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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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03/10/21

Message Overview:

Message Name:

L-ADC DATA SOURCE FAULT

Message Code:

B3-279873

Associated CAS:

None

Reporting LRU: DCU2
System Description: 31-41-00
31-45-00
34-13-00
Schematic Diagram: 31-41-00
31-45-00
34-13-00
Wiring Diagram: 31-41-11
31-41-13
31-45-01
34-13-01

Message Description:

Data Concentrator Unit (DCU) channel B indicates it is missing computed air speed from the Left Air Data Computer (ADC), while L-ADC bus is present at the Left Input/Output Concentrator (IOC) and the L-GP-5 bus is not reported inoperative by DCU channel B.

Possible Causes:

  • Left Air Data Computer 1 (ADC) (A1)
  • Left Input/Output Concentrator 1 (IOC) (A4-IOC1)
  • Data Concentrator Unit (DCU) (A14)

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Data Concentrator Unit (DCU) AMM 31-41-01-000-802
Installation of the Data Concentrator Unit (DCU) AMM 31-41-01-400-802
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 Air Data Computer AMM 34-13-01-000-801
Installation of the Air Data Computer AMM 34-13-01-400-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02
Electrical Connectors - Maintenance Practice - ALL SPM 20-20-00-02

Troubleshooting Recommendations:

  1. Reset EICAS DCU B Circuit Breaker CB2-D1, R IAPS Circuit Breaker CB2-B6 and AIR DATA 1 Circuit Breaker CB1-C1. Is the fault message still present?

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

  2. Check in the Maintenance Diagnostic Computer (MDC) in ATA 34 for fault related to the Left ADC.

    1. If other fault is posted, do the respective troubleshooting.
    2. If no other fault is posted, continue with next step.

  3. Swap R IOC with L IOC. Is the fault message still present\?

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

  4. Replace DCU (A14).
  5. Do close out.

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