What happened
On 15 March 2007, a Robinson R44, registration ZS-RFR, was conducting a commercial low-level search operation approximately 60km west of Bela Bela Aerodrome. The mission involved scanning the roadside between Bela Bela and Thabazimbi for discarded items, which required the aircraft to maintain an altitude of roughly 15ft AGL to peer through tall grass.
While flying west, the pilot observed rising terrain to the right of the flight path. In an effort to avoid the sloping ground, the pilot maneuvered the aircraft across the road to the south. During this maneuver, three power lines spanning the road at 15ft AGL were encountered. In a sudden attempt to clear the lines, the pilot rapidly lowered the collective. This maneuver caused the rotor blades to strike the wires, resulting in electrical arcing on one of the blades. Although a vibration was felt within the fuselage, the pilot was able to transition into a controlled hover and land the aircraft safely.
The investigation
Investigators examined the flight path and the pilot's actions during the low-altitude mission. The investigation confirmed that the aircraft was operating at a very low altitude to facilitate the search of the roadside. The inspection of the aircraft following the event revealed no visible damage to the rotor blades. The investigation also reviewed the maintenance history, noting that the last Mandatory Periodical Inspection had been completed approximately 71.5 flying hours prior to the incident.
Findings
- The primary cause of the incident was the impact between the helicopter blades and high-tension power lines.
- The pilot's decision to maneuver the aircraft to avoid rising terrain placed the flight path into a position where the wires were encountered.
- The pilot failed to maintain an adequate lookout for overhead hazards during the low-level flight.