EMB120 RUDDER AND RUDDER TRIM TAB FROZE WHILE APCHING ACV. CABLES WERE LOCKED BY ICE THAT HAD FORMED IN THE TAIL CONE WHEN A DRAIN HAD BECOME PLUGGED AND WATER HAD ACCUMULATED. THIS RPT CAME FROM THE PLT WHO FLEW THE ACFT IMMEDIATELY AFTER THE INCIDENT.

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THIS EVENT BEGAN WITH THE POSTFLT INSPECTION OF EMB120. THE CREW WHO HAD JUST LANDED THIS ACFT IN ARCATA RPTED THAT WHILE ON FINAL DSCNT INTO ACV THEIR RUDDER TRIM AND RUDDER PEDAL CTLS HAD FROZEN INFLT. AFTER THE ACFT WAS WRITTEN UP FOR THIS PROB A POSTFLT INSPECTION WAS PERFORMED BY A LCL A&P MECH. THE MECH DISCOVERED THAT THE MAIN TAIL CONE DRAIN TUBE HAD PLUGGED UP WITH DEBRIS CAUSING A LARGE AMOUNT OF WATER (ESTIMATED 5 GALLONS) TO ACCUMULATE IN THE TAIL CONE. THIS TRAPPED WATER HAD BEGUN TO FREEZE AND THUS CAUSED THE RUDDER CTL CABLES TO FREEZE UP. SEVERAL CHUNKS OF ICE WERE ACTUALLY REMOVED FROM INSIDE THE TAIL CONE AREA. I FEEL THAT THE BEST SOLUTION WOULD BE TO REDESIGN THE APU AIR INLET SO THAT NO WATER IS ALLOWED TO ENTER THIS COMPARTMENT WHICH ALSO HOUSES THE FLT CTL CABLES. ALSO; THE DRAIN SYS NEEDS TO BE IMPROVED SO THAT A BLOCKAGE WOULD BE EXTREMELY REMOTE. AT THE BARE MINIMUM THE TAIL CONE COMPARTMENT SHOULD BE CHKED DAILY BY MAINT PERSONNEL FOR ANY ACCUMULATION OF WATER AND ALSO THE DRAIN TUBE SHOULD BE CHKED DAILY FOR ANY OBSTRUCTIONS. I FEEL THAT THIS SIT IS POTENTIALLY VERY DANGEROUS AND SHOULD BE CORRECTED ON ALL EMB120 ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT A SVC BULLETIN HAD BEEN ISSUED PRIOR TO THIS EVENT REGARDING THIS MATTER. UNFORTUNATELY; THE ACFT INVOLVED HAD NOT YET BEEN MODIFIED. HE HAS SINCE CHKED WITH THE MAINT DEPT AND THE MODIFICATION HAS NOW BEEN PERFORMED ON THIS ACFT. HE STRESSED THAT THE AREA INVOLVED CONTAINS THE CTL CABLE FOR ALL 3 AXES; RUDDER; ELEVATOR AND AILERON. BECAUSE OF THIS; HE THINKS THIS PROB IS VERY SERIOUS. HE SAID THE AREA INVOLVED IS DIRECTLY BEHIND THE CABIN PRESSURE BULKHEAD AND THERE IS NO WAY TO INSPECT IT. THE SOURCE OF THE WATER IS A SCREENED OPENING ABOUT THE SIZE OF A PHONE BOOK IN THE UPPER SKIN OF THE FUSELAGE AT ABOUT THE 1 O'CLOCK POS. THEORETICALLY; IF THE DRAIN WAS CLOGGED AND THE ACFT WAS PARKED IN THE RAIN FOR AN EXTENDED PERIOD; A TON OF WATER COULD COLLECT THERE. HE SAID THERE IS NO APPARENT ATTEMPT TO DEFLECT WATER FROM THE INLET; EITHER INFLT OR PARKED ON THE GND. HE ADDED THAT THE INCOMING FLT HAD THE RUDDER TRIM TAB COMPLETELY FROZEN AND THAT THE RUDDER ITSELF STILL HAD SOME FREEDOM.