Incident Overview
A Cessna 210M experienced a loss of engine power and subsequently conducted a forced landing on a city street. During the landing, the aircraft collided with a pole. The event prompted a detailed investigation of the engine and its components.
Engine and Component Damage
Examination revealed that the engine crankcase was fractured. The number 5 piston connecting rod had separated from the engine and was discovered along the wreckage path. Further inspection of the number 5 cylinder wall disclosed evidence of scraping by the piston rings in the region below the normal piston stroke.
Metallurgical Analysis
According to the metallurgic report, the connecting rod for the number 5 piston failed due to a fatigue crack. The connecting rod also exhibited bending that occurred sometime after the initial engine operation. This bending was characteristic of a hydraulic lock condition, which occurs when the piston is forced against incompressible fluids between the piston and cylinder head. No indication of any metallurgical defect was observed in the connecting rod, and hardness readings, which indicate strength, conformed to material specifications.
Maintenance Records
The aircraft's maintenance records noted that a major overhaul had been accomplished 207.8 hours before the accident.