Widebody transport cargo flight has altitude deviation on descent.

Attributes
ACN	324970
Time
Date	199601
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gqe
State Reference	AB
Altitude	msl bound lower : 23600 msl bound upper : 24000
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 10000 flight time type : 2500
ASRS Report	324970
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
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:

The clearance was to descend to FL240. It was the first officer's leg and he was leveling at FL240, which I visually confirmed. I reached forward to set my speed bugs for landing and looked back to see the aircraft descending through FL236. I called the altitude deviation out as I took control of the aircraft returning the aircraft to FL240 by manually flying. I received clearance to 10000 ft and gave control of the aircraft back to the first officer. Although the first officer said he had the autoplt engaged, I do not recall disconnecting the autoplt when I took control. I believe that he forgot to engage the autoplt due to fatigue. He was awake in that his eyes were open but he was not responsive mentally in several other instances such as starting dscnts and turning to new headings. It was like his body was there but his mind had shut down, mixing night and day flying with corresponding interrupted circadian rhythms takes a heavy toll in terms of fatigue.

Original NASA ASRS Text

Title: WDB CARGO FLT HAS ALTDEV ON DSCNT.

Narrative: THE CLRNC WAS TO DSND TO FL240. IT WAS THE FO'S LEG AND HE WAS LEVELING AT FL240, WHICH I VISUALLY CONFIRMED. I REACHED FORWARD TO SET MY SPD BUGS FOR LNDG AND LOOKED BACK TO SEE THE ACFT DSNDING THROUGH FL236. I CALLED THE ALTDEV OUT AS I TOOK CTL OF THE ACFT RETURNING THE ACFT TO FL240 BY MANUALLY FLYING. I RECEIVED CLRNC TO 10000 FT AND GAVE CTL OF THE ACFT BACK TO THE FO. ALTHOUGH THE FO SAID HE HAD THE AUTOPLT ENGAGED, I DO NOT RECALL DISCONNECTING THE AUTOPLT WHEN I TOOK CTL. I BELIEVE THAT HE FORGOT TO ENGAGE THE AUTOPLT DUE TO FATIGUE. HE WAS AWAKE IN THAT HIS EYES WERE OPEN BUT HE WAS NOT RESPONSIVE MENTALLY IN SEVERAL OTHER INSTANCES SUCH AS STARTING DSCNTS AND TURNING TO NEW HDGS. IT WAS LIKE HIS BODY WAS THERE BUT HIS MIND HAD SHUT DOWN, MIXING NIGHT AND DAY FLYING WITH CORRESPONDING INTERRUPTED CIRCADIAN RHYTHMS TAKES A HVY TOLL IN TERMS OF FATIGUE.

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.