What happened
On May 25, 2002, a Schweizer Hughes 269C helicopter, registration I-TOGI, was performing aerial spraying operations to treat mosquito populations in the municipality of Frassineto Po, Italy. While conducting its fourth treatment pass, the pilot encountered difficult visibility conditions caused by mist and intense sunlight reflecting off the water in the nearby rice paddies.
During the maneuver, the pilot failed to detect a 15,000-volt ENEL medium-voltage power line spanning the field. In an attempt to avoid the obstacle, the pilot executed a sudden and violent left turn. During this maneuver, the helicopter's right spray boom struck the cables, severing approximately 100 meters of the electrical line. The impact caused the helicopter to drop vertically approximately 6 meters into the rice paddy, landing on its left side.
The investigation
The ANSV investigation focused on the environmental conditions and the pilot's ability to perceive the obstacle. The investigation confirmed that the pilot had performed an initial reconnaissance of the area prior to starting the work. Technical inspections of the aircraft revealed no mechanical failures, and the helicopter was found to be in a valid state of airworthiness, effectively ruling out technical malfunction as a cause.
Findings
- The primary cause of the accident was the collision between the helicopter and the power lines.
- The contributing factor was the pilot's failure to see the electrical cables due to the combination of mist and solar glare reflecting off the water, which likely caused temporary visual impairment or glare.
- The investigation noted that a more thorough reconnaissance of the treatment area might have prevented the collision.