Message Name:

PRESSURE SWITCH #1/#2 MISMATCH

Message Code:

3250009DWY

Associated CAS:

NOSE STEER FAIL
(Caution)

Nose Wheel Steering Control Unit (SCU) has detected a mismatch between the Nose Wheel Steering Pressure Switch 1 (S2) and the Hydraulic System 3A and 3B Pressure Switches (S39) and (S40).

• Steering Pressure Switch (S2)
• Landing Gear Selector Valve System 3 (L17)
• AC Motor Pump 3A Pressure Switch (S39)
• AC Motor Pump 3B Pressure Switch (S40)
• Steering Solenoid Valve (SSV) (L1)
• Junction Box (JB4)/PCB3
• Steering Control Unit (SCU) (A36)
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW700-32-0280 - Nose Wheel Steering - Troubleshooting of SCU GW415-8100-3
• AW700-45-0002 - CAIMS Member System Functionality Status LDI Sparrow.037

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

Flight Operation Notifications Manual (FONM): None

NOTES:

• If CAIMS message SOLENOID VALVE/WIRING (NWS FAULT 11-SELECT [SHOW DETAIL]) shown together with PRESSURE SWITCH #1/#2 MISMATCH, troubleshoot 3250008DWY first.
• CAIMS/PMAT LDI should be SPARROW.037, if it is not the case refer to AW700-45-0002

1. Check CAIMS message SOLENOID VALVE/WIRING (3250008DWY).

   1. If message is shown, perform troubleshooting of SOLENOID VALVE/WIRING (3250008DWY) and do close out.
   2. If message is not shown, continue with next step.

2. Set the Hydraulic system 3A and 3B switch to ON.
3. Set Nose Steer switch to ARMED.

   1. If the NOSE STEER FAIL (amber) message is not shown on EICAS, go to step 9.
   2. If the NOSE STEER FAIL (amber) message is shown on EICAS, continue with next step.

4. Perform a wiring check between SCU and Steering Pressure Switch 1 (S2).

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

5. Replace the Steering Pressure Switch 1 (S2). Is the fault message still present?

   1. If NO, do close out.
   2. If YES, continue with next step.

6. Make sure that the system Gear Selector Valve 3 is not failed in the open position as follows:
   WARNING: Make sure that the lockpin is installed in the door mechanism of the Nose Landing Gear. The Nose Landing Gear doors can close accidentally and cause injury to persons and damage to the equipment.

   • Make sure that the landing gear handle is in the down position
   • Gain access to the nose wheel uplock actuator through the nose landing gear wheel well
   • With the hydraulic system 3 unpressurized, manually position the nosewheel uplock hook to the locked position
   • Pressurize the hydraulic system 3 (AMM 29-10-00-862-804)
   • Verify that the nosewheel uplock hook moves to the unlocked position
   • Release pressure from the hydraulic system 3

   1. If the test is passed as described, go to step 8.
   2. If the test did not pass as described, continue with next step.

7. Disconnect the system Landing Gear Selector Valve 3 connector L17P1. Perform a continuity check between the pins of the Selector Valve as follows:

   From	To	Result
   L17J1-A	L17J1-B
   L17J1-D	L17J1-E

   1. If there is no continuity, replace the Selector Valve and do close out.
   2. If there is continuity, continue with next step.

8. Replace the Steering Solenoid Valve which may be stuck in the closed position.

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

9. Set the Hydraulic system 3A switch to OFF.

   1. If the NOSE STEER FAIL (amber) message is not shown on EICAS, go to step 12.
   2. If the NOSE STEER FAIL (amber) message is shown on EICAS, continue with next step.

10. Perform a wiring check between the Hydraulic system 3B Pressure switch (S40) and the SCU (A36).

    1. If wiring checks are not good, go to step 16.
    2. If wiring checks are good, continue with next step.

11. Replace the Hydraulic system 3B Pressure switch (S40).

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

12. Set the Hydraulic system 3A switch to ON.
13. Set the Hydraulic system 3B switch to OFF.

    1. If the NOSE STEER FAIL (amber) message is not shown on EICAS, monitor for failure and do close out.
    2. If the NOSE STEER FAIL (amber) message is shown on EICAS continue with next step.

14. Perform a continuity check between the Hydraulic system 3A Pressure switch wiring (S39) and the SCU (A36).

    1. If wiring checks are not good, go to step 16.
    2. If wiring checks are good, continue with next step.

15. Replace the Hydraulic system 3A Pressure switch (S39).

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

16. Replace JB4/PCB 3.

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

17. Replace the SCU.
18. Do close out.