LEXINGTON, KY, USA
N732UH
Cessna T210M
The Cessna 210 was cruising at 11,000 ft at night, when the engine began to run rough & lose power. The pilots attempted to fly to an airport with suitable services, but all engine power was lost. The pilots then performed a forced landing on a divided highway. During the landing, two vehicles were struck. Examination of the airplane & engine revealed oil on the underside of the fuselage & a hole on the top of the engine case. Further examination revealed the #5 exhaust valve guide had fractured just below the flange that seated the guide into the cylinder head, with evidence of fatigue. The #5 exhaust valve was fractured between the valve head & stem; but the cause of this fracture could not be determine due to impact damage to the fractured surfaces. The #5 intake valve was also partially broken, but fracture of this valve appeared to have been from overload, due to impact with debris inside the cylinder. Also, the #5 piston crown was found mutilated, & a hole was broken through the crown to the interior. Additionally, the main bearings and connecting rod bearings were damaged due to a lack of lubrication, and the #2 and #4 connecting rods had failed.
On December 20, 1996, about 2100 eastern standard time, a Cessna T210M, N732UH was substantially damaged during a forced landing on a highway, and subsequent collision with two vehicles in Lexington, Kentucky. The two pilots and two passengers on the airplane were not injured, while a third passenger received minor injuries. The occupants of the two vehicles were not injured. Night visual meteorological conditions prevailed for the flight which departed Birmingham, Alabama, at 1847. The flight was conducted on an instrument flight plan under 14 CFR Part 91. The airplane owner held a private pilot certificate, occupied the left seat, and was operating the flight controls. A commercial rated flight instructor occupied the right seat. The owner reported that they were cruising at 11,000 feet, 15 to 20 miles northeast of Lexington, when the engine began to run rough and a partial power loss occurred. The owner advised air traffic control, and requested to land at the Blue Grass Airport in Lexington. About 5 miles northeast of Lexington, the engine lost total power and the pilot positioned the airplane for a forced landing to a divided highway. During the forced landing, the airplane passed over the top of a power line, and then went under a highway overpass. The airplane struck two vehicles moving in the same direction as the airplane, and then came to rest on the highway. Both pilots reported that oil was visible on the underside of the fuselage. The airplane was examined by a Federal Aviation Administration (FAA) Airworthiness Inspector, who reported that a hole was found in the top of the crankcase near the number four cylinder. Further inspection revealed the number four connecting rod cap was separated from the connecting rod which disconnected the rod from the crankshaft. The engine was shipped to Teledyne Continental Motors (TCM), Mobil, Alabama, for further examination. The examination was conducted for the Safety Board by a FAA inspector assigned to TCM. According to the TCM report: "...Crankcase main bearings exhibited oil starvation signatures...Number 5 exhaust valve, part number SA643873 broken in the transition of the head to the valve stem...could not determine cause of fracture due to extreme impact damage to the fractured surfaces. " "The number 4 exhaust guide, part number SA636242 was broken just below the flange that seats the guide into the cylinder head. The fracture exhibited fatigue...." "Number 5 intake valve, part number SA539988 head was partially broken up. Most pieces of the valve head were not recovered. The fracture of this valve appears all overload due to impact with debris inside the cylinder."
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 damage to the engine bearings and connecting rods). Darkness and obstructions (vehicles) in the emergency landing area were related factors.
Source: NTSB Aviation Accident Database
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