Incidente de ASK 23B cerca de Lommiswil: aterrizaje de emergencia en árboles tras entrada en pérdida
El 13 de septiembre de 1990, un Alexander Schleicher ASK 23B experimentó una entrada en pérdida durante un vuelo de entrenamiento cerca de Lommiswil, Suiza. El piloto, con experiencia limitada, volaba a lo largo de una cresta cuando la velocidad del planeador cayó por debajo del nivel mínimo seguro. Incapaz de recuperar el control, el piloto desplegó los aerofrenos y realizó un aterrizaje de emergencia en las copas de los árboles. El planeador se deslizó por los árboles hasta el suelo, resultando en daños significativos a la aeronave. El piloto no resultó herido y salió del avión sin ayuda.
- Ridge training flight: During the second afternoon training flight after aerotow to 2000 m, the pilot conducted ridge soaring along the Hasenmatt between about 1200 and 1300 m, flying short figure‑eight patterns along the slope.
- Low ridge experience: The pilot had very limited overall gliding experience and only a brief prior ridge-flying checkout, so he was not familiar with windshear hazards in ridge soaring.
- Aft CG and turbulence: The glider was loaded with the center of gravity in the aft part of the allowable range, reducing longitudinal stability, and the ridge area was known for turbulent, sheared airflow with only weak ridge lift.
- Turn away from slope: While flying figure‑eights along the ridge, the pilot made a 180° left turn away from the slope and then immediately turned right, during which the airspeed dropped rapidly below the minimum safe speed.
- Stall and height loss: The glider entered a mush/stall with airspeed reported down to about 50 km/h, losing height quickly despite the pilot applying full control inputs to turn right and away from the slope.
- Emergency landing attempt: Recognizing that he could not regain sufficient airspeed or control, the pilot committed to an emergency landing and extended the airbrakes.
- Crash - no injury: The glider touched down in treetops on the slope, slid down the trees to the ground, was destroyed, and the pilot exited uninjured.