What happened
The pilot was conducting flight training that included practicing autorotative landings. During one such maneuver, the pilot initiated the flare phase of the landing slightly higher than intended. This error resulted in the helicopter impacting the ground with more force than normal. The impact caused the main rotor blades to flex downward and sweep across the tail boom structure.
The investigation
Examination of the aircraft revealed that the main rotor and tail rotor blades were damaged as a result of the contact with the tail boom. Additionally, the tail rotor drive shaft failed at its aft end, likely due to the stresses induced by the hard landing and subsequent structural interaction.
Findings
The primary factor in this incident was the pilot's decision to flare too high during the autorotative landing practice. This technique error led to a hard touchdown, which caused the main rotor blades to flex downward and strike the tail boom. The impact resulted in damage to the rotor blades and a failure of the tail rotor drive shaft.