Narrative:

Descending to FL240 first officer flying and doing good job. He used mach hold and manually retarded throttles. At FL250 I said '1 to go' and armed. He used vertical speed mode and reduced vertical speed to make a smooth leveloff. Altitude mode went to capture, plane started to level and engines came up. Vertical speed was 300-400 FPM. I looked down at altitude alert. I told him to fly it back to FL240 and he caught it 300 ft low and disconnected autoplt and initiated climb. He then overshot and we got another alert on the high side. He was trying to keep it smooth and not scare everybody. We leveled and proceeded. ATC did not say anything. Reason for fail to capture is unknown. First officer did not adjust vertical speed within 500 ft of leveloff altitude.

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Original NASA ASRS Text

Title: FO OF A SUPER MD80 OVERSHOT INTERMEDIATE DSCNT ALT DUE TO THE AUTOPLT NOT CAPTURING THE SET ALT.

Narrative: DSNDING TO FL240 FO FLYING AND DOING GOOD JOB. HE USED MACH HOLD AND MANUALLY RETARDED THROTTLES. AT FL250 I SAID '1 TO GO' AND ARMED. HE USED VERT SPD MODE AND REDUCED VERT SPD TO MAKE A SMOOTH LEVELOFF. ALT MODE WENT TO CAPTURE, PLANE STARTED TO LEVEL AND ENGS CAME UP. VERT SPD WAS 300-400 FPM. I LOOKED DOWN AT ALT ALERT. I TOLD HIM TO FLY IT BACK TO FL240 AND HE CAUGHT IT 300 FT LOW AND DISCONNECTED AUTOPLT AND INITIATED CLB. HE THEN OVERSHOT AND WE GOT ANOTHER ALERT ON THE HIGH SIDE. HE WAS TRYING TO KEEP IT SMOOTH AND NOT SCARE EVERYBODY. WE LEVELED AND PROCEEDED. ATC DID NOT SAY ANYTHING. REASON FOR FAIL TO CAPTURE IS UNKNOWN. FO DID NOT ADJUST VERT SPD WITHIN 500 FT OF LEVELOFF ALT.

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.