Narrative:

On aug/xa/99, at approximately XA35, we deviated from our assigned altitude of 17000 ft on descent into san luis obispo airport with the flight originating in sfo. Approximately 60 mi from mqo VOR we were issued a descent clearance from 19000 ft to 17000 ft. I misunderstood the clearance and read back 7000 ft. The first officer (PF) was busy identing mqo VOR and did not hear the altitude given. As we proceed through 16300 ft ZOA asked of our altitude and then what we were descending to, my reply was 16100 ft to 7000 ft. The controller then corrected me and said we were cleared to 17000 ft not 7000 ft. My reply was 'I apologize I read back 7000 ft.' he then cleared us to 7000 ft. On that route at that distance from mqo we almost always receive 7000 ft not 17000 ft, so it wasn't odd to me to receive 7000 ft. There were no TA's noted and no TCASII warnings were observed. This problem could have been avoided by possibly clrer communication on the pilot's part and the controller's part by listening to our readbacks.

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Original NASA ASRS Text

Title: FLC OF AN EMBRAER 120 OVERSHOT ASSIGNED ALT DURING DSCNT DUE TO MISINTERP THE ACTUAL ALT AS 7000 FT INSTEAD OF 17000 FT.

Narrative: ON AUG/XA/99, AT APPROX XA35, WE DEVIATED FROM OUR ASSIGNED ALT OF 17000 FT ON DSCNT INTO SAN LUIS OBISPO ARPT WITH THE FLT ORIGINATING IN SFO. APPROX 60 MI FROM MQO VOR WE WERE ISSUED A DSCNT CLRNC FROM 19000 FT TO 17000 FT. I MISUNDERSTOOD THE CLRNC AND READ BACK 7000 FT. THE FO (PF) WAS BUSY IDENTING MQO VOR AND DID NOT HEAR THE ALT GIVEN. AS WE PROCEED THROUGH 16300 FT ZOA ASKED OF OUR ALT AND THEN WHAT WE WERE DSNDING TO, MY REPLY WAS 16100 FT TO 7000 FT. THE CTLR THEN CORRECTED ME AND SAID WE WERE CLRED TO 17000 FT NOT 7000 FT. MY REPLY WAS 'I APOLOGIZE I READ BACK 7000 FT.' HE THEN CLRED US TO 7000 FT. ON THAT RTE AT THAT DISTANCE FROM MQO WE ALMOST ALWAYS RECEIVE 7000 FT NOT 17000 FT, SO IT WASN'T ODD TO ME TO RECEIVE 7000 FT. THERE WERE NO TA'S NOTED AND NO TCASII WARNINGS WERE OBSERVED. THIS PROB COULD HAVE BEEN AVOIDED BY POSSIBLY CLRER COM ON THE PLT'S PART AND THE CTLR'S PART BY LISTENING TO OUR READBACKS.

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.