NTSB Factual Report

On December 11, 2006, at 2217 central standard time, a Bell 407, N302LE, operated by CJ Systems Aviation Group (dba Life Flight Eagle), as an air ambulance helicopter, executed an emergency landing on an elementary school parking lot near Raytown, Missouri. Night visual meteorological conditions prevailed at the time of the incident. The pilot stated that he heard a bang and got a low frequency vibration during cruise flight. The helicopter received minor damage due to internal engine components exiting the engine collector and exhaust stack. The air ambulance flight was operating under Title 14 CFR Part 135. The pilot, two paramedics, and patient were uninjured. The flight last departed from Golden Valley Hospital, Clinton, Missouri, at 2154, for a patient transfer to St. Lukes Hospital, Kansas City, Missouri.

The National Transportation Safety Board Materials Lab review of the Rolls Royce Metallurgical Investigation Report focused on damage to the third stage turbine wheel where high cycle fatigue features were observed on the fracture surface of one of the blades. The fatigue initiated at the trailing edge of the airfoil and propagated 0.515 inch before a fast fracture separation. Although a small area of porosity was observed in the microstructure adjacent to the fracture, it did not intersect the fracture surface, and no evidence of porosity was observed on the fracture surface. Chemistry and hardness were as specified.

Parties to the investigation were Bell Helicopter, CJ Systems Aviation Group, FAA, Life Flight Eagle, Standard Aero, and Rolls Royce.

NTSB Probable Cause

The loss of engine power during cruise flight due to third stage turbine wheel blade fatigue and subsequent separation, which resulted in an emergency landing.