As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DEPARTURE THE CREW REPORTED THAT THE NR1 AHRS (ATTITUDE HEADING REFERENCE SYSTEM) WAS OFF BY 10 DEGREES, THEN A MOMENT LATER REPORTED THAT THE NR 2 AHRS WAS DOING THE SAME. ACFT RETURNING TO DEPARTURE. NR 1 AHRS COMPONENT REPLACED. SYSTEM GROUND CHECKED SERVICEABLE.