What happened
On March 15, 2016, a Rolladen Schneider LS6 glider, registration F-CGUG, departed from Chambéry Challes-les-Eaux for a towed flight. After approximately one hour of flight north and east of the airfield, the pilot decided to return. While flying along the western slope of Mont Revard, the aircraft encountered significant downduring due to prevailing winds.
As the aircraft moved south along the terrain, the rate of descent increased sharply. Although the pilot had the opportunity to divert to the nearby Chambéry Aix-les-Bains aerodrome, the decision to continue along the ridge resulted in a forced landing in a field located in an urban area between two residential developments. During the final approach, the pilot had to maneuver to avoid a high-voltage power line. This obstacle interfered with the flare maneuver, causing the right wing to strike the ground first and resulting in a ground loop. The aircraft was heavily damaged.
The investigation
The investigation examined the meteorological conditions, which included a northeast wind of 15 knots with gusts up to 25 knots, creating strong sink rates on the western side of the mountains. The investigators also reviewed the pilot's flight history and the sequence of maneuvers leading to the impact. The investigation established that the pilot was aware of the wind conditions prior to takeoff but encountered much more intense turbulence and sinking air than anticipated during the return leg.
Findings
- The western slope of Mont Revard was experiencing strong downdrafts caused by the northeast wind.
- The pilot's inadequate choice of return trajectory kept the aircraft too close to the terrain during periods of high sink rates.
- A late decision to perform a forced landing prevented the pilot from selecting a more suitable landing site.
- The presence of high-voltage power lines obstructed the flare, leading to the loss of control.