Incident Description
During the climb-out following a touch-and-go landing, the pilot reported that the engine began to run rough. Shortly thereafter, smoke and oil spray were observed issuing from the engine compartment. The pilot then heard a loud bang and initiated a forced landing into an area of deep grass and vegetation. During the landing roll, the airplane nosed down, resulting in damage to the left wing.
Examination and Findings
An on-site examination by the Federal Aviation Administration (FAA) revealed oil pooled beneath the engine and oil spray within the engine compartment. Further inspection uncovered a crack in the steel barrel of the #4 cylinder. The cylinder was removed for detailed analysis.
Optical examination of the fracture surfaces on cylinder #4 showed fracture markings, arrest lines, and deformation patterns consistent with fatigue progression over the entire surface of the original crack. The investigation concluded that the metal smearing and hairline cracks most likely originated during the turning operation when cutting tools had become worn. It was further noted that these surface features were of a nature non-detectable by existing non-destructive testing processes.