What happened
On July 16, 2006, at approximately 14:47, two motor gliders collided while flying in a thermal updraft near Bütthard. The first aircraft, an ASH 26E, had departed from the Unterschüpf landing field for a cross-country flight. The second aircraft, a Schempp-Hirth Ventus CM, had departed from Mannheim earlier that day for a cross-country gliding flight. Both aircraft were operating in a gliding configuration with their retractable engines stowed.
The collision occurred at an altitude of approximately 1,000 meters AGL. The impact was nearly head-on, causing the left wing of the Ventus CM to detach at the wing-fuselage junction. The cockpit area of the ASH 26E was torn apart during the impact. Following the collision, the fuselage of the Ventus CM struck overhead power lines, which ignited a fire that destroyed the wreckage. The ASH 26E fell onto the roof of a residential building in Bütthard. The collision resulted in two fatalities, as both pilots were killed.
The investigation
The BFU examined the wreckage and recovered two navigation devices, though damage prevented the extraction of flight path data. Radar records indicated three flight paths in the area at the time of the accident, though the investigators could not definitively link the two specific aircraft to the radar tracks based on radar alone. Witness statements from ground observers and another pilot helped reconstruct the flight paths, suggesting the aircraft were on nearly opposing courses.
Technical inspections of both the ASH 26E and the Ventus CM revealed no mechanical failures or technical defects. The investigation also noted that the pilot of the Ventus CM was found with an unopened emergency parachute. In the ASH 26E, the cockpit structure was severely compromised, and the pilot's seatbelts were found to be intact, though the shoulder straps had not been utilized.
Findings
- The collision was a near-frontal impact on opposing courses within a thermal updraft.
- The pilots failed to detect the approaching aircraft.
- No evasive maneuvers were observed or recorded.
- The structural integrity of both aircraft was catastrophically compromised by the impact, leading to the subsequent crash and fire.