Automatic Dependent Surveillance–Broadcast


Automatic Dependent Surveillance–Broadcast is an aviation surveillance technology and form of electronic conspicuity in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts its position and other related data, enabling it to be tracked. The information can be received by air traffic control ground-based or satellite-based receivers as a replacement for secondary surveillance radar. Unlike SSR, ADS-B does not require an interrogation signal from the ground or from other aircraft to activate its transmissions. ADS-B can also receive point-to-point by other nearby ADS-B equipped aircraft to provide traffic situational awareness and support self-separation.
ADS-B is "automatic" in that it requires no pilot or external input to trigger its transmissions. It is "dependent" in that it depends on data from the aircraft's navigation system to provide the transmitted data.
ADS-B is a key part of the International Civil Aviation Organization's approved aviation surveillance technologies and is being progressively incorporated into national airspaces worldwide. For example, it is an element of the United States Next Generation Air Transportation System, the Single European Sky ATM Research project, and India's Aviation System Block Upgrade. ADS-B equipment is mandatory for instrument flight rules category aircraft in Australian airspace; the United States has required many aircraft to be so equipped since January 2020; and, the equipment has been mandatory for some aircraft in Europe since 2017. Canada uses ADS-B for surveillance in remote regions not covered by traditional radar since 15 January 2009. Aircraft operators are encouraged to install ADS-B products that are interoperable with US and European standards, and Canadian air traffic controllers can provide better and more fuel-efficient flight routes when operators can be tracked via ADS-B.

Description

ADS-B is an airspace surveillance system which could eventually replace secondary surveillance radar as the main surveillance method for controlling aircraft worldwide. In the United States ADS-B is an integral component of the NextGen national airspace strategy for upgrading and enhancing aviation infrastructure and operations.
ADS-B enhances safety by making an aircraft visible, in realtime, to air traffic control and to other ADS-B In equipped aircraft, with position and velocity data transmitted every second. FAA program descriptions state that ADS-B Out broadcasts position and other data once per second to ground stations and other aircraft, and note that U.S. airspace and equipment-performance requirements are specified in 14 CFR §§ 91.225 and 91.227. Other uses of ADS-B data include post-flight analysis, inexpensive flight tracking, planning, and dispatch.
Within the United States, the ADS-B system has the ability to provide air traffic and government-generated graphical weather information at no cost through TIS-B and FIS-B applications.
ADS-B consists of two distinct functions - "ADS-B Out" and "ADS-B In". Each "ADS-B Out" aircraft periodically broadcasts information about itself, such as identification, current position, altitude and velocity through an onboard transmitter. ADS-B Out provides air traffic controllers with real-time aircraft position information that is, in most cases, more accurate than the information available with current radar-based systems. With more accurate information, ATC can manage and separate aircraft with improved precision and timing.
"ADS-B In" is the reception and processing of transmitted ADS-B information by other aircraft. In the US ADS-B In can also include other information for pilots transmitted from ATC ground stations such as FIS-B and TIS-B data. These ground station data broadcasts are typically made available only when an ADS-B Out broadcasting aircraft is nearby.
The ADS-B Out system relies on two avionics components aboard each aircraft: a high-integrity satellite navigation source and a datalink. There are several types of certified ADS-B data links, but the most common ones operate at 1090 MHz, essentially a modified Mode S transponder, or at 978 MHz. The FAA would like to see aircraft that operate exclusively below use the 978 MHz link, as this will alleviate congestion of the 1090 MHz frequency. To obtain ADS-B Out capability at 1090 MHz, user-operators can install a new transponder or modify an existing transponder if the manufacturer offers an ADS-B upgrade.

