NTSB Identification: NYC01IA211.
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Incident occurred Monday, August 13, 2001 in Bluefield, WV
Probable Cause Approval Date: 07/25/2002
Aircraft: Cessna 210L, registration: N732JT
Injuries: 1 Uninjured.
NTSB investigators used data provided by various sources and may have traveled in support of this investigation to prepare this aircraft incident report.
The pilot experienced a catastrophic engine failure while in cruise flight and performed a forced landing to an airport. Examination of the engine revealed a three inch hole in the engine case, adjacent to the number 2 cylinder. The airplane had been operated for about 4 hours since the number 1 and 2 cylinder and piston assemblies were replaced by a maintenance facility in Knoxville, Tennessee. A teardown of the engine revealed a separated number 2 connecting rod and significant damage to the number 2 piston and cylinder. Examination revealed heavy longitudinal scoring and metal transfer on the number 2 cylinder bore and the inboard edge of the barrel was deformed consistent with connecting rod contact. The inboard end of the number 2 connecting rod was fractured in two locations adjacent to the rod bearing area, and the surrounding area was discolored consistent with extreme localized heating. The connecting rod bolt fragment showed tensile elongation along with surface and fracture features consistent with an elevated temperature overstress separation. The crowns of both pistons indicated that they were manufactured by Superior Air Parts and were 0.010 inch oversize (P010) in diameter; however, diameter measurements made on each piston at various datum points revealed that the number 2 piston was closer in size to a standard size piston and did not contained any measurable dimensions within the P010 limits. Overall, the number 1 piston measurements tended to be closer to the P010 dimensions, and contained two locations that were in the P010 limits. Hardness measurements taken from both pistons were below the specified range for a new piston. The cylinder assemblies were supplied by an aviation facility in El Reno, Oklahoma, which used "serviceable parts." The specific service history of the pistons and piston pins could not be determined. The owner of aviation facility stated that they did not check the "piston skirt clearance" and expected the installer to check the skirt clearance per the Teledyne Continental Motors (TCM) Overhaul Manual, at the time of the installation. According to maintenance facility in Tennessee, the cylinders were installed per the TCM Overhaul Manual.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: Improper maintenance which resulted in the installation of an unserviceable piston assembly, and the subsequent catastrophic engine failure. Factors in this accident were the improper inspection by the piston supplier and the softening of the piston. Full narrative available
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