Narrative:

The captain was flying the aircraft from fat to sfo. We just passed over the mod VOR making our left turn to intercept the 245 degree radial when stockton approach asked us to descend from 11000 ft to 9000 ft. I read back the change in altitudes. We were both talking about an unrelated subject and I was working on company paperwork. The captain didn't change the alerter to 9000 ft. After a few mins stockton came back and amended our altitude to 10000 ft. (The captain had not started the descent to 9000 ft yet.) I read back the new assigned altitude but the captain did not hear it. I then prompted the captain for the descent at the same time he set the altitude alerter for 9000 ft. He didn't hear the new assigned altitude of 10000 ft. I, the PNF, didn't concur the altitude alerter assigned amended altitude of 10000 ft. The captain thought the altitude was still 9000 ft. I needed to get the ATIS for sfo, my head was down writing the information, when I noticed us going through 9500 ft, when I brought it to the attention of the captain. We stopped the descent at approximately 9400 ft, +/-100 ft. At this time, stockton approach asked us to continue the descent to 9000 ft. The controller did not mention anything to us regarding the altitude incursion. It was a crew error due to our talking and our lack of not following company SOP for altitude alerter procedures. As a crew, we talked about the situation and we both agreed to follow the company's SOP. If we had followed company SOP the situation would never have happened.

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Original NASA ASRS Text

Title: A DSNDING EMB120 OVERSHOT ITS ALT WHEN THE CREW FAILED TO COORD THE FLT'S ALT ASSIGNMENT WITH EACH OTHER.

Narrative: THE CAPT WAS FLYING THE ACFT FROM FAT TO SFO. WE JUST PASSED OVER THE MOD VOR MAKING OUR L TURN TO INTERCEPT THE 245 DEG RADIAL WHEN STOCKTON APCH ASKED US TO DSND FROM 11000 FT TO 9000 FT. I READ BACK THE CHANGE IN ALTS. WE WERE BOTH TALKING ABOUT AN UNRELATED SUBJECT AND I WAS WORKING ON COMPANY PAPERWORK. THE CAPT DIDN'T CHANGE THE ALERTER TO 9000 FT. AFTER A FEW MINS STOCKTON CAME BACK AND AMENDED OUR ALT TO 10000 FT. (THE CAPT HAD NOT STARTED THE DSCNT TO 9000 FT YET.) I READ BACK THE NEW ASSIGNED ALT BUT THE CAPT DID NOT HEAR IT. I THEN PROMPTED THE CAPT FOR THE DSCNT AT THE SAME TIME HE SET THE ALT ALERTER FOR 9000 FT. HE DIDN'T HEAR THE NEW ASSIGNED ALT OF 10000 FT. I, THE PNF, DIDN'T CONCUR THE ALT ALERTER ASSIGNED AMENDED ALT OF 10000 FT. THE CAPT THOUGHT THE ALT WAS STILL 9000 FT. I NEEDED TO GET THE ATIS FOR SFO, MY HEAD WAS DOWN WRITING THE INFO, WHEN I NOTICED US GOING THROUGH 9500 FT, WHEN I BROUGHT IT TO THE ATTN OF THE CAPT. WE STOPPED THE DSCNT AT APPROX 9400 FT, +/-100 FT. AT THIS TIME, STOCKTON APCH ASKED US TO CONTINUE THE DSCNT TO 9000 FT. THE CTLR DID NOT MENTION ANYTHING TO US REGARDING THE ALT INCURSION. IT WAS A CREW ERROR DUE TO OUR TALKING AND OUR LACK OF NOT FOLLOWING COMPANY SOP FOR ALT ALERTER PROCS. AS A CREW, WE TALKED ABOUT THE SIT AND WE BOTH AGREED TO FOLLOW THE COMPANY'S SOP. IF WE HAD FOLLOWED COMPANY SOP THE SIT WOULD NEVER HAVE HAPPENED.

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.