Narrative:

Problem reported: defective navigation and flight management computers. I was the PIC and captain of flight departing from sfo to ZZZZ. I was assisted by a flying first officer; a B777 pilot instructor from our flight training center and by two additional first officer relief pilots. Our aircraft was a boeing B777-200B. The route of flight; which was ACARS loaded directly from dispatch to our FMC was as follows: sfo direct eni direct tou J523 yzp TR19 fried direct 57n140w direct 59n150w direct vidda J501 bet direct nanza R220 nikll R220 nuzan R220 nodan R217 sde direct gtc L512 watry Y14 jec.... The flight was conducted under normal SOP's with several pilots checking the planned route of flight and position check prior to pushback. Once airborne; the flight was cleared direct tou. When this clearance was received; we selected abeam points and also route copy into route two. No other flight plan changes were made. Approximately five minutes prior to approaching fix yzp; we did a wind update through ACARS. This was received; loaded and executed. Upon passing fix yzp the aircraft commanded; through the autopilot and flight director system; a hard right turn to what might have been a reversal of course. We interrupted this immediately by selecting heading select; deselecting LNAV navigation. At this point we both wondered what had caused this interruption of our aircraft following our planned route. We observed the following: position fried the next waypoint was depicted ahead of us but was not the active waypoint. It did not appear at the top right corner of our nd and it no longer appeared on our legs page. Fried was depicted in white lettering. Position 57n140w appeared further north of fried and was now the active waypoint in magenta lettering although the aircraft was not navigating to that fix either. 57n140w was found on the legs page. Since this is almost a straight course from yzp through fried to 57n140w we found this most puzzling. No fix was listed as the active waypoint on the nd top corner. We immediately checked our position and we were still in radar contact with vancouver ATC within their fir. Our position was correct. We immediately checked our routing and for reference sake; we were able to refer back to our copy of route two to additionally verify that all our courses; headings; bearings and airways were entered correctly. Reference to our position reference also verified our correct position by GPS. There was no gross navigation error because of our quick handling of the matter; our intervention in going to heading select for navigation along our intended flight path and magenta line. We found this circumstance quite remarkable and initiated a call to maintenance and dispatch. Maintenance reported that the aircraft had received a navigation database update immediately prior to our flight. This database was loaded but was not in use as the dates for the database were in the future. Maintenance had no idea why we would have this difficulty. Our pilot instructor who has considerable experience in the aircraft was also completely surprised and could not account for the reason for the navigation disruption. We discussed this matter with our dispatcher and maintenance by satcom and they had no explanation or suggestion about a course of action; so the dispatcher called the manager on duty. We received the following ACARS note: 'duty manager wants to watch how remainder of flight goes? See if anything new develops? They also want you to call on ground and talk with him I think they are still trying to decide what to do beyond that.' the flight continued normally with extra vigilance to check positions and routings and to watch for any other aircraft or navigation anomalies. Before our satcom call with dispatch was closed; I suggested that if a navigation database could have been corrupted that perhaps other B777 aircraft in our fleet could be similarly affected. I suggested that dispatch notify other airborne aircraft to be extra vigilant. Some time later we experienced another navigation anomaly. My relief first officers were flying the aircraft. I had briefed them to be extra vigilant about any navigation or system anomaly. They observed that as the aircraft approached 59n150w that the moving map nd display depicted this fix as 58n150w! A quick reference to the position reference page did in fact show us on course approaching the correct latitude and longitude fix of 59n150w. Why the FMC or database changed the description of the fix from 59N to 58N is beyond belief. Route two information remains frozen in time and included all of our routings after tou. We continued to monitor the FMC and navigation closely and found a third anomaly. We discovered that after each waypoint fix on the progress position report page that the letter 'west' was affixed after each position so that position nalyd was shown as 'nalyd west.' this was true of the past waypoint; future EST waypoint and next waypoint. Each had a 'west.' we have never seen this before. We continued to conduct the flight with greater vigilance to our destination and after landing briefed the maintenance crew. They thought initially that we had been using the new database. This is not correct. They were confused about why or how entering a new database could corrupt an old database; if in fact; this is the problem with the aircraft.callback conversation with reporter revealed the following information: two weeks after the incident the reporter had not received any information from his company as to what may have occurred. No navigation errors occurred as the problem was quickly discovered by the flight crew.

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Original NASA ASRS Text

Title: B777 CAPT REPORTS FMC NAVIGATION DATABASE ANOMALIES DURING FLIGHT TO ASIA.

