A learjet 25 flight crew made an autoplt turn and lost 400 ft near abq.

Attributes
ACN	440051
Time
Date	199906
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	intersection : vernd
State Reference	TX
Altitude	msl bound lower : 40600 msl bound upper : 41000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab.artcc
Operator	general aviation : corporate
Make Model Name	Learjet 25
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 2900 flight time type : 800
ASRS Report	440051
Person 2
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 170 flight time total : 4500 flight time type : 500
ASRS Report	440070
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned airspace
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While cruising at FL410, the autoplt disengaged without any aural warning. It was discovered at approximately 300 ft low and was immediately corrected, however, the downward trend was such that the altitude dipped to 400 ft low for 1 second then back up to FL410. I believe this situation can be prevented by a more diligent scan even during autoplt cruise.

Original NASA ASRS Text

Title: A LEARJET 25 FLC MADE AN AUTOPLT TURN AND LOST 400 FT NEAR ABQ.

Narrative: WHILE CRUISING AT FL410, THE AUTOPLT DISENGAGED WITHOUT ANY AURAL WARNING. IT WAS DISCOVERED AT APPROX 300 FT LOW AND WAS IMMEDIATELY CORRECTED, HOWEVER, THE DOWNWARD TREND WAS SUCH THAT THE ALT DIPPED TO 400 FT LOW FOR 1 SECOND THEN BACK UP TO FL410. I BELIEVE THIS SIT CAN BE PREVENTED BY A MORE DILIGENT SCAN EVEN DURING AUTOPLT CRUISE.

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.