What happened
On February 21, 2001, a Bell 206L-1 helicopter, registration SE-HPL, was performing a utility flight near Ockelbo, Sweden. The pilot was traveling from Gävle/Sandviken airport to the village of Mo to collect a colleague. Due to strong and gusty northwesterly winds, the pilot planned an approach that would land the aircraft directly into the wind. This flight path required flying over two electrical power lines located just east of the intended landing site.
Despite being aware that low-altitude overflights of power lines should ideally occur near support towers to maintain visual references, the pilot chose to cross the lines between two towers. The pilot believed visibility was sufficient to identify all cables clearly. During a steep, 30-degree descent toward the landing area, the helicopter struck a power line. The impact caused the aircraft to tip forward and crash into a snow-covered field approximately 20 meters from the power lines. The pilot sustained serious injuries, including broken ribs, and briefly lost consciousness upon impact.
The investigation
The Swedish Accident Investigation Authority (SHK) examined the wreckage and the environmental conditions at the site. The investigation noted that the aircraft suffered extensive structural damage, including a separated tail boom and shattered rotor blades. Investigators also analyzed the configuration of the power lines, noting that thinner header cables can become visually obscured by thicker phase cables at certain approach angles.
Meteorological experts investigated the possibility of wind vortices; while they ruled out specific vortices, they confirmed that the strong, gusty winds likely created chaotic mechanical turbulence at low altitudes. The investigation also considered whether the helicopter's curved windscreen caused optical refraction, though this was deemed improbable.
Findings
- The pilot was properly qualified and the aircraft held a valid certificate of airworthiness.
- Weather conditions were characterized by strong, gusty winds.
- The approach was conducted between power line towers rather than near them.
- The pilot misjudged the distance to the nearest electrical cable.
Several factors likely contributed to this misjudgment, including the potential for the thinner header cables to be hidden behind thicker cables, the steep angle of descent potentially placing the cables below the pilot's field of view, and the influence of local turbulence on the aircraft's descent rate.