Accident Overview
During cruise flight, the pilot experienced a simultaneous loss of engine RPM and oil pressure. The pilot executed an emergency landing on a frozen lake. During the landing roll, the right wingtip struck a spruce tree, and the airplane sustained substantial damage.
Examination Findings
During an examination, the accessory section of the engine did not rotate when the propeller was turned by hand. A subsequent teardown of the engine revealed that the crankshaft was fractured at the number 3 short cheek, between the number 2 rod bearing and the number 2 main bearing. The engine contained numerous fragments originating from the number 2 main bearing. The number 2 bearing saddle was severely worn and deformed, and other bearing saddles exhibited scoring.
Metallurgical Analysis
A metallurgical examination of the crankshaft revealed a fatigue failure at the aft radius of the number 2 main bearing journal. This fatigue crack was located adjacent to heavy rubbing marks from the number 2 main bearing.