A BE1900D IS FLT TESTED FOR AILERON TRIM PROBS. TEST FLT RPTS TRIM OK. NEXT REVENUE FLT BY SAME CREW FINDS AILERON TRIM RIGGED BACKWARDS.

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ON AUG/MON/02; I CONDUCTED A TEST FLT FOR A PART 121 COMMUTER AIRLINE. THE FLT TOOK PLACE AT XA00; AFTER FLYING A 5 HR SHIFT. THE ACFT NEEDED A TEST FLT TO CHK THE AILERON TRIM. TALKING WITH THE MECHS; THEY STATED THAT 3 DEGS OF TRIM WAS NEEDED TO KEEP ACFT STRAIGHT AND LEVEL BEFORE BEING WRITTEN UP. WHILE TAXIING OUT; I CHKED THE AILERON TRIM FOR FULL MOVEMENT IN BOTH DIRECTIONS AND RESET AT 0 DEGS PRIOR TO FLT. AFTER RUN-UP; MY SEAT COULD NOT BE ADJUSTED FOR COMFORT; I LATER WROTE UP THE CAPT'S SEAT. I OPTED TO MAKE THE TKOF BECAUSE THE ACFT HAD BEEN IN MAINT FOR AN EXTENDED PERIOD OF TIME. THE ACFT HAD A STRUCTURAL INSPECTION. THE TKOF WAS NORMAL. AFTER PASSING THROUGH 1500 FT; I GAVE THE CTLS TO MY FO BECAUSE THE SEAT WAS NOT COMFORTABLE FOR FLYING. WE EXECUTED STEEP TURNS; STALLS AND AN ILS APCH TO CHK OUT AS MANY SYS AS POSSIBLE. WE NOTED A DIFFERENCE IN THE AIRSPD INDICATORS. THE FO'S SIDE WAS 10-15 KTS SLOW. THAT WAS WRITTEN UP. AFTER LNDG; I ASKED THE FO HOW THE PLANE FELT. HE SAID 'FINE.' WE SIGNED OFF THE PAPERWORK. THE FOLLOWING DAY; WE WERE ASSIGNED THE SAME ACFT FOR SCHEDULED PART 121 FLT. ON THE SECOND LEG (MY LEG); I NOTICED THAT THE AILERON TRIM WAS WORKING IMPROPERLY -- IT WAS RIGGED BACKWARDS. WE ALSO ENCOUNTERED PRESSURIZATION PROBS. AFTER LNDG; THE ACFT WAS WRITTEN UP AND GNDED UNTIL PROPER REPAIRS WERE MADE. AFTER TALKING TO CHIEF PLT AND MAINT CTL; THIS WAS NOT THE FIRST TIME THIS HAD OCCURRED. I WAS UNAWARE THAT THE AILERON TRIM HAD BEEN DISMANTLED AND RERIGGED PRIOR TO TEST FLT. MAINT NEVER TOLD ME THIS -- THEY WERE RUSHING TO GET THE PLANE OUT FOR TEST FLT. IF I HAD BEEN AWARE OF PREVIOUS PROBS OF RIGGING BACKWARDS AND EXTENT OF MAINT PROC; I WOULD HAVE BEEN LOOKING FOR THIS PROB IN THE FIRST PLACE.