What happened
On August 22, 2009, an AgustaWestland A100S Grand, registration I-REMS, was conducting a reconnaissance flight near Monte Cristallo, Italy, following reports of injuries caused by a landslide. The helicopter, operated by INAER Helicopter Italia SpA as part of the SUEM emergency medical service, had previously landed at the Rio Gere cable car parking area to provide first aid to two individuals. After dropping off a medical technician, the crew departed at approximately 15:00 local time to perform a second survey of the area.
During this second pass, the helicopter's main rotor struck medium-voltage power lines supplying the local cable car system. The impact caused the aircraft to plummet into a landslide channel, where a small stream had formed due to recent heavy rainfall. The collision resulted in four fatalities, as all four crew members on board were killed in the crash.
The investigation
The ANSV investigation examined the wreckage, the flight path, and the environmental conditions. Investigators found extensive damage to the left side of the fuselage, the tail boom, and the tail rotor. Notably, the main rotor mechanism was completely torn from its mounts, and several rotor blades were found separated from the hub or scattered downstream by the force of the landslide and water flow.
The investigation also reviewed the navigation aids available to the crew. While the aircraft was equipped with electronic navigation systems, the crew was also using hiking maps, which identified cable car infrastructure but lacked details on the supporting electrical lines. An aeronautical chart was also present, but its scale (1:500,000) was too coarse to identify the specific location of the power lines.
Findings
- The primary cause of the accident was the impact of the main rotor with medium-voltage power lines.
- The power lines were part of an isosceles triangle configuration between pylons, and the impact caused significant structural failure of the rotor system.
- There was a lack of effective marking or signaling for these specific overhead obstacles to ensure visibility for low-altitude HEMS operations.
- The crew was operating in an environment where the electrical infrastructure was not clearly identifiable on the available aeronautical charts or the hiking maps found on board.
- The investigation noted that the existing regulatory framework for marking obstacles did not provide a systematic way to ensure the visibility of such wires for low-flying emergency aircraft.
- Operational pressures, such as potential financial penalties for delayed departures from the 118 emergency dispatch center, were identified as a factor that could influence crew decision-making.