Narrative:

Air carrier flight XXX den to iah diverted to dfw due to inoperative WX radar and convective activity in iah area. This was the third consecutive flight on this aircraft with a WX radar failure. An uncommanded rudder movement: VFR on glen rose 5 arrival to dfw, 10000 ft, airspeed 210 KTS, flaps 1 degree, autoplt 'a' engaged, autoplt 'B' inoperative. First officer acting as PF, uncommanded rudder movement occurred while in a left turn to 360 degrees (per ATC not 350 degrees as published) at delmo intersection. The movement was fairly smooth, to the left, but quite noticeable to both pilots and jump seat rider -- not noticed by flight attendants or passenger. Lasted for 2-3 seconds then returned to normal. First officer's feet resting on pedals but he did not initiate movement and stated that rudder pedals did not move. At least 10 KTS extra airspeed carried from this point to touchdown at dfw. No previous or subsequent rudder problems on this flight. Landed with no problem at dfw. Notified air carrier dispatch, maintenance, and flight operations duty manager prior to next flight.

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Original NASA ASRS Text

Title: A B737-500 ON APCH AT 10000 FT EXPERIENCED AN UNCOMMANDED RUDDER MOVEMENT WITH FLAPS 1 DEG AT 250 KTS AND YAW DAMPER ENGAGED. CAUSE UNKNOWN.

Narrative: ACR FLT XXX DEN TO IAH DIVERTED TO DFW DUE TO INOP WX RADAR AND CONVECTIVE ACTIVITY IN IAH AREA. THIS WAS THE THIRD CONSECUTIVE FLT ON THIS ACFT WITH A WX RADAR FAILURE. AN UNCOMMANDED RUDDER MOVEMENT: VFR ON GLEN ROSE 5 ARR TO DFW, 10000 FT, AIRSPD 210 KTS, FLAPS 1 DEG, AUTOPLT 'A' ENGAGED, AUTOPLT 'B' INOP. FO ACTING AS PF, UNCOMMANDED RUDDER MOVEMENT OCCURRED WHILE IN A L TURN TO 360 DEGS (PER ATC NOT 350 DEGS AS PUBLISHED) AT DELMO INTXN. THE MOVEMENT WAS FAIRLY SMOOTH, TO THE L, BUT QUITE NOTICEABLE TO BOTH PLTS AND JUMP SEAT RIDER -- NOT NOTICED BY FLT ATTENDANTS OR PAX. LASTED FOR 2-3 SECONDS THEN RETURNED TO NORMAL. FO'S FEET RESTING ON PEDALS BUT HE DID NOT INITIATE MOVEMENT AND STATED THAT RUDDER PEDALS DID NOT MOVE. AT LEAST 10 KTS EXTRA AIRSPD CARRIED FROM THIS POINT TO TOUCHDOWN AT DFW. NO PREVIOUS OR SUBSEQUENT RUDDER PROBS ON THIS FLT. LANDED WITH NO PROB AT DFW. NOTIFIED ACR DISPATCH, MAINT, AND FLT OPS DUTY MGR PRIOR TO NEXT FLT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.