Primary finding
Probable cause
The instructor's failure to maintain aircraft control. A contributing factor was the windshear.
Investigator assessment
Analysis narrative
According to the flight instructor, he was demonstrating a "full-down" autorotation into a 20-knot headwind. About 20 feet above the ground, the wind diminished and the rotor RPM decayed. The pilot flared the helicopter, but it impacted the taxiway at 40 knots and at a 1,000 feet per minute descent rate. The helicopter bounced and the main rotor blades struck the tail boom. A systems examination revealed no anomalies.
Source record
Factual narrative
According to the flight instructor, he was demonstrating a "full-down" autorotation into a 20-knot headwind. About 20 feet above the ground, the wind diminished and the rotor RPM decayed. The pilot flared the helicopter, but it impacted the taxiway at 40 knots and at a 1,000 feet per minute descent rate. The helicopter bounced and the main rotor blades struck the tail boom. A systems examination revealed no anomalies.