B737-300 flight crew overshot leveloff as runway assignment change was being programmed into FMC.

Attributes
ACN	759285
Time
Date	200710
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dtw.airport
State Reference	MI
Altitude	msl single value : 12000
Environment
Flight Conditions	Marginal
Aircraft 1
Controlling Facilities	tower : dtw.tower tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	arrival star : n/s
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 80 flight time total : 13500 flight time type : 1900
ASRS Report	759285
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

First officer was PF STAR into detroit in moderate turbulence trying to meet crossing restr of 12000 ft and due to the turbulence the autoplt was not responding quickly enough so he disconnected the autoplt. Just at that time approach control changed our runway assignment to runway 22L. I was heads down installing the approach in the FMC; as well as setting up the radios for the approach. The first officer then noticed he had inadvertently descended below 12000 ft to 11700 ft; and quickly climbed back up to 12000 ft. At that time I told ATC that we had descended below 12000 ft and we were climbing back up to 12000 ft. At that time ATC cleared us to descend to 11000 ft. We then continued on to the approach and landing without further incident. The day started on west coast and had over-nighted the previous night on east coast. I believe the time zone switch coupled with long day that included delays with quick turns; little time for food; added to the incident; as well as the moderate turbulence; the disconnection of the autoplt at the time our runway was switched. In the future I will not go heads down until I'm sure the first officer communicates to me that he is situationally aware.

Original NASA ASRS Text

Title: B737-300 FLT CREW OVERSHOT LEVELOFF AS RWY ASSIGNMENT CHANGE WAS BEING PROGRAMMED INTO FMC.

Narrative: FO WAS PF STAR INTO DETROIT IN MODERATE TURB TRYING TO MEET XING RESTR OF 12000 FT AND DUE TO THE TURB THE AUTOPLT WAS NOT RESPONDING QUICKLY ENOUGH SO HE DISCONNECTED THE AUTOPLT. JUST AT THAT TIME APCH CTL CHANGED OUR RWY ASSIGNMENT TO RWY 22L. I WAS HEADS DOWN INSTALLING THE APCH IN THE FMC; AS WELL AS SETTING UP THE RADIOS FOR THE APCH. THE FO THEN NOTICED HE HAD INADVERTENTLY DSNDED BELOW 12000 FT TO 11700 FT; AND QUICKLY CLBED BACK UP TO 12000 FT. AT THAT TIME I TOLD ATC THAT WE HAD DSNDED BELOW 12000 FT AND WE WERE CLBING BACK UP TO 12000 FT. AT THAT TIME ATC CLRED US TO DSND TO 11000 FT. WE THEN CONTINUED ON TO THE APCH AND LNDG WITHOUT FURTHER INCIDENT. THE DAY STARTED ON WEST COAST AND HAD OVER-NIGHTED THE PREVIOUS NIGHT ON EAST COAST. I BELIEVE THE TIME ZONE SWITCH COUPLED WITH LONG DAY THAT INCLUDED DELAYS WITH QUICK TURNS; LITTLE TIME FOR FOOD; ADDED TO THE INCIDENT; AS WELL AS THE MODERATE TURB; THE DISCONNECTION OF THE AUTOPLT AT THE TIME OUR RWY WAS SWITCHED. IN THE FUTURE I WILL NOT GO HEADS DOWN UNTIL I'M SURE THE FO COMMUNICATES TO ME THAT HE IS SITUATIONALLY AWARE.

Data retrieved from NASA's ASRS site as of January 2009 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.