These October 2009 accident reports are provided by the National Transportation Safety Board. Published as an educational tool, they are intended to help pilots learn from the misfortunes of others.
Aircraft: Cessna 210. Injuries: 1 Minor. Location: Walsh, Colo. Aircraft damage: Substantial.
What reportedly happened: The airplane was in level cruise flight at 6,500 feet MSL when the pilot started to smell smoke. The oil pressure and oil temperature readings were normal, but the exhaust gas temperature on one of the cylinders had dropped, followed by the EGT decay of another cylinder. The pilot made an emergency landing in an open field.
Recent rains had softened the ground and when the nosewheel touched down, the airplane flipped on its back. According to the FAA inspector who examined the engine, the cylinder hold-down studs on the lower side of the No. 2 cylinder had threads, but one stud had snapped off. Further examination revealed that the lower four nuts on the No. 2 cylinder were not properly torqued, which allowed the lower side of the cylinder to move while the upper part remained fixed. A crack developed on the right side of the cylinder and propagated along the bottom lip to the left side of the cylinder, eventually reaching the point of failure.
When the annual and 100-hour inspections were done on Aug. 21, 2009, all six cylinders had been removed “due to low compression” and replaced with overhauled cylinders, new pistons and rings, and new gaskets and seals. Airframe total time was 3,797.79 hours, and the time since major engine overhaul was 1,239.82 hours. The tachometer read 2,960.72. At the accident site, the tachometer read 3,059.41 hours.
Probable cause: A partial loss of engine power due to failure of the No. 2 cylinder as a result of the failure of the repair facility to properly torque the lower four nuts on the cylinder.
For more information: NTSB.gov NTSB Identification: CEN10FA021