NTSB Factual Report

On December 3, 2009, at 0747 eastern standard time, a Cessna 208B, N701FX, operated as Wiggins Airways flight 8409, experienced a loss of engine power followed by a forced landing to a field near Rome, New York. The certificated airline transport pilot was not injured, and there was no damage to the airplane. Visual meteorological conditions prevailed at the landing site. The airplane was operating on an instrument flight rules flight plan from Syracuse Hancock International Airport (SYR), Syracuse, New York, to Plattsburgh International Airport (PBG), Plattsburgh, New York. The unscheduled cargo flight was operating under the provisions of 14 Code of Federal Regulations Part 135.

According to the company vice president of operations, the airplane was climbing through 7,500 feet when the pilot heard a “grinding noise,” and saw the Ng indication drop to zero. The engine then seized, and the pilot declared an emergency. Air traffic control provided vectors toward Griffiss International Airport (RME), Rome, New York; however, the airplane forced landed in a field about 3 miles short of runway 15.

The engine was subsequently disassembled under Federal Aviation Administration oversight at Pratt and Whitney Engine Services, Bridgeport, West Virginia. Disassembly revealed compressor turbine (CT) blade fractures at varying heights above the platform, and downstream damage to the power turbine blades. The CT disc was forwarded to Pratt and Whitney Canada facilities in Montreal, Quebec, for further examination.

According to Pratt & Whitney Canada Engine/Component Investigation Report No. 09ASA06, a total of 13 blades were fractured at the platform, with 8 of those exhibiting smooth fracture surfaces at the leading edge, consistent with fatigue. Those blades also exhibited a "dull dendritic appearance" toward the trailing edge, consistent with overload. The remaining five blades exhibited a dull dendritic appearance over the entire fracture surface, consistent with ductile overload.

During disc disassembly, only 14 of the blades were easily removed, and the others had to be pushed out, which was partially attributed to the disc having rubbed against the case.

Several other blades were extracted with little or no evidence of rubbing, suggesting they were fixed to the disc. Further examination revealed black corrosion blisters on the mating surfaces of both the blades and the disc.

Examination of blade serrations revealed an accumulation of orange dust, with black corrosion blisters also observed at various locations. Dust analysis indicated the presence of calcium and sulphur, with sulphates noted by the report as being common in "concrete, runway dust and in marine atmospheres." Analysis was also conducted on "grayish nodules" in a corroded area of one blade, which indicated features consistent with sulphidation. "The sulphur in the dust, most likely a salt, was the corrosive element."

Spectrum analysis revealed that the chemical composition of the blades and blade coatings were within specifications.

Subsequent to the incident, the operator increased engine water washes from once every 50 hours of operation to weekly, and incorporated borescope inspections into the engine maintenance program at every 100 hours of operation.

NTSB Probable Cause

The operator's inadequate engine wash intervals, which resulted in compressor turbine blade sulphidation and subsequent turbine blade failure.