Narrative:

We experienced a problem with an ATC clearance while descending to our destination of las. We were initially cleared by ZLA to descend via the lynsy 1 RNAV arrival. While descending through FL220, we were told to stop the descent at FL190. While level at FL190, the first officer was off the radio, giving the in-range PA announcement to the passenger. The captain (PF) was given a clearance to descend via the lynsy 1 arrival to maintain 10000 ft (versus 8000 ft at utare intersection). When the first officer came back into the loop, the captain had the speed brakes extended and was expediting the descent, mistakenly thinking that the clearance was to cross lynsy intersection at 10000 ft. While passing 11000 ft, prior to lynsy, ATC asked what our altitude was, and we acknowledged passing 10900 ft for 10000 ft. The controller a few mins later issued us a TRACON phone number to call. We discussed what had happened with the supervisor there. The potential for error exists for all RNAV arrs when an exception to it is given, ie, except maintain 10000 ft versus 8000 ft. In this case the error was not caught by the PNF, as he was verbally told by the PF what the clearance was. A pilot jump seater had interpreted the clearance to be the same as the PF had, so the first officer did not verify the clearance as he normally would do if in doubt. In retrospect, I did not remember exactly how I read back the clearance, as I immediately busied myself for the descent, thinking I was to cross lynsy at 10000 ft. There was no conflict with traffic in this case, and, after our conversation with the TRACON supervisor, we do not believe there is any action being taken against us.

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Original NASA ASRS Text

Title: B757 FLC HAS ALTDEV DURING RNAV ARR.

Narrative: WE EXPERIENCED A PROB WITH AN ATC CLRNC WHILE DSNDING TO OUR DEST OF LAS. WE WERE INITIALLY CLRED BY ZLA TO DSND VIA THE LYNSY 1 RNAV ARR. WHILE DSNDING THROUGH FL220, WE WERE TOLD TO STOP THE DSCNT AT FL190. WHILE LEVEL AT FL190, THE FO WAS OFF THE RADIO, GIVING THE IN-RANGE PA ANNOUNCEMENT TO THE PAX. THE CAPT (PF) WAS GIVEN A CLRNC TO DSND VIA THE LYNSY 1 ARR TO MAINTAIN 10000 FT (VERSUS 8000 FT AT UTARE INTXN). WHEN THE FO CAME BACK INTO THE LOOP, THE CAPT HAD THE SPD BRAKES EXTENDED AND WAS EXPEDITING THE DSCNT, MISTAKENLY THINKING THAT THE CLRNC WAS TO CROSS LYNSY INTXN AT 10000 FT. WHILE PASSING 11000 FT, PRIOR TO LYNSY, ATC ASKED WHAT OUR ALT WAS, AND WE ACKNOWLEDGED PASSING 10900 FT FOR 10000 FT. THE CTLR A FEW MINS LATER ISSUED US A TRACON PHONE NUMBER TO CALL. WE DISCUSSED WHAT HAD HAPPENED WITH THE SUPVR THERE. THE POTENTIAL FOR ERROR EXISTS FOR ALL RNAV ARRS WHEN AN EXCEPTION TO IT IS GIVEN, IE, EXCEPT MAINTAIN 10000 FT VERSUS 8000 FT. IN THIS CASE THE ERROR WAS NOT CAUGHT BY THE PNF, AS HE WAS VERBALLY TOLD BY THE PF WHAT THE CLRNC WAS. A PLT JUMP SEATER HAD INTERPED THE CLRNC TO BE THE SAME AS THE PF HAD, SO THE FO DID NOT VERIFY THE CLRNC AS HE NORMALLY WOULD DO IF IN DOUBT. IN RETROSPECT, I DID NOT REMEMBER EXACTLY HOW I READ BACK THE CLRNC, AS I IMMEDIATELY BUSIED MYSELF FOR THE DSCNT, THINKING I WAS TO CROSS LYNSY AT 10000 FT. THERE WAS NO CONFLICT WITH TFC IN THIS CASE, AND, AFTER OUR CONVERSATION WITH THE TRACON SUPVR, WE DO NOT BELIEVE THERE IS ANY ACTION BEING TAKEN AGAINST US.

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.