What happened
The pilot was conducting a low-altitude flight when he began checking the radio settings. Seeking to adjust the cabin environment, the pilot reached for the cabin heater lever with the intention of increasing heat. In the process, he moved the control to what he believed was the full 'on' position. However, he later realized that he had actually engaged the fuel mixture control and set it to the full 'lean' position.
The helicopter's engine subsequently failed due to this configuration error. The pilot had very little time to react to the loss of power. He attempted to initiate a stabilized autorotation but was unable to complete it successfully before touchdown. Upon contact with the ground, the helicopter slid sideways across wet sod and rolled over.
The investigation
The investigation focused on the sequence of events leading to the engine failure. It was determined that the pilot's action of moving the fuel mixture control to the full 'lean' position directly caused the engine to stop producing power. The lack of altitude prevented a safe recovery.
Findings
The primary factor in this accident was the inadvertent movement of the fuel mixture control. The pilot intended to adjust the cabin heater but instead leaned the mixture, leading to engine failure. The subsequent loss of control resulted in the aircraft rolling over on the ground.