The fracture of the crankshaft due to fatigue, the propeller separating from the airplane while in-flight, which resulted in the propeller striking the empennage structure and flight controls, yielding the airplane uncontrollable. Contributing factors to the accident were the previous damage to the crankshaft, the company/operator management disregarding the engine manufacture's service bulletin mandating an engine teardown inspection after a propeller strike event, and the inadequate inspection of the engine by the company maintenance staff.