Event Description
The pilot was demonstrating a full touchdown autorotation in wind conditions reported as from 290 degrees at 15 knots, gusting to 20 knots. According to the pilot, the touchdown was soft with a significant amount of pitch pulled in. However, after touchdown, as the pilot lowered the collective, the retreating rotor blade flexed downward and severed the aft portion of the tail boom and the tail rotor drive shaft.
Pilot Observations
The pilot believed that the collective had been lowered too quickly after touchdown, which would have allowed the blades to flap downward. Additionally, the pilot believed that the high wind conditions and reduced rotor RPM resulting from the autorotation would have contributed to excessive flapping of the retreating rotor blades.