What happened
On September 12, 2020, a student pilot was conducting a solo endurance flight in a Centrair 101 A Pégase, registration HB-3090, near the Montricher airfield in Switzerland. The flight was part of a training syllabus and was being performed under the supervision of an instructor on the ground.
During the flight, the glider was being towed by a Robin DR400. Shortly before the release of the tow rope, the aircraft encountered a period of descending air. To manage the tension of the tow rope and maintain separation from the tug, the student pilot deployed the airbrakes. At an altitude of approximately 1,850 meters, the pilot released the tow rope.
Following the release, the glider entered a series of maneuvers, including a left turn and a subsequent right turn. During this period, the aircraft experienced high sink rates. Witnesses on the ground observed the glider losing altitude rapidly and flying close to the treetops. In a final attempt to avoid the terrain, the pilot pulled back on the controls, which induced a stall at a very low altitude. The aircraft struck the ground in a forested area, resulting in one fatality.
The investigation
Sust examined the wreckage, flight data from the onboard Flarm system, and witness testimonies from the tow pilot, instructors, and nearby glider occupants. The investigation focused on the aircraft's configuration and the pilot's actions during the critical moments following the rope release.
Technical analysis of the wreckage revealed that the airbrakes were partially or fully deployed at the time of impact, and the landing gear was extended. The investigation also noted that the Emergency Locator Transmitter (ELT) was in the 'OFF' position and did not activate.
Findings
- The primary cause of the accident was a loss of control leading to a stall at low altitude.
- The deployment of the airbrakes prior to the rope release, which remained extended throughout the descent, acted as a significant contributing factor.
- The pilot likely experienced high workload during the release phase, managing both the tow rope tension and the airbrakes.
- The high sink rate caused by the extended airbrakes likely led to a situation where the pilot, attempting to avoid the trees, inadvertently triggered the fatal stall.