Air carrier mdt failed to start descent when cleared by approach controller.

Attributes
ACN	97234
Time
Date	198810
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	msl bound lower : 4000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Flight Phase	cruise other 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 : cfi
Experience	flight time last 90 days : 300 flight time total : 4300 flight time type : 1000
ASRS Report	97234
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft was in cruise mode waiting for an approach clearance. Ord approach control issued us a clearance to descend from 7000 to 4000' and intercept runway 14L localizer. First officer was PF and I set 4000' in the altitude alerter and armed the indicated airspeed mode to arm the flight director for a descent. I then turned my head to get an approach plate ready for a period of approximately 1 min. I then turned my attention back to the airplane approach control called me and told me to descend 'now' to 4000'. The first officer had never left the altitude of 7000'. The first officer then went flight idle on the power and we descended to 4000'. This was our ninth leg of the day and had flown into ord 4 times. Fatigue level was high as we were entering our thirteenth hour of duty time. On top of this we only had reduced rest of 8 hours the previous night, which translates to about 5 1/2-6 hours of sleep at the most. This reduced rest was scheduled into the trip pairing. I sincerely believe that had we gotten an 8 hour period of sleep maybe this altitude deviation wouldn't have happened. I also think the 9 leg day, 13 hour duty day, and flying into the world's busiest airport 4 times that day contributed.

Original NASA ASRS Text

Title: ACR MDT FAILED TO START DESCENT WHEN CLEARED BY APCH CTLR.

Narrative: ACFT WAS IN CRUISE MODE WAITING FOR AN APCH CLRNC. ORD APCH CTL ISSUED US A CLRNC TO DSND FROM 7000 TO 4000' AND INTERCEPT RWY 14L LOC. F/O WAS PF AND I SET 4000' IN THE ALT ALERTER AND ARMED THE INDICATED AIRSPD MODE TO ARM THE FLT DIRECTOR FOR A DSCNT. I THEN TURNED MY HEAD TO GET AN APCH PLATE READY FOR A PERIOD OF APPROX 1 MIN. I THEN TURNED MY ATTN BACK TO THE AIRPLANE APCH CTL CALLED ME AND TOLD ME TO DSND 'NOW' TO 4000'. THE F/O HAD NEVER LEFT THE ALT OF 7000'. THE F/O THEN WENT FLT IDLE ON THE PWR AND WE DSNDED TO 4000'. THIS WAS OUR NINTH LEG OF THE DAY AND HAD FLOWN INTO ORD 4 TIMES. FATIGUE LEVEL WAS HIGH AS WE WERE ENTERING OUR THIRTEENTH HR OF DUTY TIME. ON TOP OF THIS WE ONLY HAD REDUCED REST OF 8 HRS THE PREVIOUS NIGHT, WHICH TRANSLATES TO ABOUT 5 1/2-6 HRS OF SLEEP AT THE MOST. THIS REDUCED REST WAS SCHEDULED INTO THE TRIP PAIRING. I SINCERELY BELIEVE THAT HAD WE GOTTEN AN 8 HR PERIOD OF SLEEP MAYBE THIS ALT DEV WOULDN'T HAVE HAPPENED. I ALSO THINK THE 9 LEG DAY, 13 HR DUTY DAY, AND FLYING INTO THE WORLD'S BUSIEST ARPT 4 TIMES THAT DAY CONTRIBUTED.

Data retrieved from NASA's ASRS site as of August 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.