What happened
The pilot was conducting agricultural operations, specifically making cleanup swatches over an irregularly shaped section of a corn field. To complete the task, the pilot executed two consecutive turns, each spanning approximately 220 degrees, in close proximity to one another. The second turn was flown downwind relative to two previously completed swaths.
During this tight maneuver, the helicopter encountered its own rotor wash. This interaction with the downwash resulted in a loss of control or stability, causing the aircraft to strike the ground. At the time of the incident, the pilot reported that the wind conditions were light and variable, coming from the northeast.
The investigation
The investigation focused on the flight path and environmental conditions during the final phase of the operation. Examination of the event revealed that the helicopter was operating in close proximity to its own downwash while executing tight turns over uneven terrain. The pilot's report confirmed light and variable wind from the northeast, indicating that external weather factors were not the primary driver of the incident.
Findings
The critical factor in this accident was the aerodynamic interference caused by the helicopter's own rotor system. By making two tight turns in close proximity over a confined area, the pilot allowed the helicopter to enter its own downwash. This self-induced turbulence likely degraded lift and control authority at a low altitude, leading directly to the ground impact.
Safety message
Pilots conducting low-level agricultural operations should be aware of the risks associated with tight turns in confined areas. Operating in close proximity to previously completed swaths can lead to encountering one's own rotor wash, which may compromise aircraft control and lift.