WPR10LA196

The airplane was in a cruise flight configuration when the engine ceased operating without warning. The pilot made an emergency descent and the airplane collided with a fence while landing in a field. Disassembly of the engine revealed extensive mechanical damage to the number two cylinder combustion chamber and piston assembly. The exhaust valve seat insert was missing and fragments of the insert were later found in the oil sump. The exhaust valve head had separated from the valve stem. The intake valve head had approximately 50 percent of the material separated. The fracture surfaces on the exhaust valve, intake valve and exhaust valve seat were damaged such that the mode of fracture could not be definitively determined. Hardness testing of the components indicted that they were within the manufacturer’s prescribed specifications. The sequence of fractures and separations of components could not determined.

HISTORY OF FLIGHT On April 4, 2010, at 1035 Pacific daylight time, a Cessna P210N, N3599P, sustained substantial damage following a loss of engine power and subsequent forced landing near Leavenworth, Washington. The airplane was registered to Centurion Flyers, LLC, and operated by the pilot under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The commercial pilot, the sole occupant, was not injured. The flight departed Everett, Washington, at 1000 with a planned destination of Spokane, Washington. Visual meteorological conditions (VMC) prevailed at the departure and destination airports. The pilot filed an instrument flight rules (IFR) flight plan; however, VMC conditions prevailed and he elected to not activate the flight plan. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge, the pilot reported that the airplane was in a cruise flight configuration at 11,500 feet when the engine suddenly, without warning, quit. The pilot attempted to restart the engine; however, it would not start and the pilot began an emergency descent. The airplane was over mountainous terrain and an overcast layer with cloud tops estimated to be 9,500 feet mean sea level (MSL). The airplane entered instrument meteorological conditions (IMC) shortly after starting the descent. The airplane descended out of the cloud layer approximately 2,000 feet above ground level (agl) and 3.9 miles from a dirt airstrip he was attempting to reach. Unable to make the airstrip, the pilot maneuvered the airplane towards a nearby open field and lowered the gear and flaps. The pilot slipped the airplane in order to make the field. Just before touchdown, the airplane collided with a fencepost and the nose landing gear sheared off. As the airplane touched down on muddy, soft terrain, its main gear caught in the soft terrain, the airplane spun to the right, approximately 60-degrees, and the right wing impacted the ground. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the airplane sustained substantial damage to the right wing and forward undercarriage. AIRCRAFT INFORMATION The accident airplane (serial no. 00039) was equipped with a Teledyne Continental Motors TSIO 520 P engine and a three-bladed, constant-speed propeller. The owner of the airplane indicated that the engine had accumulated 726 total flight hours since new. The most recent annual inspection of the airplane, engine and propeller was completed on June 16, 2009. At the time of the accident the airplane had accumulated 4,175 total flight hours, 152 hours since the annual inspection. TESTS AND RESEARCH Disassembly of the engine revealed extensive mechanical damage to the number two cylinder combustion chamber and piston assembly. The exhaust valve seat insert was missing and fragments of the insert were later found in the oil sump. The exhaust valve head had separated from the valve stem. The intake valve headhad approximately 50 percent of the material separated. The cylinder skirt was intact and undamaged. The cylinder overhead components (rocker arms, guides, springs, retainers and shafts) were lubricated and undamaged. The piston was mechanically fragmented and the majority of the fragments were located in the oil sump. Two large fragments of the piston were found lodged between the crankshaft and crankcase. The crankshaft and counterweight assembly exhibited mechanical damage. The connecting rod exhibited mechanical damage where the I-beam was bent. The connecting rod cap remained secure and exhibited mechanical damage at its base. The connecting rod nuts and bolts were intact and secure. The rear set of counterweight assemblies exhibited mechanical damage, but were intact and free unrestricted movement was noted. The fracture surfaces on the exhaust valve, intake valve and exhaust valve seat were damaged such that the mode of fracture could not be definitively determined. Hardness testing of the components indicated that they were within the manufacturer’s prescribed specifications. The sequence of the fractured components could not determined.