Understanding ADS-B

Automatic Dependent Surveillance-Broadcast (ADS-B) is the backbone of the Federal Aviation Administration’s (FAA) Next Generation (NextGen) National Airspace System (NAS). In order to comply with the FAA and European Aviation Safety Agency (EASA) mandates for ADS-B equipage and support of NextGen navigation capability, it’s important to understand how it will affect your aircraft operations.

See what ADS-B Out solutions are available today and contact your Universal Avionics Sales Representative to learn more.

ADS-B Explained

What is Automatic Dependent Surveillance-Broadcast (ADS-B)?

Automatic Dependent Surveillance-Broadcast (ADS-B) represents a class of enablers that provide significant operational capabilities by addressing some of the limitations of the present surveillance system. It is the cornerstone of the FAA’s transition to satellite-based surveillance and navigation under the NextGen Air Transportation System plan.

The “-Broadcast” part of ADS means that the aircraft’s avionics system automatically transmits messages containing position and velocity information to the Air Traffic Control (ATC). This makes the aircraft visible, real-time, to the ATC and other appropriately equipped ADS-B aircraft. ADS-B allows ATC to monitor and separate aircraft efficiently, with more precision. Because it uses GPS signals, it expands surveillance services into areas where little or no radar coverage exists, such as in Alaska and the Gulf of Mexico.

ADS-B provides surveillance and improved situational awareness to pilots and ATC. Providing a flexible and expandable platform to accommodate future air traffic growth, ADS-B is designed to improve the safety, capacity and efficiency of the National Airspace System (NAS).

ADS-B "Out"

ADS-B “Out” involves the transmission of a GPS position from an aircraft in order to display the aircraft’s location to ATC on the ground or to pilots in the cockpits of aircraft equipped with ADS-B “In”. This technology provides aircraft position with high integrity to ATC, as well as ADS-B “In” equipment.


ADS-B “Out” benefits operators in a number of ways, it:

  • Complies with the FAA and EASA mandates for equipage and support of NextGen navigation capability.
  • Reduces separation between aircraft as a result of improved accuracy, integrity and reliability of satellite signals over radar.
  • Increases coverage since ADS-B ground stations are much easier to place than radar. Therefore, remote areas without radar coverage will be covered with ADS-B.
  • Saves time and money, while reducing fuel burn, through more direct flights. This is also directly related to Required Navigation Performance (RNP) airspace requirements as NextGen moves forward.
  • Installation of a Satellite-Based Augmentation System (SBAS)-Flight Management System (FMS) (TSO C145/C146 SBAS/GPS required for ADS-B) also provides for Localizer Performance with Vertical Guidance (LPV) approaches in the U.S. alone. The European Geostationary Navigation Overlay System (EGNOS) is now online and LPV approach capability is becoming available in Europe as well.
  • There are a number of new capabilities planned that will allow for closely-spaced parallel approaches, as well as Airport Surface Alerts, and In-Trail Procedures in remote airspaces such as the North Atlantic Tracks (NAT) to Europe.


ADS-B “Out” will eventually be mandatory in all Class A, B and C airspace. The FAA has mandated ADS-B “Out” by January 1, 2020.
EASA has set ADS-B "Out" compliance dates of June 8, 2016 for new aircraft and June 7, 2020 for aircraft needing retrofits.


The minimum set of equipment for ADS-B “Out” to satisfy the mandate is an extended squitter Mode S transponder, which accepts GPS position information from an SBAS GPS sensor, such as Universal’s line of Wide Area Augmentation System (WAAS)/SBAS-FMS. At this time, only an SBAS GPS sensor meets the ADS-B “Out” requirements.

Earlier TSO C129 GPS systems will not. Light aircraft utilize alternatives, such as a transceiver known as Universal Access Transceiver (UAT). However, this is limited to aircraft flying below FL180 and is not a viable option for transport aircraft.

