Narrative:

Our flight was the 'red eye' arriving in the bwi terminal area from the west coast (lax). We were on radar vectors to the final approach course for the ILS 33L. Approach control cleared us to descend to 3000' from our current altitude (approximately 5000-7000'). While descending (luckily at 500 FPM for the last 1000') I programmed the FMC with the FAF and active runway. The altitude alerter went off at 2700'. I immediately stopped our descent, and returned to 3000'. We did not hear any comment made to us, or instruction given to any other aircraft, reference our being 300' lower than we were assigned. About the same time we leveled at 3000', approach control cleared us to a lower initial approach altitude, and subsequently for the ILS 33L approach. In retrospect as we hear all too often I should've asked the captain (or he me) to program the FMC with the FAF and runway information. Secondly, especially on red eye flts, extra attention/vigilance needs to be paid on the part of both or all crewmembers due to crew fatigue. Even though we had a long layover in lax, I had been up for 18 hours when we arrived in bwi. And finally, thoughts about personal/family goings-on should be left until the flight/trip is completed; not during the approach phase of the flight. I was to start a long awaited 9 day vacation upon our arrival in bwi. Callback conversation with reporter revealed the following: completed the boeing study and a general lengthy discussion on the difficulty in planning a sleep schedule on a 32 hour layover.

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Original NASA ASRS Text

Title: ALT OVERSHOT ON DESCENT.

Narrative: OUR FLT WAS THE 'RED EYE' ARRIVING IN THE BWI TERMINAL AREA FROM THE WEST COAST (LAX). WE WERE ON RADAR VECTORS TO THE FINAL APCH COURSE FOR THE ILS 33L. APCH CTL CLRED US TO DSND TO 3000' FROM OUR CURRENT ALT (APPROX 5000-7000'). WHILE DSNDING (LUCKILY AT 500 FPM FOR THE LAST 1000') I PROGRAMMED THE FMC WITH THE FAF AND ACTIVE RWY. THE ALT ALERTER WENT OFF AT 2700'. I IMMEDIATELY STOPPED OUR DSNT, AND RETURNED TO 3000'. WE DID NOT HEAR ANY COMMENT MADE TO US, OR INSTRUCTION GIVEN TO ANY OTHER ACFT, REFERENCE OUR BEING 300' LOWER THAN WE WERE ASSIGNED. ABOUT THE SAME TIME WE LEVELED AT 3000', APCH CTL CLRED US TO A LOWER INITIAL APCH ALT, AND SUBSEQUENTLY FOR THE ILS 33L APCH. IN RETROSPECT AS WE HEAR ALL TOO OFTEN I SHOULD'VE ASKED THE CAPT (OR HE ME) TO PROGRAM THE FMC WITH THE FAF AND RWY INFO. SECONDLY, ESPECIALLY ON RED EYE FLTS, EXTRA ATTN/VIGILANCE NEEDS TO BE PAID ON THE PART OF BOTH OR ALL CREWMEMBERS DUE TO CREW FATIGUE. EVEN THOUGH WE HAD A LONG LAYOVER IN LAX, I HAD BEEN UP FOR 18 HOURS WHEN WE ARRIVED IN BWI. AND FINALLY, THOUGHTS ABOUT PERSONAL/FAMILY GOINGS-ON SHOULD BE LEFT UNTIL THE FLT/TRIP IS COMPLETED; NOT DURING THE APCH PHASE OF THE FLT. I WAS TO START A LONG AWAITED 9 DAY VACATION UPON OUR ARR IN BWI. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: COMPLETED THE BOEING STUDY AND A GENERAL LENGTHY DISCUSSION ON THE DIFFICULTY IN PLANNING A SLEEP SCHEDULE ON A 32 HOUR LAYOVER.

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.