What happened
During an approach to a dam for water collection, a helicopter experienced a sudden and severe loss of control. As the pilot initiated the full water bucket uplift, the aircraft began to pitch upward and roll toward the left. This instability led to a direct collision with the water surface. The aircraft subsequently became submerged.
The investigation
Investigators analyzed video footage and performed a detailed wreckage examination to determine the cause of the instability. The examination of the left rear skid and bear paw revealed striation marks, which provided evidence that the Bambi Bucket suspension cables had made contact with the skid. Video evidence confirmed that these cables were caught over the left rear skid during the water uplift phase, though it was unclear if the cables became snagged during pre-flight positioning, takeoff, or the transit flight.
Weight and balance calculations played a critical role in the reconstruction. The investigation determined that any weight exceeding 300 kg acting over the left rear skid would be enough to shift the center of gravity beyond the aircraft's operational limits. Because a full bucket can weigh up to 1,300 kg, the tethered weight created an asymmetric lifting point that pulled the center of gravity aft and to the left as the water was lifted.
Engine manufacturer analysis and wreckage inspections confirmed there were no mechanical defects present prior to the impact, and the engine was providing significant power to the transmission at the moment of impact.
Findings
- The primary cause of the loss of control was the suspension cables for the Bambi Bucket becoming entangled with the left rear skid.
- The resulting asymmetric load shifted the aircraft's center of gravity outside of safe limits during the water collection process.
- The pilot's recent helicopter underwater escape training (HUET), completed approximately 2.5 years prior, likely facilitated a successful egress from the inverted, submerged aircraft.