What happened
On a flight departing from Brunswick NAS in Maine toward Trenton, Ontario, a four-engine airplane encountered severe weather conditions during its ascent. While navigating through stormy weather, the number one engine entered a state of whirl mode and subsequently detached from the airframe. This failure caused approximately 11 feet of the left wing to separate from the aircraft. The departing wing section struck the left horizontal stabilizer, causing that component to be torn away as well.
Following this structural failure, the aircraft lost stability and entered an uncontrolled dive. The plane underwent partial disintegration before impacting the ground in the vicinity of Poland. There were eight fatalities among the occupants on board during the accident.
Findings
Investigations into the crash determined that the primary cause was the engine entering a whirl mode. This phenomenon involves low-frequency vibrations within the engine mounts, which can lead to the complete separation of an engine from the wing during flight. Additionally, it is believed that turbulence associated with the stormy weather conditions may have contributed to the instability and affected the proper functioning of the engine mounts.