Narrative:

Thunderstorms on and near msp airport. First officer was flying the aircraft on the kaspr 2 arrival from mci. ATC gave clearance to cross delzy (24 DME) fix at 11000 ft. Standard altitude calls were made during the descent and prior to leveloff. I was looking at the radar to determine thunderstorm avoidance route as we approached msp airport. I heard the altitude warning horn beep and looked up to discover we were descending through 10700 ft. I quickly advised first officer to climb back up to 11000 ft. By the time he stopped the rate of descent we were approximately 10500 ft. He immediately climbed back to 11000 ft. Nothing was ever mentioned by ZMP of the deviation. During the descent the autoplt was engaged and was being controled by the vertical speed wheel. I was then informed by the first officer he, too, was looking down at the radar screen for WX avoidance and missed the leveloff altitude. I believe a good procedure would be for PF (perhaps both) to direct full attention to aircraft leveloff the last 1000 ft prior to leveloff altitude to avoid these problems in the future.

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Original NASA ASRS Text

Title: DC9 FLC DSNDS BELOW ASSIGNED ALT ON DSCNT. WARNING HORN BEEPS AND THEY RETURN TO ASSIGNED.

Narrative: TSTMS ON AND NEAR MSP ARPT. FO WAS FLYING THE ACFT ON THE KASPR 2 ARR FROM MCI. ATC GAVE CLRNC TO CROSS DELZY (24 DME) FIX AT 11000 FT. STANDARD ALT CALLS WERE MADE DURING THE DSCNT AND PRIOR TO LEVELOFF. I WAS LOOKING AT THE RADAR TO DETERMINE TSTM AVOIDANCE RTE AS WE APCHED MSP ARPT. I HEARD THE ALT WARNING HORN BEEP AND LOOKED UP TO DISCOVER WE WERE DSNDING THROUGH 10700 FT. I QUICKLY ADVISED FO TO CLB BACK UP TO 11000 FT. BY THE TIME HE STOPPED THE RATE OF DSCNT WE WERE APPROX 10500 FT. HE IMMEDIATELY CLBED BACK TO 11000 FT. NOTHING WAS EVER MENTIONED BY ZMP OF THE DEV. DURING THE DSCNT THE AUTOPLT WAS ENGAGED AND WAS BEING CTLED BY THE VERT SPD WHEEL. I WAS THEN INFORMED BY THE FO HE, TOO, WAS LOOKING DOWN AT THE RADAR SCREEN FOR WX AVOIDANCE AND MISSED THE LEVELOFF ALT. I BELIEVE A GOOD PROC WOULD BE FOR PF (PERHAPS BOTH) TO DIRECT FULL ATTN TO ACFT LEVELOFF THE LAST 1000 FT PRIOR TO LEVELOFF ALT TO AVOID THESE PROBS IN THE FUTURE.

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.