Incident Overview
On July 11, 2021, at approximately 1000 eastern daylight time, a Cessna 172 (registration N5340R) sustained substantial damage during a forced landing near Eagle Butte, South Dakota. The pilot reported no injuries. The flight was operating under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Sequence of Events
According to the pilot, while about 6 miles from Cheyenne Eagle Butte Airport (84D), he observed high engine oil temperature and heard a clattering noise. He reduced engine power by about 100 rpm and diverted toward the airport. Approximately 2 miles from the airport, the engine lost all power. Unable to reach the runway, the pilot executed a forced landing in a wheat field. During touchdown, the nose wheel struck rising terrain, causing the airplane to bounce. The nose gear separated, and the airplane nosed over, coming to rest inverted.
Damage and Examination
The accident resulted in substantial damage to the left lift strut and fuselage. Post-accident examination revealed a large hole in the top of the engine case near the No. 6 cylinder. The No. 6 cylinder and its connecting rod were removed and sent to the NTSB laboratory for examination. Analysis of the connecting rod identified fatigue cracking along multiple locations on the outer surface at the transition from the neck to the crankshaft bore. The fatigue crack had propagated approximately halfway through the connecting rod cross section before the remaining material fractured from overstress. The fatigue initiation sites coincided with deep grinding marks on the connecting rod surface.