Narrative:

Trip las to lax. Cleared to 10 mi east of civit, then direct smo for approach to runway 6R lax. After making turn at civit (10 mi east) cleared to cross smo at 8000 ft, then descend to 4000 ft, fly 250 degree heading after smo. I was the PF. I set 8000 ft in the FCU window initially, then programmed the FMC to cross smo at 8000 ft. After putting the 8000 ft restr in the FMC, I set the 4000 ft in the FCU altitude window. Assuming that the aircraft would level off at the FMC restr. I began thinking about the approach and looking at the other traffic directed by socal approach when the captain brought to my attention that we were at 7500 ft. I immediately began to correct up to 8000 ft when socal called to point out our error, which we acknowledged. He then cleared us to maintain 7000 ft. The rest of the descent and approach were uneventful. It had been a long day. Show time at phx for the trip was XA55 for a san diego turn, a 3 hour layover, 1 leg to las vegas, a 2.5 hour layover, then the leg to lax. I was pretty tired by XM30 am. I think that in the future when given a restr to cross a fix at or above then descend to, that I will put the highest clearance altitude in the FCU window until that clearance is attained then allow the aircraft to descend. I rely heavily on automation to help out when flying late and tired, but I still need to pay attention and xchk. Supplemental information from acn 304217: my attention was diverted in order to make the required PA announcement as we approached 10000 ft. There were also 2 aircraft in the vicinity which kept my attention for several moments. Upon my return to the flight instruments I noticed we were descending through 7500 ft. Socal called to point out our error. The controller then gave us a clearance to 7000 ft. Contributing factors: 1) complacency. Last leg of the day, beautiful WX, light traffic. 2) exhaustion. Report time for this day was at XA55 the previous afternoon. First officer's day had begun much earlier, as he had to commute in for his report. 3) required PNF duties. The 10000 ft call can sometimes remove one of the pilots out of the loop.

Related reports:

Google
 

Original NASA ASRS Text

Title: AN A-320 FO RELIED ON FMC PROGRAMMING TO LEVEL AT AN INTERMEDIATE DSCNT ALT, WHILE THE FCU WAS SET FOR THE NEXT STEPDOWN. THE FLC WAS LATE TO DISCOVER THE DEP FROM THE NORM, AND ATC ISSUED LOWER.

Narrative: TRIP LAS TO LAX. CLRED TO 10 MI E OF CIVIT, THEN DIRECT SMO FOR APCH TO RWY 6R LAX. AFTER MAKING TURN AT CIVIT (10 MI E) CLRED TO CROSS SMO AT 8000 FT, THEN DSND TO 4000 FT, FLY 250 DEG HDG AFTER SMO. I WAS THE PF. I SET 8000 FT IN THE FCU WINDOW INITIALLY, THEN PROGRAMMED THE FMC TO CROSS SMO AT 8000 FT. AFTER PUTTING THE 8000 FT RESTR IN THE FMC, I SET THE 4000 FT IN THE FCU ALT WINDOW. ASSUMING THAT THE ACFT WOULD LEVEL OFF AT THE FMC RESTR. I BEGAN THINKING ABOUT THE APCH AND LOOKING AT THE OTHER TFC DIRECTED BY SOCAL APCH WHEN THE CAPT BROUGHT TO MY ATTN THAT WE WERE AT 7500 FT. I IMMEDIATELY BEGAN TO CORRECT UP TO 8000 FT WHEN SOCAL CALLED TO POINT OUT OUR ERROR, WHICH WE ACKNOWLEDGED. HE THEN CLRED US TO MAINTAIN 7000 FT. THE REST OF THE DSCNT AND APCH WERE UNEVENTFUL. IT HAD BEEN A LONG DAY. SHOW TIME AT PHX FOR THE TRIP WAS XA55 FOR A SAN DIEGO TURN, A 3 HR LAYOVER, 1 LEG TO LAS VEGAS, A 2.5 HR LAYOVER, THEN THE LEG TO LAX. I WAS PRETTY TIRED BY XM30 AM. I THINK THAT IN THE FUTURE WHEN GIVEN A RESTR TO CROSS A FIX AT OR ABOVE THEN DSND TO, THAT I WILL PUT THE HIGHEST CLRNC ALT IN THE FCU WINDOW UNTIL THAT CLRNC IS ATTAINED THEN ALLOW THE ACFT TO DSND. I RELY HEAVILY ON AUTOMATION TO HELP OUT WHEN FLYING LATE AND TIRED, BUT I STILL NEED TO PAY ATTN AND XCHK. SUPPLEMENTAL INFO FROM ACN 304217: MY ATTN WAS DIVERTED IN ORDER TO MAKE THE REQUIRED PA ANNOUNCEMENT AS WE APCHED 10000 FT. THERE WERE ALSO 2 ACFT IN THE VICINITY WHICH KEPT MY ATTN FOR SEVERAL MOMENTS. UPON MY RETURN TO THE FLT INSTS I NOTICED WE WERE DSNDING THROUGH 7500 FT. SOCAL CALLED TO POINT OUT OUR ERROR. THE CTLR THEN GAVE US A CLRNC TO 7000 FT. CONTRIBUTING FACTORS: 1) COMPLACENCY. LAST LEG OF THE DAY, BEAUTIFUL WX, LIGHT TFC. 2) EXHAUSTION. RPT TIME FOR THIS DAY WAS AT XA55 THE PREVIOUS AFTERNOON. FO'S DAY HAD BEGUN MUCH EARLIER, AS HE HAD TO COMMUTE IN FOR HIS RPT. 3) REQUIRED PNF DUTIES. THE 10000 FT CALL CAN SOMETIMES REMOVE ONE OF THE PLTS OUT OF THE LOOP.

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.