Event Sequence
During a lift-off to a hover, the helicopter began rolling to the right immediately after becoming airborne. The instructor applied left cyclic input, realizing that the pilot under instruction was also applying left cyclic. Despite these inputs, the helicopter continued its rightward roll. The instructor then lowered the collective, but the rolling motion persisted until the main rotor blades struck the ground, resulting in separation of the main rotor head. The instructor reported that the flight controls had normal feel and no unusual vibrations were present during the event.
Technical Findings
Examination of the fractured main rotor mast revealed excessive porosity in the material; however, the mast failed under overload conditions. Additionally, a gouge was observed on the ground, indicating that the rear tip of the right skid made contact with the surface during the lift-off. This contact precipitated a dynamic roll over.