Light transport flight crew had altitude deviation on descent.

Attributes
ACN	168266
Time
Date	199101
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : stl
State Reference	MO
Altitude	msl bound lower : 8500 msl bound upper : 9000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other descent other
Route In Use	enroute airway : zkc
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5600 flight time type : 600
ASRS Report	168266
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : instrument pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 1150 flight time type : 700
ASRS Report	168267
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I acknowledged center's directive to descend from 12000 to 9000' and set 9000' in the altitude alerter. Immediately after this and after the first officer initiated the descent, I went off the air to monitor lambert field's ATIS report. While writing this down, I heard the altitude alert warning and noticed the first officer had descended to 8500'. I told him to immediately climb back to 9000'. He stated that the usual altitude assignment in this area on the moduc STAR is 8000' (it is!) and this confused him, even though 9000' was clearly set in the alerter. Center made no comment re: this deviation. Contributing cause of this incident was the usual altitude assignment of 8000' was not given. Additionally I, the captain, failed to continually monitor the progress of the descent during my absence from center frequency to monitor ATIS. I must add that our company continually uses reduced rest schedules and that we had both only had 5 hours sleep the previous night. Fatigue manifested itself during this deviation, and, I believe, it was the primary cause for this error.

Original NASA ASRS Text

Title: LTT FLT CREW HAD ALT DEVIATION ON DESCENT.

Narrative: I ACKNOWLEDGED CENTER'S DIRECTIVE TO DSND FROM 12000 TO 9000' AND SET 9000' IN THE ALT ALERTER. IMMEDIATELY AFTER THIS AND AFTER THE F/O INITIATED THE DSNT, I WENT OFF THE AIR TO MONITOR LAMBERT FIELD'S ATIS RPT. WHILE WRITING THIS DOWN, I HEARD THE ALT ALERT WARNING AND NOTICED THE F/O HAD DSNDED TO 8500'. I TOLD HIM TO IMMEDIATELY CLB BACK TO 9000'. HE STATED THAT THE USUAL ALT ASSIGNMENT IN THIS AREA ON THE MODUC STAR IS 8000' (IT IS!) AND THIS CONFUSED HIM, EVEN THOUGH 9000' WAS CLEARLY SET IN THE ALERTER. CENTER MADE NO COMMENT RE: THIS DEVIATION. CONTRIBUTING CAUSE OF THIS INCIDENT WAS THE USUAL ALT ASSIGNMENT OF 8000' WAS NOT GIVEN. ADDITIONALLY I, THE CAPT, FAILED TO CONTINUALLY MONITOR THE PROGRESS OF THE DSNT DURING MY ABSENCE FROM CENTER FREQ TO MONITOR ATIS. I MUST ADD THAT OUR COMPANY CONTINUALLY USES REDUCED REST SCHEDULES AND THAT WE HAD BOTH ONLY HAD 5 HRS SLEEP THE PREVIOUS NIGHT. FATIGUE MANIFESTED ITSELF DURING THIS DEVIATION, AND, I BELIEVE, IT WAS THE PRIMARY CAUSE FOR THIS ERROR.

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.