What happened
On July 29, 2003, a single-seat Orlican Discus CS glider, registration D-8515, was performing a local flight near the Château-Arnoux Saint-Auban aerodrome. After approximately two hours of flight, the pilot was performing a climbing spiral at an altitude of roughly 2,240 meters. As the pilot exited the spiral at approximately 130 km/h, the aircraft suddenly pitched forward.
In an attempt to correct the pitch, the pilot applied back pressure, but the aircraft's stability was lost. The pilot's head struck the canopy, causing it to shatter. The glider entered a rapid right-hand rotation and subsequently inverted. Unable to regain control, the pilot deployed the emergency parachute at an estimated altitude of 500 meters and landed safely in a tree near the wreckage.
The investigation
The investigation focused on the structural integrity of the right wing. Technical examinations of the wreckage were split between the BEA and the German BFU. The external portion of the right wing was examined by the BEA, while the internal structure was analyzed by the B枚U.
Investigators examined the spar and the connection between the upper flange and the spar web. The examination of the aileron control tube revealed it had broken due to upward bending forces. Analysis of the wing skin showed evidence of both tension and compression, consistent with a structural failure under load. The investigation also looked into the manufacturing processes used by the Czech manufacturer, Orlican Akciova Spolecnost, under license from the German designer Schempp-Hirth.
Findings
Technical analysis established that the right wing separated due to a combination of upward bending and torsional loads. The primary cause of the failure was a manufacturing defect involving insufficient adhesive between the upper flange and the spar web.
Specific findings included:
- A lack of adhesive material in a significant area of the spar joint.
- Improper positioning of the upper flange, which was found to be misaligned and shifted toward the rear.
- The structural integrity of the wing was compromised by these bonding errors, making the aircraft unable to withstand standard maneuvering loads.
Safety action
Following the accident, the French aviation authority (DGAC) issued an urgent Airworthiness Directive (CNU) to suspend the Certificate of Airworthiness for French-registered Discus CS gliders, pending inspections to ensure structural integrity.