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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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03/02/21

Message Overview:

Message Name:

NO AHC2 LAT ACCEL INPUT

Message Code:

B3-372792

Associated CAS:

None

Reporting LRU: STALL COMPUTER
System Description: 27-32-00
Schematic Diagram: 27-32-00
Wiring Diagram: 27-32-01

Message Description:

No lateral acceleration data from R AHC. Verify the AHC power and mode. Input bus to SPC is R-AHC-4. Suspect failure in aircraft wiring or AHC output or SPC input.

Possible Causes:

  • Left Attitude Heading Computer (AHC) (A11)
  • Stall Protection Computer (SPC) (A178)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Functional Test of the Stall Protection System AMM 27-32-00-720-801
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 Attitude Heading Computer (AHC) AMM 34-21-01-000-801
Installation of the Attitude Heading Computer (AHC) AMM 34-21-01-400-801
Operational Test of the Attitude Heading Computer (AHC) AMM 34-21-01-710-801
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. On the RH COMPASS control panels, ensure the HEADING COMPASS is not selected (DG light is off). If DG PBA is on, push the switch to turn the DG PBA off.

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

  2. In Maintenance Main Menu, select LRU INDEX/OPERATIONS and ensure AHC is operational.

    1. If AHC Label 350 bit 11 to 29 are set to 0 (valid) and/or other R-AHC users operate normally (onside PFD shows attitude and heading), go to step 4.
    2. If AHC Label 350 bit 11 to 29 are set to 1 (invalid) and/or other R-AHC users do not operate normally (onside PFD does not show attitude and heading), continue with next step.

  3. Reset circuit breakers CB1-C2 ATT HDG 1 and CB2-C2 ATT HDG 2.

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

  4. Reset the following circuit breakers and perform the Pilot Activated Test (PAT) of the Stall Protection System on the Systems Test control-panel located on the center pedestal.

    STALL L PWR CB1-B10
    STALL R PWR CB2-B10

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

  5. Re-rack SPC.

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

  6. Do wiring check of R-AHC-4 ARINC bus from AHC to SPC. Repair as required.

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

  7. Replace AHC.

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

  8. Replace SPC.
  9. Do close out.

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