NTSB Identification: CHI04LA144.
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Accident occurred Thursday, June 03, 2004 in Strafford, MO
Probable Cause Approval Date: 06/08/2005
Aircraft: Beech M35, registration: N693V
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The airplane collided with a fence and a guy wire during a forced landing following a loss of engine power. The pilot reported he was flying at 8,500 feet mean sea level when the number 2 cylinder departed the engine resulting in a total loss of engine power. He reported that with no airports within gliding distance, he elected to land in a farmer's field where the airplane contacted a fence and a guy wire. The number 2 cylinder and the left magneto were not located after the accident. Half of the crankcase, two fractured cylinder through-bolts, two cylinder through-bolt nuts with pieces of bolts inside, four cylinder hold down nuts with pieces of studs inside, a connecting rod cap with the connecting rod cap bolt, and a connecting rod nut were submitted for a metallurgical examination. The studs and through-bolts were arbitrarily numbered clockwise starting at the upper forward stud. All of the studs and through-bolts that were examined exhibited fatigue cracking with stud 3 exhibiting the largest fatigue region. A lip was observed on the surface of the crankcase which corresponded to the forward edge of the cylinder barrel flange, adjacent to the through-bolts. Linear marks aligned with the axis of the cylinder were observed at the aft side of the cylinder hole corresponding to sliding contact with the cylinder barrel skirt. Sectioning of studs 3 and 4 revealed cracks and/or rolling laps at the thread roots. On stud 4, many of the cracks extended radially then turned. Two studs were removed from cylinder #4 and one of them also displayed sharp thread radii and cracking. This cylinder did not fail. The engine was overhauled on July 6, 2000, at a tach time of 2440.33 hours. The engine had accumulated 194.03 hours since the overhaul.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The improper installation of the cylinder during the engine overhaul which resulted in the fatigue failure of the cylinder studs and through-bolts and the subsequent separation of the cylinder. Factors associated with the accident were the fence and the guy wire which the airplane contacted during the forced landing. Full narrative available
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