Aterrizaje duro del ASK 21 durante entrenamiento en el aeródromo de Gruyère tras simulación de rotura de cable

El 12 de junio de 1994, un Alexander Schleicher ASK 21 experimentó un aterrizaje duro en el aeródromo de Gruyère durante un vuelo de entrenamiento. El instructor simuló una rotura de cable de cabrestante poco después del despegue, lo que llevó a una ascensión pronunciada por parte del piloto estudiante. El planeador fue controlado nuevamente cerca del suelo, pero se produjo un aterrizaje duro. El instructor sufrió lesiones graves, mientras que el piloto estudiante tuvo un leve dolor de espalda. El tren de aterrizaje y el fuselaje del planeador resultaron dañados. El informe oficial identificó una pérdida de sustentación cerca del suelo y un despliegue prematuro de los aerofrenos como causas.

1. Winch launch climb: During a dual training winch launch from runway 36, the ASK 21 transitioned from the initial acceleration into a steep climb of about 40° shortly after liftoff.
2. Simulated cable break: At approximately 20 m above ground and 1–2 seconds after rotation into the steep climb, the instructor released the winch cable to simulate a cable break.
3. Low altitude exercise: The cable break simulation was conducted at very low height near the start of the steep winch climb, leaving little altitude margin for recovery.
4. Premature airbrake use: Airbrakes were observed extended shortly after the transition to glide, reducing acceleration and adding a nose-down pitching moment during the recovery.
5. Student pushes nose down: The student immediately pushed the control stick forward to lower the nose and attempt to land ahead, causing the glider to pitch increasingly toward the ground.
6. Instructor flare and stall: As the glider approached the ground in a steep descent, the instructor pulled the stick back sharply to arrest the sink, and the glider stalled at low height and sank almost flat onto the surface.
7. Crash - serious injury: The glider impacted the ground very hard near the runway threshold, seriously injuring the instructor, slightly injuring the student, and damaging the landing gear and airframe.