Heading track position deviation in an overwater, night operation, in foreign airspace.

Attributes
ACN	293573
Time
Date	199501
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : rjtg
State Reference	FO
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	L-1011-1 100/200/250
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute : other oceanic enroute : pacific enroute airway : rjtg
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time total : 8500
ASRS Report	293573
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

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.

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.