NTSB Factual Report

On October 27, 1009, approximately 1700 mountain daylight time, a Cessna 210, N5464E registered to and piloted by an airline transport-certificated pilot, was substantially damaged when it nosed over and impacted terrain following a loss of engine power near Walsh, Colorado. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91, and a VFR (visual flight rules) flight plan had been filed and activated. The pilot, the sole occupant on board, sustained minor injuries. The cross-country flight originated at Ulysses, Kansas, approximately 1730 central daylight time, and was en route to Farmington, New Mexico.

According to the pilot, he was in level cruise flight at 6,500 feet msl (above mean sea level) when he "detected a slight smoke smell." Oil pressure and oil temperature readings were normal, but he noticed the EGT (exhaust gas temperature) on one of the cylinders had dropped, followed shortly thereafter by the EGT decay of another cylinder. He diverted towards Springfield, Colorado, Municipal Airport, but was forced to make an emergency landing in an open field near Walsh, Colorado. Recent rains had softened the ground and when the nose wheel touched down, the airplane nosed over.

An FAA airworthiness inspector went to the scene and examined the engine. He noted that the cylinder hold-down studs on the lower side of the number 2 cylinder had threads, but one stud had snapped off.

The wreckage was verbally released to the owner’s attorney on January 20, 2010, and the engine was transported to the facilities of Air Salvage of Dallas where, on March 2, 2010, it was disassembled and examined. NTSB and FAA attended. NTSB’s air safety investigator said that it appeared that the lower four nuts on the number two cylinder were not properly torque, 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, it reached the point of failure.

Examination of the maintenance records revealed that when the annual and 100-hour inspections were done on August 21, 2009, all 6 cylinders were removed “due to low compression,” and replaced with overhauled cylinders, new pistons and rings, and new gaskets sand seals. Airframe total time was 3,797.79 hours, and the time since engine major overhaul was 1,239.82 hours. The tachometer read 2960.72. At the accident site, the tachometer read 3059.41 hours.

NTSB 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.