Challenger 300 Aircraft Nose Wheel Steering Manifold, Service Bulletin 100-32-25

Are you receiving an amber NWS Fail messages or experiencing uncommanded steering operations? If so, you may want to look at Service Bulletin (SB) 100-32-25. It is applicable to the Challenger 300*, BD-100-1A10 aircraft, S/Ns 20003 thru 20383. It has been determined that moisture in the Electrical Hydraulic Servo Valve (EHSV) of the steering manifold could be contributing to these anomalies. 

The EHSV receives electrical signals from the steering computer to port fluid thru the Bypass valve and onto the steering actuators. The EHSV incorporates a linear variable differential transducer (LVDT); which provides feedback on the EHSV position to the steering computer. Moisture in these sensitive components could cause issues with the proper functioning of the steering system.

The SB provides instruction to replace the manifold, with a new manifold, with improved sealing features to prevent moisture ingress. The SB is on a dedicated schedule so preplanning and parts procurement in advance is necessary to avoid delays and extended down time, but well worth the increased reliability, reduction in troubleshooting, maintenance time and cost.

*Trademarks of Bombardier Inc. or its subsidiaries