Air carrier crew descends below assigned altitude.

Attributes
ACN	446197
Time
Date	199908
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sfo.airport
State Reference	CA
Altitude	msl bound lower : 7700 msl bound upper : 9000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 140 flight time total : 17000 flight time type : 1400
ASRS Report	446197
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : commercial pilot : flight engineer pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 200 flight time total : 7750 flight time type : 750
ASRS Report	446200
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	aircraft equipment : altitude alert other flight crewa
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I was the PNF for descent and landing into sfo. We were in a descending left turn onto a downwind leg. I made the 1000 ft call for 9000 ft going to 8000 ft and the first officer acknowledged. I was heads down identing the OM for the approach. Supplemental information from acn 446200: I was the PF for descent and landing into sfo airport. We were in a descending turn onto downwind. I received and acknowledged the 1000 ft to go callout made by the captain. My attention was outside the aircraft when the altitude light and aural activated. I immediately recovered the aircraft to the assigned altitude.

Original NASA ASRS Text

Title: ACR CREW DSNDS BELOW ASSIGNED ALT.

Narrative: I WAS THE PNF FOR DSCNT AND LNDG INTO SFO. WE WERE IN A DSNDING L TURN ONTO A DOWNWIND LEG. I MADE THE 1000 FT CALL FOR 9000 FT GOING TO 8000 FT AND THE FO ACKNOWLEDGED. I WAS HEADS DOWN IDENTING THE OM FOR THE APCH. SUPPLEMENTAL INFO FROM ACN 446200: I WAS THE PF FOR DSCNT AND LNDG INTO SFO ARPT. WE WERE IN A DSNDING TURN ONTO DOWNWIND. I RECEIVED AND ACKNOWLEDGED THE 1000 FT TO GO CALLOUT MADE BY THE CAPT. MY ATTN WAS OUTSIDE THE ACFT WHEN THE ALT LIGHT AND AURAL ACTIVATED. I IMMEDIATELY RECOVERED THE ACFT TO THE ASSIGNED ALT.

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.