What was found
FLT 1056 - MKE-IND - THE CREW FOUND THE AILERON TRIM TAB FROZE UP IN FLIGHT. ONCE ON THE GROUND IN IND OUTSTATION. MAINTENANCE LUBRICATED THE TRIM TAB ACTUATOR AND FOUND IT TO BE WORKING NORMALLY. DURING THE RETURN FLIGHT TO MKE THE AILERON TRIM TAB FROZE UP AGAIN, ONCE ON THE GROUND IN MKE MAINTENANCE INSPECTED THE TRIM TAB ACTUATOR AND FOUND IT CORRODED. THE ACTUATOR WAS REPLACED AND THE A/C WAS RETURNED TO SERVICE. (M)