Tödlicher Strukturversagen während Windenstart der SZD 24-4A Foka 4 auf dem Flugplatz Bicester

Am 8. August 2010 erlitt eine SZD 24-4A Foka 4 während eines Windenstarts auf dem Flugplatz Bicester in Oxfordshire ein katastrophales Strukturversagen. Die Tragflächen trennten sich kurz nach dem Start vom Rumpf, was zu einem tödlichen Unfall für den Piloten führte, der der einzige Insasse war. Die Untersuchung ergab, dass der untere Kegelbolzen der Hauptflügelbefestigung beim Aufrüsten nicht vollständig eingerastet war, was zum Versagen führte. Das Segelflugzeug wurde bei dem Vorfall zerstört, und infolge der Ergebnisse wurden zwei Sicherheitsempfehlungen ausgesprochen.

1. Preflight assembly: On the morning of the accident, the pilot and friends rigged G-DBZZ for flight at Bicester Airfield, carefully consulting the Flight Manual as none of them had rigged this type before.
2. Wing joint misrigged: During rigging, the lower bevel bolt of the wing main fitting did not fully engage with the lower lug stack of the main spar joint, leaving the primary wing attachment only partially secured and undetectably misrigged.
3. Engagement not verifiable: The design of the wing main fitting allowed the pilots to complete the specified number of turns and feel little resistance, yet provided no means to verify full engagement of the lower bevel bolt.
4. Pilot reassurance: After a first, uneventful but low winch launch during which the canopy opened, the pilot discussed the rigging and canopy issue with the owner by telephone and was reassured that the rigging had been done correctly.
5. Winch launch - climb: On the second winch launch, the glider accelerated and rotated into a climb that some witnesses perceived as slightly fast and steep, remaining on the cable as it climbed through several hundred feet.
6. Wing attachment failure: While still on the winch, the left wing bent upward about 20 degrees followed by the right wing, the lower bevel bolt failed, and both wings folded upwards and separated from the fuselage while remaining attached to each other at the main spar joint.
7. Crash - fatal: With the wings detached, the fuselage pitched steeply nose-down and struck the ground, destroying the glider and fatally injuring the pilot.