What happened
On August 12, 1997, at 16:04 local time, a Club Libelle 205 Mod., registration HB-1260, was performing a winch-assisted takeoff from runway 21 at Samedan Airport. During the initial phase of the launch, the glider experienced a shallow climb. As the aircraft attempted to transition into a steady climb, the flight attitude became unstable, causing the glider to bank heavily to the left. In an attempt to correct the flight path using standard winch-launch procedures, the pilot inadvertently increased the instability. At an altitude of approximately 50 meters, the aircraft suffered a stall, resulting in a left-wing drop. The glider subsequently struck the paved runway in an inverted position with the nose leading, resulting in the total destruction of the aircraft and the death of the pilot.
The investigation
Investigators examined the mechanical condition of the glider and the operational environment. The aircraft's weight and balance were found to be within prescribed limits, and a visual inspection of the control linkages, bellcranks, and cables revealed no pre-existing defects. The winch system provided sufficient power and cable speed, even accounting for a 5-knot tailwind component. Meteorological data indicated visibility of 30 km, temperatures of 22°C, and variable winds up to 5 knots. The pilot held a valid license and possessed significant total flight experience, though experience specifically with this aircraft type was limited to approximately 53 hours. Notably, the pilot had been previously advised by an instructor during earlier launches on this specific aircraft regarding the risk of insufficient airspeed during the transition to a climb.
Findings
- The primary cause of the accident was the loss of control following a stall during the winch launch.
- The pilot attempted to pitch the aircraft up as if performing a standard launch, despite insufficient airspeed.
- The aircraft did not exhibit a natural tendency to pitch up after liftoff, requiring careful airspeed management.
- While the pilot had extensive general flight experience, recent experience with the HB-1260 was very low, with only three winch launches performed on this specific model in the preceding 90 days.
- Weather conditions, specifically the variable wind and air density, were not optimal for the launch.