The intents of CS-ACNS and AMC 20-24 are different. The former provides the means to comply with the rules set forth in the Commission Implementing Regulation (EU) No 1207/2011 (amended by (EU) No 1028/2014) (‘SPI regulation’) and supports applications where the ADS-B could be used to replace Radar (RAD) applications with a 3 Nm separation between aircraft. The latter is intended to support Non-Radar Areas (NRA) applications, with a 5 Nm separation and less stringent integrity and continuity needs.
For certification of ADS-B installations, CS-ACNS applies to aircraft with a maximum certified take-off mass exceeding 5700 kg or having a maximum cruising true airspeed capability greater than 250 knots.
Compliance to CS-ACNS (including book 2) has to be demonstrated for the initial airworthiness and changes to those aircraft. For a new TC, CS-ACNS is expected to be part of the certification basis.
For other aircraft, the applicant may elect to use AMC 20-24 instead of CS-ACNS.