Narrative:

Cleared by ZLA to cross lynsy intersection at 12000 ft, 250 KTS. Approaching lynsy, changed to las approach control. Cleared to descend via lynsy 1, except cross utare at 8000 ft. I read back clearance and checked published altitude, on STAR, at lynsy. STAR indicated utare at 8000 ft, 210 KTS. First officer and I were both unsure of this clearance. The STAR shows fix after utare, dusjo, at 6500 ft. I asked if controller meant, cross utare at and maintain 8000 ft. New clearance given, cross utare at and maintain 8000 ft. During this exchange, the aircraft began to capture 12000 ft and slow to 250 KTS. After the clearance was verified, first officer selected 8000 ft on FCU and we verified change using altitude awareness procedures. I checked STAR again to be sure we were set up correctly for the arrival. During this time, I realized the aircraft was not in managed descent mode. We were now in vertical speed approaching 11000 ft. We had not reached mirok intersection, with its restr of at or above 11000 ft. I instructed first officer to level until mirok and then resume a managed descent to 8000 ft. If the altitude alerter is changed on this aircraft while in the capture mode, it reverts to vertical speed. This appears to be what occurred. Approach indicated our altitude at lynsy was 11200 ft instead of the required 12000 ft. Several factors contributed to this error. The wording of the original clearance created confusion in the cockpit. Approach indicated the aircraft ahead of us had a similar problem understanding what the controller wanted. This occurred at XA00, but the crew was on last leg of a long day with body clocks on XD00. I think fatigue slowed our response time. The reversions on this aircraft are a known problem and we have been well trained to be vigilant for them. Still we failed to catch it promptly. I believe it would be safer not to be cleared to descend via a STAR if intermediate leveloffs are desired by ATC. This was the first time either of us had flown this STAR. We had thoroughly briefed it and had we been told to descend without the unpublished restr, I don't think we would have had this deviation. This is the first time either of us could remember receiving a clearance like this. Supplemental information from acn 558465: about this time, las approach cleared us to las via the lynsy RNAV 1 arrival, except to cross utare waypoint at 8000 ft. I immediately put 8000 ft in the altitude window in the FCU panel. I did not notice on the FMA that the altitude capture had been armed to leveloff at 12000 ft. When I selected 8000 ft in the altitude window, the altitude capture was no longer armed and the airplane continued to descend in a vertical speed mode to 8000 ft. We did not realize we had descended below 12000 ft before we crossed the lynsy intersection. What we both missed from the original clearance was to maintain 8000 ft to utare. I think factors contributing to this incident were our misunderstanding of the initial clearance and my failure to monitor the FMA on the pfd.

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Original NASA ASRS Text

Title: AN A319 CREW, DSNDING INTO LAS, MISINTERPED ATC'S INSTRUCTIONS, OVERSHOOTING A PUBLISHED XING RESTR.

Narrative: CLRED BY ZLA TO CROSS LYNSY INTXN AT 12000 FT, 250 KTS. APCHING LYNSY, CHANGED TO LAS APCH CTL. CLRED TO DSND VIA LYNSY 1, EXCEPT CROSS UTARE AT 8000 FT. I READ BACK CLRNC AND CHKED PUBLISHED ALT, ON STAR, AT LYNSY. STAR INDICATED UTARE AT 8000 FT, 210 KTS. FO AND I WERE BOTH UNSURE OF THIS CLRNC. THE STAR SHOWS FIX AFTER UTARE, DUSJO, AT 6500 FT. I ASKED IF CTLR MEANT, CROSS UTARE AT AND MAINTAIN 8000 FT. NEW CLRNC GIVEN, CROSS UTARE AT AND MAINTAIN 8000 FT. DURING THIS EXCHANGE, THE ACFT BEGAN TO CAPTURE 12000 FT AND SLOW TO 250 KTS. AFTER THE CLRNC WAS VERIFIED, FO SELECTED 8000 FT ON FCU AND WE VERIFIED CHANGE USING ALT AWARENESS PROCS. I CHKED STAR AGAIN TO BE SURE WE WERE SET UP CORRECTLY FOR THE ARR. DURING THIS TIME, I REALIZED THE ACFT WAS NOT IN MANAGED DSCNT MODE. WE WERE NOW IN VERT SPD APCHING 11000 FT. WE HAD NOT REACHED MIROK INTXN, WITH ITS RESTR OF AT OR ABOVE 11000 FT. I INSTRUCTED FO TO LEVEL UNTIL MIROK AND THEN RESUME A MANAGED DSCNT TO 8000 FT. IF THE ALT ALERTER IS CHANGED ON THIS ACFT WHILE IN THE CAPTURE MODE, IT REVERTS TO VERT SPD. THIS APPEARS TO BE WHAT OCCURRED. APCH INDICATED OUR ALT AT LYNSY WAS 11200 FT INSTEAD OF THE REQUIRED 12000 FT. SEVERAL FACTORS CONTRIBUTED TO THIS ERROR. THE WORDING OF THE ORIGINAL CLRNC CREATED CONFUSION IN THE COCKPIT. APCH INDICATED THE ACFT AHEAD OF US HAD A SIMILAR PROB UNDERSTANDING WHAT THE CTLR WANTED. THIS OCCURRED AT XA00, BUT THE CREW WAS ON LAST LEG OF A LONG DAY WITH BODY CLOCKS ON XD00. I THINK FATIGUE SLOWED OUR RESPONSE TIME. THE REVERSIONS ON THIS ACFT ARE A KNOWN PROB AND WE HAVE BEEN WELL TRAINED TO BE VIGILANT FOR THEM. STILL WE FAILED TO CATCH IT PROMPTLY. I BELIEVE IT WOULD BE SAFER NOT TO BE CLRED TO DSND VIA A STAR IF INTERMEDIATE LEVELOFFS ARE DESIRED BY ATC. THIS WAS THE FIRST TIME EITHER OF US HAD FLOWN THIS STAR. WE HAD THOROUGHLY BRIEFED IT AND HAD WE BEEN TOLD TO DSND WITHOUT THE UNPUBLISHED RESTR, I DON'T THINK WE WOULD HAVE HAD THIS DEV. THIS IS THE FIRST TIME EITHER OF US COULD REMEMBER RECEIVING A CLRNC LIKE THIS. SUPPLEMENTAL INFO FROM ACN 558465: ABOUT THIS TIME, LAS APCH CLRED US TO LAS VIA THE LYNSY RNAV 1 ARR, EXCEPT TO CROSS UTARE WAYPOINT AT 8000 FT. I IMMEDIATELY PUT 8000 FT IN THE ALT WINDOW IN THE FCU PANEL. I DID NOT NOTICE ON THE FMA THAT THE ALT CAPTURE HAD BEEN ARMED TO LEVELOFF AT 12000 FT. WHEN I SELECTED 8000 FT IN THE ALT WINDOW, THE ALT CAPTURE WAS NO LONGER ARMED AND THE AIRPLANE CONTINUED TO DSND IN A VERT SPD MODE TO 8000 FT. WE DID NOT REALIZE WE HAD DSNDED BELOW 12000 FT BEFORE WE CROSSED THE LYNSY INTXN. WHAT WE BOTH MISSED FROM THE ORIGINAL CLRNC WAS TO MAINTAIN 8000 FT TO UTARE. I THINK FACTORS CONTRIBUTING TO THIS INCIDENT WERE OUR MISUNDERSTANDING OF THE INITIAL CLRNC AND MY FAILURE TO MONITOR THE FMA ON THE PFD.

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.