AMC1 ACNS.D.ADSB.080 Data sources as defined by Mode S elementary and enhanced surveillance

(a)     General requirements

For the requirements and general guidance on the data sources providing the Mode S elementary and enhanced surveillance parameters, the following references to CS ACNS.D.ELS and CS ACNS.D.EHS apply:

(1)     Aircraft Identification: CS ACNS.D.ELS.030(a)(3);

(2)     Mode A Code: CS ACNS.D.ELS.030(a)(1);

(3)     SPI: CS ACNS.D.ELS.030(a)(2);

(4)     Emergency Mode/Status: CS ACNS.D.ELS.030(a)(1);

(5)     Pressure Altitude: CS ACNS.D.ELS.025;

(6)     MCP/FCU Selected Altitude: AMC1 ACNS.D.EHS.015(c)(1);

(7)     Barometric Pressure Setting:AMC1 ACNS.D.EHS.015(c)(3);

(8)     ACAS Operational/Resolution Advisory: AMC1 ACNS.D.ELS.015; and

(9)     ICAO 24 bit Address: CS ACNS.D.ELS.050.

(b)     Emergency Status

When transmitting the Mode A emergency status codes, the additional specific bits should be set (see Appendix H, Part 1, Definition 10).

(c)      Pressure Altitude — NICbaro

For aircraft with an approved, non-Gillham altitude source, the Barometric Altitude Integrity Code ‘NICbaro’ should be set to ‘one’.

For aircraft where the pressure altitude that is based on a Gillham coded input that has not been cross-checked against another source of pressure altitude, the ‘NICbaro’ should be set to ‘zero’. Otherwise, the ‘NICbaro’ should be set to ‘one’.

For general guidance on the ADS-B ‘NICbaro’ indicator that is associated with Pressure Altitude information, refer to Appendix H, Part 1, Definition 9.

(d)     Vertical Rate

The Vertical Rate information should come from the most accurate and steady source.

In order to ensure that minimum performance requirements are met for Vertical Rate information, the following source prioritisation should be applied:

—          Hybrid Vertical Rate Source: the information may be taken from a hybrid system which filters barometric vertical rate with an inertial reference unit (IRU) vertical rate and GNSS vertical rate, provided the accuracy of the vertical rate output is at least as good as barometric vertical rate sources (e.g. ETSO-C106).

—          Blended Vertical Rate Source: the information may be taken from a blended system which filters IRU vertical rate and barometric vertical rate, provided the accuracy of the vertical rate output t is at least as good as barometric vertical rate sources (e.g. ETSO-C106).

—          Barometric Vertical Rate Source: the information may be taken from an air data computer (ADC) holding an EASA equipment authorisation in accordance with ETSO-C106 or a vertical velocity instrument holding an EASA equipment authorisation in accordance with applicable revisions of ETSO-C8().

—          GNSS Vertical Rate Source: GNSS vertical velocity equipment which have not been qualified in accordance with CS ACNS.D.ADSB.070 should not be interfaced with the ADS‑B transmit unit.

Vertical Rate from an inertial sensor that is not blended with barometric altitude should not be transmitted. Neither should ADS-B transmit units derive a barometric altitude rate by sampling barometric altitude measurements.

The source bit for vertical rate (1090 ES register 09₁₆, message bit ‘36’) should be coded as barometric when utilising barometric rate from an air data computer, or when using a blended or hybrid vertical rate. The source bit for vertical rate should only be coded as geometric when using vertical rate from a GNSS source.

Note: due to differences in the respective transmit formats, the above source prioritisation differs in some parts with the guidance applicable to Mode S Enhanced Surveillance as provided in AMC1 ACNS.D.EHS.015.

For general guidance on Vertical Rate data sources, refer to Appendix H, Part 1, Definition 14.

(e)     Selected altitude (and related modes)

With respect to the various status and mode fields contained in Register 6216 (Subtype 1), the respective provisions of AMC1 ACNS.D.EHS.015(c)(1) apply to the ‘Selected Altitude Type’, ‘Status of MCP/FCU Mode Bits’, ‘VNAV Mode Engaged’, ‘Altitude Hold Mode’, and ‘Approach Mode’ information.

The population of the additional Autopilot Engaged and LNAV Mode Engaged fields status bits are optional but should be populated where the data is available.

[Issue: CS-ACNS/4]