What happened
On March 27, 2003, at approximately 11:20 local time, a Eurocopter SA 315B (registration I-SERY) was engaged in aerial firefighting operations in the Ligurian mountains. Operating on behalf of Star Work Sky s.a.s., the aircraft was tasked with suppressing a wildfire on the western slope of Monte Mignano.
After completing several successful water drops, the pilot was performing a fifth water pickup from a nearby basin. While climbing along a flight path parallel to the mountain slope at an altitude of approximately 2,000 feet, the helicopter struck a suspended steel cable. The impact shattered the cockpit's plexiglass windows and caused a 1.5-meter section of the cable to break off and enter the cockpit. The pilot immediately ceased the climb, released the water load, and performed necessary system checks before landing safely at a nearby clearing.
The investigation
The ANSV investigation focused on the physical evidence within the cockpit and the condition of the cable. Investigators recovered a 1.5-meter segment of 8mm diameter steel cable from the cabin. Analysis revealed that the cable was heavily corroded, with significant loss of cross-sectional area due to oxidation and no evidence of protective coatings like galvanization. The cable ends showed irregular fractures consistent with dynamic failure under overload.
Subsequent inquiries by the State Forestry Corps identified the presence of an abandoned, disused ropeway (teleferica) in the area, though its ownership and origin were unknown. The investigation also examined the environmental conditions, noting that while visibility was good (over 10 km), the landscape was characterized by a uniform green color from dense vegetation and a slight haze caused by evaporation. This created a lack of visual contrast, making the thin, dark cable nearly impossible to detect against the mountain backdrop.
Findings
- The primary cause of the accident was the collision with a suspended cable that lacked any form of marking or signaling.
- The cable was rendered invisible to the pilot due to specific environmental conditions, where high solar luminosity and a uniform landscape color reduced visual acuity and contrast.
- The cable was part of an abandoned ropeway, with its support structures hidden within the dense vegetation.
- The severity of the damage to the Eurocopter SA 315B was mitigated by the advanced state of corrosion on the cable, which had significantly weakened its structural integrity.