What happened
A cargo flight departing from runway 33L at Boston-Logan Airport entered an uncontrolled descent shortly after takeoff. The aircraft, a four-engine airplane, was operating a route to Luton via Shannon and was transporting a shipment of computers. During the initial climb phase, the aircraft encountered challenging meteorological conditions characterized by fog, snow showers, and visibility restricted to 800 meters.
At an altitude of approximately 1,700 feet, the flight lost control and struck trees in a wooded area located roughly 17 miles northwest of Boston-Logan Airport. The accident resulted in seven fatalities and one serious injury among the eight people on board.
Findings
The investigation determined that the primary cause was the loss of aerodynamic performance, which exceeded the operational limits of the aircraft. This degradation was caused by the buildup of snow and ice on the airframe prior to departure, followed by additional ice accumulation as the plane flew through moderate to severe icing conditions during the climb.
Several other factors contributed to the accident:
- Encountering windshear, turbulence, and downdraughts during the ascent.
- The flight crew's failure to secure a sufficient preflight weather briefing.
- The failure of the National Weather Service to notify the crew regarding an active SIGMET for severe icing.