Narrative:

We were at a cruise altitude of FL380. I anticipated a crossing altitude of 20 NM west of osi at 8000 ft, and put that in the legs page. Oakland then gave us a clearance to cross runway 30 west of osi at 8000 ft. I reprogrammed the change, and a new descent point came up that looked good. The aircraft started down when it was supposed to and we descended about 500 ft, when the copilot decided he wanted to descend at a faster speed than the normal speed, and so selected vertical speed at 500 FPM. When we were about 6000 ft above the v-nav path, he selected 320 KTS in the speed window and disconnected the autoplt. He hand flew the rest of the descent. We were slowly catching the path, but not close, when we passed through FL180. I suggested that he would have to use the speed brake, which he did after a delay. He was far enough behind the path that it took full speed brake deflection to have the green arc show that we were going to make the crossing. Due to the high rate of descent, the flight director captured the target altitude at about 9700 ft. That caused the autothrottles to bring the power up, and we began to level. At this point, my copilot said he was having trouble with the throttles, and began leveling off. He slowed the descent and stopped slightly above 9000 ft, at which point I reminded him of the 8000 ft crossing. He failed to return to a descent to be at 8000 ft by 30 NM west of osi. I believe from his statement to me, that he momentarily became confused and believed that the target altitude was 9000 ft, because he perceived that the aircraft wanted him to level off. I believe he responded too slowly to my reminder, because of his perception. We crossed the 30 NM fix at 9000 ft, and descended to 8000 ft about 3 NM later. We were fortunate that it was a clear evening and no other aircraft was near. This would not have happened if we had remained on v-nav. I think that my copilot wanted to gain experience hand-flying the aircraft, and did not anticipate the power coming up so early in the descent, causing the incident.

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Original NASA ASRS Text

Title: B777 INBOUND TO SFO MISSED ALT RESTR ON DSCNT.

Narrative: WE WERE AT A CRUISE ALT OF FL380. I ANTICIPATED A XING ALT OF 20 NM W OF OSI AT 8000 FT, AND PUT THAT IN THE LEGS PAGE. OAKLAND THEN GAVE US A CLRNC TO CROSS RWY 30 W OF OSI AT 8000 FT. I REPROGRAMMED THE CHANGE, AND A NEW DSCNT POINT CAME UP THAT LOOKED GOOD. THE ACFT STARTED DOWN WHEN IT WAS SUPPOSED TO AND WE DSNDED ABOUT 500 FT, WHEN THE COPLT DECIDED HE WANTED TO DSND AT A FASTER SPD THAN THE NORMAL SPD, AND SO SELECTED VERT SPD AT 500 FPM. WHEN WE WERE ABOUT 6000 FT ABOVE THE V-NAV PATH, HE SELECTED 320 KTS IN THE SPD WINDOW AND DISCONNECTED THE AUTOPLT. HE HAND FLEW THE REST OF THE DSCNT. WE WERE SLOWLY CATCHING THE PATH, BUT NOT CLOSE, WHEN WE PASSED THROUGH FL180. I SUGGESTED THAT HE WOULD HAVE TO USE THE SPD BRAKE, WHICH HE DID AFTER A DELAY. HE WAS FAR ENOUGH BEHIND THE PATH THAT IT TOOK FULL SPD BRAKE DEFLECTION TO HAVE THE GREEN ARC SHOW THAT WE WERE GOING TO MAKE THE XING. DUE TO THE HIGH RATE OF DSCNT, THE FLT DIRECTOR CAPTURED THE TARGET ALT AT ABOUT 9700 FT. THAT CAUSED THE AUTOTHROTTLES TO BRING THE PWR UP, AND WE BEGAN TO LEVEL. AT THIS POINT, MY COPLT SAID HE WAS HAVING TROUBLE WITH THE THROTTLES, AND BEGAN LEVELING OFF. HE SLOWED THE DSCNT AND STOPPED SLIGHTLY ABOVE 9000 FT, AT WHICH POINT I REMINDED HIM OF THE 8000 FT XING. HE FAILED TO RETURN TO A DSCNT TO BE AT 8000 FT BY 30 NM W OF OSI. I BELIEVE FROM HIS STATEMENT TO ME, THAT HE MOMENTARILY BECAME CONFUSED AND BELIEVED THAT THE TARGET ALT WAS 9000 FT, BECAUSE HE PERCEIVED THAT THE ACFT WANTED HIM TO LEVEL OFF. I BELIEVE HE RESPONDED TOO SLOWLY TO MY REMINDER, BECAUSE OF HIS PERCEPTION. WE CROSSED THE 30 NM FIX AT 9000 FT, AND DSNDED TO 8000 FT ABOUT 3 NM LATER. WE WERE FORTUNATE THAT IT WAS A CLR EVENING AND NO OTHER ACFT WAS NEAR. THIS WOULD NOT HAVE HAPPENED IF WE HAD REMAINED ON V-NAV. I THINK THAT MY COPLT WANTED TO GAIN EXPERIENCE HAND-FLYING THE ACFT, AND DID NOT ANTICIPATE THE PWR COMING UP SO EARLY IN THE DSCNT, CAUSING THE INCIDENT.

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.