What happened
Following a standard takeoff under visual meteorological conditions, the pilot executed a planned cross-country flight under IFR flight plan protocols. Approximately eight minutes into the flight, radar tracking showed the aircraft type at an altitude of 11,200 feet msl, traveling at 180 knots on a heading of 241 degrees. Shortly thereafter, the aircraft disappeared from radar without any distress signals or further communication from the cockpit.
The aircraft subsequently entered an uncontrolled descent and struck the ground. The impact and subsequent fire were so intense that no complete systems remained intact at the wreckage site. During the investigation, the right wing tip tank was found detached from the main wreckage, located 0.18 nautical miles away. The landing gear and flaps were observed in the retracted position at the time of the crash.
Findings
Post-accident examinations of both engines confirmed that the power sections were rotating and operational at the moment of impact. However, investigators identified a fatigue failure in the right propeller shaft coupling. Metallurgical analysis revealed that the coupling had fractured through 360 degrees due to fatigue, a condition that developed during service rather than as a result of the crash. The specific origin of the fatigue crack was obscured by significant corrosion on the fracture surface.
Records showed the failed component had been in service for roughly 4,000 hours since new and 1,250 hours since its last overhaul. While the manufacturer had previously issued service bulletins to address similar fatigue issues in this component, the failure of this specific coupling led to the engine core rotating independently from the propeller shaft. Additionally, the separation of the right wing tip tank was determined to be caused by an overstress fracture of the attachment fittings, triggered by a spin rate of approximately 35.9 RPM.