On August 28, 2000, a Cessna T210N (registration N6993N) was involved in an aviation accident near Council, ID. Investigators recorded the probable cause as: Application of a sealant not called for in the engine overhaul manual to the mating faces of the main bearing saddles, which led to a loss of proper crankcase clamping pressure, resulting in bearing shift and scoring of the crankshaft journal, and subsequent… This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During cruise, manifold pressure dropped; pilot diverted. Engine failed four miles from alternate. Forced landing in field; nose wheel hit soft ground from irrigation, nosed over. Investigation found crankshaft fatigue due to improper sealant during overhaul.
Accident Description
While in cruise flight, the turbocharged aircraft experienced a drop in manifold pressure. Despite the engine running smoothly, the pilot elected to divert to an alternate airport for inspection. Approximately four miles from the alternate airport, the engine began to run rough and subsequently ceased producing power. The pilot performed a forced landing in an open field short of the airport. During the landing roll, the nose wheel encountered an area softened by irrigation, causing the aircraft to nose over.
Investigation Findings
Examination of the engine revealed that the crankshaft had failed due to fatigue crack initiation in the number two main journal cheek. Further inspection determined that a sealant had been applied to the mating faces of the main bearing saddles during the last engine overhaul. This sealant was not specified in the engine overhaul manual. Its application led to a loss of proper crankcase clamping pressure in the area of the main bearing saddle through-bolts. The loss of clamping pressure resulted in bearing shift and scoring of the crankshaft journal.
Probable cause
Application of a sealant not called for in the engine overhaul manual to the mating faces of the main bearing saddles, which led to a loss of proper crankcase clamping pressure, resulting in bearing shift and scoring of the crankshaft journal, and subsequent fatigue crack initiation and failure.