NTSB Identification: CHI04LA283.
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Accident occurred Saturday, September 18, 2004 in Houstonia, MO
Probable Cause Approval Date: 09/13/2005
Aircraft: Cessna 172M, registration: N80237
Injuries: 2 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The airplane sustained impact and fire damage when it cart-wheeled during a forced landing following a loss of engine power. The pilot reported that 30 minutes into the flight he heard a "clunk", the engine stopped running, and the propeller was not windmilling. He stated he attempted to restart the engine to no avail. The pilot was attempting an off airport landing in a bean field when the right wing contacted the ground, the airplane cart wheeled, and a post impact fire ensued. Inspection of the engine revealed the piston and piston pin on the number 4 cylinder were separated from the connecting rod. The metallurgical examination of the number 4 connecting rod noted the piston pin end of the rod was fractured and the fractured ends were deformed inward. The fractured surface revealed an area typical of a fatigue crack that started at the forging parting plane on the exterior surface. The fatigue origin areas contained ratchet marks indicating that fatigue cracking initiated at multiple sites and the crack extended through approximately 60% of the wall thickness. The engine, a Lycoming O-320-E2D, was overhauled on August 11, 2003, at an engine total time of 3,918.7 hours. The engine had accumulated approximately 70 hours since the overhaul. Maintenance records indicate the connecting rods were magnafluxed, rebushed, checked for alignment, and reinstalled in the engine during the overhaul. The connecting rods were the original engine rods.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The fatigue failure of the piston end of the connecting rod and the pilot's failure to maintain aircraft control during the forced landing. Full narrative available
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