LJ60 suffers altitude deviation when autoplt fails at FL410.

Attributes
ACN	712328
Time
Date	200609
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : hrv.vortac
State Reference	LA
Altitude	msl bound lower : 36000 msl bound upper : 41000
Aircraft 1
Controlling Facilities	artcc : zfw.artcc
Operator	general aviation : corporate
Make Model Name	Learjet 60
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : level ground : maintenance
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 130 flight time total : 23000 flight time type : 4500
ASRS Report	712328
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude
Resolutory Action	aircraft : equipment problem dissipated controller : issued new clearance flight crew : overcame equipment problem
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

We were at FL410 over gulf of mexico airspace between srq and hrv 230 K mi north of hrv. Working with ZFW; we lost the autoplt which failed mach trim and so had to reduce speed below .76 mach. Because of nature of the lear 60 we lost altitude and requested FL360. Initially we lost 500 ft due to mis-trim resulting from loss of autoplt. ATC did not make any comment other than asking if we wanted to declare emergency. We declined and regained the use of the autoplt. Without autoplt we cannot maintain rvsm standards. In descent from FL410 to FL360 we regained use of the autoplt.

Original NASA ASRS Text

Title: LJ60 SUFFERS ALTDEV WHEN AUTOPLT FAILS AT FL410.

Narrative: WE WERE AT FL410 OVER GULF OF MEXICO AIRSPACE BTWN SRQ AND HRV 230 K MI N OF HRV. WORKING WITH ZFW; WE LOST THE AUTOPLT WHICH FAILED MACH TRIM AND SO HAD TO REDUCE SPD BELOW .76 MACH. BECAUSE OF NATURE OF THE LEAR 60 WE LOST ALT AND REQUESTED FL360. INITIALLY WE LOST 500 FT DUE TO MIS-TRIM RESULTING FROM LOSS OF AUTOPLT. ATC DID NOT MAKE ANY COMMENT OTHER THAN ASKING IF WE WANTED TO DECLARE EMER. WE DECLINED AND REGAINED THE USE OF THE AUTOPLT. WITHOUT AUTOPLT WE CANNOT MAINTAIN RVSM STANDARDS. IN DSCNT FROM FL410 TO FL360 WE REGAINED USE OF THE AUTOPLT.

Data retrieved from NASA's ASRS site as of January 2009 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.