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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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03/30/21

Message Overview:

Message Name:

NO L-FMC-3 BUS TO L-CDU

Message Code:

B3-230869

Associated CAS:

None

Reporting LRU: FMC 1
System Description: 34-61-00
Schematic Diagram: 34-61-00
Wiring Diagram: 31-45-01
34-61-03

Message Description:

L-FMC-3 data bus not received at L-CDU.

Possible Causes:

  • Left Flight Management Computer 1 (FMC) (A4-FMC)
  • Left Control Display Unit 1 (CDU) (A69)
  • 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:

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 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
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Repair Wiring SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset L IAPS circuit breaker CB1-B6 and CDU 1 circuit breaker CB1-A4. Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

  2. Do wiring check between IAPS (A4) and CDU 1 (A69) for the following wires:

    From To Result
    Conn. A4P1 - 29 Conn. A69P1 - 61
    Conn. A4P1 - 28 Conn. A69P1 - 62

    1. If the check is satisfactory, continue with next step.
    2. If the check is not satisfactory, repair defective wire.

  3. Swap FMC 1 with FMC 2. Is the fault message still present\?

    1. If YES, continue with next step.
    2. If NO, replace defective FMC.

  4. Swap CDU 1 (A69) with CDU 2 (A68). Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, replace defective CDU.

  5. Replace IAPS Card Cage (A4).
  6. Do close out.

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