Narrative:

We were cleared for the civet 1 arrival, ILS to runway 25L. We requested the ILS to runway 24R approaching braemr intersection (cross at 12). Next point was arnes (cross at 10000 ft) which was set in FCU. After my request for runway 24R, the controller gave us turn right to 270 degrees, intercept the 24R localizer maintain 12000 ft. I acknowledged the clearance right 270 degrees, intercept the localizer runway 24R, maintain 12000 ft. As the PNF, I was to bring up the secondary flight plan in the mdcu, which we had put the ILS runway 4 approach into as a backup. We must have been past braemr intersection, when the captain started his turn to 270 degrees. I was changing the flight plan in the mdcu when the captain asked what altitude should we be at. I replied that the controller said maintain 12000 ft and looked at the altimeter, descending to 11400 ft. Captain requested I verify with the controller. Before I could, the controller said to maintain 9000 ft. Nothing else was said about altitude from the controller. Before updating the mdcu in such a busy environment as lax, I should have made sure the captain had set the requested altitude in the FCU, instead of hurrying the actuation of the secondary approach. We wanted the approach in the mcdu quickly since we weren't too far from the runway 24R localizer. The captain and I have discussed this thoroughly. Contributing factor was that in such an automated aircraft the next altitude had been set in and the autoplt was already descending us to that altitude, when given the amended clearance from the controller. It may also be better for the PNF to set the altitude alert even when the PF is flying the aircraft with autoplt engaged. Currently the PF does this with autoplt engaged and the PNF sets the altitude when the PF is hand flying the aircraft. Supplemental information from acn 294240: I never heard the clearance. Lax is a very busy airport and these sidestep maneuvers can be tricky. We briefed well in advance. My not hearing the altitude to maintain and turning before I clarified the complete clearance probably contributed to the situation. In these new aircraft when you have multiple altitude constraints entered into the mcdu you put the lowest altitude in the FCU altitude window when cleared for an arrival then check all constraints as you arrive over each one. However, if you go heading select the aircraft goes into heading and vertical speed. In our case 10000 ft being set, the aircraft continued in vertical speed. The first officer was briefed to repeat the clearance and confirm that I have heard and set the proper altitude in the FCU in the future.

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Original NASA ASRS Text

Title: ALT BUST IN AN A-320.

Narrative: WE WERE CLRED FOR THE CIVET 1 ARR, ILS TO RWY 25L. WE REQUESTED THE ILS TO RWY 24R APCHING BRAEMR INTXN (CROSS AT 12). NEXT POINT WAS ARNES (CROSS AT 10000 FT) WHICH WAS SET IN FCU. AFTER MY REQUEST FOR RWY 24R, THE CTLR GAVE US TURN R TO 270 DEGS, INTERCEPT THE 24R LOC MAINTAIN 12000 FT. I ACKNOWLEDGED THE CLRNC R 270 DEGS, INTERCEPT THE LOC RWY 24R, MAINTAIN 12000 FT. AS THE PNF, I WAS TO BRING UP THE SECONDARY FLT PLAN IN THE MDCU, WHICH WE HAD PUT THE ILS RWY 4 APCH INTO AS A BACKUP. WE MUST HAVE BEEN PAST BRAEMR INTXN, WHEN THE CAPT STARTED HIS TURN TO 270 DEGS. I WAS CHANGING THE FLT PLAN IN THE MDCU WHEN THE CAPT ASKED WHAT ALT SHOULD WE BE AT. I REPLIED THAT THE CTLR SAID MAINTAIN 12000 FT AND LOOKED AT THE ALTIMETER, DSNDING TO 11400 FT. CAPT REQUESTED I VERIFY WITH THE CTLR. BEFORE I COULD, THE CTLR SAID TO MAINTAIN 9000 FT. NOTHING ELSE WAS SAID ABOUT ALT FROM THE CTLR. BEFORE UPDATING THE MDCU IN SUCH A BUSY ENVIRONMENT AS LAX, I SHOULD HAVE MADE SURE THE CAPT HAD SET THE REQUESTED ALT IN THE FCU, INSTEAD OF HURRYING THE ACTUATION OF THE SECONDARY APCH. WE WANTED THE APCH IN THE MCDU QUICKLY SINCE WE WEREN'T TOO FAR FROM THE RWY 24R LOC. THE CAPT AND I HAVE DISCUSSED THIS THOROUGHLY. CONTRIBUTING FACTOR WAS THAT IN SUCH AN AUTOMATED ACFT THE NEXT ALT HAD BEEN SET IN AND THE AUTOPLT WAS ALREADY DSNDING US TO THAT ALT, WHEN GIVEN THE AMENDED CLRNC FROM THE CTLR. IT MAY ALSO BE BETTER FOR THE PNF TO SET THE ALT ALERT EVEN WHEN THE PF IS FLYING THE ACFT WITH AUTOPLT ENGAGED. CURRENTLY THE PF DOES THIS WITH AUTOPLT ENGAGED AND THE PNF SETS THE ALT WHEN THE PF IS HAND FLYING THE ACFT. SUPPLEMENTAL INFO FROM ACN 294240: I NEVER HEARD THE CLRNC. LAX IS A VERY BUSY ARPT AND THESE SIDESTEP MANEUVERS CAN BE TRICKY. WE BRIEFED WELL IN ADVANCE. MY NOT HEARING THE ALT TO MAINTAIN AND TURNING BEFORE I CLARIFIED THE COMPLETE CLRNC PROBABLY CONTRIBUTED TO THE SIT. IN THESE NEW ACFT WHEN YOU HAVE MULTIPLE ALT CONSTRAINTS ENTERED INTO THE MCDU YOU PUT THE LOWEST ALT IN THE FCU ALT WINDOW WHEN CLRED FOR AN ARR THEN CHK ALL CONSTRAINTS AS YOU ARRIVE OVER EACH ONE. HOWEVER, IF YOU GO HDG SELECT THE ACFT GOES INTO HDG AND VERT SPD. IN OUR CASE 10000 FT BEING SET, THE ACFT CONTINUED IN VERT SPD. THE FO WAS BRIEFED TO REPEAT THE CLRNC AND CONFIRM THAT I HAVE HEARD AND SET THE PROPER ALT IN THE FCU 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.