Flight crew on arrival descends below assigned altitude.

Attributes
ACN	328600
Time
Date	199602
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dfw
State Reference	TX
Altitude	msl bound lower : 10600 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : dfw tower : pdx
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 220 flight time total : 22000 flight time type : 4400
ASRS Report	328600
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 105 flight time total : 5600 flight time type : 2800
ASRS Report	328603
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I had been flying into dfw all month using the 'boids' arrival and landing south (crossing rhome at 9000 ft). This particular flight, dfw was landing north which meant our clearance was to cross 'didly' at 11000 ft. During the descent ATC cleared us to cross didly at 11000 ft which was set in the altitude window of the flight guidance panel. As I approached 11000 ft I began to slow to 250 KTS. The first officer went off frequency to get the ATIS while I was looking for traffic, all the time thinking I had to be at 9000 ft in just a few mi. I left 11000 ft to descend to 9000 ft. At 10700 ft I got the altitude warning at which time the first officer said 'our clearance is to 11000 ft.' I immediately began the recovery to 11000 ft. ATC did not mention the deviation and altitude 'loss' was no more than 400 ft. I still cannot explain why it happened other than a high workload period, a 9000 ft mindset on my part and habit of being assigned 9000 ft on that particular arrival. Supplemental information from acn 328603: the deviation occurred due to following routine/familiar habit patterns during a high workload period when the 'PNF' was not monitoring.

Original NASA ASRS Text

Title: FLC ON ARR DSNDS BELOW ASSIGNED ALT.

Narrative: I HAD BEEN FLYING INTO DFW ALL MONTH USING THE 'BOIDS' ARR AND LNDG S (XING RHOME AT 9000 FT). THIS PARTICULAR FLT, DFW WAS LNDG N WHICH MEANT OUR CLRNC WAS TO CROSS 'DIDLY' AT 11000 FT. DURING THE DSCNT ATC CLRED US TO CROSS DIDLY AT 11000 FT WHICH WAS SET IN THE ALT WINDOW OF THE FLT GUIDANCE PANEL. AS I APCHED 11000 FT I BEGAN TO SLOW TO 250 KTS. THE FO WENT OFF FREQ TO GET THE ATIS WHILE I WAS LOOKING FOR TFC, ALL THE TIME THINKING I HAD TO BE AT 9000 FT IN JUST A FEW MI. I LEFT 11000 FT TO DSND TO 9000 FT. AT 10700 FT I GOT THE ALT WARNING AT WHICH TIME THE FO SAID 'OUR CLRNC IS TO 11000 FT.' I IMMEDIATELY BEGAN THE RECOVERY TO 11000 FT. ATC DID NOT MENTION THE DEV AND ALT 'LOSS' WAS NO MORE THAN 400 FT. I STILL CANNOT EXPLAIN WHY IT HAPPENED OTHER THAN A HIGH WORKLOAD PERIOD, A 9000 FT MINDSET ON MY PART AND HABIT OF BEING ASSIGNED 9000 FT ON THAT PARTICULAR ARR. SUPPLEMENTAL INFO FROM ACN 328603: THE DEV OCCURRED DUE TO FOLLOWING ROUTINE/FAMILIAR HABIT PATTERNS DURING A HIGH WORKLOAD PERIOD WHEN THE 'PNF' WAS NOT MONITORING.

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.