What happened
On February 5, 2013, a single-pilot aerial work flight departed from a private helipad in Bourg-Saint-Maurice, France, bound for the Roselend Dam. During the approach to the destination, the pilot encountered a cloud mass that prevented further progress toward the dam. Unable to return to the valley due to worsening weather, the pilot performed a precautionary landing at Cormet de Roselend to wait for improved conditions.
As the skids of the Eurocopter AS350 B3, registration F-GYBH, made contact with the ground, the pilot reduced the collective pitch. After mechanically locking the controls, the helicopter tipped onto its right side. The pilot was unable to regain control of the aircraft because the controls had already been locked into position. The aircraft was destroyed in the accident.
The investigation
The investigation focused on the landing conditions and the pilot's actions during the final moments of the flight. Investigators noted that the site was covered in approximately 50 cm of fresh snow, which obscured irregularities in the underlying terrain. Meteorological data at the time indicated winds from 240° at 5 to 10 knots, with gusts reaching 30 knots, and scattered clouds between 1,200 and 3,000 meters.
The pilot, a highly experienced professional with 9,000 total flight hours (including 8,800 on type), had determined at the start of the flight that the mission was feasible. However, due to the rapid degradation of visibility, the pilot did not perform a reconnaissance of the landing area before touchdown.
Findings
- The primary cause of the accident was inappropriate landing technique on snowy ground.
- The pilot failed to ensure the stability of the helicopter before engaging the mechanical control lock and shutting down the engine.
- The thick layer of fresh snow made it difficult to identify terrain irregularities, complicating the selection of a suitable landing spot.