What happened
During low-level aerial spraying operations, the pilot of a Robinson R44, registration ZWK, was maneuvering the aircraft over a bridge. While managing the demands of the flight and monitoring equipment for the spraying task, the pilot momentarily lost awareness of a powerline spanning a nearby drainage channel. This loss of situational awareness resulted in the helicopter striking the narrow-gauge, unmarked powerline, which subsequently caused the aircraft to collide with the terrain. The impact destroyed the helicopter, though no post-impact fire occurred.
The investigation
The investigation focused on the factors contributing to the pilot's loss of awareness and the visibility of the hazard. Investigators found that the pilot had successfully flown under the same powerline earlier in the day, indicating the hazard was known. However, during the maneuver over the bridge, the pilot's attention was diverted by the operational requirements of the spraying activity.
Furthermore, the presence of native vegetation near the power poles obscured visual cues that might have alerted the pilot to the line's location. The investigation also noted that the powerline was difficult to detect due to its narrow gauge and lack of markings, a common challenge in low-level flight. The aircraft was equipped with a bladder-type fuel tank, which investigators determined likely prevented a fuel leak and subsequent fire following the terrain impact.
Findings
- The pilot's attention was diverted by the immediate demands of navigating the bridge and managing spraying equipment.
- The pilot's momentary loss of awareness of the powerline's position caused the collision.
- Native vegetation near the poles reduced the visibility of the powerline.
- The powerline lacked markings and was difficult to see due to its narrow gauge.
- The pilot was not wearing a helmet at the time of the accident.
- The use of a bladder-type fuel tank in the R44 likely mitigated the risk of a post-impact fire.