Narrative:

Airbus 320 -- autoplt and automatic throttle active, initially cleared from FL310 to FL280, told to 'hurry down.' aircraft captain selected 'open descent' which brings thrust to idle -- speed controled by pitch angle. 1/2 speed brakes used to expedite descent. Aircraft has approximately 3100 FPM rate and starting to level off by 28700 ft when ZOB cleared us on down to FL240, which was quickly selected so aircraft would not capture FL280 which was seconds from happening. Then ZOB reversed himself and told us to maintain FL280. Aircraft is still in descent mode (vertical speed). It descends on down to 27500 ft then finally reverts to climb mode about the time ATC questions our altitude. Aircraft should have been disconnected off autoplt and aggressively leveled off by captain. Instead, he elected to use FCU (flight control unit). The flight computers, not knowing the urgency, tend to do things softly for passenger comfort.

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Original NASA ASRS Text

Title: LGT USING FLT COMPUTERS OVERSHOOT DSCNT ALT.

Narrative: AIRBUS 320 -- AUTOPLT AND AUTO THROTTLE ACTIVE, INITIALLY CLRED FROM FL310 TO FL280, TOLD TO 'HURRY DOWN.' ACFT CAPT SELECTED 'OPEN DSCNT' WHICH BRINGS THRUST TO IDLE -- SPD CTLED BY PITCH ANGLE. 1/2 SPD BRAKES USED TO EXPEDITE DSCNT. ACFT HAS APPROX 3100 FPM RATE AND STARTING TO LEVEL OFF BY 28700 FT WHEN ZOB CLRED US ON DOWN TO FL240, WHICH WAS QUICKLY SELECTED SO ACFT WOULD NOT CAPTURE FL280 WHICH WAS SECONDS FROM HAPPENING. THEN ZOB REVERSED HIMSELF AND TOLD US TO MAINTAIN FL280. ACFT IS STILL IN DSCNT MODE (VERT SPD). IT DSNDS ON DOWN TO 27500 FT THEN FINALLY REVERTS TO CLB MODE ABOUT THE TIME ATC QUESTIONS OUR ALT. ACFT SHOULD HAVE BEEN DISCONNECTED OFF AUTOPLT AND AGGRESSIVELY LEVELED OFF BY CAPT. INSTEAD, HE ELECTED TO USE FCU (FLT CTL UNIT). THE FLT COMPUTERS, NOT KNOWING THE URGENCY, TEND TO DO THINGS SOFTLY FOR PAX COMFORT.

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.