Narrative:

On takeoff climbing through 1200 ft a noticeable right wing down aileron input was required for 10 seconds to keep wings level followed by a reverse to a left wing down aileron input for 10 seconds. During this period no rudder pedal displacement was noted nor were there any unusual discrepancies in the flap/slat retraction sequence or engine parameters. This same situation occurred on our previous leg from atl to tlh, just following a brief and mild encounter with wake turbulence. At that time I considered the wake turbulence to be the cause of that input. However, after the same thing occurred again leaving tlh in smooth air, I decided it was time to write this up. Neither event was excessive or abrupt but I felt needed the attention of our maintenance. Callback conversation with reporter revealed the following information: the reporter stated the 10 second right and left wing down maneuver happened twice. The reporter said it first happened in turbulent air and the second time in still air. The reporter said maintenance replaced the rudder power unit, checked flap and slat rig and operation. The reporter stated the flight test was normal.

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Original NASA ASRS Text

Title: A B737-300 IN CLB AT 1200 FT EXPERIENCED A NOTICEABLE R WING DOWN CONDITION THEN A L WING DOWN CONDITION FOR A PERIOD OF 10 SECONDS.

Narrative: ON TKOF CLBING THROUGH 1200 FT A NOTICEABLE R WING DOWN AILERON INPUT WAS REQUIRED FOR 10 SECONDS TO KEEP WINGS LEVEL FOLLOWED BY A REVERSE TO A L WING DOWN AILERON INPUT FOR 10 SECONDS. DURING THIS PERIOD NO RUDDER PEDAL DISPLACEMENT WAS NOTED NOR WERE THERE ANY UNUSUAL DISCREPANCIES IN THE FLAP/SLAT RETRACTION SEQUENCE OR ENG PARAMETERS. THIS SAME SIT OCCURRED ON OUR PREVIOUS LEG FROM ATL TO TLH, JUST FOLLOWING A BRIEF AND MILD ENCOUNTER WITH WAKE TURB. AT THAT TIME I CONSIDERED THE WAKE TURB TO BE THE CAUSE OF THAT INPUT. HOWEVER, AFTER THE SAME THING OCCURRED AGAIN LEAVING TLH IN SMOOTH AIR, I DECIDED IT WAS TIME TO WRITE THIS UP. NEITHER EVENT WAS EXCESSIVE OR ABRUPT BUT I FELT NEEDED THE ATTN OF OUR MAINT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE 10 SECOND R AND L WING DOWN MANEUVER HAPPENED TWICE. THE RPTR SAID IT FIRST HAPPENED IN TURBULENT AIR AND THE SECOND TIME IN STILL AIR. THE RPTR SAID MAINT REPLACED THE RUDDER PWR UNIT, CHKED FLAP AND SLAT RIG AND OP. THE RPTR STATED THE FLT TEST WAS NORMAL.

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.