A FOKKER 100 IMMEDIATELY AFTER TKOF EXPERIENCED A MALFUNCTIONING L AILERON. L AILERON SYS DEPRESSURIZED AND ACFT DIVERTED.

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AFTER TKOF FROM ORD ACFT WAS DIFFICULT TO HOLD WINGS LEVEL OR MAINTAIN A HEADING. HAD FO TRY WITH SAME RESULT. INPUT TO AILERON WOULD LAG ABOUT 3-5 SECONDS. AUTOPLT HAD SAME RESULT; WITH JERKY MOVEMENT. I REASONED THAT SINCE L AILERON HAD SEVERAL WRITE-UPS; IT WAS THE PROB. TURNED OFF SYS #1 L AILERON. ACFT FLEW FINE THEN. ORD WX WAS 100 FT OVCST WITH 1/4 MI VISIBILITY. ELECTED TO PRESS ON TO AUS. WX IN AUS WAS NOT GOOD DUE TO TSTM. AFTER CONSULTING WITH DISPATCH ELECTED TO FLY TO DFW AND EVALUATE WX. DIDN'T WANT TO BE SHOOTING AN APCH WITH TSTM AND FLT CTL PROB. WX IN AUS UNACCEPTABLE DIVERTED AND LANDED DFW WITHOUT FURTHER PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A FOKKER 100 AND THE CORRECTIVE ACTION WAS THE REPLACEMENT OF THE TRIM LOCKOUT ACTUATOR AFTER TWO PREVIOUS AILERON PWR CTL UNITS WERE REPLACED. THE RPTR SAID THAT A PREFLT REVIEW OF THE LOGBOOK AND MAINT HISTORY OF THE L AILERON PROB PREPARED THE CREW FOR POSSIBLE L AILERON TROUBLE. THE RPTR STATED THE L AILERON HAD A LONG TIME LAG BTWN THE CTL INPUT AND THE ACTUAL AILERON MOVEMENT WHICH BECAME EXCESSIVE. THE RPTR STATED THE CTL PROB WAS OVERCOME BY TURNING OFF HYD SYS #1 DEPRESSURIZING THE L AILERON. THE RPTR SAID THE WX WOULD NOT PERMIT RETURN TO ORD AND THE FLT WAS DIVERTED TO DFW.