Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 98; Flight Crew Total 7437; Flight Crew Type 253
Human-Machine Interface; Communication Breakdown; Distraction
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Inflight Event / Encounter Loss Of Aircraft Control
Air Traffic Control Issued Advisory / Alert; Flight Crew Regained Aircraft Control; Flight Crew Returned To Clearance
Aircraft; Weather; Human Factors
I was cruising at 8;000 MSL on a clearance direct to HEVVN Intersection. The autopilot was engaged in NAV mode and ALT HOLD and the heading bug was centered on my current heading. I was in VMC conditions. There were some build ups in the area; but none along my flight path at that moment. The autopilot made an uncommanded hard left bank (I believe the autopilot disengaged but I am not sure.) I took the controls; pressed the autopilot disengage button; and smoothly rolled wings level and then returned back on course. There were no unusual attitudes and minimal change in altitude. I believe the change in heading was close to 90 degrees by the time I rolled wings level and then into the right hand turn. Once back on course; I reengaged the autopilot and there were no further issues the remainder of the flight.As I was recovering the aircraft; I received a call from ATC scolding me for deviating 'for weather' and that I was on an IFR flight plan and had to ask before doing so. I would like to reiterate that this was not a weather deviation. I also explained to the controller that it was and autopilot malfunction not an intended deviation. I also had every intention of contacting ATC to let them know that a deviation had occurred; but I wanted to FLY the aircraft first and then communicate.
A BE36 pilot was distressed that ATC scolded him for a purposeful track deviation for weather when; in actuality; his autopilot had malfunctioned and turned the aircraft some 90 degrees left before he could disconnect it and return to his cleared track.