Narrative:

I was given a descent to cross lizio at FL250. As there was WX underneath us, I elected to wait until the last moment to descend. The FMC was programmed and, as I approached the descent point, my finger on the flight level change button, I noticed a skip on the screen and we were past the descent point. I selected flight level change and closed the throttles. The descent point at FL250 now showed beyond lizio. The speed brake was deployed half-way and the descent arc showed at lizio. After a min, the descent arc went beyond lizio and more speed brake was deployed, bringing the arc back to lizio. Just before lizio, I was given a descent to 15000 ft, so the speed brake was left in the deployed position and I was descending at more than 6000 FPM. As the mileage at lizio went to zero, I was out of FL265 and, several seconds later, out of FL250, resulting in being too high at lizio. Nothing was said, and the rest of the flight continued normally. My conclusion is that I did not have a screen shift, but that I had fixated on the screen, eyes wide open, and had a sleep event. This all happened in a short period of time, while the first officer was getting the ATIS and calling company.

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Original NASA ASRS Text

Title: THE CAPT OF A B757-200 THINKS HE MAY HAVE EXPERIENCED A MICRO-SLEEP EVENT, DURING AN APCH WITH ZDC, CAUSING HIM TO CROSS LIZIO ABOVE HIS ASSIGNED ALT.

Narrative: I WAS GIVEN A DSCNT TO CROSS LIZIO AT FL250. AS THERE WAS WX UNDERNEATH US, I ELECTED TO WAIT UNTIL THE LAST MOMENT TO DSND. THE FMC WAS PROGRAMMED AND, AS I APCHED THE DSCNT POINT, MY FINGER ON THE FLT LEVEL CHANGE BUTTON, I NOTICED A SKIP ON THE SCREEN AND WE WERE PAST THE DSCNT POINT. I SELECTED FLT LEVEL CHANGE AND CLOSED THE THROTTLES. THE DSCNT POINT AT FL250 NOW SHOWED BEYOND LIZIO. THE SPD BRAKE WAS DEPLOYED HALF-WAY AND THE DSCNT ARC SHOWED AT LIZIO. AFTER A MIN, THE DSCNT ARC WENT BEYOND LIZIO AND MORE SPD BRAKE WAS DEPLOYED, BRINGING THE ARC BACK TO LIZIO. JUST BEFORE LIZIO, I WAS GIVEN A DSCNT TO 15000 FT, SO THE SPD BRAKE WAS LEFT IN THE DEPLOYED POS AND I WAS DSNDING AT MORE THAN 6000 FPM. AS THE MILEAGE AT LIZIO WENT TO ZERO, I WAS OUT OF FL265 AND, SEVERAL SECONDS LATER, OUT OF FL250, RESULTING IN BEING TOO HIGH AT LIZIO. NOTHING WAS SAID, AND THE REST OF THE FLT CONTINUED NORMALLY. MY CONCLUSION IS THAT I DID NOT HAVE A SCREEN SHIFT, BUT THAT I HAD FIXATED ON THE SCREEN, EYES WIDE OPEN, AND HAD A SLEEP EVENT. THIS ALL HAPPENED IN A SHORT PERIOD OF TIME, WHILE THE FO WAS GETTING THE ATIS AND CALLING COMPANY.

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.