Aircraft Stall and Spin During Circling Instrument Approach (N959MJ)

Approach and Descent Event Report details indicate that the pilot was conducting a GPS circling instrument approach in instrument meteorological conditions to a familiar airport. During the final minute of the flight, the aircraft descended to and leveled off near the minimum descent altitude (MDA) of approximately 600 feet mean sea level (msl). At this time, the groundspeed decreased from about 90 knots to a low of 65 knots. Shortly after reaching 65 knots, the flight track abruptly turned left off course, and the aircraft rapidly descended. The final radar point was recorded at 200 feet msl, less than 1/10 mile from the accident site. Two home surveillance cameras captured the final seconds of the flight. The first video showed the aircraft in a shallow left bank that rapidly increased until it descended in a steep left bank out of view below a line of trees. The second video captured the final 4 seconds, showing the aircraft entering the frame already in a steep left bank near treetop level, continuing to roll left and descend out of view. Both videos showed the aircraft flying below an overcast cloud ceiling, and engine noise was audible until impact. Postaccident examination revealed no preimpact mechanical malfunctions that would have precluded normal operation. Propeller signatures, witness impact marks, audio recordings, and witness statements were consistent with the engines producing power at impact. The pilot likely encountered restricted visibility of about 2 statute miles with mist and ceilings about 700 feet msl. When the aircraft deviated from the final approach course and descended below the MDA, the destination airport remained 3.5 statute miles to the northeast. Although the aircraft was observed flying below the overcast cloud layer, the restricted visibility likely prevented the pilot from visually identifying the airport or runway environment at any point during the approach. According to airplane flight manual supplements, the stall speed likely varied from 76 to 67 knots indicated airspeed. The exact weight and balance and configuration of the aircraft could not be determined. Based on surveillance video, witness accounts, and automatic dependent surveillance-broadcast data, it is likely that, as the pilot leveled off the aircraft near the MDA, the airspeed decayed below the aerodynamic stall speed, and the aircraft entered an aerodynamic stall and spin from which the pilot was unable to recover. A readout of the pilot’s cardiac monitoring device and autopsy findings indicated that, while the pilot had a remote history of arrhythmia, sudden incapacitation was not a factor in this accident. Autopsy findings suggested that the pilot’s traumatic injuries were not immediately fatal; soot material in both the upper and lower airways provided evidence that the pilot inhaled smoke. This autopsy evidence supports that the pilot’s elevated carboxyhemoglobin level was from smoke inhalation during the postcrash fire. No distress calls were received from the pilot, and there was no evidence of an in-flight fire. Thus, carbon monoxide exposure, as determined by the carboxyhemoglobin level, was not a contributing factor to the accident.