Narrative:

Uncommanded roll during ILS runway 4 lga beginning at 1200 ft MSL after selecting flaps 40 degrees. Aircraft on autoplt began to oscillate left to right, as if bad localizer signal clicked off autoplt and autothrottle. Still wanted to turn left, and had to continuously till touchdown, 'keep correcting course.' followed immediate action items for uncommanded roll -- autoplt off, autothrottle off, yaw dampers off. No split flaps, throttles or apparent spoiler deployment. Landing successful. +10 vref at touchdown! Callback conversation with reporter revealed the following information: reporter states that the rudder trim was repeatedly checked before and after the uncommanded roll and that even after the autoplt was disconnected, the aircraft continued to roll left when ever manual control pressure was lessened. He states that the aircraft was immediately grounded and inspected following the incident. The air carrier maintenance facility determined that a worn flap track fairing prevented the flaps on 1 side only from moving to the full 40 degree position. The reporter states that the flaps indicated full 40 degrees on both sides at the time of the incident and that the flight crew was fatigued as this was the final leg of a long and trying day. The air carrier and reporter made appropriate company irregularity and FAA reports concerning the incident.

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Original NASA ASRS Text

Title: B737-300 RPTS UNCOMMANDED ROLL AFTER SELECTING FLAPS 40 DEGS ON APCH TO LGA.

Narrative: UNCOMMANDED ROLL DURING ILS RWY 4 LGA BEGINNING AT 1200 FT MSL AFTER SELECTING FLAPS 40 DEGS. ACFT ON AUTOPLT BEGAN TO OSCILLATE L TO R, AS IF BAD LOC SIGNAL CLICKED OFF AUTOPLT AND AUTOTHROTTLE. STILL WANTED TO TURN L, AND HAD TO CONTINUOUSLY TILL TOUCHDOWN, 'KEEP CORRECTING COURSE.' FOLLOWED IMMEDIATE ACTION ITEMS FOR UNCOMMANDED ROLL -- AUTOPLT OFF, AUTOTHROTTLE OFF, YAW DAMPERS OFF. NO SPLIT FLAPS, THROTTLES OR APPARENT SPOILER DEPLOYMENT. LNDG SUCCESSFUL. +10 VREF AT TOUCHDOWN! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THE RUDDER TRIM WAS REPEATEDLY CHKED BEFORE AND AFTER THE UNCOMMANDED ROLL AND THAT EVEN AFTER THE AUTOPLT WAS DISCONNECTED, THE ACFT CONTINUED TO ROLL L WHEN EVER MANUAL CTL PRESSURE WAS LESSENED. HE STATES THAT THE ACFT WAS IMMEDIATELY GNDED AND INSPECTED FOLLOWING THE INCIDENT. THE ACR MAINT FACILITY DETERMINED THAT A WORN FLAP TRACK FAIRING PREVENTED THE FLAPS ON 1 SIDE ONLY FROM MOVING TO THE FULL 40 DEG POS. THE RPTR STATES THAT THE FLAPS INDICATED FULL 40 DEGS ON BOTH SIDES AT THE TIME OF THE INCIDENT AND THAT THE FLC WAS FATIGUED AS THIS WAS THE FINAL LEG OF A LONG AND TRYING DAY. THE ACR AND RPTR MADE APPROPRIATE COMPANY IRREGULARITY AND FAA RPTS CONCERNING THE INCIDENT.

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.