On December 21, 1996, a Cessna T210M (registration N732UH) operated by Daniel N. Garon was involved in an aviation accident near Lexington, KY. Investigators recorded the probable cause as: failure of #5 exhaust valve and/or #5 exhaust valve guide, which resulted in a progressive engine failure (debris puncturing the #5 piston crown, exhaust gasses entering the crankcase, loss of oil through the breather system, oil exhaustion, and subsequent… This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A Cessna 210 experienced engine roughness and power loss at night, leading to a forced landing on a divided highway. Two vehicles were struck. Post-accident examination revealed fatigue fractures in the #5 exhaust valve guide and other internal damage.
Incident Overview
A Cessna 210 was cruising at 11,000 feet during nighttime conditions when the engine began to run rough and lose power. The pilots attempted to divert to an airport with suitable services, but all engine power was subsequently lost. A forced landing was performed on a divided highway, during which two vehicles were struck.
Examination Findings
Post-accident examination of the airframe and engine revealed oil on the underside of the fuselage and a hole on the top of the engine case. Further inspection identified that the #5 exhaust valve guide had fractured just below the flange that seated the guide into the cylinder head, with evidence of fatigue present on the fracture surface. The #5 exhaust valve was fractured between the valve head and stem; however, the cause of this fracture could not be determined due to impact damage to the fractured surfaces. The #5 intake valve was partially broken, but the fracture appeared to have resulted from overload due to impact with debris inside the cylinder. Additionally, the #5 piston crown was mutilated, and a hole was broken through the crown to the interior. The main bearings and connecting rod bearings were damaged due to a lack of lubrication, and the #2 and #4 connecting rods had failed.