What happened
On 22 December 2023, a Robinson R4/4 Raven II helicopter, registration ZS-RTJ, was performing a crop-spraying mission near Dalton, KwaZulu-Natal. The flight, conducted under visual meteorological conditions, moved from Long Hill Farm to Seven Oaks Farm as part of a Part 137 agricultural operation.
While the pilot was engaged in spraying maize crops, they identified power lines to the right of the flight path and adjusted the aircraft's direction accordingly. However, as the aircraft approached the spraying area, it struck power lines that were not initially visible. The pylon supporting these lines was obscured from the pilot's view by nearby trees.
Following the impact, the pilot attempted to flare the aircraft to reduce speed, but the power lines became entangled in the tail rotor, severing it. This caused a loss of directional control and a rightward yaw. The pilot managed to close the throttle and use the collective to cushion the touchdown. The helicopter rolled onto its right side upon landing. The pilot was uninjured and successfully exited the aircraft after securing the fuel and master switch.
The investigation
SACAA AIID examined the circumstances surrounding the collision and the pilot's pre-flight preparations. The investigation confirmed that the pilot was fully qualified, holding a valid Commercial Pilot Licence and meeting all experience requirements set by the operator. The aircraft's maintenance records showed it was within its inspection interval, having flown approximately 50 hours since its last periodic inspection.
Investigators reviewed the operator's standard operating procedures, which mandate that pilots carefully survey each field for obstructions before spraying. The investigation also looked into the pilot's pre-flight risk analysis, which had identified some power lines but failed to account for the specific lines connected to the obscured pylon.
Findings
- The primary cause of the accident was the failure to notice the obscured pylon and its associated power lines during the spraying operation.
- An inadequate risk analysis or field survey prior to the operation contributed to the accident, as the hidden obstacle was not identified.
- The impact with the lines led to the severance of the tail rotor, resulting in the loss of rotor control.