Narrative:

Arrival to lax, originally filed the civet 4 arrival to lax. Shortly before civit intersection we were advised to expect the mitts one arrival. I believe we were at or had been cleared to FL180 prior to being advised of the mitts arrival. Shortly after the mitts advisory we were cleared by socal approach to descend on the mitts one arrival. I was PNF the captain was PF. The captain selected 8000 ft in the altitude window. This was the descent limit on the arrival at denay intersection. I confirmed 8000 ft. I confirmed at or above 12000 ft at snrkl intersection the first altitude constraint after civit. The cockpit was a busy place at this point. We had just scrambled to reprogram the mitts arrival and runway 24R instead of civit and runway 25L. Both of us were still shuffling approach charts. After civet intersection at approximately 14000 ft I was mostly heads down performing descent and approach check duties and confirming the changes programmed into the mcdu. When I looked up we were a couple of mi before snrkl intersection at approximately 11000 ft instead of 12000 ft. The captain caught the altitude deviation and mentioned it. I confirmed 12000 ft at snrkl. We crossed snrkl at approximately 11300 ft. Approach control then mentioned the altitude deviation. The captain then answered the radio call acknowledging the deviation to approach control. I'm not sure but the captain may have gone to an open descent instead of a managed descent. On the A320 an open descent would be an idle descent to the 8000 ft in the altitude window. A managed descent would have honored constraints. High workload times in the cockpit require extra vigilance in performing your duties.

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Original NASA ASRS Text

Title: A320 SHORTLY AFTER LAST MIN APCH ARR CHANGE ON DSCNT INTO LAX.

Narrative: ARR TO LAX, ORIGINALLY FILED THE CIVET 4 ARR TO LAX. SHORTLY BEFORE CIVIT INTXN WE WERE ADVISED TO EXPECT THE MITTS ONE ARR. I BELIEVE WE WERE AT OR HAD BEEN CLRED TO FL180 PRIOR TO BEING ADVISED OF THE MITTS ARR. SHORTLY AFTER THE MITTS ADVISORY WE WERE CLRED BY SOCAL APCH TO DSND ON THE MITTS ONE ARR. I WAS PNF THE CAPT WAS PF. THE CAPT SELECTED 8000 FT IN THE ALT WINDOW. THIS WAS THE DSCNT LIMIT ON THE ARR AT DENAY INTXN. I CONFIRMED 8000 FT. I CONFIRMED AT OR ABOVE 12000 FT AT SNRKL INTXN THE FIRST ALT CONSTRAINT AFTER CIVIT. THE COCKPIT WAS A BUSY PLACE AT THIS POINT. WE HAD JUST SCRAMBLED TO REPROGRAM THE MITTS ARR AND RWY 24R INSTEAD OF CIVIT AND RWY 25L. BOTH OF US WERE STILL SHUFFLING APCH CHARTS. AFTER CIVET INTXN AT APPROX 14000 FT I WAS MOSTLY HEADS DOWN PERFORMING DSCNT AND APCH CHK DUTIES AND CONFIRMING THE CHANGES PROGRAMMED INTO THE MCDU. WHEN I LOOKED UP WE WERE A COUPLE OF MI BEFORE SNRKL INTXN AT APPROX 11000 FT INSTEAD OF 12000 FT. THE CAPT CAUGHT THE ALTDEV AND MENTIONED IT. I CONFIRMED 12000 FT AT SNRKL. WE CROSSED SNRKL AT APPROX 11300 FT. APCH CTL THEN MENTIONED THE ALTDEV. THE CAPT THEN ANSWERED THE RADIO CALL ACKNOWLEDGING THE DEV TO APCH CTL. I'M NOT SURE BUT THE CAPT MAY HAVE GONE TO AN OPEN DSCNT INSTEAD OF A MANAGED DSCNT. ON THE A320 AN OPEN DSCNT WOULD BE AN IDLE DSCNT TO THE 8000 FT IN THE ALT WINDOW. A MANAGED DSCNT WOULD HAVE HONORED CONSTRAINTS. HIGH WORKLOAD TIMES IN THE COCKPIT REQUIRE EXTRA VIGILANCE IN PERFORMING YOUR DUTIES.

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.