Narrative:

The flight had been cleared to climb to FL390, due to poor climb performance, passing approximately FL375, clearance to return to and maintain FL370 was requested by the crew and received from ZAB. As the aircraft was passing FL377, I was instructed to select the flight level change mode on the autoplt. I did so, and at the same time, also set a lower mach number in the speed window since we were very near vmo, I did not want to set off the speed warning siren. I was unaware that the captain had turned off the autothrottle and manually advanced the throttles to maximum climb. Apparently he had misread the altimeter. Even so, instead of descending as commanded, the autoplt did not, and apparently attempted to maintain the set speed of mach .82. At approximately FL379 to FL380, I questioned why we were still climbing, and selected the vertical speed mode on the autoplt to initiate the descent. The captain immediately contacted center. The controller acknowledged and the aircraft was quickly returned to FL370. Crew fatigue was undoubtedly a factor. This was the third leg of an all night xcontinent flight at that period just before dawn, where the effects of flying on the 'backside of the clock' seem most severe. Supplemental information from acn 334680: the aircraft needed to descend to FL370 and I believed it needed to climb. I made the situation worse by disengaging the autothrottles and manually selecting climb thrust. At that thrust and speed the aircraft could not descend without reducing power. As the autothrottles were disengaged the autoplt could not control thrust. Due to the early hour there was no other traffic. Had I verbalized what I thought the situation was, the first officer would have corrected me.

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Original NASA ASRS Text

Title: WHEN A B757 WAS UNABLE TO CLB TO THE ASSIGNED ALT DUE TO ITS HVY WT, THE FLC OBTAINED A CLRNC FOR A LOWER ALT. THE PF MISREAD THE ALTIMETER AND INITIATED CONFLICTING COMMANDS BY DISENGAGING THE AUTOTHROTTLES AND MANUALLY SELECTING CLB THRUST WHILE THE PNF WAS SELECTING THE FLT LEVEL CHANGE MODE ON THE AUTOPLT FOR A DSCNT BACK DOWN TO FL370. THE ACFT CONTINUED TO CLB. BOTH CREW MEMBERS RPT FATIGUE AS A CONTRIBUTING FACTOR.

Narrative: THE FLT HAD BEEN CLRED TO CLB TO FL390, DUE TO POOR CLB PERFORMANCE, PASSING APPROX FL375, CLRNC TO RETURN TO AND MAINTAIN FL370 WAS REQUESTED BY THE CREW AND RECEIVED FROM ZAB. AS THE ACFT WAS PASSING FL377, I WAS INSTRUCTED TO SELECT THE FLT LEVEL CHANGE MODE ON THE AUTOPLT. I DID SO, AND AT THE SAME TIME, ALSO SET A LOWER MACH NUMBER IN THE SPD WINDOW SINCE WE WERE VERY NEAR VMO, I DID NOT WANT TO SET OFF THE SPD WARNING SIREN. I WAS UNAWARE THAT THE CAPT HAD TURNED OFF THE AUTOTHROTTLE AND MANUALLY ADVANCED THE THROTTLES TO MAX CLB. APPARENTLY HE HAD MISREAD THE ALTIMETER. EVEN SO, INSTEAD OF DSNDING AS COMMANDED, THE AUTOPLT DID NOT, AND APPARENTLY ATTEMPTED TO MAINTAIN THE SET SPD OF MACH .82. AT APPROX FL379 TO FL380, I QUESTIONED WHY WE WERE STILL CLBING, AND SELECTED THE VERT SPD MODE ON THE AUTOPLT TO INITIATE THE DSCNT. THE CAPT IMMEDIATELY CONTACTED CTR. THE CTLR ACKNOWLEDGED AND THE ACFT WAS QUICKLY RETURNED TO FL370. CREW FATIGUE WAS UNDOUBTEDLY A FACTOR. THIS WAS THE THIRD LEG OF AN ALL NIGHT XCONTINENT FLT AT THAT PERIOD JUST BEFORE DAWN, WHERE THE EFFECTS OF FLYING ON THE 'BACKSIDE OF THE CLOCK' SEEM MOST SEVERE. SUPPLEMENTAL INFO FROM ACN 334680: THE ACFT NEEDED TO DSND TO FL370 AND I BELIEVED IT NEEDED TO CLB. I MADE THE SIT WORSE BY DISENGAGING THE AUTOTHROTTLES AND MANUALLY SELECTING CLB THRUST. AT THAT THRUST AND SPD THE ACFT COULD NOT DSND WITHOUT REDUCING PWR. AS THE AUTOTHROTTLES WERE DISENGAGED THE AUTOPLT COULD NOT CTL THRUST. DUE TO THE EARLY HR THERE WAS NO OTHER TFC. HAD I VERBALIZED WHAT I THOUGHT THE SIT WAS, THE FO WOULD HAVE CORRECTED ME.

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.