NTSB Identification: ERA10IA094
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Incident occurred Thursday, December 03, 2009 in Rome, NY
Probable Cause Approval Date: 08/03/2011
Aircraft: CESSNA 208B, registration: N701FX
Injuries: 1 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
The airplane was climbing through 7,500 feet when the pilot heard a grinding noise and saw that the gas generator speed indicator had dropped to zero. The engine then seized and the pilot declared an emergency. An air traffic controller provided vectors toward an airport; however, the airplane landed in a field about 3 miles short of the runway. Subsequent disassembly of the engine revealed compressor turbine blade fractures at varying heights above the platform and downstream damage to the power turbine blades. Further examination revealed that 13 blades were fractured at the platform, with 8 of those exhibiting fatigue fractures at the leading edge, and overload fractures toward the trailing edge. The remaining five blades exhibited ductile overload fractures over the entire fracture surface. A number of blades were also fixed to the disc, with the mating surfaces of both the blades and the disc exhibiting corrosion. Examination of blade serrations revealed an accumulation of orange dust, with black corrosion blisters observed at various locations. Dust analysis revealed sulphidation, with airborne salts likely reacting with the oxide layer on the blades to result in oxide layer decay. Subsequent to the incident, the operator increased engine water washes from once every 50 hours of engine operation to weekly, and incorporated borescope inspections into the engine maintenance program at every 100 hours of operation.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The operator's inadequate engine wash intervals, which resulted in compressor turbine blade sulphidation and subsequent turbine blade failure. Full narrative available
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