What happened
On April 16, 2016, a Grob G10SB Twin Astir II glider, registration F-CFKJ, was conducting a general aviation flight near La Motte-Chalancon, France. The pilot, flying from the rear seat, was accompanied by a student passenger. After approximately 90 minutes of flight, the pilot decided to return to the departure airfield at Aubenasson. During the return, the pilot realized they had drifted too far west and attempted to divert to the La Motte-Chalancon altiport.
While flying into the wind, the crew encountered strong sink rates. Realizing the altiport was no longer reachable, the pilot opted to perform an emergency landing in a nearby field. The pilot chose a landing approach facing north to utilize a clearer final approach and an estimated rising slope, despite the wind blowing from the south-southeast.
GNSS data indicated the aircraft maintained an average ground speed of 85 km/h during the tailwind leg and 140 km/h during the final approach, significantly exceeding the manual's recommended approach speed of 95 km/h. The glider passed over trees at an altitude of approximately 20 meters and touched down 40 meters before the end of the field. The momentum caused the glider to lift off again, striking a hedge and then the roof of a house, before falling approximately eight meters.
The investigation
The investigation focused on the pilot's decision-making and the aircraft's flight parameters during the approach. Investigators examined GNSS data, which revealed a high-speed approach. The investigation also looked into the pilot's experience levels, noting that while the pilot had 350 total hours, this was their first time operating this specific aircraft type from the rear seat. The presence of the passenger in the front seat was also analyzed for its impact on visual references.
Findings
- The primary cause of the accident was the pilot underestimating the influence of the wind, which led to a landing attempt that was both too fast and too long.
- The pilot's lack of experience with the Grob G103 Twin Astir II and the specific challenges of operating from the rear seat contributed to the accident.
- The shift in visual references caused by the passenger's presence in the front seat, combined with obstacles at the start of the field, likely hindered the pilot's ability to adjust the approach slope and touchdown point.
- A sense of overconfidence from successful earlier flight segments contributed to the delayed decision to turn back.