AMC1 ACNS.D.ELS.015 Data transmission

Data transmission verifications

(a)     Table 1 below provides the parameters that should be verified for Mode S elementary surveillance.

Table 1 — List of parameters to be verified on an ELS installation

Note 1: Information about how Mode S ELS data is used by Mode S ground systems can be found in Subpart D, Appendix B.

Note 2: Downlink formats (DFs) are defined in ICAO Annex 10, Volume IV and EUROCAE ED-73E. A summary can also be found in Subpart D, Appendix B.

Note 3: It is not recommended to have 2 transponders installed without a common control panel.

(b)     Pressure Altitude

(1)     The consistency of the altitude reported in Mode C replies and Mode S replies should be checked.

Note: An incorrect installation of altimeters using Gillham encoding may result in altitude transmitted in Mode C replies and no altitude transmitted in Mode S replies.

(2)     For aircraft transmitting parameters via the Extended Squitter, for which compliance with Subpart D section 4 is not required, the pressure altitude data should be checked in the Extended Squitter register for airborne position (register 05₁₆).

(c)      Pressure altitude resolution transmission

(1)     The resolution of the transmitted pressure altitude should be 7.62 m (25 ft) for aircraft equipped with a pressure altitude source having a resolution better than 7.62 m (25 ft) for all altitudes except those above 15 298 m (50 187.5 ft).

(2)     Aircraft equipped with altimeters that have a resolution greater than 7.62 m (25 ft) (e.g. 30.48 m (100 ft)) should report their altitude in 30.48 m (100 ft) encoding.

(3)     Verify that the encoding of the altitude is appropriate to the altimeter resolution as defined in paragraphs 1 and 2 above.

(4)     For aircraft transmitting parameters via the Extended Squitter, for which compliance with Subpart D section 4 is not required, the pressure altitude resolution data should be checked in the Extended Squitter register for airborne position (register 05₁₆).

(d)     Aircraft Identification

(1)     For aircraft transmitting parameters via the Extended Squitter, for which compliance with Subpart D section 4 is not required, the Aircraft Identification received via the Extended Squitter should be checked to ensure that it is identical to the information transmitted in register 20₁₆.

(e)     Special Position Indication (SPI)

The FS field should report FS = 4 or 5 for 18 seconds (+/-1 second) in replies DF4, DF5, DF20 or DF21 after the SPI (IDENT) has been manually activated.

Note: Flight Status values can be found in ICAO Annex 10, Vol IV, paragraph 3.1.2.6.5.1.

(f)      ACAS active Resolution Advisory report

For aircraft that have ACAS II installed, no undue RA report should be announced (DR field never set to 2, 3, 6 or 7) within (5 minutes).

(g)     Common usage GICB capability report: BDS 17₁₆ = 0 is an acceptable means of compliance for transponders that are strictly ELS (not transmitting other parameters).

(h)     Transmission of other parameters

When one or more other airborne data items are transmitted, they should be verified as proposed in AMC1 ACNS.D.EHS.015.

Note 1: The minimum data transmission verification of transponder also having ADS-B ES capabilities has been defined above. Transponders that are transmitting parameters other than the minimum tested above, are encouraged to demonstrate compliance with Subpart D section 4.

Note 2: The implementation of registers E3₁₆, E4₁₆, E5₁₆ and E6₁₆ is recommended.

[Issue: CS-ACNS/4]