What happened
On August 16, 2008, a Discus b glider, registration HB-3038, was involved in a fatal accident near the village of Buttwil, Switzerland. The aircraft was being operated under VFR private flight conditions. After being towed to an altitude of approximately 1,300 meters, the pilot released the tow rope at roughly 700 meters above ground level.
While circling in an updraft, the glider entered an uncontrolled spin. Observers noted that the pilot made no visible attempts to recover the aircraft from the spin. The descent ended when the nose of the glider struck the roof of a building, causing the aircraft to flip and come to rest upside down on another structure. The pilot was ejected from the cockpit upon impact and died from his injuries. The collision also caused damage to two nearby houses.
The investigation
Investigators examined the pilot's training records, the aircraft's configuration, and the club's induction procedures. The investigation established that while the pilot had significant general glider experience, he had only completed a very limited number of hours specifically on the Discus b model.
Technical analysis of the aircraft's weight and balance showed that the center of gravity was located near the rear limit of the allowable range. Although the aircraft was within legal limits, the specific loading configuration increased the risk of a spin. The investigation also reviewed the induction process used by the Zurich Gliding Group, noting that the pilot had performed several flights without the required supervision from an instructor.
Findings
- The primary cause of the accident was the aircraft entering an unintentional spin that the pilot was unable to recover from before impact.
- The aircraft's center of gravity was positioned near the aft limit, which increased the likelihood of a spin.
- The pilot had limited flight experience specifically with the Discus b model.
- The pilot lacked specific training or instruction on how to prevent or recover from a spin in this aircraft type.
- The pilot was not fully familiar with the club's required induction procedures.
- There was a lack of adequate oversight and enforcement of the club's induction and supervision protocols.