Narrative:

Flight was en route from lax to sbp, we had been cleared direct to the morro bay VOR which was our filed route. As we approached the VOR we requested verification of our route after the VOR. At this time we were approximately 5 DME from the VOR. As we reached the VOR the controller cleared us to frams intersection and then to crepe intersection to maintain 7000'. Within approximately 30 seconds the controller reissued the clearance to read direct crepe intersection and cross crepe at 5000' and hold efc at YY55. These instructions were read back to controller including the 5000' altitude restriction. We continued the descent to 5000' after passing the VOR. As we descended through 6400' the controller advised us to maintain 7000' as that was our assigned altitude. We reached 6300' and climbed immediately to 7000'. The controller advised us of an altitude deviation and to call the ARTCC. I called the center and the supervisor advised that he listened to tapes and the controller had issued us 7000' however we read back 5000' and the controller failed to catch the error resulting in an ARTCC operational error. I feel that the controller failed to act in a timely manner in issuing a clearance beyond the VOR resulting in 2 clearance changes within a 30 second period, thus increasing his and our workload to make a decision on what action to take next. The over workload resulted in the flight crew mistaking the altitude issued as 5000' and the controller mistaking the readback. Due to the number of apches performed at sbp an approach control facility needs to be installed or a separate center sector created.

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Original NASA ASRS Text

Title: CLRNC MISINTERP AND POOR COM TECHNIQUE RESULTS IN OPERATIONAL DEVIATION AND AN ALT DEVIATION.

Narrative: FLT WAS ENRTE FROM LAX TO SBP, WE HAD BEEN CLRED DIRECT TO THE MORRO BAY VOR WHICH WAS OUR FILED ROUTE. AS WE APCHED THE VOR WE REQUESTED VERIFICATION OF OUR ROUTE AFTER THE VOR. AT THIS TIME WE WERE APPROX 5 DME FROM THE VOR. AS WE REACHED THE VOR THE CTLR CLRED US TO FRAMS INTXN AND THEN TO CREPE INTXN TO MAINTAIN 7000'. WITHIN APPROX 30 SECONDS THE CTLR REISSUED THE CLRNC TO READ DIRECT CREPE INTXN AND CROSS CREPE AT 5000' AND HOLD EFC AT YY55. THESE INSTRUCTIONS WERE READ BACK TO CTLR INCLUDING THE 5000' ALT RESTRICTION. WE CONTINUED THE DSCNT TO 5000' AFTER PASSING THE VOR. AS WE DESCENDED THROUGH 6400' THE CTLR ADVISED US TO MAINTAIN 7000' AS THAT WAS OUR ASSIGNED ALT. WE REACHED 6300' AND CLIMBED IMMEDIATELY TO 7000'. THE CTLR ADVISED US OF AN ALT DEVIATION AND TO CALL THE ARTCC. I CALLED THE CENTER AND THE SUPVR ADVISED THAT HE LISTENED TO TAPES AND THE CTLR HAD ISSUED US 7000' HOWEVER WE READ BACK 5000' AND THE CTLR FAILED TO CATCH THE ERROR RESULTING IN AN ARTCC OPERATIONAL ERROR. I FEEL THAT THE CTLR FAILED TO ACT IN A TIMELY MANNER IN ISSUING A CLRNC BEYOND THE VOR RESULTING IN 2 CLRNC CHANGES WITHIN A 30 SECOND PERIOD, THUS INCREASING HIS AND OUR WORKLOAD TO MAKE A DECISION ON WHAT ACTION TO TAKE NEXT. THE OVER WORKLOAD RESULTED IN THE FLT CREW MISTAKING THE ALT ISSUED AS 5000' AND THE CTLR MISTAKING THE READBACK. DUE TO THE NUMBER OF APCHES PERFORMED AT SBP AN APCH CTL FAC NEEDS TO BE INSTALLED OR A SEPARATE CENTER SECTOR CREATED.

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.