Bonanza 36
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 15; Flight Crew Total 1750; Flight Crew Type 1600
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Became Reoriented; Flight Crew FLC Overrode Automation; Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control
Human Factors; Weather; Aircraft
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.
BE-36 pilot experienced autopilot failure in IMC on ILS approach.