What happened
Shortly after departing from the end of runway 34, the aircraft type experienced a sudden loss of engine power. A witness reported hearing a sound similar to a rapid misfire or a pop, followed by the cessation of audible engine noise. At the time of the engine failure, the aircraft was positioned approximately 300 to 400 feet above the ground. Following the loss of power, the aircraft performed a series of maneuvers, including a right turn and a left bank that brought the wing to a vertical position, before leveling the wings and descending into the terrain. The interval between the audible engine malfunction and the impact was estimated to be between two and three seconds. The accident resulted in 0 fatalities and the total destruction of the airframe.
Findings
Post-accident investigations of the engine revealed a cracked crankshaft propeller flange. Further inspection of the turbocharger system's exhaust bypass valve assembly showed that the butterfly valve was stuck in the extended closed position. Subsequent testing demonstrated that reinstalling the original exhaust bypass valve assembly caused the wastegate to bind again, leading to a loss of engine power. A detailed examination of the bypass valve assembly identified a bent wastegate shaft. Additionally, the valve assembly lever arm showed evidence of pre-impact tool marks, suggesting that pliers may have been used in an attempt to loosen the bound shaft.
Investigation also noted that the pilot operating handbook (POH) lacked specific emergency procedures for handling turbocharger failures. While maintenance manuals required the wastegate to be checked during 100-hour inspections, they did not provide a specific procedure for verifying its operational condition. The aircraft had flown only 8.7 hours since its most recent annual inspection.