Date: 201210
Local time of day: 1801-2400
Location: DFW.Airport, MI
Aircraft: MD-82
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground DFW
Aircraft component: Rudder Control System
Component problem: Improperly Operated; Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Training / Qualification; Communication Breakdown; Human-Machine Interface
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; General Maintenance Action
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Ambiguous

Narrative: During the Before Taxi Checklist; the flaps were extended. As the flaps extended I checked the rudder movement. After 1/3 rudder travel; the rudder jammed on the right side. I noticed the Rudder Manual Control light flicker during the check. I released the rudder and tried the left side and the rudder again jammed after 1/3 rudder movement. I reported the event to Maintenance and returned to the gate. I have had this occur three other times and Maintenance has taken the aircraft out of service. After we returned to the gate; a Mechanic showed up and I explained exactly what I had done. He left and checked the hydraulic levels and rudder. When he came back to the cockpit we accomplished the check as before and had the same results. After a period of time; I was informed by an unknown Maintenance source that I had performed an 'inappropriate check' and to check the rudder only after the hydraulic load [from extending the flaps] had diminished. I cannot find this warning note in any of my operational manuals. The flow of the checklist calls for the flaps to be extended and shortly after the checklist calls for a flight control check. If this is a [known and appropriate] hydraulic issue; I think there should be some notation in our manual.


Second narrative: While this [troubleshooting was] going on; the Captain was notified by a Maintenance person that he was doing an unauthorized check. There is nothing in any of the pilot manuals stating this; or explaining why. We later pushed back and did rudder check after hydraulic load diminished as per the Maintenance personnel with no issues; but no explanation as to why rudder jammed under load. Continued on with no issues; but also no answer to why or why not.Everyone I have flown with has checked rudder movement during these times.


Synopsis: After encountering abnormal rudder response during their pre-takeoff checks; the flight crew returned to the gate for maintenance. During the maintenance diagnosis the flight crew was advised they were performing the check improperly while the flaps were being extended; thus loading the hydraulic system. The flight crew is unaware of any such published operational restriction. A subsequent check after the flap extension was complete was normal.