Narrative:

This flight was the 2ND all nighter on the backside of the backside of the clock. All the crew were not time zoned yet. After passing chkpoint omlet, first officer made a random heading check and discovered aircraft was approximately 13.5 degrees from proper heading. Winds were westerly approximately 150 KTS. We were heading south at FL370. Autoplt roll computer had failed. I 'the captain' tried to slew aircraft to proper heading with 'heading select' knob. No response. Tried 'heading hold' mode. No response. Then disconnected autoplt and hand flew aircraft to proper heading to reintercept airway. When the roll computer failed aircraft went into a 2-3 degree left bank, not enough of a bank to notice. This turn plus westerly wind of 150 KTS blew us approximately 45 NM east of course before we realized something was amiss. Until I disconnected the autoplt, even though the roll computer had failed (we did not know what was wrong with the aircraft until the next night's flight when I checked with maintenance) the autoplt stayed engaged and nothing abnormal was annunciated. This is particularly insidious because at high altitudes, low airspds, high winds 150-200 KTS, crab angle can exceed 20 degrees. I reestimated the next chkpoint 7 mins later to tyo control. 5 mins later they called back and asked us to confirm our estimate. We did and that was it so far. Lessons learned: 1) something is needed to annunciate a massive course deviation such as we experienced. 2) when the entire crew is very tired it is essential that constant aircraft checks are made. I have flown international approximately 6 yrs of my career and this is the first time something this gross has happened to me. It will not happen again!

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Original NASA ASRS Text

Title: GROSS NAV ERROR EVOLVES FROM HDG TRACK POS DEV. ACFT EQUIP PROB MALFUNCTION.

Narrative: THIS FLT WAS THE 2ND ALL NIGHTER ON THE BACKSIDE OF THE BACKSIDE OF THE CLOCK. ALL THE CREW WERE NOT TIME ZONED YET. AFTER PASSING CHKPOINT OMLET, FO MADE A RANDOM HDG CHK AND DISCOVERED ACFT WAS APPROX 13.5 DEGS FROM PROPER HDG. WINDS WERE WESTERLY APPROX 150 KTS. WE WERE HDG S AT FL370. AUTOPLT ROLL COMPUTER HAD FAILED. I 'THE CAPT' TRIED TO SLEW ACFT TO PROPER HDG WITH 'HDG SELECT' KNOB. NO RESPONSE. TRIED 'HDG HOLD' MODE. NO RESPONSE. THEN DISCONNECTED AUTOPLT AND HAND FLEW ACFT TO PROPER HDG TO REINTERCEPT AIRWAY. WHEN THE ROLL COMPUTER FAILED ACFT WENT INTO A 2-3 DEG L BANK, NOT ENOUGH OF A BANK TO NOTICE. THIS TURN PLUS WESTERLY WIND OF 150 KTS BLEW US APPROX 45 NM E OF COURSE BEFORE WE REALIZED SOMETHING WAS AMISS. UNTIL I DISCONNECTED THE AUTOPLT, EVEN THOUGH THE ROLL COMPUTER HAD FAILED (WE DID NOT KNOW WHAT WAS WRONG WITH THE ACFT UNTIL THE NEXT NIGHT'S FLT WHEN I CHKED WITH MAINT) THE AUTOPLT STAYED ENGAGED AND NOTHING ABNORMAL WAS ANNUNCIATED. THIS IS PARTICULARLY INSIDIOUS BECAUSE AT HIGH ALTS, LOW AIRSPDS, HIGH WINDS 150-200 KTS, CRAB ANGLE CAN EXCEED 20 DEGS. I REESTIMATED THE NEXT CHKPOINT 7 MINS LATER TO TYO CTL. 5 MINS LATER THEY CALLED BACK AND ASKED US TO CONFIRM OUR ESTIMATE. WE DID AND THAT WAS IT SO FAR. LESSONS LEARNED: 1) SOMETHING IS NEEDED TO ANNUNCIATE A MASSIVE COURSE DEV SUCH AS WE EXPERIENCED. 2) WHEN THE ENTIRE CREW IS VERY TIRED IT IS ESSENTIAL THAT CONSTANT ACFT CHKS ARE MADE. I HAVE FLOWN INTL APPROX 6 YRS OF MY CAREER AND THIS IS THE FIRST TIME SOMETHING THIS GROSS HAS HAPPENED TO ME. IT WILL NOT HAPPEN AGAIN!

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.