Narrative: PROBLEM REPORTED: DEFECTIVE NAVIGATION AND FLIGHT MANAGEMENT COMPUTERS. I WAS THE PIC AND CAPTAIN OF FLT DEPARTING FROM SFO TO ZZZZ. I WAS ASSISTED BY A FLYING FO; A B777 PILOT INSTRUCTOR FROM OUR FLIGHT TRAINING CENTER AND BY TWO ADDITIONAL FO RELIEF PILOTS. OUR AIRCRAFT WAS A BOEING B777-200B. THE ROUTE OF FLIGHT; WHICH WAS ACARS LOADED DIRECTLY FROM DISPATCH TO OUR FMC WAS AS FOLLOWS: SFO DIRECT ENI DIRECT TOU J523 YZP TR19 FRIED DIRECT 57N140W DIRECT 59N150W DIRECT VIDDA J501 BET DIRECT NANZA R220 NIKLL R220 NUZAN R220 NODAN R217 SDE DIRECT GTC L512 WATRY Y14 JEC.... THE FLIGHT WAS CONDUCTED UNDER NORMAL SOP'S WITH SEVERAL PILOTS CHECKING THE PLANNED ROUTE OF FLIGHT AND POSITION CHECK PRIOR TO PUSHBACK. ONCE AIRBORNE; THE FLIGHT WAS CLEARED DIRECT TOU. WHEN THIS CLEARANCE WAS RECEIVED; WE SELECTED ABEAM POINTS AND ALSO ROUTE COPY INTO ROUTE TWO. NO OTHER FLIGHT PLAN CHANGES WERE MADE. APPROXIMATELY FIVE MINUTES PRIOR TO APPROACHING FIX YZP; WE DID A WIND UPDATE THROUGH ACARS. THIS WAS RECEIVED; LOADED AND EXECUTED. UPON PASSING FIX YZP THE AIRCRAFT COMMANDED; THROUGH THE AUTOPILOT AND FLIGHT DIRECTOR SYSTEM; A HARD RIGHT TURN TO WHAT MIGHT HAVE BEEN A REVERSAL OF COURSE. WE INTERRUPTED THIS IMMEDIATELY BY SELECTING HEADING SELECT; DESELECTING LNAV NAVIGATION. AT THIS POINT WE BOTH WONDERED WHAT HAD CAUSED THIS INTERRUPTION OF OUR AIRCRAFT FOLLOWING OUR PLANNED ROUTE. WE OBSERVED THE FOLLOWING: POSITION FRIED THE NEXT WAYPOINT WAS DEPICTED AHEAD OF US BUT WAS NOT THE ACTIVE WAYPOINT. IT DID NOT APPEAR AT THE TOP RIGHT CORNER OF OUR ND AND IT NO LONGER APPEARED ON OUR LEGS PAGE. FRIED WAS DEPICTED IN WHITE LETTERING. POSITION 57N140W APPEARED FURTHER NORTH OF FRIED AND WAS NOW THE ACTIVE WAYPOINT IN MAGENTA LETTERING ALTHOUGH THE AIRCRAFT WAS NOT NAVIGATING TO THAT FIX EITHER. 57N140W WAS FOUND ON THE LEGS PAGE. SINCE THIS IS ALMOST A STRAIGHT COURSE FROM YZP THROUGH FRIED TO 57N140W WE FOUND THIS MOST PUZZLING. NO FIX WAS LISTED AS THE ACTIVE WAYPOINT ON THE ND TOP CORNER. WE IMMEDIATELY CHECKED OUR POSITION AND WE WERE STILL IN RADAR CONTACT WITH VANCOUVER ATC WITHIN THEIR FIR. OUR POSITION WAS CORRECT. WE IMMEDIATELY CHECKED OUR ROUTING AND FOR REFERENCE SAKE; WE WERE ABLE TO REFER BACK TO OUR COPY OF ROUTE TWO TO ADDITIONALLY VERIFY THAT ALL OUR COURSES; HEADINGS; BEARINGS AND AIRWAYS WERE ENTERED CORRECTLY. REFERENCE TO OUR POS REF ALSO VERIFIED OUR CORRECT POSITION BY GPS. THERE WAS NO GROSS NAVIGATION ERROR BECAUSE OF OUR QUICK HANDLING OF THE MATTER; OUR INTERVENTION IN GOING TO HEADING SELECT FOR NAVIGATION ALONG OUR INTENDED FLIGHT PATH AND MAGENTA LINE. WE FOUND THIS CIRCUMSTANCE QUITE REMARKABLE AND INITIATED A CALL TO MAINT AND DISPATCH. MAINT REPORTED THAT THE AIRCRAFT HAD RECEIVED A NAVIGATION DATABASE UPDATE IMMEDIATELY PRIOR TO OUR