Incident Overview
During a training flight, a helicopter executed a practice autorotation under the guidance of a certified flight instructor (CFI) and a student pilot. The maneuver was part of routine flight instruction. While performing the autorotation, the main rotor low revolutions per minute (RPM) horn activated, signaling a decrease in rotor speed. The CFI noted that the airspeed had dropped 10 knots below the minimum speed recommended for autorotations.
Instructor Actions
In response, the CFI lowered the collective pitch control while simultaneously pushing the carburetor heat control knob to the "off" position. As the CFI leaned forward to confirm the knob's position, he perceived the helicopter beginning to settle. With the ground approaching rapidly, the CFI configured the helicopter in a level attitude. He made the decision not to flare, as he believed that flaring would cause the tail boom to contact the surface first.
Outcome
The helicopter struck the ground hard, and the main rotor blades severed the tail boom during the impact. The CFI reported that he was unaware of any mechanical malfunctions or failures with the helicopter prior to the incident. No further details were provided regarding the aircraft type, registration, or other specific identifiers.
Probable Cause
The source did not assign a probable cause for the incident.