What happened
The aircraft departed at 2040 CST as part of a flight of two on a ferry mission. Shortly after leveling off at an altitude of 700 feet, with engine power stabilized at 72% torque, the engine failed. The aircraft immediately yawed left and right in response to the loss of thrust.
The pilot initiated an autorotation into a soft plowed field that featured a slight downward slope. Upon touchdown, the nose of the aircraft rocked forward. According to the pilot's account, the main rotor blade struck the tailboom at the horizontal stabilizer, severing it completely.
The investigation
Mechanical examination of the failed engine involved complete disassembly. This process revealed that the number 2 bearing had failed. The specific cause of this bearing failure was not determined. However, the failure allowed the compressor impeller to move forward, resulting in contact with the inner diameter of the compressor shroud housing.
Findings
The sequence of events indicates that a mechanical failure within the engine's compressor section led to an immediate loss of power. The subsequent aerodynamic instability caused significant yawing motion. The forced landing, while executed via autorotation, resulted in substantial airframe damage due to the interaction between the main rotor and the tail structure upon impact with the ground.