up information on the ADS-B. Today Vincent Capezzuto, the FAA's Director of Surveillance and Broadcast Services Program Office, testified before the U.S. Congessional Committee on Transportation and Infrastructure, Subcommittee on Aviation on Nextgen, regarding the Automatic Dependent Surveillance-Broadcast Contract.

Click here to read Mr. Capezzuto's testimony about ADS-B.