What happened
The pilot, holding commercial certificates for fixed-wing aircraft but operating as a student pilot in helicopters, was conducting practice autorotations. During one of these maneuvers, the helicopter experienced an unexpected loss of engine power. The specific cause of this mechanical failure remained undetermined.
To maintain control following the power loss, the pilot initiated a full autorotation. The subsequent landing was executed with significant force, resulting in a hard impact with the ground. This impact caused excessive flexing of the main rotor system, which ultimately severed the tail boom structure. Environmental conditions at the time included a density altitude of 9,000 feet.
The investigation
The investigation focused on the mechanical integrity of the aircraft following the incident. Examination revealed that the main rotor had flexed excessively during the hard landing. This structural deformation was sufficient to cut through the tail boom attachment points or structure itself.
Findings
Contributing factors included the hard landing resulting from the autorotation maneuver and the density altitude of 9,000 feet, which may have affected aircraft performance. The pilot's status as a student pilot in helicopters was noted, though no specific error was cited beyond the event itself.
Safety message
This incident highlights the risks associated with high-density altitude operations and the structural limits of rotorcraft during emergency landing procedures.