As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOST HDG/ATT INDICATION ON LIFT OFF FROM BOS. ALSO, HAD IND OF NR 2 PLATFORM AHRS FAILED. INST LOST WERE ON FIRST OFFICER'S SIDE. WHEN EFIS WAS SELECTED TO BOTH ON ATT INFO WAS REGAINED ON FIRST OFFICER'S SIDE. REPLACED NR 2 AHRS UNIT AND NR 2 SYMBOL GEN, BOTH CK PER MM OPERATION NOW NORMAL IN ALL MODES. PERFORMED RETURN TO SERV TEST, ALL OK.