Janus B stall and crash into trees at Schänerberg, Switzerland
On July 16, 1991, a Schempp-Hirth Janus B glider, carrying a pilot and a passenger, crashed at Schänerberg, Switzerland. After being released from tow at 1700 meters, the glider attempted to gain altitude in weak to moderate thermals. While maneuvering at approximately 100 meters above ground, the glider stalled during a right turn with a 50° bank angle and collided with trees. Both occupants sustained serious injuries, and the glider was destroyed. The investigation confirmed that the stall occurred due to insufficient airspeed during the turn.
- Ridge thermaling flight: After aerotow release at about 1700 m, the pilot flew weak to moderate thermals and then began ridge-soaring along the Schänerberg with flaps set to +8°.
- Low climb, low margin: In weak lift the pilot needed about 30 minutes to gain only 400 m, continuing to operate close to the terrain with limited altitude margin.
- High bank near terrain: At about 1300 m MSL and roughly 100 m above ground, the pilot flew steep ridge turns with 45–50° bank despite the weak updraft conditions.
- Flap setting +8°: The glider remained in +8° flap setting, increasing stall speed in banked turns, which the pilot did not adequately account for.
- Right turn at low speed: While turning right back toward the slope with about 50° bank at roughly 90 km/h, the glider’s airspeed was below the required minimum for that configuration and bank angle.
- Stall and spin entry: The glider stalled and entered a spin at approximately 100 m above ground, leaving insufficient height for recovery.
- Crash - serious injury: In a right-hand spin the glider struck 20 m high trees on the steep Schänerberg slope and was destroyed, seriously injuring both occupants.