What happened
The aircraft was operating in cruise flight when the engine experienced a complete failure while positioned over Lake Tahoe, California. The pilot attempted to maintain control and navigate toward the nearest suitable airfield but was unable to reach land before the powerplant ceased functioning entirely. With no other options available, the pilot executed an emergency water landing, commonly referred to as a ditching, in the lake.
The investigation
Following the recovery of the aircraft components, investigators conducted a thorough examination of the failed engine. The primary focus was on the crankshaft, which showed clear signs of catastrophic structural failure. A detailed metallurgical analysis was performed on the shaft material to determine the root cause of the breakage.
Findings
The technical investigation revealed that the crankshaft failure was not caused by operational overload or maintenance error in the traditional sense. Instead, the metallurgical examination disclosed that the failure resulted from fatigue induced by a non-metallic inclusion within the shaft material. This manufacturing defect created a stress concentration point that eventually led to crack propagation and final fracture during normal engine operation.
Safety message
This incident highlights the critical importance of quality control in aerospace component manufacturing. Non-metallic inclusions, though microscopic, can serve as initiation sites for fatigue cracks in high-stress rotating components like crankshafts. Manufacturers must ensure rigorous material purity standards to prevent such latent defects from reaching operational aircraft.