AMC1.ACNS.B.DLS.B1.015 Dual Data Link Capabilities (Dual stack)

ED Decision 2013/031/R

Note: A Dual stack system is either a bilingual system capable of automatically selecting the data link network or a dual system that use manual selection with an interlock system.

The data link system should comply with ED-154A, interoperability requirements IR-207, IR-209, IR-210, IR-211, IR-212, IR-214, and IR-215 to ensure seamless transition between two adjacent ATSUs, one using FANS 1/A+ and the other using ATN B1.

The data link system should demonstrate common accessibility to the FANS 1/A and ATN B1 CPDLC applications. Accessibility demonstration should include common controls (i.e. line select keys) or, where different, the potential to introduce confusion or unacceptable flight crew workload  should be evaluated.

The data link system should demonstrate common control and input procedures for retrieving and responding to FANS 1/A and ATN B1 uplink messages.

The data link system should demonstrate common control and input procedures for composing and sending FANS 1/A and ATN B1 downlink messages.

The data link system should demonstrate common flight deck indications for incoming FANS 1/A and ATN B1 messages.  Where common alerting is not demonstrable, the alerting scheme evaluate to ensure that neither confusion nor unnecessary flight crew workload is introduced.

Annunciations and indications should be clear, unambiguous, timely, and consistent with the flight deck philosophy.

FANS 1/A differentiates messages alerting between normal and Urgent. Upon receipt of a high alert CPDLC message, the data link system should indicate it to the flight crew.

Note: FANS 1/A standard (ED-100A) identifies the term ‘IMMEDIATELY’, within the phraseology standardised for CPDLC communications. This term is to be understood within the required communications performance scope (RCP), which for oceanic and remote operations is either 240 seconds or 400 seconds. The use of these terms ‘IMMEDIATELY’ and ‘EXPEDITE’ are not to be confused with the terminology used in material related to CS 25.1322. However, annunciations and indications should allow flight crews to easily identify these messages (associated with Urgent and Distress urgency attribute) among the normal messages.

Flight Deck Display of Messages from either FANS 1/A or ATN B1 CPDLC Applications: 

A common flight deck display should be capable of displaying messages with the same operational intent resulting from same message elements that may be implemented differently between FANS 1/A and ATN B1 CPDLC applications.  The common format to display FANS 1/A messages may be in accordance with the preferred format denoted in Annex A of ED 122, which is consistent with Doc 4444, 15th Ed, and ATN B1 message formats.

Dual Stack ATS Data Link System Status Indication: 

The system should provide the flight crew with a means to  clearly identify the status of different modes of the data link system that affect significant operational capability.  Examples of different modes of data link may include situations when downlink messages are available in one airspace, but not the other; or messages that may or may not be loadable depending on system status, i.e., ATN B1 or FANS 1/A.

ATSU Connections and Handoffs:

The system should be capable of the following functions:

(1)     Proper connection and termination for FANS 1/A ATSU. 

(2)     Proper connection and termination for ATN B1 ATSU.

(3)     Transfer to next data authority (e.g., FANS 1/A ATSU to ATN B1 ATSU), in both directions. This should include proper connection, maintenance of connection and connection termination protocol to ensure that aircraft does not hold two simultaneous active CPDLC connections.

(4)     Ability for flight crew to manually terminate existing connection and establish new connection, initiate a DLIC ‘logon’ in both directions (i.e., FANS 1/A-to-ATN B1 and ATN B1-to-FANS 1/A).

(5)     Ability for flight crew to verify current and next facility designation or name.

Note: FAA AC 20-140A provides adequate guidance related to the application interoperability, sub-networks and performance designators. (refer to Tables 5.1 and 5.2).