FLIGHT. THIS DATABASE WAS LOADED BUT WAS NOT IN USE AS THE DATES FOR THE DATABASE WERE IN THE FUTURE. MAINT HAD NO IDEA WHY WE WOULD HAVE THIS DIFFICULTY. OUR PILOT INSTRUCTOR WHO HAS CONSIDERABLE EXPERIENCE IN THE AIRCRAFT WAS ALSO COMPLETELY SURPRISED AND COULD NOT ACCOUNT FOR THE REASON FOR THE NAVIGATION DISRUPTION. WE DISCUSSED THIS MATTER WITH OUR DISPATCHER AND MAINT BY SATCOM AND THEY HAD NO EXPLANATION OR SUGGESTION ABOUT A COURSE OF ACTION; SO THE DISPATCHER CALLED THE MGR ON DUTY. WE RECEIVED THE FOLLOWING ACARS NOTE: 'DUTY MANAGER WANTS TO WATCH HOW REMAINDER OF FLT GOES? SEE IF ANYTHING NEW DEVELOPS? THEY ALSO WANT YOU TO CALL ON GROUND AND TALK WITH HIM I THINK THEY ARE STILL TRYING TO DECIDE WHAT TO DO BEYOND THAT.' THE FLIGHT CONTINUED NORMALLY WITH EXTRA VIGILANCE TO CHECK POSITIONS AND ROUTINGS AND TO WATCH FOR ANY OTHER AIRCRAFT OR NAVIGATION ANOMALIES. BEFORE OUR SATCOM CALL WITH DISPATCH WAS CLOSED; I SUGGESTED THAT IF A NAVIGATION DATABASE COULD HAVE BEEN CORRUPTED THAT PERHAPS OTHER B777 AIRCRAFT IN OUR FLEET COULD BE SIMILARLY AFFECTED. I SUGGESTED THAT DISPATCH NOTIFY OTHER AIRBORNE AIRCRAFT TO BE EXTRA VIGILANT. SOME TIME LATER WE EXPERIENCED ANOTHER NAVIGATION ANOMALY. MY RELIEF FIRST OFFICERS WERE FLYING THE AIRCRAFT. I HAD BRIEFED THEM TO BE EXTRA VIGILANT ABOUT ANY NAVIGATION OR SYSTEM ANOMALY. THEY OBSERVED THAT AS THE AIRCRAFT APPROACHED 59N150W THAT THE MOVING MAP ND DISPLAY DEPICTED THIS FIX AS 58N150W! A QUICK REFERENCE TO THE POS REF PAGE DID IN FACT SHOW US ON COURSE APPROACHING THE CORRECT LATITUDE AND LONGITUDE FIX OF 59N150W. WHY THE FMC OR DATABASE CHANGED THE DESCRIPTION OF THE FIX FROM 59N TO 58N IS BEYOND BELIEF. ROUTE TWO INFORMATION REMAINS FROZEN IN TIME AND INCLUDED ALL OF OUR ROUTINGS AFTER TOU. WE CONTINUED TO MONITOR THE FMC AND NAVIGATION CLOSELY AND FOUND A THIRD ANOMALY. WE DISCOVERED THAT AFTER EACH WAYPOINT FIX ON THE PROGRESS POS REPORT PAGE THAT THE LETTER 'W' WAS AFFIXED AFTER EACH POSITION SO THAT POSITION NALYD WAS SHOWN AS 'NALYD W.' THIS WAS TRUE OF THE PAST WAYPOINT; FUTURE EST WAYPOINT AND NEXT WAYPOINT. EACH HAD A 'W.' WE HAVE NEVER SEEN THIS BEFORE. WE CONTINUED TO CONDUCT THE FLIGHT WITH GREATER VIGILANCE TO OUR DESTINATION AND AFTER LANDING BRIEFED THE MAINTENANCE CREW. THEY THOUGHT INITIALLY THAT WE HAD BEEN USING THE NEW DATABASE. THIS IS NOT CORRECT. THEY WERE CONFUSED ABOUT WHY OR HOW ENTERING A NEW DATABASE COULD CORRUPT AN OLD DATABASE; IF IN FACT; THIS IS THE PROBLEM WITH THE AIRCRAFT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: TWO WEEKS AFTER THE INCIDENT THE REPORTER HAD NOT RECEIVED ANY INFORMATION FROM HIS COMPANY AS TO WHAT MAY HAVE OCCURRED. NO NAV ERRORS OCCURRED AS THE PROBLEM WAS QUICKLY DISCOVERED BY THE FLT CREW.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.