01/28/21
Message Overview:
Message Description:
The cyan 'NWS FAULT' advisory CAS message indicates that hydraulic pressure is sensed in the Steering System while the Steering Selector Valve (SSV) is commanded shut.
NOTE: Switching the NWS PBA to 'OFF' or removing power from the aircraft will clear the 'NWS FAULT' advisory CAS message. If the fault is still present, it will not be shown again until the next Weight-Off-Wheel condition with hydraulic pressurized and NWS PBA set to 'ON'.
NOTE: The SCU memory does not record this fault and the 7-segment display will indicate '0', no fault.
Possible Causes:
- Steering Selector Valve (SSV) (V07)
- Steering Pressure Switch (S10)
- Steering Control Unit (SCU) (A73)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
Troubleshooting Tips:ATA 32-51-00 NOSEWHEEL STEERING SYSTEM
Quick Links:
| Put the Aircraft in a Weight-Off-Wheel Configuration with the Aircraft on the Ground | AMM 32-61-00-867-801 |
| Remove the Aircraft from a Weight-Off-Wheel Configuration with the Aircraft on the Ground | AMM 32-61-00-867-802 |
| Operational Test of the Nosewheel-Steering Control System | AMM 32-51-00-710-801 |
| Pressurize the Left and Right Hydraulic Systems | AMM 29-10-00-862-801 |
| Release Hydraulic Pressure - Left and Right Hydraulic Systems | AMM 29-10-00-862-802 |
| Rigging of the Nosewheel-Steering Control System | AMM 32-51-00-820-801 |
| 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 Selector Valve | AMM 32-51-09-000-801 |
| Installation of the Steering Selector Valve | AMM 32-51-09-400-801 |
| Removal of the Steering Pressure Switch | AMM 32-51-25-000-801 |
| Installation of the Steering Pressure Switch | AMM 32-51-25-400-801 |
| 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:
- Make sure left hydraulic system is depressurized (AMM TASK 29-10-00-862-802).
- Make sure NWS PBA is selected 'OFF' (OFF legend is lighted).
- Measure resistance at the Pressure Switch (S10) receptacle per the following table:
FROM TO EXPECTED RESULTS ACTUAL RESULTS A B OPEN (∞Ω) B CASING OPEN (∞Ω) - If there is continuity, replace Pressure Switch S10.
- If no fault found, go to the next step.
- Access and disconnect the Stall Protection Computer (SPC). Measure resistance at the Pressure Switch harness connector (aircraft side) (S10P1) per the following table:
FROM TO EXPECTED RESULTS ACTUAL RESULTS B GND OPEN (∞Ω) - If there is continuity, repair defective wiring as required.
- If there is no continuity, continue with next step.
NOTE: Always establish Left Hydraulic System pressure before switching the NWS System to 'ON' as it may trigger and record a false 'NWS FAIL' message if any NWSS component is out of neutral position.
- Pressurize left hydraulic system (AMM TASK 29-10-00-862-801).
- Set the NWS PBA to ON (OFF legend is extinguished).
- Put the Aircraft in a Weight-Off-Wheel configuration with the aircraft on the ground (AMM TASK 32-61-00-867-801) using the MDC Override Mode Discrete Output.
- If the cyan 'NWS FAULT' EICAS message is displayed, replace SSV.
- If not, the SSV is no longer stuck open.
NOTE: It is recommended to carry out the Operational Test of the Nosewheel-Steering System (AMM TASK 32-51-00-710-801), doing 10 full-swings of the steering system to flush out any particle that may have jammed the SSV.
- Depressurize the Left Hydraulic System (AMM TASK 29-10-00-862-802).
- Do close out.