Based on the aircraft configuration, ARINC 429 Loop Back Test for LRU with ACARS interface installed is available for line maintenance examination. When Loop Back Test is initiated, prompt changes to TEST, indicating the outgoing of the loop back word, then to PASS when the same loop back is received back from the LRU or FAIL when ACARS CMU failed to receive the loop word back from the LRU.
Communication Auditing
To verify ACARS outgoing and incoming message traffic, use ACARS COMM audit screen.
This audit function sends a copy of the message traffic to the cockpit printer. With hardcopy available, user can verify that a data message is generated by CMU or received by CMU as expected.
Audit feature uses a lot of paper ! Beware to disable this function at the completion of work.
COMM Audit
Print all ACARS message activity, to and/or from the Outside World
Setting VHF or SAT AUDIT to ON enables Auditing. Auditing can be limited to only UPLINKS or DOWNLINKS and filtered to print only the selected label. Warning ! Whilst AUDIT function is very handy for troubleshooting, it uses LOTS OF PAPER ! Use this feature with care and remember to disable this audit function at the completion of work to avoid wasting paper.
Communication Statusing
To verify communication status of ACARS CMU, use ACARS COMM STATUS screen.
This screen will display the COMM/NOCOMM status of the downlink media as well as DATA/VOICE status of the media under operation.
Number of unsent downlinks queued up to go are stored in the memory buffer and will be displayed for reference.
COMM Status
Shows current communication status and number of queued message in ACARS CMU memory.
CMU Maintenance Screen (Hidden)
System Initialization is not common. CMU should obtain Airline ID from Database. CMC Programs initialization defines the generation of CMC reports and UTC/Date Initialization initializes the ACARS clock for operation via different sources.
INIT MENU
AIRLINE ID
Display AIRLINE ID INIT Screen.
CMC PROG
Display CMC PROG Screen.
UTC
Display UTC/Date INIT Screen
Airline ID INIT
Allows user to supply an airline ID manual via LSK 2L. Airline ID as defined in Database is displayed on screen for reference. Via LSK 4L, user can select ACARS CMU to operate either a manual supplied airline ID or database pre-defined airline ID. Test Frequency is for test VHF Data Comm using temporary frequency not defined in ACARS VHF Data Frequency Table.
CMC Programming
User selects to toggle between YES and NO to enable or disable the downlink of CMC reports via label 270 broadcast.
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