What happened
During a business flight departing from runway 31, a twin-engine airplane experienced a sudden loss of power in its right engine. An eyewitness observed the aircraft at an altitude of approximately 100 feet above the ground, roughly halfway down the 6,5-foot runway, when a loud noise occurred and the right propeller began to slow. Following the engine failure, the aircraft yawed to the right and entered a turn toward runway 18 while the right propeller was windmilling. The aircraft cleared a nearby tree line by approximately 150 feet before rolling to the right and descending into the ground, resulting in a post-impact fire.
Findings
Investigation of the right engine revealed a fractured crankshaft near the No. 2 main bearing, which had rotated within its housing. The crankcase halves showed signs of fretting near the through-stud locations, a condition consistent with inadequate clamping force caused by improper torque on the through-stud nuts. Records showed that all six cylinders on this engine had been replaced during an annual inspection eight months prior to the accident, a process requiring the removal of these specific nuts. It is believed that the nuts were not sufficiently tightened during that maintenance procedure, allowing the case halves to shift and causing the bearing to spin and the crankshaft to break.
During the emergency, the pilot attempted a right turn to return to the airport but failed to feather the propeller of the failed engine. This left the propeller in a windmilling state, generating significant drag. The combination of the turn toward the failed engine, the excessive drag from the unfeathered propeller, and the pilot allowing the airspeed to drop below the minimum control threshold resulted in the loss of control of the aircraft.