Accident
On November 6, 2010, at approximately 1430 mountain daylight time, a Cessna T210N, registration N6179Y, impacted terrain during a forced landing about 30 miles north of Baggs, Wyoming. The commercial pilot and passenger were not injured. The aircraft, owned and operated by the pilot, sustained substantial damage. The personal cross-country flight had departed Broken Bow, Nebraska, about two hours earlier and was en route to Brigham City, Utah. The flight was conducted under visual meteorological conditions, and no flight plan was filed.
Sequence of Events
According to the pilot, while in cruise flight he heard and felt a solid "thump" from the engine compartment. Shortly thereafter, oil pressure began to drop, and the engine lost power. About two minutes later, the engine made a knocking sound and the propeller slowed. The engine eventually stopped producing power, and the pilot attempted a forced landing on a nearby narrow dirt road. The touchdown was successful, but the pilot could not keep the aircraft aligned with the rough and rutted road, causing it to depart the road surface and enter rough, uneven terrain. The nose dug in, and the aircraft flipped onto its top.
Post-Accident Examination
An on-scene inspection by an Airworthiness Inspector from the Casper Flight Standards District Office (FSDO) revealed a hole in the engine crankcase, through which much of the engine oil had escaped.
The aircraft was moved to Beegles Aircraft Service in Greeley, Colorado, for a full teardown inspection under FAA oversight. The teardown included inspection of all engine accessories and external components, as well as separation of the crankcase halves to examine internal components. No anomalies, contamination, or evidence of malfunction were found in the magnetos, ignition harness, spark plugs, fuel pump, oil pump, fuel manifold valve, fuel injection nozzles, oil cooler, or oil filter. The cylinders, pistons, and valve train showed no evidence of anomaly or malfunction.
Upon splitting the crankcase, all main journal bearings exhibited significant wear, with some underlying copper showing, but no significant thermal damage. The crankshaft main journals also lacked significant thermal damage, and there was no evidence of hard particle passage on their surfaces. The slot holding the retention tang for one-half of the number two main bearing had elongated, but the bearing had not shifted and lubricating oil flow had not been interrupted.
Inspection of the crankshaft revealed severe thermal stress in the area of the number one and number two connecting rod journals. Both journals displayed characteristics consistent with heat buildup due to localized lack of lubrication, appearing light reddish tan and completely devoid of lubrication. The number two connecting rod remained attached but its large end and rod cap retaining bolts were reddish tan and without lubrication. The number one connecting rod had separated from its journal; one side of the rod cap was missing its retaining bolt. The distorted large end and remaining bolt were similarly discolored and unlubricated. The castellated nut end of the missing bolt, along with damaged connecting rod bearing material, was found in the oil sump. The recovered bolt section showed fracture damage but no evidence of overheating. Due to damage around the fracture surface and the absence of the bolt head, the failure mode could not be determined.
Aircraft History
A review of the aircraft logbooks showed that from October 3, 2007, to May 3, 2010 – a period of 31 months – the airplane accumulated only 4.0 flight hours. During this period, no annual inspections were performed, and no entries indicated compliance with engine preservation procedures outlined in Teledyne Continental Motors Service Letter SIL99-1. From May 3, 2010, to October 20, 2010, under new ownership, the airplane accumulated about 242 flight hours. At the time of the accident, the engine had 1,591 hours since its last major overhaul. Teledyne Continental Motors Service Letter SIL98-9A recommends a time between major overhauls of 1,400 hours for the TSIO-520-R series engine. A logbook entry from October 20, 2010, indicated that the number two and three cylinders had been reinstalled after being overhauled due to low compression.