As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: FLIGHT CREW REPORTED THAT IR1 HAD BLANKED OUT AND AFTER A RESET ON THE OVERHEAD PANEL ALL INDICATIONS WERE THAT THE IR1 WAS OPERATING NORMALLY, HOWEVER IT WAS APPARENT THAT THE MCDU WAS NOT RECEIVING ANY INFORMATION FROM IRI. THE FLIGHT RETURNED TO DEPARTURE WHERE MAINTENANCE REPLACED THE NR 1 ADIRU IAW AMM 34-34-400-001-A. A SATISFACTORY OPS CHECK WAS ACCOMPLISHED IAW AMM 22-96-00-710-001-A & AMM 22-97-00-710-001-A.