NTSB Identification: SEA05FA074.
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Nonscheduled 14 CFR
Incident occurred Tuesday, April 12, 2005 in Roosevelt Roads, PR
Probable Cause Approval Date: 05/30/2006
Aircraft: Cessna 208B, registration: N1241X
Injuries: 4 Uninjured.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The airplane experienced a total loss of engine power during a domestic passenger cross-country flight. Following the loss of power, the pilot successfully landed the airplane at a nearby Naval Air Station. The pilot reported that during cruise flight, he heard a loud bang and oil became visible on the aircraft's windshield. He stated that concurrent with the loud bang, the propeller came to an abrupt stop. Postaccident examination of the engine revealed extensive corrosion and mechanical damage throughout the compressor and power turbine assemblies. The compressor disk assembly was essentially intact, however, all of the compressor turbine blades were fractured and displaced. The fracture surfaces were all approximately .250 inches above the corresponding blade platform. Examination of the fractured compressor turbine blades revealed the blades fractured in a tensile overload condition. The overload fractures associated with the compressor turbine blades was due to a weakening of the underlying base material due to the presence of sulphidation corrosion. The sulphidation corrosion was evident through approximately half of the thickness of the blades airfoil reducing the blades effective load bearing capabilities. The material composition of the turbine blades met drawing requirements and no metallurgical anomalies were found.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The fracture of multiple compressor turbine blades while the airplane was in a cruise flight configuration resulting in a loss of engine power. Sulphidation type corrosion was a factor in failure of the blades. Full narrative available
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