Incident Overview
During cruise flight, the engine experienced a loss of power. The pilot declared an emergency and opted for a forced landing in a nearby field. While maneuvering for the emergency landing, the airplane collided with a tree short of the intended landing area. The aircraft then fell to the ground and burst into flames.
Engine Examination Findings
Post-accident examination of the engine revealed no measurable quantity of oil remaining in the sump; only residual oil was present, which was dark black in color. The crankcase was breached, with large holes observed above the #2 and #6 cylinders. Internal components of the valve train were examined, and widespread spalling of the tappet bodies was noted. Severe wear of the camshaft was also observed, with four of the nine cam lobes exhibiting severe wear. The crankshaft main bearings showed dirt and particle embedment from metal particles contaminating the oil supply.
Relevant Service Information
According to Lycoming Service Letter No. SL206A, dated May 5, 1985, which addresses field reconditioned tappet bodies, such tappet bodies often lead to camshaft and tappet body problems in a short time, necessitating their removal and replacement. The service letter states that severe wear or spalling of the cam lobes and tappet bodies can result in metal particles contaminating the oil supply.