A lear 25 flight crew experienced an autoplt pitch up while in ZHU airspace.

Attributes
ACN	436932
Time
Date	199905
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : jan.airport
State Reference	MS
Altitude	msl bound lower : 41000 msl bound upper : 41400
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu.artcc
Operator	general aviation : corporate
Make Model Name	Learjet 25
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : multi engine
Experience	flight time last 90 days : 120 flight time total : 4500 flight time type : 1100
ASRS Report	436932
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Qualification	pilot : commercial pilot : multi engine pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe 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	Aircraft
Primary Problem	Aircraft

Narrative:

At cruise at FL410 approximately 1 hour into our flight, we had an autoplt pitch up that caused us to climb approximately 400 ft above assigned altitude (41400 ft). We advised ZHU of the problem and corrected our altitude. We also advised the next controller we would have to hand fly the rest of the trip and stay below .78 mach. The rest of the flight was uneventful. We had our company chief of maintenance check out the autoplt, no problem was found. We have had several write-ups on the autoplt pitch. However maintenance could not duplicate the problem.

Original NASA ASRS Text

Title: A LEAR 25 FLC EXPERIENCED AN AUTOPLT PITCH UP WHILE IN ZHU AIRSPACE.

Narrative: AT CRUISE AT FL410 APPROX 1 HR INTO OUR FLT, WE HAD AN AUTOPLT PITCH UP THAT CAUSED US TO CLB APPROX 400 FT ABOVE ASSIGNED ALT (41400 FT). WE ADVISED ZHU OF THE PROB AND CORRECTED OUR ALT. WE ALSO ADVISED THE NEXT CTLR WE WOULD HAVE TO HAND FLY THE REST OF THE TRIP AND STAY BELOW .78 MACH. THE REST OF THE FLT WAS UNEVENTFUL. WE HAD OUR COMPANY CHIEF OF MAINT CHK OUT THE AUTOPLT, NO PROB WAS FOUND. WE HAVE HAD SEVERAL WRITE-UPS ON THE AUTOPLT PITCH. HOWEVER MAINT COULD NOT DUPLICATE THE PROB.

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.