What happened
While cruising at 4,000 feet, the crew observed light icing accumulating on the windshield and subsequently engaged the aircraft's deicing system. Following two operational cycles of the deicer, the occupants detected the scent of alcohol within the cockpit, accompanied by smoke rising from the control yoke.
In an effort to reach Providence, RI, the crew attempted an emergency descent; however, the situation escalated as heavy black smoke and visible flames filled the cockpit. Unable to reach the airport due to the intensity of the fire, the crew performed an emergency landing on a reservoir, specifically onto a layer of ice approximately 10 to 12 inches thick.
During the impact with the frozen surface, the left main landing gear collapsed and the right wing was severed from the fuselage. The accident resulted in one fatality and eleven injuries among the occupants.
Findings
Investigations into the incident identified that a defective design of the isopropyl alcohol windshield washer/deicer system, combined with improper maintenance of said system, led to the development of the in-flight fire. While the fire was the primary driver of the emergency, investigators were unable to pinpoint the specific ignition source.