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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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02/26/21

Message Overview:

Message Name:

NO HSTECU-1 BUS TO L-IOC

Message Code:

B3-006861

Associated CAS:

STAB TRIM FAULT
(Advisory)

Reporting LRU: HORIZ TRIM ECU
System Description: 27-41-00
Schematic Diagram: 27-41-00
31-45-00
Wiring Diagram: 27-41-21

Message Description:

Left Input/Output Concentrator (L-IOC) is not receiving data from the Horizontal Stabilizer Electronic Control Unit (HSTECU) over the HSTECU-1 bus.

Possible Causes:

  • Left Input/Output Concentrator (IOC) (A4-IOC1)
  • Right Input/Output Concentrator (IOC) (A4-IOC2)
  • Horizontal Stabilizer Trim Electronic Control Unit (HST ECU) (A130)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

  • AW300-27-0081 - Spoiler Electronic Control Unit (SECU) and Horizontal Stabilizer Electronic Control Unit (HSTECU) - Cold Temperature Circuit Breaker Reset Procedure (20501 - 20999)

Forum Articles/Infoservice/Newsletter: None

Perform the AW300-27-0081 reset procedure for the HST ECU if the message is displayed during initial power-up in cold temperature. The stab trim position indication on EICAS can also flash on and off.

Quick Links:

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 Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) AMM 27-41-21-000-801
Installation of the Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) AMM 27-41-21-400-801
Operational Test of the Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) AMM 27-41-21-710-801
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
Operational Test of the Input/Output Concentrator Unit (IOC) AMM 31-45-05-710-801
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. Pull the HST ECU breaker CB1 - B15 and breaker CB2 - B13, reset after a couple seconds. This will re-boot the HST ECU.

    1. If fault is cleared after latency check has been completed, 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. Perform wiring check between IAPS (L IOC) and HST ECU.

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

  4. Replace HST ECU.
  5. Do close out.

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