NTSB Identification: SEA08LA156
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Monday, June 30, 2008 in Bend, OR
Probable Cause Approval Date: 05/06/2009
Aircraft: CESSNA TR182, registration: N7XZ
Injuries: 1 Serious,1 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 pilot reported that, during cruise flight, the engine began to run rough as she noticed that the propeller rpm was beyond the red line indication and that oil was coming from the forward cowling area behind the propeller. The oil began coating the windscreen and made forward visibility nearly impossible as the pilot initiated an off-airport landing in an adjacent open field. During the landing roll, the airplane struck a barbed wire fence and came to rest on a two-lane highway, which resulted in substantial damage to the right wing and engine firewall. A postaccident examination of the engine revealed that the crankshaft was cracked about 380 to 400 degrees around the circumference of the forward bearing journal, originating from the oil-through hole and progressing in a direction opposite of the rotation of the crankshaft. A metallurgical examination of the fracture region revealed that the origin of the fracture was consistent with a brittle intergranular fracture through the nitride layer and exhibited numerous crack arrest marks. Beyond the fatigue fracture area, the fracture was on a slant plane consistent with overstress separation. The source of the loading that lead to the initial crack formation at the oil through-hole could not be determined. Review of aircraft logbook records revealed that an engine overhaul was completed on May 1, 2006. The most recent annual inspection of the engine and airframe was conducted on May 30, 2008, 252.3 hours since the engine's last major overhaul.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The failure of the crankshaft during cruise flight due to fatigue.

Full narrative available

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