What was found
(CAN) ON ROUTE FROM FORT ST. JOHN (YXJ) TO FORT NELSON (YYE), CANADIAN REGIONAL AIRCRAFT C-FDND,S/N 129 REPORTED THROUGH YXJ OPS THAT THE #1 ADI AND HSI WERE BOTH FLAGGED. ALL ATTEMPTS BY THE CREW TO RESURRECT FAILED. DECISION MADE TO REROUTE AIRCRAFT TO EDMONTON (YEG) FOR REPAIRS.MAINTENANCE INSPECTION FOUND THE AHRS DATA INVALID - #1 ALTITUDE SHOWED 25-30 DEGREES NOSE DOWN.MAINTENANCE REPLACED AHRS UNIT, S/N: ON 86010321, S/N: OFF 87080756 AND THE SYSTEM TESTED SERVICEABLE. AIRCRAFT RETURNED TO SERVICE WITH NO FURTHER INCIDENTS TO REPORT.