What happened
On April 18, 2018, a Centraible 101-A glider, registration F-CHFT, took off from the Bagnères-de-Luchon aerodrome using a winch launch. After releasing the cable at approximately 930 meters, the pilot performed a right-hand turn and began executing figure-eight maneuvers on the southern slope of the terrain, reaching a maximum altitude of 1,600 meters.
As the flight progressed toward the north, the pilot approached a south-north oriented ridge that reaches an elevation of 1,624 meters. Realizing that the clearance above the trees was insufficient and that a left-hand turn would not allow for obstacle avoidance, the pilot attempted a right-hand turn. During this maneuver, the pilot experienced a loss of lift, leading to a collision with the treetops and subsequent impact with the ground. The pilot sustained one injury, and the aircraft was destroyed.
The investigation
The BEA examined the wreckage and the accident site, noting that the right wing struck vegetation prior to the ground impact and that the aircraft was in a significant nose-down attitude at the moment of collision. Meteorological data at the time indicated clear skies with light turbulence and a south wind of 9 to 11 knots, with gusts reaching 16 to 20 knots.
Analysis of the onboard Flarm traffic and obstacle detection system provided critical trajectory data. During the final 40 seconds of the flight, the glider's altitude increased by approximately 60 meters, while the height above terrain dropped from 100 meters to 30 meters. Simultaneously, the groundspeed decreased from 120 km/h to 20 km/h, indicating that the pilot had converted kinetic energy into potential energy in an attempt to maintain clearance from the terrain.
Findings
Investigation findings established that the pilot underestimated the minimum altitude required to safely fly a straight path over the ridge, particularly given the prevailing wind conditions (a south wind creating an upslope effect). The pilot continued the flight without gaining sufficient altitude, prioritizing the maintenance of a minimum height at the expense of airspeed. This resulted in a late decision to maneuver, which reduced the margin for obstacle clearance and left the pilot unable to avoid the trees on the ridge.