scope:

This standard provides:

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

b. Interoperability requirements for the B2 aircraft system to interoperate with known B1 compliant ground implementations. See paragraph 2.3.

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.

PURPOSE

By design, a Baseline 2 (B2) system is not able to communicate with a Baseline 1 (B1) system.

This document provides the additional interoperability requirements to allow backward compatibility as depicted in FIGURE 1-1 between:

• B2 ground systems and B1 aircraft systems; or

• B2 aircraft systems and B1 ground systems.

NOTE:

1. The Baseline 1 ground systems compliant with the Data Link Implementing Rule are identified in this document as "B1" systems.

2. The definition of the air (A'x') and ground (G'x') configurations identified in the figures below is provided in the ATS INTEROP document [7].