Narrative:

First officer PF of 3-MAN crew with also 1 jumpseater of same company and type rating. Departed lszh on runway 34; deges 1F. Autoplt and LNAV engaged and active at 500 ft AGL. Shortly after departure; around 2400 ft AGL; aircraft made sharp 90 degree turn to the left; while the FMS magenta track still showed/displayed a forward track-continuation of runway centerline extension. First officer exclaimed 'what's it doing?' since the magenta track did not update itself with new current direction. Air speed was at approximately 178 KTS to maintain SID climb gradient. None of the pilots offered any explanation. Captain said to kick it off autoplt and fly the magenta track. As the aircraft was returned to the magenta track; tower asked why the turn was delayed. Captain responded with 'FMS discrepancy.' nothing further was said. Crew was on a long duty day; totaling 19 hours 15 mins. This was the second leg. First officer had also previously flown first leg 6 hours 9 mins; and at request of captain remained in seat for second leg. First officer had flown first leg without crew rotation rest. First officer was on 30TH day of trip and total block hours of just over 111 hours. Also; captain wanted to make critical slot time for takeoff to prevent further delays. I believe the rush; fatigue; and this airport being a first time for all crew members contributed to the delay in recognition of what the FMS tracking may have been indicating.

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Original NASA ASRS Text

Title: B747 CREW HAS COURSE DEV ON DEGES 1F DEP LEAVING LSZH.

Narrative: FO PF OF 3-MAN CREW WITH ALSO 1 JUMPSEATER OF SAME COMPANY AND TYPE RATING. DEPARTED LSZH ON RWY 34; DEGES 1F. AUTOPLT AND LNAV ENGAGED AND ACTIVE AT 500 FT AGL. SHORTLY AFTER DEP; AROUND 2400 FT AGL; ACFT MADE SHARP 90 DEG TURN TO THE L; WHILE THE FMS MAGENTA TRACK STILL SHOWED/DISPLAYED A FORWARD TRACK-CONTINUATION OF RWY CTRLINE EXTENSION. FO EXCLAIMED 'WHAT'S IT DOING?' SINCE THE MAGENTA TRACK DID NOT UPDATE ITSELF WITH NEW CURRENT DIRECTION. AIR SPD WAS AT APPROX 178 KTS TO MAINTAIN SID CLB GRADIENT. NONE OF THE PLTS OFFERED ANY EXPLANATION. CAPT SAID TO KICK IT OFF AUTOPLT AND FLY THE MAGENTA TRACK. AS THE ACFT WAS RETURNED TO THE MAGENTA TRACK; TWR ASKED WHY THE TURN WAS DELAYED. CAPT RESPONDED WITH 'FMS DISCREPANCY.' NOTHING FURTHER WAS SAID. CREW WAS ON A LONG DUTY DAY; TOTALING 19 HRS 15 MINS. THIS WAS THE SECOND LEG. FO HAD ALSO PREVIOUSLY FLOWN FIRST LEG 6 HRS 9 MINS; AND AT REQUEST OF CAPT REMAINED IN SEAT FOR SECOND LEG. FO HAD FLOWN FIRST LEG WITHOUT CREW ROTATION REST. FO WAS ON 30TH DAY OF TRIP AND TOTAL BLOCK HRS OF JUST OVER 111 HRS. ALSO; CAPT WANTED TO MAKE CRITICAL SLOT TIME FOR TKOF TO PREVENT FURTHER DELAYS. I BELIEVE THE RUSH; FATIGUE; AND THIS ARPT BEING A FIRST TIME FOR ALL CREW MEMBERS CONTRIBUTED TO THE DELAY IN RECOGNITION OF WHAT THE FMS TRACKING MAY HAVE BEEN INDICATING.

Data retrieved from NASA's ASRS site as of January 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.