Robinson R22 N410MM accident near Sterling City, Texas

Probable cause

The pilot’s improper decision to exit the helicopter without shutting down the engine, which allowed the collective/throttle to increase and resulted in a loss of control of the unattended helicopter.

NTSB analysis

The pilot exited the helicopter with the engine set to idle power. Subsequently, the collective/throttle increased due to the engine vibrations, and the helicopter became light on the skids. The helicopter rocked back on the tail, which separated the tail rotor from the helicopter and damaged the main rotor blades. The manufacturer had previously issued a safety notice, which stated to never exit the helicopter unattended with the engine running and the rotors turning because the collective can "creep up, increasing both pitch and throttle, allowing the helicopter to lift off or roll out of control," as occurred in this accident.

Text from the NTSB. Open the NTSB docket for CEN18CA294 for the full record.