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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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03/31/21

Message Overview:

Message Name:

NO L-IRS-1 BUS OUTPUT

Message Code:

B3-539777

Associated CAS:

None

Reporting LRU: IRS 1
System Description: 34-00-00
Schematic Diagram: 34-45-00
Wiring Diagram: 34-45-05

Message Description:

No L-IRS-1 data received at (L-IOC and SPC).

Possible Causes:

  • Inertial Reference Unit (IRU) No. 1 (A233)
  • Junction Box (JB1)
  • Stall Protection Computer (SPC) (A178)
  • Left Input/Output Concentrator Unit (IOC) (A4-IOC1)
  • 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 Junction Box JB1 AMM 24-63-01-000-802
Installation of the Junction Box JB1 AMM 24-63-01-400-802
Removal of the Stall Protection Computer AMM 27-32-01-000-801
Installation of the Stall Protection Computer AMM 27-32-01-400-801
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 Inertial Reference Unit (IRU) AMM 34-45-01-000-801
Installation of the Inertial Reference Unit (IRU) AMM 34-45-01-400-801
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Repair Wiring SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset IRU 1 (CB1-C2) circuit breaker.

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

  2. Swap IRUs.

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

  3. Do wiring check of the ARINC 429 data bus L-IRS-1 from IRU 1 connector A233P1, Junction Box #1, SPC connector A178AP1 and IAPS connector A4P1. 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.

  4. Swap IOCs.

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

  5. Replace Stall Protection Computer (SPC).

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

  6. Replace IAPS Card Cage (ICC).
  7. Do close out.

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