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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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04/02/21

Message Overview:

Message Name:

NO RALT-1 BUS OUTPUT

Message Code:

B3-648324

Associated CAS:

None

Reporting LRU: RAD ALT 4000
System Description: 34-44-00
Schematic Diagram: 34-44-00
Wiring Diagram: 34-44-01

Message Description:

RALT-1 bus data absent at L-IOC.

Possible Causes:

  • Radio Altimeter Transceiver (RAD ALT-4000) (A32)
  • Input/Output Concentrator Unit 1 (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 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 Radio Altimeter Transceiver AMM 34-44-01-000-801
Installation of the Radio Altimeter Transceiver AMM 34-44-01-400-801
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Repair Wiring SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset RALT (CB1-A7) circuit breaker.

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

  2. Swap IOCs.

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

  3. Do a wiring check of the data bus RALT-1 between Radio Altimeter receiver connector A32P1 and the IAPS connector A4P1. Repair/replace as required.

    1. If system checks are good, 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. Replace Radio Altimeter Transceiver.

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

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

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