ADS-B "In"

ADS-B “In” is the ability of an aircraft to receive information transmitted from ADS-B ground stations and from other aircraft. ADS-B “In” pilot cockpit advisory services consist of Flight Information Service-Broadcast (FIS-B) and Traffic Information Service-Broadcast (TIS-B). These free services are automatically transmitted to aircraft equipped to receive ADS-B “In”.

ADS-B “In” broadcast services do not require subscription or usage fees.


  • Real-time situational awareness to both high- and low-altitude operators by providing highly accurate traffic data.
  • Low-altitude users are offered essential flight data such as weather and Sense and Avoid (SAA) information.
  • Reduced separation of aircraft, more precise navigation and more efficient ATC.
  • FIS-B provides a broad range of textual/graphical weather products and other flight information to the general aviation community.
  • TIS-B increases pilots’ situational awareness by providing traffic information on all transponder-based aircraft within the vicinity of the ADS-B “In” equipped aircraft receiving the data.
  • ADS-B traffic, weather and aeronautical information services are available free of charge.
  • There are a number of new capabilities planned that will allow for closely-spaced parallel approaches, as well as Airport Surface Alerts, and In-Trail Procedures in remote airspaces such as the NAT tracks to Europe.


ADS-B “In” is not mandated by the ADS-B “Out” Final Rule.

FAA Advisory Circular (AC) 20-172 contains information about rule-compliant equipment installation and certification requirements and ADS-B “In” requirements.


  • ADS-B “In” requires either a Technical Standard Order (TSO) C166b or C154c compatible device, along with a processing system and cockpit display that conforms to TSO C 195.
  • FIS-B is only available on 978MHz UAT equipment.
  • TIS-B is available to both 1090ES and UAT equipment users.

FAA ADS-B Guidance

Benefits of ADS-B

The precision and accuracy of the information received from the Global Positioning System (GPS) satellites allows for reduced separation between aircraft, which provides substantial benefits – even in areas with and without existing radar coverage.

Airport Benefits

As ADS-B ground stations across the NAS are deployed, surveillance, situational awareness and safety will improve at airports with ATC radar services.

Flight Operations Benefits

All aircraft operators in the NAS will benefit from two significant categories of improvement; efficiency and capacity, and access. Capacity improvements are made possible by the safe distance reduction for aircraft separation, decreased delays from weather and other disruptions, and increased flight path and procedures options for ATC maintaining the flow of traffic.

Surface Collaboration Benefits

ADS-B offers surveillance and situational awareness capabilities, enabling pilots and ATC to see properly equipped ground vehicles and aircraft, even when visibility is reduced by weather. With ADS-B, ATC can use airspace more efficiently and will become more effective guardians of safety through automation, implementation of the Safety Management System (SMS) process and simplification of routine tasks. Also, there is better awareness of conditions in the airspace that the ATC controls. ADS-B will update activity on ATC more regularly and with increased accuracy, delivering information such as aircraft type, call sign, heading, altitude and speed.

ADS-B advancements in situational awareness will heighten both ATCs’ and pilots’ individual and combined ability to evade possible danger and provide beneficial time savings in Search and Rescue (SAR) efforts. In addition, advancements in tracking and managing operations on airport surfaces will make runway incursions less likely.


Surveillance Manufacturer Model # Approved Position Source
Honeywell RCZ-8XXM UNS-Xw
Raytheon APX-119 UNS-Xw
RCI TDR-94(D)-501 UNS-Xw


United States

Required in 2020 with WAAS Receiver


Required with WAAS Receiver on June 8, 2016 for new aircraft and June 7, 2020 for aircraft needing retrofits


Required in 2013 - FL290 and above


Required in 2009 - Hudson Bay FL350 - FL400
Required entirely by 2020

Hong Kong, Singapore & Vietnam

Required in 2013 - FL290 & Above, Specified Airways

White Paper

Understanding ADS-B Whitepaper
Download the ADS-B White Paper

For detailed information about ADS-B, download Universal Avionics White Paper, “Understanding Compliance with Automatic Dependent Surveillance – Broadcast (ADS-B) Out”. Written by the experts at Universal Avionics, it provides more detail about how to comply with regulatory requirements around the world, and equipage needs for your aircraft.

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