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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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02/07/20

Message Overview:

SCU Fault Code:

'A'

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 flashing SCU Fault Code 'A' on the 7-segment display indicates rigging is in progress

A solid SCU Fault Code 'A' on the 7-segment display indicates that the SCU is in Maintenance mode.

Possible Causes:

  • Jumper wire installed between pins 4 and 7 on the SCU DB25 connector
  • Steering Control Unit (SCU) (A73)

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
Pressurize the Left and Right Hydraulic Systems AMM 29-10-00-862-802
Release Hydraulic Pressure - Left and Right Hydraulic Systems AMM 29-10-00-862-802
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. If installed, disconnect the breakout box from the SCU.
  2. Make sure that the jumper wire between pins 4 and 7 on the DB25 connector is removed.
  3. Select the NWS PBA to 'OFF' (OFF legend is lighted)
  4. Make sure the Handwheel, Rudder Pedals, and Nosewheel are in their neutral position (0°).
  5. Pressurize the Left Hydraulic System (AMM TASK 29-10-00-862-801).
    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.
  6. Set the Steering Control Unit (SCU) PBA to 'ON' (OFF legend is extinguished).
  7. Wait 120 seconds.
  8. If SCU Fault Code 'A' is still showing on the 7-segment display, replace the SCU.
  9. Depressurize the Left Hydraulic System per AMM TASK 29-10-00-862-802.
    steering_control_unit

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