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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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05/10/21

Message Overview:

Message Name:

NO FIREX-1 BUS TO DCU

Message Code:

B3-006746

Associated CAS:

FIRE SYS FAULT
(Caution)

Reporting LRU: FIREX CTRL UNIT
System Description: 26-00-00
Schematic Diagram: 26-11-00
Wiring Diagram: 26-21-13

Message Description:

FIREX-1 BUS is missing at both DCU channels.

Possible Causes:

  • Fire-Detection-and-Extinguishing (FIREX) Control-Unit (A91)
  • Data Concentrator Unit (DCU) (A14)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

  • AW300-26-0249 - Landing GEAR BAY DET FAIL EICAS Message (20501 - 20999)

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Fire-Detection-and-Extinguishing (FIREX) Control-Unit AMM 26-11-01-000-801
Installation of the Fire-Detection-and-Extinguishing (FIREX) Control-Unit AMM 26-11-01-400-801
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
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset FIREX Control Unit (A91) circuit breakers CB1-A11, CB2-A11, CB5-A3 and CB6-A4. Is the fault message still present?

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

  2. Access the MDC and navigate to the Detailed Diagnostic Data. Check that Label 357 bit 21 displays valid data.

    1. If YES & fault is not posted do close out.
    2. If NO continue with next step.

  3. Do wiring check of the following wires:

    From To Results
    FIREX conn. A91P2 - 58 DCU conn. A14EP1 - 5A
    FIREX conn. A91P2 - 52 DCU conn. A14EP1 - 5B

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

  4. Replace FIREX Control Unit (A91). Is the fault message still present?

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

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

300_2611_004

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