Narrative:

We were approaching our destination, ord. Our airplane was an airbus A320. I was the PF. We had been given a descent clearance to FL250. As we were descending and approximately 175 NM from ord (between keokk intersection and bdf) the first officer went off the #1 radio to get the ATIS on #2 and call in-range to operations. I was talking to ZAU on frequency 135.15. As I was approaching FL250, center gave me further descent to FL240. I entered the altitude into the altitude selector on the FCU and initiated a managed descent. Then I went to the mcdu and entered a new cruise altitude of FL240 on the progress page. As I was approaching FL240, ZAU handed me off to another sector on frequency 124.55. When I checked in with the new controller, I said '...leveling at 240, ahh, descending through FL240 for FL230.' I had glanced at the FCU altitude window and it showed FL230. This is what caused me to revise my statement to the center controller. The controller acknowledged my transmission. I continued the descent towards FL230 and entered the new cruise altitude into the mcdu progress page. At about FL233, the center controller told me to 'get back up to FL240.' I climbed back up to FL240. At this time, the first officer came back on to the #1 radio. Having realized my mistake, I notified my first officer that I had busted an altitude.

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Original NASA ASRS Text

Title: CAPT OF AN AIRBUS A320 OVERSHOT ASSIGNED ALT ON A STAR ARR DUE TO CAPT'S FMS PROGRAM ERROR.

Narrative: WE WERE APCHING OUR DEST, ORD. OUR AIRPLANE WAS AN AIRBUS A320. I WAS THE PF. WE HAD BEEN GIVEN A DSCNT CLRNC TO FL250. AS WE WERE DSNDING AND APPROX 175 NM FROM ORD (BTWN KEOKK INTXN AND BDF) THE FO WENT OFF THE #1 RADIO TO GET THE ATIS ON #2 AND CALL IN-RANGE TO OPS. I WAS TALKING TO ZAU ON FREQ 135.15. AS I WAS APCHING FL250, CTR GAVE ME FURTHER DSCNT TO FL240. I ENTERED THE ALT INTO THE ALT SELECTOR ON THE FCU AND INITIATED A MANAGED DSCNT. THEN I WENT TO THE MCDU AND ENTERED A NEW CRUISE ALT OF FL240 ON THE PROGRESS PAGE. AS I WAS APCHING FL240, ZAU HANDED ME OFF TO ANOTHER SECTOR ON FREQ 124.55. WHEN I CHKED IN WITH THE NEW CTLR, I SAID '...LEVELING AT 240, AHH, DSNDING THROUGH FL240 FOR FL230.' I HAD GLANCED AT THE FCU ALT WINDOW AND IT SHOWED FL230. THIS IS WHAT CAUSED ME TO REVISE MY STATEMENT TO THE CTR CTLR. THE CTLR ACKNOWLEDGED MY XMISSION. I CONTINUED THE DSCNT TOWARDS FL230 AND ENTERED THE NEW CRUISE ALT INTO THE MCDU PROGRESS PAGE. AT ABOUT FL233, THE CTR CTLR TOLD ME TO 'GET BACK UP TO FL240.' I CLBED BACK UP TO FL240. AT THIS TIME, THE FO CAME BACK ON TO THE #1 RADIO. HAVING REALIZED MY MISTAKE, I NOTIFIED MY FO THAT I HAD BUSTED AN 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.