What was found
(CAN) PROBLEM ORIGINALLY OCCURRED LAST YEAR, HOWEVER WAS ONLY RECENTLY REPORTED TO THE EQUIPMENT MANUFACTURER. TWO ACFT PH-PXB & PH-PXE AFFECTED. WHEN FLYING IN REGION WHERE MAGNETIC VARIATION IS CLOSE TO ZERO DEGREES, THERE IS A POSSIBILITY THAT THE FMS CAUSES A 180 DEGREES INVERSION OF THE COMPASS MAP ON THE HSI DISPLAY. THE FOLLOWING HSI PICTURE TAKEN IN FLIGHT SHOWS THE HELICOPTER FLYING TOWARD 297 DEGREES WHILE THE ACTUAL TRACK & DESIRED TRACK ARE 117 DEGREES. PROBLEM IS OBSERVABLE ON INSTALLATION USING THE FMS PROVIDED MAGNETIC VARIATION ENCODED IN ARINC 429 LABEL 147. CMC HAS CONVENED SAFETY REVIEW BOARD & HAS LOGGED FAULT INVESTIGATION WITH INTENT TO PROVIDE CORRECTIVE ACTION.