What happened
On May 25, 2012, a Schempp-Hirth Nimbus 4, registration D-7035, was performing a towed takeoff from the unpaved runway 36 at the Bailleau Armenonville airfield. After approximately 30 minutes of flight, the pilot transitioned to a tailwind approach for runway 08. During the final approach, the pilot observed that the glider preceding them was still stationary on the central portion of the runway. To avoid the other aircraft, the pilot elected to land on the left side of the runway.
Immediately after the main wheel made contact with the ground, the glider experienced a sudden roll and a sharp leftward ground loop, rotating approximately 200 degrees before coming to a halt. The impact resulted in the tail boom breaking at the empennage level, leaving the glider heavily damaged.
The investigation
The investigation focused on the runway conditions and the pilot's awareness of the surface state. While the central part of runway 08 had shorter grass due to frequent use, the left side of the runway featured much denser and taller vegetation, measuring approximately 40 cm in height.
Investigators found that a morning briefing at the gliding center had specifically warned participants that the grass was high in certain areas and advised landing on the central part of runway 08. However, the pilot of D-7035, who was the owner of the aircraft, had not attended this briefing and was unaware of the specific runway conditions prior to takeoff. The grass on the takeoff runway (runway 36) was significantly shorter than that on runway 08.
Findings
- The primary cause of the accident was a roll excursion occurring shortly after the main wheel touchdown.
- The left wing dipped into high, dense vegetation, which acted as a brake and destabilized the aircraft, triggering the ground loop.
- The pilot's lack of knowledge regarding the current state of the runway surface contributed to the occurrence.