Narrative:

On 4/91, I was the captain on flight from narita, japan to ord. I'm an international relief captain. My job is to relieve the captain, first officer and second officer on flts of 12 hours or more in length. On this particular flight, the rest periods were approximately 3 hours in length each; i.e., I took the first 3 hours off, then I relieved the second officer for 3 hours, the first officer for 3 hours, and finally the captain for the last 3 hours of the trip. The trip left narita 40 mins late. Prior to the normal report time of 1 hour before departure time, I had been up for approximately 9 hours (this was due to time lag, having arrived in narita the day before on flight fri from ord). Flight on sat was uneventful up to the point just prior to landing. I was flying the aircraft and approach control at ord was vectoring us for the approach to runway 9R at ord. It is normal procedure for the PNF (in this case, the first officer) to manually set the adjustable speed bug on the both airspeed indicators. The PNF sets his and PF's with a remote knob located on the autoplt/flight director control panel, as the flap confign is changed. We were descending to assigned altitudes when the first officer noted that the speed bugs were not corresponding with inputs from the remote knob. As we approached our assigned altitude of 8000', I realized that I was following the erroneous speed bug and was getting too slow. I applied power and maintained my pitch attitude to accelerate, descending through our assigned altitude of 8000' to approximately 7400', at which point I climbed back to 8000'. The excursion lasted approximately 30 seconds. During recovery (climbing through 7800'), approach control asked us our altitude. We told them 7800' and returning to 8000'. This was the only communication re: the incident. At the time of the excursion I was quite fatigued, having been awake for approximately 22 hours. I erroneously followed the incorrect speed bug rather than the v-spd bugs set on the airspeed indicator, allowing my speed to drop off too rapidly. I feel more study should be given to the problem of crew fatigue, particularly on extended, international flts.

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Original NASA ASRS Text

Title: ACR PIC ON APCH CITES PLT DISTR ACFT EQUIPMENT PROBLEM AND PLT BEHAVIOR FATIGUE AS FACTORS IN ALT DEVIATION.

Narrative: ON 4/91, I WAS THE CAPT ON FLT FROM NARITA, JAPAN TO ORD. I'M AN INTL RELIEF CAPT. MY JOB IS TO RELIEVE THE CAPT, F/O AND S/O ON FLTS OF 12 HRS OR MORE IN LENGTH. ON THIS PARTICULAR FLT, THE REST PERIODS WERE APPROX 3 HRS IN LENGTH EACH; I.E., I TOOK THE FIRST 3 HRS OFF, THEN I RELIEVED THE S/O FOR 3 HRS, THE F/O FOR 3 HRS, AND FINALLY THE CAPT FOR THE LAST 3 HRS OF THE TRIP. THE TRIP LEFT NARITA 40 MINS LATE. PRIOR TO THE NORMAL RPT TIME OF 1 HR BEFORE DEP TIME, I HAD BEEN UP FOR APPROX 9 HRS (THIS WAS DUE TO TIME LAG, HAVING ARRIVED IN NARITA THE DAY BEFORE ON FLT FRI FROM ORD). FLT ON SAT WAS UNEVENTFUL UP TO THE POINT JUST PRIOR TO LNDG. I WAS FLYING THE ACFT AND APCH CTL AT ORD WAS VECTORING US FOR THE APCH TO RWY 9R AT ORD. IT IS NORMAL PROC FOR THE PNF (IN THIS CASE, THE F/O) TO MANUALLY SET THE ADJUSTABLE SPD BUG ON THE BOTH AIRSPD INDICATORS. THE PNF SETS HIS AND PF'S WITH A REMOTE KNOB LOCATED ON THE AUTOPLT/FLT DIRECTOR CTL PANEL, AS THE FLAP CONFIGN IS CHANGED. WE WERE DSNDING TO ASSIGNED ALTS WHEN THE F/O NOTED THAT THE SPD BUGS WERE NOT CORRESPONDING WITH INPUTS FROM THE REMOTE KNOB. AS WE APCHED OUR ASSIGNED ALT OF 8000', I REALIZED THAT I WAS FOLLOWING THE ERRONEOUS SPD BUG AND WAS GETTING TOO SLOW. I APPLIED PWR AND MAINTAINED MY PITCH ATTITUDE TO ACCELERATE, DSNDING THROUGH OUR ASSIGNED ALT OF 8000' TO APPROX 7400', AT WHICH POINT I CLBED BACK TO 8000'. THE EXCURSION LASTED APPROX 30 SECS. DURING RECOVERY (CLBING THROUGH 7800'), APCH CTL ASKED US OUR ALT. WE TOLD THEM 7800' AND RETURNING TO 8000'. THIS WAS THE ONLY COM RE: THE INCIDENT. AT THE TIME OF THE EXCURSION I WAS QUITE FATIGUED, HAVING BEEN AWAKE FOR APPROX 22 HRS. I ERRONEOUSLY FOLLOWED THE INCORRECT SPD BUG RATHER THAN THE V-SPD BUGS SET ON THE AIRSPD INDICATOR, ALLOWING MY SPD TO DROP OFF TOO RAPIDLY. I FEEL MORE STUDY SHOULD BE GIVEN TO THE PROB OF CREW FATIGUE, PARTICULARLY ON EXTENDED, INTL FLTS.

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.