What happened
During takeoff and subsequent climb through 4,000 feet, the aircraft experienced an immediate yaw and roll to the right. The crew observed the number two throttle slam and lock into the idle position while a continuous buffet began across the airframe. Shortly after these symptoms started, the number two engine separated from the aircraft, causing the buffet to cease. A passenger reported seeing the aft end of the engine droop approximately 30 degrees just before separation. The engine impacted an open field located six miles from the airport.
Following the separation, the 'B' hydraulic system lost pressure, which restricted the trailing edge flaps to a maximum extension of 10 degrees. The crew executed an emergency gear extension and utilized differential braking for steering control during the approach. The aircraft landed safely without further incident.
The investigation
Examination of the recovered engine components revealed that the aft mount cone bolt for the number two engine had failed due to fatigue. The fracture occurred through the thread relief undercut radius. Fatigue cracks were found to have initiated on diametrically opposite sides of this radius. Subsequent failure of the forward mount cone bolts and the secondary support cable was determined to be a result of overload caused by the initial bolt failure.
Findings
The mechanical failure sequence began with fatigue fracture of the aft mount cone bolt. This allowed the engine to droop, leading to the separation of the powerplant from the airframe. The loss of the engine resulted in immediate hydraulic system degradation and required emergency landing procedures.