Incident Overview
On 20 December 2023, at approximately 1130Z, a Bell 407 helicopter registered ZS-RXO departed from Landing Zone T306 at the Majuba Venus power station in KwaZulu-Natal Province, South Africa. The flight was conducted under visual meteorological conditions (VMC) by day, as part of aerial work operations under Part 127 of the Civil Aviation Regulations. On board were a pilot and two transmission line workers.
Flight and Task
The crew flew about 20 nautical miles south of Ladysmith to the T299 mast area, where they planned to install bird diverters on the earth conductor. The terrain at the installation site was a down slope. The pilot positioned the helicopter with its nose pointing away from the slope, then the first worker, secured to the helicopter by a safety harness, sat on the right skid gear and began installing the diverters. The second worker, seated in the cabin behind the pilot and using a seatbelt, handed the bird diverters to the first worker. Communication was via headsets.
Incident
While the first worker was installing a bird diverter, the pilot heard a 'pop' sound but did not feel any vibrations through the controls. Concerned, she aborted the task and landed the helicopter safely at a designated landing zone near the T299 mast. None of the three occupants were injured.
Post-Inspection Findings
After landing, the pilot inspected the helicopter and discovered damage to the main rotor blade tips; they had struck the earth conductor during the installation. The earth conductor wire strands were protruding from the protective loom. The helicopter was subsequently loaded onto a flatbed truck and transported to an approved maintenance organisation (AMO) for a thorough inspection, which confirmed that all four blade tips had sustained damage. The damage was classified as minor.
Investigation Results
The investigation determined that during a hover out of ground effect, the retreating main rotor blades made contact with the down-sloping earth conductor. The pilot had misjudged the distance between the rotor blades and the conductor. Weather was not a factor in the incident. The helicopter's maintenance and documentation were found to be in order, and the pilot held a valid Commercial Pilot Licence and medical certificate.
The probable cause of the incident was the inadvertent contact of the main rotor blades with the earth conductor during the bird diverter installation. No contributing factors or safety recommendations were identified.