What happened
On November 29, 2016, at 18:40 UTC, a Robinson R44 II helicopter, registration PR-JRL, was performing agricultural spraying operations over a cornfield in Lajeado Grande, Santa Catarina. The aircraft was operated by Quimigel Indústria, Comércio e Serviços Aéreos Especializados Ltda.
During the final pass of the spraying mission, the pilot attempted to fly beneath a high-voltage power line network. As the pilot executed a left turn to clear the area, the main rotor blades struck the electrical wires. The impact caused a wire to fall in front of the aircraft and another to strike the fuselage. The pilot performed an autorotation and executed a running landing in a nearby soybean field. During the landing, the main rotor blades struck the tail cone, causing it to sever. The pilot and the passenger both escaped the accident uninjured, though the aircraft sustained substantial damage.
The investigation
CENIPA investigators examined the flight history, aircraft maintenance records, and environmental conditions. The investigation confirmed that the aircraft was airworthy, within weight and balance limits, and properly maintained. The pilot was experienced, holding a valid medical certificate and an agricultural helicopter pilot license.
Investigators analyzed the aerodynamics of the turn, noting that the wind was coming from the right at 6 knots. This created an asymmetry of lift that likely increased the aircraft's bank angle during the left turn. Furthermore, the investigation noted that the clearance between the wires and the ground was only 7 meters. Given the 11.6-meter diameter of the R44's main rotor disk, a turn with a bank angle greater than 37 degrees would have made a collision unavoidable.
Additionally, the investigation highlighted that the operator was using a specialized support truck with a suspended platform for takeoff and refueling—a pioneering method in Brazil that, at the time of the accident, had not been formally certified or regulated by the National Civil Aviation Agency (ANAC).
Findings
- Inadequate flight planning, specifically the decision to fly beneath high-voltage power lines.
- Improper pilot judgment regarding the execution of a turn with insufficient clearance relative to the electrical wires.
- Environmental influences, including the aerodynamic effects of wind asymmetry and the low visibility of thin wires.
- The use of an uncertified takeoff and refueling platform on a support truck.