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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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06/10/25

Message Overview:

Message Name:

RELAY FAILED

Message Code:

B3-006884

Associated CAS:

SEC STAB TRIM FAIL
(Caution)

Reporting LRU: HST ENGAGE RELY2
System Description: 27-41-00 -  Pitch Trim System
Schematic Diagram: 27-41-00 -  Pitch Trim System
Wiring Diagram: 27-41-03 -  Pitch Trim System

Message Description:

The Horizontal Stabilizer Electronic Control Unit (HST ECU) has detected a Secondary Engage Relay fault.

NOTE: Consequently the failures described above will trigger in the MDC the corresponding Label 352 bit 22.

Possible Causes:

  • DC Power Center (DCPC) Relay (RH) (K45)
  • Horizontal-Stabilizer-Trim Electronic-Control Unit (HST ECU) (A130)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

Quick Links:

Standard Aircraft Configuration for Maintenance AMM 12-00-00-867-803
Electrical/Electronic Safety Precautions AMM 24-00-00-910-801
Electrostatic-Discharge Safety Precautions AMM 24-00-00-910-802
Connect Electrical Power to the Aircraft AMM 24-00-00-861-801
Removal of the DC Power-Center Relays AMM 24-61-81-000-801
Installation of the DC Power-Center Relays AMM 24-61-81-400-801
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

Troubleshooting Recommendations:

  1. Pull the circuit breakers that follow and reset after a few seconds:

    PRI STAB TRIM/RUD LIM CB1 - B15
    SEC STAB TRIM/RUD LIM CB2 - B13
    PRI STAB MOTOR LCDPC - A4
    SEC STAB MOTOR RDCPC - A5

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

  2. Interchange engage Relays K45 with K44.

    1. If fault transfer to PRI, replace defective relay, do close out.
    2. If fault remains, continue with next step.

  3. Do wiring checks between relays and HST ECU. Repair as required.

    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.

stab_trim_fail

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