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WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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06/22/21

Message Overview:

Message Name:

ACARS DMU FAIL ON FMS CDU

Message Code: 232OBS001
Effectivity: All
System: Airborne Data Link System
System Description: 23-23-00
Schematic Diagram: 23-23-00 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wiring Diagram: 23-23-01 [ Global Express ]  [ G5000 ]  [ Global XRS ]
23-23-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Message Description:

The ACARS DMU FAIL message shows on the Flight Management System Control Display Unit (FMS CDU) when the Integrated Avionics Computer (IAC)/FMS does not receive the correct health status from Airborne Data Link Unit (ADLU) on the ARINC 429 bus.

Possible Causes:

  • Airborne Data Link Unit (ADLU) (A239)
  • Secondary Power Distribution Assembly (SPDA) 4 (A16)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

Forum Articles/Infoservice/Newsletter: None

NOTE 1: If the A/C has implemented the IAC Batch 3.3 software and is now experiencing an intermittent ACARS DMU FAIL Message on the FMS CDU, please make sure to review the content of AW700-31-0563 and fill out the questionnaire before attempting any troubleshooting.

NOTE 2: Resetting the DATALINK circuit breaker via the EMS CDU (Electrical Management System Control Display Unit) may clear the active fault.

Quick Links:

Operational Test of the Data Link System AMM 23-23-00-710-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Removal of the Airborne Data-Link Unit AMM 23-23-01-000-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Installation of the Airborne Data-Link Unit AMM 23-23-01-400-801 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Access to Active Faults AMM 45-45-00-970-802 [ Global Express ]  [ G5000 ]  [ Global XRS ]
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02 [ Global Express ]  [ G5000 ]  [ Global XRS ]

Troubleshooting Recommendations:

  1. Reset the DATALINK circuit breaker via the EMS CDU.
  2. Does the message ACARS DMU FAIL continues to show on the FMS CDU?

    1. If YES, go to step 5.
    2. If NO, continue with next step.D

  3. On the CAIMS PMAT find and record the related active/stored faults. Check faults listed under ATA 23-20 AIRBORNE DATA LINK UNIT. Refer to AMM 45-45-00-970-802. Did you record any fault messages in CAIMS (Active or Stored)?

    1. If YES, go to the applicable troubleshooting by CAIMS fault codes and do close out.
    2. If NO, continue with next step.

  4. Perform the operational test of the Airborne Data Link System (Refer to AMM 23-23-00-710-801) and do close out. Monitor ADLS within next few flights.

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

  5. Perform a power check for the airborne data-link unit (ADLU). On the connector A239CP1, check if there is +28 VDC as follows:

    From To Expected Result Result
    A239CP1-2 A239CP1-4 28 VDC

    1. If there is +28 VDC, go to step 7.
    2. If there is no +28 VDC, continue with next step.

  6. Repair or replace the defective wiring between the ADLU and the SPDA 4. Is the fault still present?

    1. If NO, perform the fault isolation for the SPDA 4 and do close out.
    2. If YES, continue with next step.

  7. Perform a wiring check between the ADLU and the FMS CDUs and between the ADLU and the IACs (FMS). Refer to wiring diagram manual WM 23-23-00. Is the wiring checks satisfactory?

    1. If YES, go to step 9.
    2. If NO, repair or replace the defective wiring as required and continue with next step.

  8. Perform the operational test of the Airborne Data Link System (Refer to AMM 23-23-00-710-801).

    1. If system checks are good, do close out.
    2. If fault remains, continue with next step.

  9. Replace the Airborne DATALINK Unit (ADLU).
  10. Do close out. Monitor ADLS within next few flights.

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