B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Other / Unknown
Aircraft Equipment Problem Less Severe
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Procedure
We arrived for an aircraft swap early. During my (Captain) preflight flow I always check the standby rudder. As I selected standby rudder the Standby Rudder light illuminated as normal but I had no rudder authority; when I moved to switch back to normal the Standby Rudder on light remained illuminated. Maintenance was called and replaced the overhead module to see if it was an electrical issue. With no change the aircraft was taken out of service. I spoke with two instructors and was told this was not the first occurrence of this problem. I'm concerned to think about the aircraft potentially flying for a period of time before we discovered the problem.Put this check back into our preflight flow.
B737NG Captain reported that he did not have rudder authority when he used the rudder standby system.