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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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02/11/21

Message Overview:

SCU Fault Code:

'7'

Associated CAS:

NWS FAIL
(Caution)

DDG Reference: None
Reporting LRU: Steering Control Unit
System Description: 32-51-00
Schematic Diagram: 32-51-00
Wiring Diagram: 32-51-01
32-51-13
32-51-29

Fault Description:

A '7' on the 7-segment display indicates that the Nose Wheel Steering System is out of rigging or there is a fault on the SCU rigging board.

NOTE: When the Steering Control Unit (SCU) is replaced, it is normal to have an SCU Fault Code '7' flashing on the 7-Segment display. Carry out rigging of the Nosewheel Steering Control System NWSS (AMM TASK 32-51-00-820-801).

NOTE: If SCU Fault Code '7' is flashing with another code, carry out SCU Fault Code '7' troubleshooting before addressing any other fault.

Possible Causes:

  • Nosewheel Feedback Rotary Variable Transducer (RVT)
  • Steering Control Handwheel (HW) (MT85)
  • Rudder Pedal Transducer (RP) (MT86)
  • Steering Control Unit (SCU) (A73)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Troubleshooting Tips:

Quick Links:

Automatic Download of the Steering Control Unit (SCU) Non-Volatile Memory (NVM) AMM 32-51-01-970-801
Manual Download of the Steering Control Unit (SCU) Non-Volatile Memory (NVM) AMM 32-51-01-970-802
Removal of the Steering Control Unit AMM 32-51-01-000-801
Installation of the Steering Control Unit AMM 32-51-01-400-801
Removal of the Steering Control Handwheel AMM 32-51-05-000-801
Installation of the Steering Control Handwheel AMM 32-51-05-400-801
Removal of the Rudder Pedal Transducer AMM 32-51-17-000-801
Installation of the Rudder Pedal Transducer AMM 32-51-17-400-801
Calibration of the Steering Control Handwheel AMM 32-51-05-820-802
Rigging of the Rudder Pedal Transducer AMM 32-51-17-820-802
Standard Practices - Continuity and Insulation Check SPM 20-12-01-05
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:

Fault Isolation Procedure:

  1. Before starting the following Fault Isolation Procedure, make sure the SCU Fault Confirmation Procedure is carried out to ensure the correct fault code is being addressed.
  2. Carry out the Rigging of the Nosewheel-Steering Control System (AMM TASK 32-51-00-820-801).
    → If a null voltage is found out of tolerance and cannot be adjusted, replace the applicable component and carry out the rigging procedure again.
  3. Carry out the Operational Test of the Nosewheel-Steering Control System (AMM TASK 32-51-00-710-801).
    NOTE: Always establish Left Hydraulic System pressure before switching the NWS System to 'ON' as it may trigger and record a false 'NWS FAIL' CAS message if any NWSS component is out of neutral position.

    1. If the 7-segment display indicates '0', no other maintenance action is required.
    2. If an SCU Fault Code '7' is displayed, go to the next step.

  4. Replace Steering Control Unit (SCU).
    steering_control_handwheelsteering_control_unitsteering_manifoldsteering_manifold_2

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