What happened
On June 26, 1999, near Bad Salzdetfurth, Germany, two gliders were engaged in thermalling maneuvers when they collided in mid-air. The first aircraft, a single-seat Schleicher KA6CR, had departed from the Steinberg-Wesseln glider field via winch launch approximately ten minutes before the second aircraft. The second aircraft, a two-seat Schleicher ASK13, was operated by a student pilot performing a similar thermalling mission.
As the student pilot began circling in an updraft south of the airfield, the pilot of the KA6CR moved toward the same thermal area to gain altitude. While both aircraft were circling to the left, the KA6CR successfully utilized the lift to reach the same altitude as the ASK13. During this process, the pilots lost visual contact with one another. The student pilot reported seeing a shadow approaching from the front left, followed by a heavy impact on the right wing of the ASK13.
The collision caused the left outer wing of the KA6CR to break off approximately 2.5 meters from the fuselage. This structural failure sent the aircraft into an immediate spiral dive. The pilot of the KA6CR attempted an emergency parachute deployment, but the altitude was insufficient to deploy the chute before the aircraft struck a residential garden. The pilot sustained one fatality.
In the ASK13, the impact caused significant damage to the right wing and impaired flight controls. Following radio instructions to bail out, the student pilot successfully deployed their parachute and landed safely in a nearby meadow.
The investigation
The BFU investigation focused on the flight paths and the circumstances surrounding the loss of visual contact. Investigators examined the wreckage of both aircraft and found no evidence of technical malfunctions; both gliders were properly maintained and airworthy. The investigation also reviewed the qualifications of the pilots, noting that the pilot of the KA6CR was experienced and properly licensed, while the pilot of the ASK13 was a student with approximately 20 hours of flight time.
Findings
- The collision occurred because the flight paths of the two aircraft intersected at the same altitude.
- The pilot of the KA6CR had altered their circling pattern to better utilize the updraft, which caused them to climb above the ASK13 and cross its flight path.
- The pilots failed to recognize the converging flight paths in time to avoid the collision.
- The structural failure of the KA6CR's wing was the direct cause of the subsequent fatal spiral dive.