B747 crew distraction watching for traffic, overshot assigned altitude.

Attributes
ACN	496743
Time
Date	200012
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sfo.airport
State Reference	CA
Altitude	msl bound lower : 10600 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Navigation In Use	other Other
Flight Phase	descent : vacating altitude
Route In Use	arrival star : eni. goldn4
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : o90.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : vacating altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time type : 2278
ASRS Report	416743
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Experience	flight time last 90 days : 19 flight time total : 7000 flight time type : 19
ASRS Report	496742
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Approaching sfo VOR at 11000 ft in VNAV with autoplt in command, given clearance to cross sfo VOR at 11000 ft, then descend and maintain 6000 ft. As the PNF, I set 6000 ft in the MCP altitude window. Shortly thereafter, the aircraft started to descend. The first officer quickly noticed the early descent and selected vertical speed and commanded the aircraft back to 11000 ft. The controller had earlier pointed out departing traffic climbing to 10000 ft below us which we had previously reported in sight.

Original NASA ASRS Text

Title: B747 CREW DISTR WATCHING FOR TFC, OVERSHOT ASSIGNED ALT.

Narrative: APCHING SFO VOR AT 11000 FT IN VNAV WITH AUTOPLT IN COMMAND, GIVEN CLRNC TO CROSS SFO VOR AT 11000 FT, THEN DSND AND MAINTAIN 6000 FT. AS THE PNF, I SET 6000 FT IN THE MCP ALT WINDOW. SHORTLY THEREAFTER, THE ACFT STARTED TO DSND. THE FO QUICKLY NOTICED THE EARLY DSCNT AND SELECTED VERT SPD AND COMMANDED THE ACFT BACK TO 11000 FT. THE CTLR HAD EARLIER POINTED OUT DEPARTING TFC CLBING TO 10000 FT BELOW US WHICH WE HAD PREVIOUSLY RPTED IN SIGHT.

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.