What happened
On 20 January 2006, a Eurocopter AS350B2 helicopter, registration G-BXGA, was performing aerial work involving the transfer of stone bags from a scree slope to a nearby footpath. Following the completion of the lifting task, the pilot attempted to land at a site near the Corrie of Clova, approximately 16 nautical miles northwest of Forfar, Scotland.
While hovering at 1,900 feet amsl to assess a potential landing area, the pilot encountered a turbulent crosswind. The wind was recorded at 250 degrees at 20 to 30 knots, which, given the aircraft's 350-degree heading, created significant turbulence. During this hover, the main rotor blades made contact with a boulder located at the two o'clock position relative to the aircraft. The pilot immediately climbed away from the obstacle and subsequently selected a third landing site, where the aircraft landed without further incident. After the engine was shut down, an inspection confirmed damage to the tips of all three main rotor blades, though no other structural damage was found.
The investigation
The investigation examined the flight conditions and the aircraft's performance limits. It was noted that the pilot's experience included 4,100 total flying hours, with 511 hours on this specific type. The investigation reviewed the aircraft's flight manual, which specifies that while the helicopter is substantiated for winds up to 17 knots in certain configurations, such as a sea-level hover at maximum weight, it is not explicitly limited to 30-knot winds.
Findings
- The primary cause of the incident was the drift of the helicopter caused by turbulent crosswinds while the pilot was attempting to land on a small, restricted surface.
- The pilot's assessment of the landing site was interrupted by the sudden impact with the boulder.
- The aircraft sustained damage to the tips of all three main rotor blades.