Incident de formation DFS Kranich II lors de l'approche à Löhningen, Suisse

Le 5 décembre 1959, un DFS Kranich II a subi un décrochage et une vrille lors d'un vol d'entraînement à Löhningen, Suisse. L'incident s'est produit lorsque l'élève-pilote a dépassé l'angle d'attaque critique de l'appareil en effectuant un cercle complet pour perdre de l'altitude avant l'atterrissage. Le planeur est entré en vrille à environ 80 mètres du sol, entraînant un crash. L'instructeur de vol a subi des blessures légères, tandis que l'élève-pilote a été grièvement blessé. L'appareil a été détruit, et des divergences dans les indicateurs de vitesse ont été notées mais non confirmées comme causales.

1. Training circuit flight: During a winch-launch training flight, the instructor and student flew a second circuit in the Kranich II with the student flying and the instructor supervising.
2. Student flies too slowly: On both the first and second flights the student repeatedly tended to fly below the instructed normal approach speed of about 70 km/h, only briefly correcting when prompted by the instructor.
3. Low height for maneuvering: On the second circuit the glider remained too high for landing, leading the instructor to have the student fly additional 360° turns at relatively low altitude to lose excess height.
4. Overshoot of stall in turn: While completing the second left 360° turn at about 80 m above ground, the student increased bank and applied strong right rudder, causing the aircraft to exceed its critical angle of attack in the low-speed turn.
5. Late instructor intervention: The instructor reported attempting to take over the controls as the bank and rudder input became excessive, but his intervention came too late to prevent the stall and spin entry.
6. Stall and spin at 80 m: The glider abruptly stalled from the left turn, dropped into a left spin from about 80 m above ground, and completed nearly two turns with no altitude available for recovery.
7. Crash - serious injury: The glider impacted the soft ground steeply and was destroyed, the instructor received minor injuries, and the student sustained serious injuries.