Incident Overview
During a helicopter flight, an engine fire warning light illuminated in the cockpit. The pilot observed smoke coming from the helicopter and pulled the fire extinguisher handle for the number 2 engine. He initiated a rapid descent to the airport, dropped the long line, and landed without further incident.
Post-Landing Examination
After landing, an examination of the helicopter revealed that the external surfaces of the number 2 engine were covered in soot. A hole was observed on the gas generator case at the 5 o'clock position (aft looking forward), which appeared to originate inside the engine.
Engine Teardown and Inspection
A post-accident disassembly and inspection were performed on the number 2 engine. During the teardown, investigators found foreign debris, consistent in appearance to a stator vane, lodged in a diffuser pipe. The diffuser pipe, which directs compressor discharge air to the combustion area, was located at approximately the 5 o'clock position (aft looking forward). Further inspection revealed a fractured stator vane in the compressor second stage stator assembly. Due to impact and heat damage to the stator vane fracture surface, the cause of cracking could not be determined.
Investigative Conclusion
Pratt & Whitney Canada investigators, in the presence of Federal Aviation Administration inspectors, concluded the following: "The perforation of the gas generator case was most likely caused by a disturbance of compressed air flow from the diffuser pipes. The restriction in airflow caused by the lodged stator vane limited the flow of combustion liner cooling air, resulting in a localized increase in temperature and subsequent burning through the combustion liner and the gas generator case." The engine teardown and inspection revealed no other significant anomalies.