Crash du Blanik L-13 lors d'un entraînement acrobatique près de l'aérodrome de Schänis

Le 19 octobre 1968, un LET L-13 Blanik s'est écrasé lors d'un entraînement acrobatique près de l'aérodrome de Schänis en Suisse. Le pilote, sous la supervision d'un instructeur de vol, n'a pas pu sortir d'une spirale abrupte et l'appareil a percuté le sol. Le pilote a subi de graves blessures et l'appareil a été détruit. Les conditions météorologiques étaient favorables et n'ont pas contribué à l'accident. L'enquête n'a pas déterminé de cause définitive pour l'incapacité du pilote à récupérer de la manœuvre.

1. Aerotow aerobatic training: During the third aerotow training flight of the day, the pilot conducted a sequence of aerobatic figures in the Blanik L-13 under supervision of a flight instructor.
2. Entry to steep left spiral: After completing the aerobatic sequence and flying straight for 1–2 km at about 400–500 m AGL, the pilot began practicing left spirals, entering a steep left spiral at relatively low height.
3. Limited aerobatic recency: The pilot had modest aerobatic experience and was resuming Blanik aerobatic training after a break of over two and a half months, potentially reducing proficiency and confidence.
4. Aft-CG spiral behavior: Flight tests with a similar aft center-of-gravity position showed that in steep left spirals the Blanik could be slow to roll out when the stick was only moved to the right knee, giving little recovery response until full lateral deflection was applied.
5. Ineffective recovery inputs: When the aircraft did not recover from the steep left spiral, the pilot reported that the control stick stopped slightly right of center and he unsuccessfully tried with both hands to apply more right aileron while the glider continued descending rapidly.
6. Continued descent in spiral: Unable to arrest the steep spiral and losing height quickly, the pilot considered but rejected bailing out at about 250 m AGL and did not deploy airbrakes, remaining in a tightening low-altitude left turn.
7. Crash - serious injury: Still in a left turn, the glider stalled or dropped over the left wing and impacted an orchard meadow, first striking the left wingtip and then the nose before overturning, seriously injuring the pilot and destroying the aircraft.