NTSB Identification: ATL05LA052.
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Accident occurred Wednesday, February 23, 2005 in Macedonia, SC
Probable Cause Approval Date: 02/28/2006
Aircraft: WSK PZL Mielec M-18A, registration: N2296Y
Injuries: 1 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.
While approaching Moncks Corner Airport to land, the airplane's engine seized and the pilot was forced to land on tree tops about 400 feet from the runway. Post-accident examination of the engine assembly revealed four fatigue cracks on the planetary carrier housing that propagated outboard and caused the housing to fracture into multiple pieces. The teeth around the sun gear in the area that corresponds to the planetary gears were fractured and exhibited deformation. The teeth of the planetary gears showed deformation. The splined lock was examined and exhibited fretting damage. The width of the fretting/galling damage on the four flat surfaces was wider compared to the thickness of the mating square slot on the cap, consistent with lateral movement between the splined lock and cap. All spine teeth on the splined lock showed deformation. Dimensional inspection of the gears were performed on the engine approximately 98 hours prior to the accident. At that time, a new sun gear was installed in the engine. The mating four planetary gears were not replaced and not required to be replaced. Uneven wear between gear faces caused stresses to be distributed unevenly between the gears, resulting in accelerated wear of the gears. Wear of the planetary gears are required to be evaluated when the engine is overhauled, but there is no record of a recent engine overhaul.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The fatigue cracking of the planetary gear housing, which resulted in the loss of engine power. Full narrative available
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