Primary finding
Probable cause
The pilot’s failure to maintain adequate rotor rpm during landing which resulted in a premature landing on uneven ground and a subsequent rollover.
Investigator assessment
Analysis narrative
The pilot of the helicopter reported that while he was on approach to land, he attempted to slow his descent by pulling aft on the cyclic and increased the collective pitch. The low rotor rpm horn sounded as he was beginning to hover in ground effect, and he then began to fly forward slowly. At 20 knots, the low rotor rpm horn sounded again, and his altitude increased to 40 ft above ground level. The rotor speed did not recover, and the helicopter descended until it landed on an uneven berm. The helicopter then pitched forward, the main rotor blades impacted the ground, and the helicopter rolled onto its left side. The helicopter’s tail boom was substantially damaged. The pilot reported that there were no preimpact mechanical malfunctions or failures of the helicopter that would have precluded normal operation.