Unfall des Pilatus B4-PC 11AF während Kunstflugprüfung in Zweisimmen

Am 19. Juli 1986 war ein Pilatus B4-PC 11AF in einen Unfall in Zweisimmen, Schweiz, während einer Kunstflugprüfung verwickelt. Nach dem Ausklinken des Schleppseils in etwa 700 Metern Höhe führte der Pilot eine Reihe von Kunstflugmanövern durch. Die Manöver wurden zunächst korrekt ausgeführt, aber die Spiralen waren zu eng, was zu einem erheblichen Höhenverlust führte. Beim Endanflug kam es zu einem Strömungsabriss, und das Segelflugzeug stürzte in die Simme. Der Pilot erlitt schwere Verletzungen und Unterkühlung, überlebte jedoch. Das Flugzeug wurde zerstört.

1. Aerotow aerobatics flight: The pilot aerotowed from Zweisimmen runway 35 to about 700 m AGL and began the planned aerobatic exam sequence overhead the airfield.
2. Overly steep spirals: During the three right spirals, the bank angle was about 80°, causing an abnormally high sink rate and greater than expected loss of altitude.
3. Low exit altitude: Despite the examiner’s relayed request to stop the program, which the pilot did not acknowledge, he completed the third spiral and exited into downwind at only about 80 m AGL and 85 km/h, well below the recommended spiral exit height.
4. Low-speed turn to final: From this low downwind, the pilot initiated a 180° left turn toward final for runway 35 at a speed near minimum flying speed and with possible sideslip and tailwind gust influence.
5. Stall and wing drop: After turning about 150° and as the nose was raised toward the runway heading, the pilot felt a jolt and tail lift, and the glider abruptly rolled steeply left into a stall from which recovery was not possible at the low height.
6. Crash - serious injury: The glider impacted nose-down in the Simme river near the airfield, was destroyed, and the pilot sustained serious injuries and severe hypothermia while trapped for about 90 minutes in cold water.