What happened
While operating in cruise flight, the aircraft experienced a contained in-flight failure of the right engine. At a cruise altitude of 9,000 feet, approximately 60 miles east of the intended destination, the pilot reported hearing a loud bang. Following the noise, the engine RPM and engine temperature gauges indicated that the right engine had failed.
The pilot responded by securing the right engine and declaring an emergency to air traffic control. The flight concluded with an uneventful landing.
The investigation
An examination of the propeller shaft coupling was conducted following the incident. Investigators discovered a fracture caused by a fatigue crack. This crack originated from the corner radius of a lubrication slot at the point where the corner radius converges with the root of an inner spline. At the time of the engine failure, the engine had accumulated 6,010.2 total hours since its last overhaul.