Accident Details
The pilot was relocating a Cessna 172E for its annual maintenance inspection. During the flight, the engine experienced a partial loss of power and began to shake and misfire violently. The pilot attempted to control the engine by adjusting the throttle and mixture controls, but these actions did not resolve the issue.
Emergency Landing
As the airplane descended, the pilot searched for a suitable landing area and spotted an open field. After turning final, the pilot extended the wing flaps to the 40-degree position and touched down. During the emergency landing, the airplane approached a ditch. The pilot attempted to clear the ditch by raising the flaps, but the airplane struck the far side of the ditch.
Postaccident Examination
A postaccident examination of the engine revealed that the No. 2 cylinder's exhaust valve rocker arm was fractured and had separated into two parts. The initial fracture on the exhaust valve rocker arm was on the push rod side and exhibited features indicative of overstress. The fracture on the valve side was secondary to the overstress fracture on the push rod side. Fatigue cracking at that location appeared to result from bending loads generated after the push rod side fracture. The push rod side fracture was generated from some type of high load event, possibly during an overhaul 34.8 hours prior to the accident. The pilot/owner had purchased one of the cylinders on eBay, and there were discrepancies in the engine maintenance records.