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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-CDU-6 BUS INPUT

Message Code:

B3-648371

Associated CAS:

None

Reporting LRU: VHF 1
System Description: 23-11-00
34-00-00
Schematic Diagram: 23-11-00
34-61-00
Wiring Diagram: 23-11-01
34-61-05

Message Description:

L-CDU-6 data absent at L-VHF and NOT absent at least 3-of (L-IOC, L-NAV (ADF/VIR), L-DME). Not incl: TSS, T-VHF and L-HF.

Possible Causes:

  • Left VHF Communication Unit (VHF 1)
  • Junction Box (JB3)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the VHF Communication Unit AMM 23-11-01-000-801
Installation of the VHF Communication Unit AMM 23-11-01-400-801
Removal of the Junction Box JB3 AMM 24-63-09-000-802
Installation of the Junction Box JB3 AMM 24-63-09-400-802
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 - Wire Repair SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset COM 1 (CB1-B2) circuit breaker.

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

  2. Swap VHFs (only VHF 1 and VHF 2 are interchangeable).

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

  3. Do the wiring check of the ARINC 429 databus L-CDU-6 between CDU1 connector A69P1, through Junction Box 3, to VHF 1 connector A7P1. Repair/replace as required.
  4. Do close out.

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