Narrative:

Was called to report to work for charter flight at early a.M. In louisville, ky. Received our freight at XA30 a.M. And departed approximately XA45 a.M. For oakland, ca. Made fuel stop in publication. I flew second leg, publication-oak. Received descent clearance from FL310 to FL280 approximately 45 DME from manteca VOR. Started descending and my attention was drawn away by a garbled radio call, calling with our down time, and a pilot's microphone that wasn't transmitting. The captain, was also distracted, but pointed to the altitude alert and said you are supposed to be at FL280. I was descending through FL256. I immediately and rapidly climbed back up to FL280. The controller made no mention of the mistake. We continued on the madwin arrival into san francisco. The altitude alert horn was inoperative in the aircraft, which is supposed to alert us 1000 ft prior to the altitude set in the windows. We didn't realize it until we were underway. We immediately wrote it up on the maintenance log upon landing. Also, improvement on our vigilance of cockpit procedures even though we are fatigued is a must.

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Original NASA ASRS Text

Title: CHARTER CARGO FLT HAS ALTDEV ON DSCNT.

Narrative: WAS CALLED TO RPT TO WORK FOR CHARTER FLT AT EARLY A.M. IN LOUISVILLE, KY. RECEIVED OUR FREIGHT AT XA30 A.M. AND DEPARTED APPROX XA45 A.M. FOR OAKLAND, CA. MADE FUEL STOP IN PUB. I FLEW SECOND LEG, PUB-OAK. RECEIVED DSCNT CLRNC FROM FL310 TO FL280 APPROX 45 DME FROM MANTECA VOR. STARTED DSNDING AND MY ATTN WAS DRAWN AWAY BY A GARBLED RADIO CALL, CALLING WITH OUR DOWN TIME, AND A PLT'S MIKE THAT WASN'T XMITTING. THE CAPT, WAS ALSO DISTRACTED, BUT POINTED TO THE ALT ALERT AND SAID YOU ARE SUPPOSED TO BE AT FL280. I WAS DSNDING THROUGH FL256. I IMMEDIATELY AND RAPIDLY CLBED BACK UP TO FL280. THE CTLR MADE NO MENTION OF THE MISTAKE. WE CONTINUED ON THE MADWIN ARR INTO SAN FRANCISCO. THE ALT ALERT HORN WAS INOP IN THE ACFT, WHICH IS SUPPOSED TO ALERT US 1000 FT PRIOR TO THE ALT SET IN THE WINDOWS. WE DIDN'T REALIZE IT UNTIL WE WERE UNDERWAY. WE IMMEDIATELY WROTE IT UP ON THE MAINT LOG UPON LNDG. ALSO, IMPROVEMENT ON OUR VIGILANCE OF COCKPIT PROCS EVEN THOUGH WE ARE FATIGUED IS A MUST.

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.