A LR35 captain reported that climbing to 10;000 ft the aircraft compass froze and as the autopilot t...

Attributes
ACN	981574
Time
Date	201111
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Make Model Name	Learjet 35
Operating Under FAR Part	Part 91
Flight Phase	Climb
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	Compass (HSI/ETC)
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Flight Instructor Flight Crew Flight Engineer Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 20 Flight Crew Total 24000 Flight Crew Type 3000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Overshoot Deviation - Procedural Clearance

Narrative:

Departing and climbing to initial assigned altitude 4;000 MSL autopilot was engaged after 4;000 MSL and subsequent step climb to 10;000 MSL through various altitudes. At 9;000 MSL made a 1;000 ft to go call and noticed problems with HSI. The compass card not matching with the RMI; it froze at 180 degrees opposite to RMI and failed. No flags on the instrument observed. Autopilot started deviating to unknown heading. Autopilot in the heading mode was following the heading bug to a completely different heading. The altitude hold button was depressed at 10;000 MSL but the autopilot did not capture and altitude alert did not chime. At this point in time ATC alerted me to maintain 10;000 MSL. I noticed the aircraft was climbing through 10;000 MSL. Autopilot was disengaged and I took control of the aircraft to rapidly descend to 10;000 MSL. It took a few seconds to level off at 10;000 MSL. It was a series of failures in the equipment that compounded to the altitude infraction. Aircraft is going for maintenance today.

Original NASA ASRS Text

Title: A LR35 Captain reported that climbing to 10;000 FT the aircraft Compass froze and as the autopilot tried to follow an incorrect heading he became distracted and overshot his altitude.

Narrative: Departing and climbing to initial assigned altitude 4;000 MSL autopilot was engaged after 4;000 MSL and subsequent step climb to 10;000 MSL through various altitudes. At 9;000 MSL made a 1;000 FT to go call and noticed problems with HSI. The compass card not matching with the RMI; it froze at 180 degrees opposite to RMI and failed. No flags on the instrument observed. Autopilot started deviating to unknown heading. Autopilot in the heading mode was following the heading bug to a completely different heading. The altitude hold button was depressed at 10;000 MSL but the autopilot did not capture and altitude alert did not chime. At this point in time ATC alerted me to maintain 10;000 MSL. I noticed the aircraft was climbing through 10;000 MSL. Autopilot was disengaged and I took control of the aircraft to rapidly descend to 10;000 MSL. It took a few seconds to level off at 10;000 MSL. It was a series of failures in the equipment that compounded to the altitude infraction. Aircraft is going for maintenance today.

Data retrieved from NASA's ASRS site as of April 2012 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.

A LR35 captain reported that climbing to 10;000 ft the aircraft compass froze and as the autopilot tried to follow an incorrect heading he became distracted and overshot his altitude.