What happened
The aircraft was conducting a test flight designed to establish aft center of gravity limits as part of a Supplemental Type Certificate (STC) modification. During the takeoff phase, the pilot lifted off with the front skids in a high attitude. Immediately after becoming airborne, the helicopter entered an uncommanded right roll. The pilot applied full left cyclic control input in an attempt to arrest the roll, but the maneuver was unsuccessful. The aircraft continued to roll over completely.
The investigation
Analysis of the event identified environmental factors as significant contributors to the accident. Gusty winds were present at the time of the incident. Additionally, mechanical turbulence generated by nearby buildings exacerbated the situation. These conditions combined with the flight dynamics during the high-attitude lift-off contributed to the dynamic rollover.
Findings
The sequence of events indicates that the helicopter was unable to recover from the roll due to the combination of control inputs and external aerodynamic disturbances. The presence of gusty winds and building-induced turbulence played a critical role in the loss of control.