Description / Abstract: This standard provides:

a. Interoperability requirements for the B2 ground systems to interoperate with known B1 compliant airborne implementations. See paragraph 2.1

b. Interoperability requirements for the B2 aircraft system to interoperate with known B1 compliant ground implementations. See paragraph 2.4.

Note: This standard provides a separated set of requirements for each of these two capabilities, which can be implemented and qualified independently.

This standard defines the backward compatibility interoperability requirements on air and ground systems compliant with the ATS Interoperability Standard [7] in order to support the CDR, IER, ACM and AMC services when talking to B1 ground and air implementations.

Backward requirements are defined to permit as much as possible uplink messages supported by B2 ground systems but not implemented by B1 aircraft to be sent as free text messages or equivalent messages.

Note:

1. No backward compatibility requirements are defined for D-TAXI, ITP, OCL, DCL CPDLC services and ADS-C services. These B2 services are never provided to or by B1 systems.

2. No backward compatibility requirements are defined for CM. The B1 and B2 CM applications are fully compatible.

This document (EUROCAE ED-231A / RTCA DO-353A) supersedes EUROCAE ED- 231 / RTCA DO-353.