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Technology Overview |
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Technology Overview |
The following sections describe the ADS-B and Broadcast Service functional capabilities currently being deployed in the National Airspace System (NAS).
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System Functional Architecture
ADS-B is an aircraft-based surveillance service being deployed in selected areas of the NAS. This underlying technology broadcasts a radio transmission approximately once-per-second from the aircraft containing its position, velocity, identification, and other pertinent information. ADS-B can also receive reports from other suitably equipped aircraft within reception range. No ground infrastructure is necessary for ADS-B equipped aircraft to detect each other. These reports can be transmitted to ground based transceivers (GBTs) and used to provide air traffic surveillance services and fleet operator monitoring of aircraft.
[Top][ADS-B][TIS-B][FIS-B][Flight Monitoring][Avionics]
The TIS-B service is intended to improve the pilot’s ability to visually see other traffic in the air and on the airport surface so that pilots can more effectively apply traditional “see-and-avoid” techniques.
TIS-B is NOT intended to be used as a collision avoidance system and does NOT relieve the pilot of responsibility to "see-and-avoid" other aircraft. (See Aeronautical Information Manual, Paragraph 5-5-8, “See and Avoid”). TIS-B shall not be used for avoidance maneuvers during times when there is no visual contact with the intruding aircraft. No avoidance maneuvers are provided for, nor authorized, as a direct result of a TIS-B target being displayed in the cockpit.
TIS-B is a ground-based broadcast service that provides secondary surveillance radar (SSR)-derived traffic data. Messages are uplinked over the ADS-B data link system to the aircraft. This is a different technology than is used for Traffic Information Service (TIS), which relies solely on Mode S terminal radars. The TIS-B service is intended to provide ADS-B equipped aircraft with a more complete traffic picture in situations where all other nearby aircraft are not equipped with ADS-B.
Only conventional Mode C and Mode S transponder-equipped targets reporting their barometric altitude will be included in a TIS-B broadcast. This means most Mode C and Mode S transponders with altitude encoders that are within sight of both nearby radars and GBTs will be shown on the receiving aircraft’s Cockpit Display of Traffic Information (CDTI). Aircraft that have Mode-A transponders (i.e., transponders without altitude reporting capability) and aircraft without transponders will not be displayed on the receiving aircraft’s CDTI.
Receiving aircraft must be in both radar coverage and GBT coverage in a given area to receive TIS-B service in that area. To reduce display clutter, the TIS-B service is only providing traffic information below 18,000 feet.
Updates of TIS-B traffic will occur less often than ADS-B updates because the update rates for SSRs are approximately once every five to twelve seconds, compared to the once-per-second update rate available with ADS-B.
There may be, on occasion, “shadowing” or “ghosting” observed of either one’s own ship symbol or another depicted target aircraft on the CDTI. This may be caused by the ADS-B-to-SSR target association process within the ground system. This can result in duplicate targets for equipped or receiving aircraft. This phenomenon may be minimized by standardized filtering software implemented into the aircraft avionics. Some pilots are making productive use of this capability to confirm that their encoder/transponder combination is transmitting their correct altitude.
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FIS-B is the ground-to-air broadcast service of weather and other non-control, aeronautical information that allows pilots to operate more safely and efficiently. FIS-B products can be textually or graphically depicted.
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ADS-B data can be used for flight monitoring, flight management, surface traffic airline asset management, and other safety and efficiency purposes contingent upon appropriate FAA authorization and approvals. Please review the FAA's Phase I policy guidance (pdf) on Flight Monitoring.
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There are two basic aircraft equipage data link configurations that provide ADS-B capabilities:
1) Transmit-only systems
2) Combined transmit and receive systems.
Users that desire only to be “seen” by other aircraft or ground stations may elect to equip with the transmit-only capability system, a less expensive solution. A transmit-only configuration does not have provisions for a CDTI or the ability to receive and display up linked broadcast services. For a transmit-only ADS-B system, two main avionics components are required:
1090 Extended Squitter (1090ES) or UAT data link transmitter, and
A GPS receiver or another suitable position source able to provide the aircraft’s ADS-B transmit system with “own-ship” position with suitable integrity and other Message Set Elements (MSEs) for transmission over the selected data link transmitter.
In a combined ADS-B transmit and receive system, there are three main avionics components required:
1090ES or UAT data link transceiver
A Global Positioning System receiver (or other position source) that provides one’s “own-ship” position with suitable data integrity, plus other MSEs, and
A single or multifunction display and processing system for managing and displaying the broadcast data. CDTIs can be installed in the instrument panel or be portable, depending upon the specific aircraft equipage implementation and/or aircraft certification basis.
For the purpose of FAA operational approval authorization, aircraft that do not have an installed CDTI or that do not have a data link modem certified to either TSO C-154 (UAT) or TSO C-166 (1090ES) do not fall under the umbrella of those aircraft equipped with surveillance systems that require operational approval. First generation 1090ES systems that were certified under TSO C-112A may not be used for any ground-based surveillance function except the flight monitoring function, unless the equipment has been shown to function satisfactorily in the NAS.
ADS-B avionics systems need to be properly installed and maintained. This is called continued airworthiness. Follow the manufacturer’s recommendations to ensure initial and continued airworthiness. Care should be given to ensure that all components are specifically approved for installation in the particular make / model aircraft. Maintenance programs should identify inspection items, establish in-service intervals for maintenance and inspections, and include any calibration procedures necessary to ensure continued airworthiness. [full continued airworthiness guidance document]