Narrative:

FMS primary navigation system went into frozen state and was unable to unfreeze or use it. Reverted to omegas (2 on board) but they soon went in 'dr' dead reckoning and I noticed we had deviated off course, approximately 15 mi south of airway G581. According to j-aid, greater than 10 NM offshore, up to 20 NM off course is allowed. We had only gone off course approximately 15 mi, but would like to file this report anyway as a safety precaution. We contacted tokyo control and advised them of our navigation malfunction and that we were correcting to the left bank on course. No other comments/discussion were made.

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Original NASA ASRS Text

Title: HDG TRACK POS DEV IN AN OVERWATER, NIGHT OP, IN FOREIGN AIRSPACE.

Narrative: FMS PRIMARY NAV SYS WENT INTO FROZEN STATE AND WAS UNABLE TO UNFREEZE OR USE IT. REVERTED TO OMEGAS (2 ON BOARD) BUT THEY SOON WENT IN 'DR' DEAD RECKONING AND I NOTICED WE HAD DEVIATED OFF COURSE, APPROX 15 MI S OF AIRWAY G581. ACCORDING TO J-AID, GREATER THAN 10 NM OFFSHORE, UP TO 20 NM OFF COURSE IS ALLOWED. WE HAD ONLY GONE OFF COURSE APPROX 15 MI, BUT WOULD LIKE TO FILE THIS RPT ANYWAY AS A SAFETY PRECAUTION. WE CONTACTED TOKYO CTL AND ADVISED THEM OF OUR NAV MALFUNCTION AND THAT WE WERE CORRECTING TO THE L BANK ON COURSE. NO OTHER COMMENTS/DISCUSSION WERE MADE.

Data retrieved from NASA's ASRS site as of July 2007 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.