What was found
A POST MAINT FLIGHT CHECK OF ACFT WAS CONDUCTED DUE TO AN ENG CHANGE, PROPELLER CHANGE, MULTIPLE FLT CONTROL SURFACE, CONTROL SURFACE CABLE CHANGES, & AN EXTENDED PERIOD OF DOWN TIME IN MAINT (APPROX. 6YRS.) DUE TO EXTREME CORROSION & OTHER MX ITEMS. AFTER TAKING OFF FOR FLIGHT CHECK, PILOT EXPERIENCED ACFT HAVING A NOSE DOWN TENDENCY. PILOT ADJUSTED ELEVATOR TRIM TO CORRECT ATTITUDE, BUT CONDITION WORSENED. PILOT NOTIFIED ATC THAT HE WOULD NEED TO RETURN TO AIRPORT & IT WAS GRANTED. AIRCRAFT LANDED WITHOUT FURTHER INCIDENT & RETURNED TO MAINT HANGAR. ON INVESTIGATION, DISCOVERED THE ELEVATOR TRIM TAB WAS INSTALLED WITH A TWIST IN THE CABLE RESULTING IN OPERATION OF ELEV TRIM TO BE REVERSED. TWIST IN ELEV CABLE CORRECTED, TRIM ACTUATOR & TRIM CABLE TENSION ADJUSTED IAW MM. CONTROL SURFACES RE-INSPECTED TO VERIFY CORRECT INSTALLATION & OPERATION. SECOND FLIGHT CHECK RESULTED IN SATISFACTORY OPS OF ACFT.