FAQ n.44273

What are the requirements on the GNSS source?


The requirements are described in AMC 20-24 and CS-ACNS. 

Note that:

  • Position and velocity information must come from the same source.
  • ETSO-C129A is the minimum equipage qualification in Europe. 
  • For compliance with CS-ACNS, the applicable ETSOs (C129a/196/145/146) alone does not guarantee that the unit is suitable as an ADS-B position source. Further demonstration is required (see in particular AMC1 ACNS.D.ADSB.070 and .080).
  • The System Design Assurance (SDA) parameter can be set to 2 without analysis if the GPS and ADS-B unit are both qualified (ETSO’d) and directly connected (i.e. direct wiring from GPS to receiver with no routing through other equipment). Aircraft with other architectures require a system safety analysis to set the SDA.
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