What happened
The accident occurred during a flight operation specifically arranged as an autorotation demonstration for the local police department. The maneuver was intended to be performed with power recovery, requiring precise timing of collective pitch application to arrest the descent and transition to forward flight.
During the execution of this phase, the pilot applied power too late in the flare sequence. This delay resulted in a hard landing impact with the ground. Immediately following the initial touchdown, the helicopter bounced upward due to the energy absorbed by the landing gear and airframe structure. During this bounce, the main rotor system flexed significantly, causing the blades to strike the tail boom.
The investigation
Post-accident examination of the aircraft revealed that the tail boom had been severed. The damage was consistent with impact from the main rotor blades during the uncontrolled vertical oscillation following the hard landing. No other mechanical failures or pre-existing defects were cited as contributing factors in the narrative provided.
Findings
The sequence of events indicates that the primary factor leading to the structural failure was the delayed application of power during the recovery from autorotation. This timing error caused a high sink-rate impact, which generated sufficient bounce to flex the rotor system into the tail boom structure. The incident highlights the critical importance of precise timing and control input during low-altitude flight maneuvers involving power recovery.