What happened
While in cruise flight, the pilot observed a simultaneous loss of oil pressure and engine RPM. In response to the engine malfunction, the pilot executed an emergency landing on a frozen lake. As the aircraft performed its landing roll, the right wingtip made contact with a spruce tree. The impact resulted in substantial damage to the airplane.
The investigation
Mechanical examination of the engine revealed that the accessory section would not rotate when the propeller was manually turned. A subsequent teardown of the engine identified that the crankshaft had fractured at the number 3 short cheek, located between the number 2 main bearing and the number 2 rod bearing.
Investigators found numerous fragments from the number 2 main bearing within the engine. The saddle for the number 2 bearing was found to be severely deformed and worn, while other bearing saddles showed evidence of scoring. A metallurgical analysis of the crankshaft confirmed a fatigue failure at the aft radius of the number 2 main bearing journal, which was adjacent to heavy rubbing marks caused by the number 2 main bearing.