What happened
On 24 June 2006, a Eurostar EV-97 ultralight aircraft, registered 9-249, crashed in the Ova Spin area near Zernez, Switzerland. The aircraft had departed from Mollis at approximately 17:30 LT as part of a sightseeing flight following a microlight fly-in event. The flight was intended to traverse a route through the Engadine region. During the flight, the aircraft's left wing structure suffered a forced rupture, leading to a loss of control and a fatal impact. The two occupants of the aircraft were fatally injured in the crash.
The investigation
The investigation conducted by the AAIB focused on the structural integrity of the wing and the environmental conditions at the time of the accident. Investigators examined the wreckage and performed detailed metallurgical and mechanical analyses of the wing components. The examination of the lower spar cap revealed a significant reduction in material quality, characterized by an extrusion weld and a coarse grain structure.
Technical assessments included calculations of wing loading and stress concentrations. The investigation also looked into the manufacturer's testing protocols, specifically the static load tests used to verify the aircraft's strength. Furthermore, the investigators evaluated the atmospheric conditions in the Zernez area, noting the presence of convective air currents and the pilot's experience with mountainous terrain.