Primary finding
Probable cause
The fracture of the number four cylinder's connecting rod cap.
Investigator assessment
Analysis narrative
The airplane experienced a total loss of engine power while in cruise flight. The pilot attempted to land on a nearby road, but was unable to see powerlines and a utility pole obstructing his glide path due to a film of oil on the wind shield from the ruptured engine case. The airplane struck the powerlines and pole and landed in an adjacent field. Examination of the engine disclosed a fractured connecting rod cap and rod cap bolt in the number 4 cylinder. Both of the castellated nuts were gone from the rod cap bolts. One of the bolts had remnants of a cotter key remaining in the keyway, the other bolt did not. One castellated nut fitting a rod cap bolt was found in the oil pan. The nut's normally sharp edges were worn smooth and shiny, giving the appearance the nut had been in the sump for a long period of time. The engine's last major overhaul was 946 service hours prior to the accident flight.
Source record
Factual narrative
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