Struktureller Ausfall der S-18 während des Windenstarts auf dem Flugplatz Bad Ragaz führt zu Todesfall

Am 1. Januar 1964 erlitt ein AG Wynau S 18 M während eines Windenstarts auf dem Flugplatz Bad Ragaz in der Schweiz einen strukturellen Ausfall in der Luft. Das Segelflugzeug zerbrach, bevor es den Scheitelpunkt des Starts erreichte, was zu einem tödlichen Absturz führte. Der Pilot, ein Schüler mit begrenzter Solo-Flugerfahrung, kam beim Aufprall ums Leben. Die Untersuchung ergab, dass der strukturelle Ausfall auf langfristige Schwächen in der Konstruktion des Flugzeugs zurückzuführen war, die während der Wartung nicht ausreichend behoben wurden. Die Wetterbedingungen waren zum Zeitpunkt des Vorfalls klar mit variablen Winden.

1. Winch launch climb: During a training winch launch in calm weather, the S-18 glider climbed normally toward the apex of the launch with the student pilot at the controls.
2. Aged weakened structure: The glider’s rear fuselage structure around frame 8a had long‑term weakening from design discontinuities, moisture, multiple past damage events, and some unsatisfactory repairs that were not fully recognized or corrected in maintenance.
3. Over-strong weak link: The winch cable was fitted with a supposed 540 kg weak link that in fact had a measured breaking load of about 800 kg, allowing higher tow loads to be transmitted to the airframe than intended.
4. Structural failure in climb: Shortly before reaching the launch apex at about 180 m above ground, the rear fuselage between wing and tail deformed and the plywood skin began to crack and shed pieces as the weakened structure failed under winch tow loads.
5. Fuselage breaks apart: The fuselage burst apart with the tail section hinging downward, leading to loss of structural integrity and control as the glider rolled right and pitched into a steep dive.
6. Winch cable released: The winch operator cut the tow cable after seeing the breakup, but the glider was already uncontrollable and continued descending in a steep, rolling attitude.
7. Crash - fatal: The glider impacted the ground in a steep inverted attitude near the airfield, was completely destroyed, and the student pilot was killed on impact.