The pilot reported that, about six miles from Cheyenne Eagle Butte Airport (84D), he noticed that the engine’s oil temperature was high, and he heard a “clattering noise.” He reduced the engine power by about 100 rpm and diverted to 84D.
About two miles from the airport, the engine lost all power. Unable to reach the runway, he performed a forced landing to a wheat field. During touchdown, the nosewheel hit rising terrain, the Cessna 172 bounced, the nose gear separated, and the airplane nosed over, coming to rest inverted.
The airplane sustained substantial damage to the left lift strut and fuselage.
Examination revealed a large hole in the top of the engine case adjacent to the #6 cylinder.
The cylinder and connecting rod were removed and sent for examination at the NTSB laboratory in Washington, D.C. The examination of the connecting rod revealed fatigue cracking in multiple locations along the outer surface at the transition from the neck to the crankshaft bore. The fatigue crack propagated about halfway through the connecting rod cross section before the remainder fractured from overstress. The fatigue initiation sites were collocated with deep grinding marks.
Probable Cause: A total loss of engine power due to the fatigue failure of the #6 connecting rod.
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This July 2021 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Most failures of this type are manufacturing flaws that eventually surface.
Really ? After 56 years and 3,800+ hours. ?
Most manufacturing/ assembly defects show up as what’s known as ‘ infant failures ‘, usually in the first few 100’s of hours.
I’ll go with …’t he pilot ran the engine out of oil’ cause.
Hey NTSB..!! where’s the rest of the investigation. ??
Did you look at the engine log to see what work had been done on the engine.?
From the pics, the #6 cylinder had ‘gobs’ of epoxy on the pushrod tubes…not an acceptable fix for oil leaks.
I suspect that the engine was using a lot of oil, [ from the fine wire lower plugs ].
From the report of high oil temp, it was being starved of oil and the #6 rod bearing spun, seized on the crank and pulled the cap off.
So, where are the pics of the crankshaft…probably with scoring of the rod journals.
This engine didn’t come apart for no reason…. !