Narrative:

After signing on with southern california approach, I told my first officer he had #1 communication. We were level at 13000 ft. I then gave the passenger the safety briefing for landing, talked to company (in range call) and copied ATIS. The ATIS broadcast had just come up. While I was off frequency. I saw the first officer dial up 7000 ft in the altitude alerter and begin a descent. I came on frequency at about 10200 ft and heard the controller tell us to pick our speed up to 210 at bayst. I repeated this back. At about 9800 ft, the controller said to stop our descent at 10000 ft and then he said to climb back to 10000 ft. We were climbing again and descended no lower than 9600 ft. The controller gave us a 727 traffic at 9000 ft. We said we had him. The controller said to maintain visual on him which we did. After talking to the first officer he told me that he had been told to level off at 10000 ft north and then go down to 7000 ft but was not clear on the level off point, we think it was bayst intersection. We were on duty 15 hour and 18 min the day before. The first officer should have asked for a clarification of the clearance. Supplemental information from acn 282304: while the captain was off the frequency we were given a descent from 13000 ft to 7000 ft maintain 10000 ft till what I thought was sadde intersection (later realized controller meant bayst intersection). If controller wants us to only descend to 10000 ft he should not include further clearance to 7000 ft.

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Original NASA ASRS Text

Title: POTENTIAL CONFLICT, DSCNT TOWARDS OCCUPIED ALT.

Narrative: AFTER SIGNING ON WITH SOUTHERN CALIFORNIA APCH, I TOLD MY FO HE HAD #1 COM. WE WERE LEVEL AT 13000 FT. I THEN GAVE THE PAX THE SAFETY BRIEFING FOR LNDG, TALKED TO COMPANY (IN RANGE CALL) AND COPIED ATIS. THE ATIS BROADCAST HAD JUST COME UP. WHILE I WAS OFF FREQ. I SAW THE FO DIAL UP 7000 FT IN THE ALT ALERTER AND BEGIN A DSCNT. I CAME ON FREQ AT ABOUT 10200 FT AND HEARD THE CTLR TELL US TO PICK OUR SPD UP TO 210 AT BAYST. I REPEATED THIS BACK. AT ABOUT 9800 FT, THE CTLR SAID TO STOP OUR DSCNT AT 10000 FT AND THEN HE SAID TO CLB BACK TO 10000 FT. WE WERE CLBING AGAIN AND DSNDED NO LOWER THAN 9600 FT. THE CTLR GAVE US A 727 TFC AT 9000 FT. WE SAID WE HAD HIM. THE CTLR SAID TO MAINTAIN VISUAL ON HIM WHICH WE DID. AFTER TALKING TO THE FO HE TOLD ME THAT HE HAD BEEN TOLD TO LEVEL OFF AT 10000 FT N AND THEN GO DOWN TO 7000 FT BUT WAS NOT CLR ON THE LEVEL OFF POINT, WE THINK IT WAS BAYST INTXN. WE WERE ON DUTY 15 HR AND 18 MIN THE DAY BEFORE. THE FO SHOULD HAVE ASKED FOR A CLARIFICATION OF THE CLRNC. SUPPLEMENTAL INFO FROM ACN 282304: WHILE THE CAPT WAS OFF THE FREQ WE WERE GIVEN A DSCNT FROM 13000 FT TO 7000 FT MAINTAIN 10000 FT TILL WHAT I THOUGHT WAS SADDE INTXN (LATER REALIZED CTLR MEANT BAYST INTXN). IF CTLR WANTS US TO ONLY DSND TO 10000 FT HE SHOULD NOT INCLUDE FURTHER CLRNC TO 7000 FT.

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.