Crash de l'ASK 13 à l'aérodrome de Grenchen suite à une libération de remorquage inattendue

Le 9 avril 1980, un élève-pilote pilotant un Alexander Schleicher ASK 13 a décollé pour un vol d'entraînement en solo depuis l'aérodrome de Grenchen. Peu après le décollage, à environ 80 mètres d'altitude, le câble de remorquage s'est libéré de manière inattendue de l'avion remorqueur. Le planeur a entamé un virage à gauche qui s'est accentué de manière incontrôlable, entraînant un crash à 15h59 heure locale. L'élève-pilote a subi des blessures mortelles, et l'ASK 13 a été détruit. L'incident a été attribué à la perte de contrôle suite à la libération de remorquage inattendue.

1. Aerotow initial climb: The student pilot departed solo in ASK-13 HB-926 on aerotow from Grenchen and climbed normally to about 80 m above ground.
2. Unexpected tow release: Shortly after passing the western end of the airfield at approximately 80 m AGL, the tow cable unexpectedly released from the tow aircraft while the glider was flying slightly low behind it.
3. Low altitude, student pilot: The cable release occurred at very low altitude with a relatively inexperienced student pilot who had previously shown anxiety in unexpected situations.
4. Left turn after release: After recognizing the situation and transmitting 'cable break' on the radio, the student initiated a left turn instead of maintaining straight-ahead flight and building speed over suitable landing terrain ahead.
5. Steepening descending turn: The left turn became progressively steeper with the glider increasingly nose-down, airspeed apparently low, and the aircraft entering an uncontrolled, high pitch-down attitude with about 300° change in heading.
6. Crash - fatal: The glider, still attached to the tow rope at its nose hook, impacted the ground in a steep nose-down attitude with slight left bank, fatally injuring the student pilot and destroying the aircraft.