What happened
On August 3 31, 2008, a Bell 206L-1 helicopter, N37AE, was returning to its base in Rushville, Indiana, after the crew had attended a community fundraising event in Burney. The flight departed Burney at 1317 under visual meteorological conditions. Witnesses observed the helicopter depart the fire station without difficulty and clear high-tension power lines. However, they subsequently saw components separate from the aircraft before it descended into a cornfield approximately 1.2 miles north-northeast of the departure point. The impact and subsequent fire resulted in 3 fatal injuries to the pilot, flight nurse, and paramedic.
The investigation
Investigators examined the wreckage and found that the main rotor blade/hub assembly had separated from the aircraft. The fuselage was found nearly inverted and had been consumed by fire. The main rotor mast exhibited a fracture surface consistent with overload failure.
Metallurgical examination of the failed main rotor blade, a bonded assembly, revealed a complete fracture approximately 8 feet from the tip. The examination identified fatigue cracking originating from the inner face of the spar at the transition radius between the leading edge and the upper wall. This fatigue crack originated at a location where a large void existed in the adhesive between the inside surface of the spar and the internal lead weight.