Benefits

ADS-B provides many benefits to both pilots and air traffic control that improve both the safety and efficiency of flight.
When using an ADS-B In system, a pilot is able to view traffic information about surrounding aircraft if those aircraft are equipped with ADS-B Out. This information includes altitude, heading, speed, and distance to the aircraft. In addition to receiving position reports from ADS-B Out participants, in the US, TIS-B can provide position reports on non-ADS-B Out-equipped aircraft if suitable ground equipment and ground radar exist. ADS-R re-transmits ADS-B position reports between UAT and 1090 MHz frequency bands.
Aircraft equipped with universal access transceiver ADS-B In technology will be able to receive weather reports, and in the US, weather radar through flight information service-broadcast, which also transmits readable flight information such as temporary flight restrictions and NOTAMs.
ADS-B ground stations are significantly cheaper to install and operate compared to primary and secondary radar systems used by air traffic control for aircraft separation and control.
Unlike some alternative in-flight weather services currently being offered commercially, there will be no subscription fees to use ADS-B services or its various benefits in the US. The aircraft owner will pay for the equipment and installation, while the Federal Aviation Administration will pay for administering and broadcasting all the services related to the technology.

Safety

Situational awareness

ADS-B makes flying significantly safer for the aviation community by providing pilots with improved situational awareness. Pilots in an ADS-B In equipped cockpit will have the ability to see, on their in-cockpit flight display, other traffic operating in the airspace and have access to clear and detailed weather information. They will also be able to receive pertinent updates ranging from temporary flight restrictions to runway closings.

Improved visibility

Even aircraft only equipped with ADS-B Out will benefit from air traffic controllers' ability to more accurately and reliably monitor their position. When using this system both pilots and controllers will see the same radar picture. Other fully equipped aircraft using the airspace around them will be able to more easily identify and avoid conflict with an aircraft equipped with ADS-B Out. With past systems such as the Traffic alert and Collision Avoidance System aircraft could only see other aircraft equipped with the same technology. With ADS-B, information is sent to aircraft using ADS-B In, which displays all aircraft in the area, provided those aircraft are equipped with ADS-B Out. ADS-B provides better surveillance in fringe areas of radar coverage. ADS-B does not have the siting limitations of radar. Its accuracy is consistent throughout the range. In both forms of ADS-B, the position report is updated once per second. The 978 MHz UAT provides the information in a single, short-duration transmission. The 1090ES system transmits two different kinds of position reports randomly. To decode the position unambiguously, one position report of both kinds or a reference position nearby is needed.
ADS-B enables improved safety by providing:
  • Radar-like IFR separation in non-radar airspace
  • Increased VFR flight following coverage
  • ATC final approach and runway occupancy, reducing runway incursions on the ground
  • More accurate search and rescue response: ADS-B was demonstrated to the Civil Air Patrol in March 2003 by AOPA via flight demonstrations for possible integration of the technology in CAP activities.
  • Helps pilots to see and avoid other aircraft
  • Cockpit final approach and runway occupancy
  • Visual separation in VFR and MVFR conditions
  • VFR-like separation in all weather conditions
  • Real-time cockpit weather display
  • Real-time cockpit airspace display

    Efficiency

Reduced environmental impact

ADS-B technology provides a more accurate report of an aircraft's position. This allows controllers to guide aircraft into and out of crowded airspace with smaller separation standards than it was previously possible to do safely. This reduces the amount of time aircraft must spend waiting for clearances, being vectored for spacing and holding. Estimates show that this is already having a beneficial impact by reducing pollution and fuel consumption.

Traffic capacity improvement

ADS-B enables increased capacity and efficiency by supporting:
  • Better ATC traffic flow management
  • Merging and spacing
  • Self-separation or station keeping
  • Enhanced visual approaches;
  • Closely spaced parallel approaches;
  • Reduced spacing on final approach;
  • Reduced aircraft separations;
  • Enhanced operations in high altitude airspace for the incremental evolution of the "free flight" concept;
  • Surface operations in lower visibility conditions;
  • Near visual meteorological conditions capacities throughout the airspace in most weather conditions;
  • Improved air traffic control services in non-radar airspace;
  • Trajectory-based operations provide a gently ascending and descending gradient with no step-downs or holding patterns needed. This will produce optimal trajectories with each aircraft becoming one node within a system-wide information management network connecting all equipped parties in the air and on the ground. With all parties equipped with NextGen equipment, benefits will include reduced gate-to-gate travel times, increased runway utilization capacity, and increased efficiency with carbon conservation.