Be-36 pilot experienced autopilot failure in IMC on ILS approach.

Attributes
ACN	1647423
Time
Date	201905
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Bonanza 36
Operating Under FAR Part	Part 91
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Component
Aircraft Component	Autopilot
Person 1
Function	Single Pilot
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Commercial
Experience	Flight Crew Last 90 Days 15 Flight Crew Total 1750 Flight Crew Type 1600
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types Inflight Event / Encounter Loss Of Aircraft Control

Narrative:

On an instrument flight plan to ZZZ in IFR; flight was at 7;000 feet above cloud tops which were between 3-6000 feet on the STAR. We had been advised that we would be vectored for the xxr ILS approach to ZZZ and instructed to descend to 5000.as we began our descent into IMC; the autopilot seemed to roll into a right descending turn; and I saw our heading change to approximately a 170 degree heading (or more); where we had been assigned 070. We quickly regained control of the aircraft and began to hand fly it.once control was regained; we called ATC immediately on their approach frequency; to alert them to our deviation. They asked only if we needed help. I told them to standby while we sorted through things. I called a second time to say that we reestablished our assigned heading and altitude. We called out that we had the field and they switched us over to the tower who advised us to land on runway xy; which we did without incident.

Original NASA ASRS Text

Title: BE-36 pilot experienced autopilot failure in IMC on ILS approach.

Narrative: On an instrument flight plan to ZZZ in IFR; flight was at 7;000 feet above cloud tops which were between 3-6000 feet on the STAR. We had been advised that we would be vectored for the XXR ILS approach to ZZZ and instructed to descend to 5000.As we began our descent into IMC; the autopilot seemed to roll into a right descending turn; and I saw our heading change to approximately a 170 degree heading (or more); where we had been assigned 070. We quickly regained control of the aircraft and began to hand fly it.Once control was regained; we called ATC immediately on their approach frequency; to alert them to our deviation. They asked only if we needed help. I told them to standby while we sorted through things. I called a second time to say that we reestablished our assigned heading and altitude. We called out that we had the field and they switched us over to the Tower who advised us to land on runway XY; which we did without incident.

Data retrieved from NASA's ASRS site 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.