Date: 201404
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Parked
ATC / advisory: Ramp ZZZ
Aircraft component: Rudder
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Confusion; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Maintenance Action
Contributing factors: Procedure; Aircraft; Company Policy
Primary problem: Ambiguous

Narrative: As a habit of muscle memory I will on occasion do the standby rudder test; which has been eliminated from our procedures without even thinking about it. This happened to me today on Aircraft X. Interestingly the aircraft failed the standby rudder test. After making a logbook entry of the discrepancy; I called Station Maintenance. The Mechanic found that the 'B' system standby rudder valve motor was running continuously and was so hot that it burned his hand when he touched it. While Maintenance had a new valve; the new valve did not include the required packing rings; which go on behind the 'O' rings on the valve shaft. More interesting was that he showed me the old valve and said that the packing rings were not installed correctly on the old valve.I am submitting this report because I am concerned that by eliminating the Standby Rudder Check we are compromising Safety on several levels. This is the second aircraft I have had this happen on. The first one was the result of a relay failure; this one the result of the standby rudder valve failure. If we are not as a matter of procedure checking the standby rudder; how do we know it will work when we desperately need it to work? Second; how do we verify the standby hydraulic pump is operable? Finally; on this particular event where the 'B' system standby rudder valve was generating so much heat...was there a wheel-well fire hazard as the valve motor was operating continuously? As stated; this is the second aircraft I have had that failed the standby rudder test; which is no longer a procedural test. It is my belief that we are compromising safety by not doing this test as part of the originating preflight checks given the importance of standby rudder operation.

Callback: The reporter stated that while troubleshooting the pump problem; the Mechanic stated the pump in addition to the overheat; was not continuously pumping fluid. He estimated one out of every four demands produced flow. This was the second malfunction of the Standby Rudder System this reporter has seen; although for different reasons. He has not heard anything back from his Company about this; but he is concerned that not conducting a system integrity check on older generation aircraft when a valid check methodology is available may cause failures to go undetected. He is fairly certain that since two B737 accidents have been attributed to the Rudder System many changes have been incorporated which should make everyone more vigilant about the system.



Synopsis: A B737 failed the preflight Standby Rudder Check which the Captain performed out of habit even though this preflight procedure was eliminated. This pilot has discovered two malfunctioning systems since the procedure was discontinued.