Narrative:

While the first officer (PF) was flying an medium large transport on final approach into lax-24L, the captain (PNF) on command by the PF, moved flaps from 25 degrees to 30 degrees (the final setting). The aircraft developed an uncommanded left rolling movement which required 1/2 aileron control deflection the right by the PF to counter the aircraft's sudden and persistent rolling movement. The PF countered the rolling movement before the aircraft reached a 10 degree bank angle and continued to fly the visual approach wings level with 1/2 control yoke aileron input to the right. Within a five second span after the uncommanded left roll, the PF asked the PNF to check fuel balance, leading edge devices, flap indications, spdbrakes, and all associated green or possible amber lights. All lights and indications displayed green and normal respectively. All indications were normal with an uncommanded left rolling motion. At this point, about 600 ft AGL, the first officer transferred the flight controls to the captain so he, the captain, could get a better feel for what the aircraft was doing. The captain, now the PF, confirmed that the aircraft was ctlable in its present confign, (i.e., gear down, flaps 30 degrees, engines spooled, on GS, on target speed -- 127 KTS, with 1/2 aileron control to the right) and the best course of action was to land the aircraft, which he did without incident. After landing safely, we left the aircraft in landing confign for maintenance inspection at the gate (i.e., flaps 30 degrees, spdbrake armed). We were unable to get much information from the line maintenance crew before deadheading back to sfo. This particular aircraft had a history of trailing edge and leading edge device problems. During our briefing prior to this flight (incident), the captain noted and briefed 3 previous maintenance write-ups indicating a chronic problem with both leading edge and trailing edge devices (i.e., popped circuit breakers, split flaps on final approach) which occurred 2 days prior to our flight on jul/mon/93. Maintenance action was indicated for each of the 3 write-ups followed by appropriate ground checks which checked out 'ok' on jul/93.

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Original NASA ASRS Text

Title: ACFT EXPERIENCES A ROLL ON FINAL DUE TO AN ASYMMETRIC FLAP SIT AS FINAL FLAPS ARE EXTENDED.

Narrative: WHILE THE FO (PF) WAS FLYING AN MLG ON FINAL APCH INTO LAX-24L, THE CAPT (PNF) ON COMMAND BY THE PF, MOVED FLAPS FROM 25 DEGS TO 30 DEGS (THE FINAL SETTING). THE ACFT DEVELOPED AN UNCOMMANDED L ROLLING MOVEMENT WHICH REQUIRED 1/2 AILERON CTL DEFLECTION THE R BY THE PF TO COUNTER THE ACFT'S SUDDEN AND PERSISTENT ROLLING MOVEMENT. THE PF COUNTERED THE ROLLING MOVEMENT BEFORE THE ACFT REACHED A 10 DEG BANK ANGLE AND CONTINUED TO FLY THE VISUAL APCH WINGS LEVEL WITH 1/2 CTL YOKE AILERON INPUT TO THE R. WITHIN A FIVE SECOND SPAN AFTER THE UNCOMMANDED L ROLL, THE PF ASKED THE PNF TO CHK FUEL BAL, LEADING EDGE DEVICES, FLAP INDICATIONS, SPDBRAKES, AND ALL ASSOCIATED GREEN OR POSSIBLE AMBER LIGHTS. ALL LIGHTS AND INDICATIONS DISPLAYED GREEN AND NORMAL RESPECTIVELY. ALL INDICATIONS WERE NORMAL WITH AN UNCOMMANDED L ROLLING MOTION. AT THIS POINT, ABOUT 600 FT AGL, THE FO TRANSFERRED THE FLT CTLS TO THE CAPT SO HE, THE CAPT, COULD GET A BETTER FEEL FOR WHAT THE ACFT WAS DOING. THE CAPT, NOW THE PF, CONFIRMED THAT THE ACFT WAS CTLABLE IN ITS PRESENT CONFIGN, (I.E., GEAR DOWN, FLAPS 30 DEGS, ENGS SPOOLED, ON GS, ON TARGET SPD -- 127 KTS, WITH 1/2 AILERON CTL TO THE R) AND THE BEST COURSE OF ACTION WAS TO LAND THE ACFT, WHICH HE DID WITHOUT INCIDENT. AFTER LNDG SAFELY, WE LEFT THE ACFT IN LNDG CONFIGN FOR MAINT INSPECTION AT THE GATE (I.E., FLAPS 30 DEGS, SPDBRAKE ARMED). WE WERE UNABLE TO GET MUCH INFO FROM THE LINE MAINT CREW BEFORE DEADHEADING BACK TO SFO. THIS PARTICULAR ACFT HAD A HISTORY OF TRAILING EDGE AND LEADING EDGE DEVICE PROBS. DURING OUR BRIEFING PRIOR TO THIS FLT (INCIDENT), THE CAPT NOTED AND BRIEFED 3 PREVIOUS MAINT WRITE-UPS INDICATING A CHRONIC PROB WITH BOTH LEADING EDGE AND TRAILING EDGE DEVICES (I.E., POPPED CIRCUIT BREAKERS, SPLIT FLAPS ON FINAL APCH) WHICH OCCURRED 2 DAYS PRIOR TO OUR FLT ON JUL/MON/93. MAINT ACTION WAS INDICATED FOR EACH OF THE 3 WRITE-UPS FOLLOWED BY APPROPRIATE GND CHKS WHICH CHKED OUT 'OK' ON JUL/93.

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.