What happened
On May 18, 2014, a Rolladen Schneider LS4 glider, registration F-CFZL, departed from the Saint-Martin-de-Londres airfield for a local flight. During the initial hour of the flight, the pilot successfully utilized thermal lift to maintain altitude. However, due to the arrival of maritime air and southerly winds, thermal activity diminished significantly.
By approximately 15:00, the pilot noted a rapid loss of altitude and realized they were no longer within visual range of the departure airfield. While near the "Coupiac" field, the pilot attempted to regain altitude by performing ridge soaring along the southern face of the Montagne de la Séranne. During this maneuver, the right wing of the glider struck a tree, leading to a loss of control and a subsequent impact with the ground. The glider was destroyed in the accident.
The investigation
The investigation focused on the pilot's decision-making process and the meteorological conditions at the time of the accident. Investigators examined the flight path, the pilot's experience, and the suitability of ridge soaring under the prevailing wind conditions. The pilot, who had 700 total flight hours, noted that recent personal issues and a lack of recent flight experience might have influenced their decisions. The investigation also reviewed the technical requirements for effective ridge soaring as outlined in the pilot's manual.
Findings
- The primary cause of the accident was the pilot's decision to continue the flight rather than performing a precautionary landing in a suitable field, despite the loss of thermal lift and increasing difficulty in maintaining altitude.
- The pilot attempted to utilize ridge soaring on the southern slope of the mountain, a terrain feature they were less familiar with than the northern slope.
- Meteorological conditions were not conducive to ridge soaring; the wind speed was only 7 knots, whereas the pilot's manual indicates that ridge lift is typically only effective with winds exceeding 12 to 15 knots.