Incident Overview
A pilot reported that during cruise flight, the engine rpm increased to an overspeed condition. After increasing power, the pilot could not keep the rpm below redline and elected to perform a forced landing. During the landing, the landing gear collapsed, resulting in substantial damage to the aircraft.
Engine History and Maintenance
The pilot stated that the aircraft had been experiencing difficulty obtaining full rpm from the engine. The propeller governor had been adjusted several times, but full rpm was never achieved. On November 16, 2005, at an engine tachometer time of 1,959.37 hours, the oil and filter were removed and replaced, and an oil sample was sent for analysis. The analysis indicated "excessive wear."
Post-Accident Examination
Removal of the oil suction screen revealed metal contamination both inside and outside the screen. Examination of the propeller governor revealed that the adjustment screw had been adjusted beyond its maximum stop. The propeller governor was removed, and the screen between the governor and the engine was entirely obstructed with metal contamination. Removal and examination of the oil filter also revealed metal contamination. Broken portions of the number two main bearing were found within the oil sump. Breakaway torque values showed that the number two and number three cylinder throughbolt nuts, at the cylinder flange, were loose at 500 inch-pounds. Further examination revealed metal contamination throughout the engine, including the oil pump and the oil cooler. No other anomalies were noted with the airframe, propeller, or engine.
Conclusion
Engine failure due to internal metal contamination and a compromised propeller governor led to the overspeed condition and subsequent forced landing. The landing gear collapse occurred during the landing.