What happened
On June 18, 2007, a Robinson R44 helicopter, registration CS-HDB, was performing aerial spraying operations over an agricultural property near Vila Chã de Ourique, Portugal. The mission involved flying at low altitudes to disperse products across fields intersected by medium-voltage electrical power lines.
During the final passes of the day, the pilot was flying toward the west. As the sun approached the horizon, light suddenly broke through a gap in the cloud cover, directly striking the pilot's face. This intense glare caused a sudden loss of visibility and spatial orientation. Aware of the nearby power lines, the pilot attempted an instinctive evasive maneuver by banking left and lowering the nose. However, the maneuver was insufficient to clear the obstacles, and the aircraft's tail boom and main rotor collided with the cables.
The impact caused an electrical discharge that destroyed one of the main rotor blades. The tail rotor assembly also struck the lines, causing the tail boom to fracture and separate from the tail cone. Following the structural failure, the pilot lost control of the aircraft, which plummeted to the ground approximately 30 meters from the initial point of impact. The aircraft sustained extensive damage to the fuselage, rotor system, and spraying equipment, resulting in a total loss of the airframe.
The investigation
The GPIAAF investigation established that the aircraft was properly maintained and the pilot held a valid commercial license with the necessary qualifications for the mission. The investigation focused on the flight path, which had been intentionally designed to fly perpendicular to the power lines to minimize time spent underneath them. Investigators examined the meteorological conditions, noting that while the day had been mostly overcast, the sudden appearance of the setting sun through the clouds was the critical factor in the loss of visual reference.