What happened
Shortly before the accident, the aircraft was traveling northeast at 17,10-feet. After receiving instructions from air traffic controllers to contact Boston Center, the pilot acknowledged the command, but no subsequent radio communications were recorded. Radar monitoring showed the aircraft maintained a steady altitude of 17,100 feet and a groundspeed of 255 knots for roughly two minutes following the final transmission.
Following this period, the aircraft climbed 300 feet before undergoing a sudden descent of 10,700 feet over the course of 46 seconds. While the groundspeed remained near 255 knots, the aircraft then attempted a climb from 6,700 feet to 7,600 feet. After briefly stabilizing at 7,600 feet for 4 seconds, the plane entered a continuous descent, reaching a final radar altitude of 2,400 feet. Witnesses on the ground observed the aircraft in a flat spin with the engines still operational prior to the impact.
Findings
Weather analysis indicated the presence of light-to-moderate precipitation in the area, with cloud tops reaching approximately 17,000 feet near the site. At the time of the flight, AIRMET Zulu was active, warning of icing conditions between the freezing level and 22,000 feet. Furthermore, several pilot reports (PIREPs) had noted light-to-moderate rime or mixed icing in clouds up to 16,000 feet.
Post-accident inspections of the engines and airframe showed no mechanical failures or anomalies prior to the crash. However, investigators noted that the overhead switch panel for the propeller de-ice, engine intake heat, windshield anti-ice, and wing de-ice systems were all set to the 'off' position. Additionally, toxicology analysis of the pilot's urine revealed the presence of pseudoephedrine and diphenhydramine.