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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
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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02/24/21

Message Overview:

Message Name:

NO L-RIU-12 BUS OUTPUT

Message Code:

B3-648648

Associated CAS:

None

Reporting LRU: RIU 1
System Description: 23-51-00
Schematic Diagram: 23-51-00
Wiring Diagram: 23-51-21
23-51-27

Message Description:

L-RIU-12 bus absent at R-IOC and R-CDU and R FMC. L-RIU-11 bus is present at L-IOC.

Possible Causes:

  • Left Radio Interface Unit (RIU) (A17)
  • Connector Plug 2000
  • Right Control Display Unit (CDU)
  • Right Input/Output Concentrator Unit (IOC) (A4-IOC2)
  • Right Flight Management Computer (FMC) (A4-FMC2)
  • Right File Server Unit (FSU) (A222)
  • Integrated-Avionics Processor System (IAPS) Card Cage (ICC) (A4)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Troubleshooting Recommendations:

  1. Reset RIU 1A (CB1-B5) and RIU 1B/AURAL (CB1-B4) circuit breaker.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  2. Do the wiring check of the ARINC 429 data bus L-RIU-11 between RIU 1 connector A17P2, through Connector J2000, to the right CDU connector A68P1, to the right FSU connector A222P1 and to the IAPS connectors A4P103 (R FMC input) & A4P101 (R-IOC input). Repair/replace as required.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.
      NOTE: An internal short of any LRUs connected to this data bus might cause this failure.

  3. Swap FMCs.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  4. Swap IOCs.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  5. Swap CDUs.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  6. Swap FSUs.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  7. Replace the left RIU.

    1. If system check passes, do close out.
    2. If fault remains, continue with next step.

  8. Replace ICC.
  9. Do close out.

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Removal of the Radio Interface Unit (RIU) AMM 23-51-21-000-801
Installation of the Radio Interface Unit (RIU) AMM 23-51-21-400-801
Removal of the Junction Box 1 AMM 24-63-01-000-802
Installation of the Junction Box 1 AMM 24-63-01-400-802
Removal of the Integrated Avionics Processor System (IAPS) Card Cage (ICC) AMM 31-45-01-000-801
Installation of the Integrated Avionics Processor System (IAPS) Card Cage (ICC) AMM 31-45-01-400-801
Removal of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-000-801
Installation of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-400-801
Removal of the Flight Management Computer (FMC) AMM 34-61-01-000-801
Installation of the Flight Management Computer (FMC) AMM 34-61-01-400-801
Removal of the Control Display Unit (CDU) AMM 34-61-05-000-801
Installation of the Control Display Unit (CDU) AMM 34-61-05-400-801
Removal of the File Server Unit (FSU) AMM 46-21-01-000-801
Installation of the File Server Unit (FSU) AMM 46-21-01-400-801
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Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02
Electrical Connectors - Maintenance Practice - ALL SPM 20-20-00-02