MAINTENANCE WORK BEING DONE IN THE COCKPIT RESULTED IN FULL RUDDER TRIM GOING UNNOTICED BY THE FLT CREW.

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THIS HAZARDOUS INCIDENT OCCURRED ON AN ADVANCED MLG ACFT AND WOULD NOT HAVE BEEN POSSIBLE IN THE OLDER MLG. IT INVOLVES THE RUDDER TRIM SYS. WE WERE LATE DUE TO A FUEL GAUGE PROB. WE THOUGHT MAINT WAS DONE TROUBLE-SHOOTING AND WE WAITED ON THE ACFT LOGBOOK. WE ACCOMPLISHED THE BEFORE START CHKLIST AND AS PART OF THAT CHKLIST; CHKED THE RUDDER AND AILERON TRIM AT NEUTRAL. MAINT CAME BACK IN THE COCKPIT AND PROCEEDED TO WORK OVER THE PEDESTAL TO SWAP FUEL GAUGES AND FINISH THE LOGBOOK. THE PF WAS A CAPT UPGRADE DOING IOE IN THE LEFT SEAT. WE HAD A STRONG XWIND (20 GUSTING TO 30 KTS) AND NEITHER PLT NOTICED ANYTHING WRONG UNTIL AIRBORNE WHEN INSTEAD OF WX VANING INTO THE WIND WHEN RUDDER WAS RELEASED; THE PLANE ROLLED AWAY FROM THE XWIND AND FULL YOKE INTO THE WIND WAS REQUIRED TO STOP THE ROLL. WE THEN DISCOVERED THE RUDDER TRIM WAS FULL RIGHT (15 UNITS) OPP THE LEFT XWIND. APPARENTLY THE MECH WHILE WORKING OVER THE PEDESTAL INADVERTENTLY ACTUATED. THE RUDDER TRIM WHICH IS ELECTRICALLY OPERATED ON THE MLG. ALL CHKLIST AND COMPANY PROCS WERE FOLLOWED YET THIS STILL OCCURRED. THIS IS AN INHERENTLY BAD DESIGN AND MFG SHOULD KNOW IT! THEY USED A SPLIT SWITCH WITH PROTECTIVE RAILS TO GUARD THE AILERON TRIM; BUT NOTHING GUARDS THE RUDDER TRIM SWITCH. THE FAA SHOULD REQUIRE MFG TO MODIFY THIS SWITCH. PERHAPS A SQUEEZE AND TWIST SWITCH OR ONE THAT MUST BE PULLED UP TO ENERGIZE THE RUDDER TRIM. AT LEAST MAKE THE SWITCH SHORTER AND PLACE PROTECTIVE RAILS AROUND IT. I IMAGINE THIS SCENARIO MAY ALSO BE POSSIBLE ON OTHER NEW COMPANY SUCH AS THE WDB; LGT AND WDB.