Chapter 8. Communication equipment

8.6. Automatic Dependent Surveillance ADS-B

The concept of Automatic Dependent Surveillance - Broadcast (ADS-B) began to be implemented from 2005 in the EU member FAA and Eurocontrol (fig. 123) [80, p. 13].

ADS-B equipment allows pilots and controllers to obtain information about the ATS air traffic around the aircraft via the display, like a radar display. This information is provided in real-time. The accuracy of the location in the aircraft system is provided by GNSS. In addition, these systems allow the pilot to have access to meteorological data, geodetic and cartographic data and Flight Information Services (FIS). Increased awareness of the pilot in the air situation around the aircraft, based on accurate data allows you to keep a safe distance between your aircraft and reduce the workload air traffic controllers of ATS.

ADS-B components

The main components of the concept of ADS-B are:

  • automatic. Periodic transmission of information from the aircraft without the knowledge of the pilot;
  • dependent. Location of the aircraft and velocity vector is determined using GNSS network and functional additions EGNOS, WAAS, which increase positioning accuracy;
  • surveillance. It provides each users location information, altitude, speed, course and other data of flight;
  • broadcast. Information from the aircraft transmitted in all directions and anyone can get it.

ADS-B concept

The concept of ADS-B put the possibility of determining location using satellite navigation systems. To improve the accuracy GNSS positioning is proposed to use the station differential corrections WAAS [60; 89] and EGNOS. This requires the deployment of a network of ground stations. The resulting aircraft location coordinates with other information about the aircraft passed through one of the digital data transmission standards. Ground the radio receives and transmits them via terrestrial digital data network dispatcher and all those who need it. In addition, other aircraft also take this data and display them in a special display for the pilot (fig. 124).

Fig. 124. Operation of ADS-B

To display the aircraft that are not equipped with transmitters ADS B, mapping services offered air traffic based on data from the secondary radar (Traffic Information Service – Broadcast – TIS-B) [61]. That location information received from the aircraft radar using a special digital channel data transmitted on board all aircrafts equipped with components of ADS-B and displayed to the pilot (fig. 125).

Fig. 125. Display data from TIS-B [61]

The use of ADS-B concept closely related to the services provided by Flight Information Service – Broadcast (FIS-B). FIS-B provides transfer any graphical weather information, aeronautical maps and other graphic information on board in broadcast mode (fig. 126).

Fig. 126. Display data from FIS-B [61]

ADS-B advantages

The main advantages of ADS-B is:

  • Low maintenance cost compared to systems providing radar coverage area;
  • High accuracy of the location of the aircraft;
  • Reliability, which is achieved through data in digital form;
  • The possibility of improving and increasing functionality.

The primary means of transmitting information from the aircraft in accordance with the concept of ADS-B is the use of Mode-S and specialized protocol data 1090 ES (Extended Squitter) at frequencies 1090/1030 MHz. In addition, alternative channel data can be provided Universal Access Transceiver (UAT) at a frequency of 978 MHz or equipment VDL Mode 4, which has a large number of operating frequencies in the range of VHF. Concomitant use 1090 ES and VDL Mode 4 ensures high throughput and high information security pilots.

Under the concept of ADS-B aircraft must each contain a modified airplane mode «S», providing message transmission mode 1090 ES. An example of this is the on-board equipment module data in digital form (Air Transport Data Link - ATDL) XS-950 company ACSS.

Basic requirements for the data in ADS-B concept outlined in the documents: – Mode S 1090ES – DO-260B, TSO-166b; – UAT – DO-282B, TSO-154c.

ADS-B Data

Typical information ADS-B message shall contain the information [82]:

  • The geometric dimensions of the plane (m);
  • Aircraft location (latitude and longitude system WGS-84);
  • Barometric altitude (coding scale 25 feet);
  • Speed (m / s);
  • Availability of TCAS on board ("Yes" or "No");
  • There is a message from the RA systems TCAS («Yes" or "No");
  • ATC code aircraft defendant;
  • Number of aircraft call sign;
  • The existence of an emergency (alerts when an emergency on board);
  • IDENT (message identifier aircraft defendant);
  • ICAO aircraft number (24-bit number of aircraft issued by ICAO);
  • Aircraft type (light aircraft category);
  • ID presence on board equipment receiving data ADS-B («Yes" or "No");
  • Geometric altitude (altitude encoding system WGS-84).

Avionics equipment [33] required in accordance with the concept of ADS-B, can have a different configuration depending on their functions. In general, the structure of on-board equipment ADS-B may have the form shown in Fig. 127.

Fig. 127. The typical structure of onboard equipment ADS-B concept

Navigation equipment is a source of information on the location of the aircraft in space and speed, and GNSS equipment and IRU - coordinate information.

Equipment and receiving data collecting and coding information required to build message ADS-B. The resulting information message is emitted through the top and bottom of the antenna system. In addition, this unit can run function receiving and decoding incoming ADS-B.

Equipment data display is optional. If onboard receiver signal ADS-B aircraft neighboring location can be displayed on a map along with the underlying surface navigation elements through electronic display.

Message ADS-B accepted not only airborne and ground aircraft. In particular international firms Airnav and Kinetic avionics developed and offer Radio amateur receiver signal ADS-B, which give the decoded message from ADS-B aircraft. Especially popular is the use of equipment in the aircraft flight simulator users. The spread of such equipment in the population contributed to the amateur aeronautical information networks [63; 64; 107]. At present these open computer network covering the entire airspace and allow you to track the movement of aircraft globally in real time, which is a threat to the safety of air traffic.

AVIONICS training course materials represented only in demonstrative mode. If it useful, all grammar mistakes will be corrected and more documents will be added. Let me know if you interest in avionics.
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Avionics training in details by
Ostroumov IvanOSTROUMOV Ivan, PhD
Associate Professor, www.ostroumov.sciary.com