DIVERSION TO ANOTHER ARPT WHEN A FAR EAST DESTINED B777 FLT CREW IS UNABLE TO CLR MULTIPLE MESSAGES OF 'ATT' -- 'SAARU EICAS MESSAGE' AND 'NO LAND #3' REGARDING A FAILURE OF THEIR BACKUP SYS FOR THEIR ADIRU NAV SYS ON FREQ WITH ARTCC.

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APPROX 1 HR ELAPSED FLT TIME AT XA15; FO AND I WERE WORKING OUT A BLEED AIR PROB WITH DISPATCH AND TECHNICIAN; WHEN WE RECEIVED A SAARU (BACKUP STANDBY ATT REF UNIT TO ADIRU) STATUS MESSAGE ALONG WITH A 'NO LAND #3' EICAS MESSAGE; AND AN AMBER 'ATT' (SYMBOL THAT REPLACES THE 'GLASS' STANDBY ATTITUDE INDICATOR; NOT AVAILABLE) BOX IN PLACE OF THE STANDBY ATTITUDE INDICATOR. IN COMPLETE CORPORATION AND COORD WITH TECHNICIAN; THE RELIEF PLT ATTEMPTED TO RESTORE THE SAARU (BACKUP STANDBY ATT REF UNIT TO ADIRU) IN THE E&E COMPARTMENT; UNSUCCESSFULLY. DECIDED TO DIVERT TO ZZZ1. DECLARED AN EMER; AND WITH THE ADVICE OF DISPATCH DUMPED FUEL TO MAX LNDG WT. NORMAL LNDG AT ZZZ1. NOTE: KUDOS TO RELIEF PLT AND EXTRA RELIEF PLT FOR EFFORTS ABOVE AND BEYOND; AND ALSO; AN OUTSTANDING JOB BY OUR ENTIRE FLT ATTENDANT CREW. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: DECISION MADE BY ALL PARTICIPANTS TO DIVERT TO ZZZ1. RPTR STATED THAT THERE WAS NO WAY THAT THE FLT COULD PROCEED ON A 12 HR FLT OVER THE NW TERRITORIES AND POLAR RTES WITH THE LACK OF A STANDBY ATTITUDE INDICATOR AND BACKUP NAV AND INST DISPLAY SYS. THE BLEED AIR PROB WAS A REPEAT ITEM THAT WAS NOT FIXED WITH THE REPAIRS MADE PRIOR TO DEP. THE ACFT WAS TURNED OVER TO MAINT; ANOTHER ACFT WAS USED WITH A NEW CREW AFTER A 3 HR DELAY. RPTING CREW AND FLT ATTENDANTS WENT OFF SCHEDULE; DEADHEADING HOME. RPTR STATED THAT THIS WAS HIS FIRST 'SOLO' TRIP AFTER COMPLETING HIS IOE ON THE B777.