Incident
On December 3, 2009, at 0747 eastern standard time, a Cessna 208B, registration N701FX, operating as Wiggins Airways flight 8409, experienced a loss of engine power during climb. The pilot heard a grinding noise and observed the Ng indication drop to zero. The engine subsequently seized, prompting the pilot to declare an emergency. Air traffic control provided vectors toward Griffiss International Airport (RME) in Rome, New York, but the airplane forced landed in a field approximately 3 miles short of runway 15. The certificated airline transport pilot was not injured, and the airplane sustained no damage. Visual meteorological conditions prevailed at the landing site. The unscheduled cargo flight was operating under 14 CFR Part 135 on an instrument flight rules flight plan from Syracuse Hancock International Airport (SYR) to Plattsburgh International Airport (PBG).
Investigation
The engine was disassembled under Federal Aviation Administration oversight at Pratt and Whitney Engine Services in Bridgeport, West Virginia. Disassembly revealed fractures in the compressor turbine (CT) blades at varying heights above the platform, along with downstream damage to the power turbine blades. The CT disc was forwarded to Pratt and Whitney Canada facilities in Montreal, Quebec, for further examination.
Engine Examination
According to Pratt & Whitney Canada Engine/Component Investigation Report No. 09ASA06, a total of 13 blades were fractured at the platform. Of these, 8 blades exhibited smooth fracture surfaces at the leading edge, consistent with fatigue, and a dull dendritic appearance toward the trailing edge, consistent with overload. The remaining five blades showed a dull dendritic appearance over the entire fracture surface, consistent with ductile overload. During disc disassembly, only 14 blades were easily removed; the others had to be pushed out, partly 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 showed 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 as common in concrete, runway dust, and marine atmospheres. Analysis of grayish nodules in a corroded area of one blade revealed features consistent with sulphidation. The report stated that the sulphur in the dust, most likely a salt, was the corrosive element. Spectrum analysis confirmed that the chemical composition of the blades and blade coatings were within specifications.
Post-Incident Actions
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.