CS ACNS.D.ADSB.020 ADS-B Out Data Parameters
ED Decision 2013/031/R
(See AMC1 ACNS.D.ADSB.020(a-b))
(a) The ADS-B Out system provides the following minimum set of data parameters:
(1) Aircraft Identification;
(2) Mode A Code;
(3) ICAO 24-bit aircraft address;
(4a) Airborne Horizontal Position — Latitude and Longitude;
(4b) Airborne Navigation Integrity Category: NIC;
(4c) Airborne/Surface Navigation Accuracy Category for Position: NACp;
(4d) Airborne/Surface Source Integrity Level: SIL;
(4e) Airborne/Surface System Design Assurance: SDA;
(5) Pressure Altitude (incl. NICbaro);
(6) Special Position Identification (SPI);
(7a) Emergency Status;
(7b) Emergency Indication;
(8) 1090 ES Version Number;
(9a) Airborne velocity over Ground — (East/West and North/South);
(9b) Airborne/Surface Navigation Accuracy Category for Velocity: NACv;
(10) Emitter Category;
(11) Vertical Rate;
(12a) Surface Horizontal Position — Latitude and Longitude;
(12b) Surface Navigation Integrity Category: NIC;
(13) Surface Ground Track;
(14) Movement (surface ground speed);
(15) Length/width of Aircraft;
(16) GPS Antenna Longitudinal Offset;
(17a) Geometric Altitude; and
(17b) Geometric Altitude Quality: GVA.
(b) Where available in a suitable format, the ADS-B Out system provides the following data parameters:
(1) Selected Altitude;
(2) Barometric Pressure Setting; and
(3) ACAS Resolution Advisory.
AMC1 ACNS.D.ADSB.020(a-b) ADS-B Out data parameters
ED Decision 2013/031/R
During ADS-B Out system installation testing, all the parameters that are broadcast should be demonstrated to be correct for each installed ADS-B transmit unit, i.e. the transmitted data should be in line with the respective source data.
The Emitter Category, Aircraft Length and Width and GPS Antenna Offset parameters might be either configured as a fixed value during ADS-B Out system installation, or provided via a variable data interface. In both cases, during installation, the respective settings should be verified to be correctly set.
The ADS-B Horizontal Position System Design Assurance (SDA) parameter indicates the probability of an ADS-B Out system malfunction causing false or misleading position information or position quality metrics to be transmitted. SDA may be pre-set at installation for systems that do not utilise multiple position sources with different design assurance levels, otherwise the system should be capable of adjusting the SDA broadcast parameter to match the position source being employed at the time of transmission.
ADS-B transmit equipment that is compliant with AMC1 ACNS.D.ADSB.030 and that is directly connected to a position source compliant with AMC1 ACNS.D.ADSB.070 may set the SDA to ‘two’ without further analysis. For more complex ADS-B installations, a system safety assessment is required to set the SDA. Basically, the lowest design assurance level of one system in the horizontal position data transmission chain should define the SDA value.
Additional guidance material on the required surveillance data parameters are provided in Appendix H Part 1 and Part 2.
Appendix H Part 6 provides matrices of the so-called BDS register fields as used by the 1090 ES ADS-B transmit unit to broadcast the ADS-B Out parameters. These matrices detail the ADS-B Out data requirements at data field level for general understanding and in support of integration testing, as appropriate.
If installations transmit ADS-B Out data that do not meet some requirements of the Subpart D Section 4, the respective data should only be transmitted with a ‘zero’ quality indication (if a quality indication is defined in the ADS-B Out transmit system).
CS ACNS.D.ADSB.025 Provision of data
ED Decision 2022/008/R
(See AMC1 ACNS.D.ADSB.025(a) and (c))
(a) All data provided by the ADS-B Out system comes from approved sources.
(b) The data transmitted by the ADS-B Out system originates from the same data source as used in the transponder replies to Mode S interrogations.
(c) When a data quality indication is required, it is provided to the ADS-B transmit unit together with the associated data parameter and it expresses the actual quality of the respective data as valid at the time of applicability of the measurement.
[Issue: CS-ACNS/4]
AMC1 ACNS.D.ADSB.025(a) Provision of data — Approved sources
ED Decision 2013/031/R
(a) See AMC1 ACNS.D.ADSB.070-090 for details on the approval of the respective data sources.
(b) For transmission of optional data items, the following provisions should be considered:
(1) Airspeed
In case of a loss of GNSS horizontal velocity data, the ADS-B transmit unit normally switches to broadcast airspeed information (using subtypes 3 and 4 of register 0916).
Therefore, if airspeed data is provided to the ADS-B transmit unit, it should be provided by an approved airspeed source that is providing data intended for use by the flight crew. An air data computer meeting the minimum performance requirements of holding an EASA equipment authorisation in accordance with ETSO-C106 (JTSO-C106) is an acceptable source.
(2) Heading
In case of a loss GNSS ground track and if heading is provided to the ADS-B transmit unit, the heading source should hold an EASA equipment authorisation in accordance with ETSO-C5e (JTSO-C5e) or any revision of ETSO-C6d (JTSO-C6d).
(3) Other Data Parameters
The Intent Change Flag should be set as appropriate to indicate the availability of information in the Mode S registers 4016 to 4216.
If available, Selected Heading information should come from approved data sources.
The 1090 ES IN capability field should be set correctly.
AMC1 ACNS.D.ADSB.025(c) Provision of data – Data quality indication and associated data
ED Decision 2013/031/R
Data quality indications for the horizontal position containment bound (NIC) and horizontal position accuracy bound (NACp) should be provided to the ADS-B transmit unit together with the corresponding horizontal position information within the same data set.
Data quality indications for the horizontal position source integrity level (SIL) and system design assurance level (SDA) may be preset at installation. Systems that utilise multiple GNSS-based position sources with different design assurance levels or source integrity levels, should be capable of adjusting the SDA and SIL quality indications to match the position source that is employed at the time of transmission.
The horizontal velocity accuracy bound (NACv) and vertical geometric altitude accuracy bound (GVA) should be dynamically provided to the ADS-B transmit unit together with the corresponding velocity and geometric altitude information within the same data set. However, NACv and GVA may be also preset at installation.
For further guidance on the ADS-B data quality indicators, refer to AMC1 ACNS.D.ADSB.070(a).