Engine Failure Prompts Emergency Highway Landing After Cylinder Fatigue Crack (N4882S)

Event Description

While in level cruise flight at night, the pilot noticed sparks and flames emanating from the engine cowling. Shortly thereafter, the engine began running roughly and then seized completely. After declaring an emergency, air traffic control cleared the pilot for a straight-in approach to a runway approximately 28 miles away. However, the pilot determined that the aircraft could not reach that runway and opted to execute an emergency landing on an unlighted stretch of interstate highway. During the landing roll, the right wing struck a guard rail, causing the aircraft to veer to the right. The impact collapsed the main landing gear.

Investigation Findings

Examination of the engine revealed that the No. 3 cylinder had separated into two pieces. The separation was caused by a fatigue crack that had initiated at the inner diameter of the cylinder. Investigators were unable to determine the root cause of the fatigue initiation. Further evidence indicated that the fatigue crack had been present for a period exceeding the 26 hours that had elapsed since the last 100-hour inspection, suggesting the crack existed prior to that inspection.