Incident Overview
A flight instructor was demonstrating a "full-down" autorotation into a 20-knot headwind when the training maneuver led to an unintended ground impact. Approximately 20 feet above the ground, the wind abruptly diminished, resulting in a decay of the rotor RPM. The pilot attempted to arrest the descent by flaring the helicopter, but the aircraft impacted the taxiway at a forward speed of 40 knots and a descent rate of 1,000 feet per minute.
Sequence of Events
Upon touchdown, the helicopter bounced. The main rotor blades then struck the tail boom, causing structural damage. A post-accident systems examination revealed no anomalies in the helicopter's mechanical or flight control systems.
Findings
The investigation noted that the wind loss during the critical low-altitude phase of the autorotation led to insufficient rotor RPM to cushion the landing. The pilot's flare input was unable to prevent the high-energy impact. The absence of system malfunctions indicates the event resulted from the unexpected change in wind conditions.