CEN10LA450

The pilot reported that, while en route to spray a field, the engine lost power and the windshield became obscured with oil. The pilot immediately turned into the wind and made a forced landing into a nearby cornfield. A postaccident examination revealed that the No. 2 connecting rod had separated from the engine crankshaft. Metallurgical examinations found polishing and wear patterns indicative of relative motion between the connecting rod components and an associated rod bolt head/nut. The nut threads were sheared as result of overload failure, consistent with impulse loading. The observed anomalies were consistent with an insufficient fastener preload on installation of the connecting rod bolt. The engine had accumulated 1,193 hours since its last major overhaul. It is likely that the rod bolt head/nut became loose during operation, which led to a failure of the assembly due to impulse loading.

On July 29, 2010, at 1320 eastern daylight time, a Cessna model T188C airplane, N2085J, was substantially damaged during a forced landing following a total loss of engine power near Montezuma, Indiana. The pilot was not injured. The airplane was registered to and operated by Swing Wings, Inc., under the provisions of 14 Code of Federal Regulations Part 137 without a flight plan. Day visual meteorological conditions prevailed for the aerial-application flight that originated from Clinton Airport, Clinton, Indiana, at 1315. The pilot reported that while en route to the field to be sprayed there was total loss of engine power and the windshield became obscured with oil. The pilot immediately turned into the wind and made a forced landing into a nearby corn field. The airframe was substantially damaged after touchdown when the left main landing gear collapsed and the left wing impacted terrain. A postaccident examination conducted by a Federal Aviation Administration inspector established that the No. 2 connecting rod had separated from the engine crankshaft. A portion of the No. 2 connecting rod was found protruding through a hole in the engine crankcase. The engine was partially disassembled and the connecting rod components were sent to the National Transportation Safety Board's (NTSB) Materials Laboratory Division for metallurgical examination. The NTSB lab examination established that there were polishing and wear patterns on the washer faces of one rod bolt and a corresponding nut. Further examinations found similar wear and polishing on the No. 2 connecting rod and a rod cap. The observed polishing and wear patterns were indicative of relative motion between the connecting rod components and associated rod bolt head/nut. The nut threads were sheared, consistent with impulse loading. A review of available maintenance information revealed that the engine, a Continental model TSIO-520-T, had accumulated 1,193 hours since its last major overhaul. At 1325, the automated surface observing system at the Edgar County Airport, located about 16 miles west of the accident site, reported the following weather conditions: variable wind direction at 6 knots; visibility 10 miles; scattered clouds between 3,000 and 4,400 feet above ground level (agl); temperature 28 degrees Celsius; dew point 21 degrees Celsius; altimeter setting 30.10 inches of mercury.