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Detailed Operation
Automatic Dependent Surveillance-Broadcast (ADS-B) is a surveillance technology being deployed in selected
areas of the NAS. ADS-B broadcasts a radio transmission approximately once per second containing the
aircraft’s position, velocity, identification, and other information. ADS-B can also receive reports from other
suitably equipped aircraft within reception range. Additionally, these broadcasts can be received by Ground
Based Transceivers (GBTs) and used to provide air traffic surveillance services, along with fleet operator moni-
toring of aircraft. No ground infrastructure is necessary for ADS-B equipped aircraft to detect each other.
In the United States, two different data links have been adopted for use with ADS-B: 1090 MHz Extended
Squitter (1090 ES) and the Universal Access Transceiver (UAT). The 1090 ES link is intended for aircraft that
primarily operate at FL180 and above, whereas the UAT link is intended for use by aircraft that primarily
operate at 18,000 feet and below. From a pilot’s standpoint, the two links operate similarly and support ADS-B
and Traffic Information Service-Broadcast (TIS-B). The UAT link additionally supports Flight Information
Services-Broadcast (FIS-B).
ADS-B equipment may be certified as an air-to-air system for enhancing situational awareness and as a surveil-
lance source for air traffic services. Refer to the aircraft’s flight manual supplement for the specific aircraft
installation.
ADS-B enables improved surveillance services, both air-to-air and air-to-ground, especially in areas where radar is
ineffective due to terrain or where it is impractical or cost prohibitive. Initial NAS applications of air-to-air ADS-B
are for “advisory” use only, enhancing a pilot’s visual acquisition of other nearby equipped aircraft either when
airborne or on the airport surface. Additionally, ADS-B may enable ATC and fleet operators to monitor aircraft
throughout the available ground station coverage area. Other applications of ADS-B may include enhanced search
and rescue operations and advanced air-to-air applications such as spacing, sequencing, and merging.
ADS-B avionics typically allow pilots to enter the aircraft’s call sign and Air Traffic Control (ATC)-assigned
transponder code, which will be transmitted to other aircraft and ground receivers. Pilots are cautioned to use
care when selecting and entering the aircraft’s identification and transponder code.
Some ADS-B avionics panels are not interconnected to the transponder. Therefore, it is extremely
important to ensure that the transponder code is identical in the ADS-B and transponder panels.
ADS-B Traffic