Pérdida de sustentación y choque del Janus B contra árboles en Schänerberg, Suiza
El 16 de julio de 1991, un planeador Schempp-Hirth Janus B, con un piloto y un pasajero a bordo, se estrelló en Schänerberg, Suiza. Después de ser liberado a 1700 metros, el planeador intentó ganar altitud en térmicas de débiles a moderadas. Al maniobrar a aproximadamente 100 metros sobre el suelo, el planeador entró en pérdida durante un giro a la derecha con un ángulo de inclinación de 50° y colisionó con árboles. Ambos ocupantes sufrieron heridas graves y el planeador fue destruido. La investigación confirmó que la pérdida de sustentación ocurrió debido a una velocidad insuficiente durante el giro.
- 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.